Vandana Shiva

Industrial globalized agriculture is heavily implicated in climate change. It contributes to the three major greenhouse gases: carbon dioxide (CO₂) from the use of fossil fuels, nitrogen oxide (N₂O) from the use of chemical fertilizers and methane (CH₄) from factory farming. According to the Intergovernmental Panel on Climate change (IPCC), atmospheric concentration of CO₂ has increased from a pre–industrial concentration of about 280 parts per million to 379 parts per million in 2005. The global atmospheric concentration of CH₄ has increased from pre–industrial concentration of 715 parts per billion to 1774 parts per billion in 2005. The global atmospheric concentration of N₂O, largely due to use of chemical fertilizers in agriculture, increased from about 270 parts per billion to 319 parts per billion in 2005.

Industrial agriculture is also more vulnerable to climate change which is intensifying droughts and floods. Monocultures lead to more frequent crop failure when rainfall does not come in time, or is too much or too little. Chemically fertilized soils have no capacity to withstand a drought. And cyclones and hurricanes make a food system dependent on long distance transport highly vulnerable to disruption.

Genetic engineering is embedded in an industrial model of agriculture based on fossil fuels. It is falsely being offered as a magic bullet for dealing with climate change.

Monsanto claims that Genetically Modified Organisms are a cure for both food insecurity and climate change and has been putting the following advertisement across the world in recent months.

9 billion people to feed.
A changing climate
Now what?
Producing more
Conserving more
Improving farmers lives
That’s sustainable agriculture
And that’s what Monsanto is all about.

All the claims this advertisement makes are false.

GM crops do not produce more. While Monsanto claims its GMO Bt cotton gives 1500 Kg/acre, the average is 300–400 Kg/acre.

The claim to increased yield is false because yield, like climate resilience is a multi–genetic trait. Introducing toxins into a plant through herbicide resistance or Bt. Toxin increases the “yield” of toxins, not of food or nutrition.

Even the nutrition argument is manipulated. Golden rice genetically engineered to increase Vitamin A produces 70 times less Vitamin A than available alternatives such as coriander leaves and curry leaves.

The false claim of higher food production has been dislodged by a recent study titled, Failure to Yield by Dr. Doug Gurian Sherman of the Union of Concerned Scientists, who was former biotech specialist for the U.S. Environmental Protection Agency and former adviser on GM to the U.S Food and Drug Administration. Sherman states, “Let us be clear. There are no commercialized GM crops that inherently increase yield. Similarly there are no GM crops on the market that were engineered to resist drought, reduce fertilizer pollution or save soil. Not one.”

There are currently two predominant applications of genetic engineering: one is herbicide resistance, the other is crops with Bt. toxin. Herbicides kill plants. Therefore they reduce return of organic matter to the soil. Herbicide resistant crops, like Round Up Ready Soya and Corn reduce soil carbon, they do not conserve it. This is why Monsanto’s attempt to use the climate negotiations to introduce Round Up and Round Up resistant crops as a climate solution is scientifically and ecologically wrong.

Monsanto’s GMOs, which are either Round Up Ready crops or Bt toxin crops do not conserve resources. They demand more water, they destroy biodiversity and they increase toxics in farming. Pesticide use has increased 13 times as a result of the use Bt cotton seeds in the region of Vidharbha, India.

Monsanto’s GMOs do not improve farmers’ lives. They have pushed farmers to suicide. 200,000 Indian farmers have committed suicide in the last decade. 84% of the suicides in Vidharbha, the region with highest suicides are linked to debt created by Bt–cotton. GMOs are non–renewable, while the open pollinated varieties that farmers have bred are renewable and can be saved year to year. The price of cotton seed was Rs 7/kg. Bt cotton seed price jumped to Rs 1,700/kg.

This is neither ecological nor economic or social sustainability. It is eco–cide and genocide.

Genetic engineering does not “create” climate resilience. In a recent article titled, “GM: Food for Thought” (Deccan Chronicle, August 26, 2009), Dr. M.S. Swaminathan wrote “we can isolate a gene responsible for conferring drought tolerance, introduce that gene into a plant, and make it drought tolerant.”

Drought tolerance is a polygenetic trait. It is therefore scientifically flawed to talk of “isolating a gene for drought tolerance.“ Genetic engineering tools are so far only able to transfer single gene traits. That is why in twenty years only two single gene traits for herbicide resistance and Bt. toxin have been commercialized through genetic engineering.

Navdanya’s recent report titled, “Biopiracy of Climate Resilient Crops: Gene Giants are Stealing farmers’ innovation of drought resistant, flood resistant and salt resistant varieties,” shows that farmers have bred corps that are resistant to climate extremes. And it is these traits which are the result of millennia of farmers’ breeding which are now being patented and pirated by the genetic engineering industry. Using farmers’ varieties as “genetic material,” the biotechnology industry is playing genetic roulette to gamble on which gene complexes are responsible for which trait. This is not done through genetic engineering; it is done through software programs like athlete. As the report states, “Athlete uses vast amounts of available genomic data (mostly public) to rapidly reach a reliable limited list of candidate key genes with high relevance to a target trait of choice. Allegorically, the Athlete platform could be viewed as a ‘machine’ that is able to choose 50–100 lottery tickets from amongst hundreds of thousands of tickets, with the high likelihood that the winning ticket will be included among them.”

Breeding is being replaced by gambling, innovation is giving way to biopiracy, and science is being substituted by propaganda. This cannot be the basis of food security in times of climate vulnerability.

While genetic engineering is a false solution, over the past 20 years, we have built Navdanya, India’s biodiversity and organic farming movement. We are increasingly realizing there is a convergence between objectives of conservation of biodiversity, reduction of climate change impact and alleviation of poverty. Biodiverse, local, organic systems produce more food and higher farm incomes, while they also reduce water use and risks of crop failure due to climate change.

Biodiversity offers resilience to recover from climate disasters. After the Orissa Super Cyclone of 1998, and the Tsunami of 2004, Navdanya distributed seeds of saline resistant rice varieties as “Seeds of Hope” to rejuvenate agriculture in lands reentered saline by the sea. We are now creating seed banks of drought resistant, flood resistant and saline resistant seed varieties to respond to climate extremities.

Navdanya’s work over the past twenty years has shown that we can grow more food and provide higher incomes to farmers without destroying the environment and killing our peasants. Our study on “Biodiversity based organic farming: A new paradigm for Food Security and Food Safety” has established that small biodiverse organic farms produce more food and provide higher incomes to farmers.

Biodiverse organic and local food systems contribute both to mitigation of and adaptation to climate change. Small, biodiverse, organic farms especially in Third World countries are totally fossil fuel free. Energy for farming operations comes from animal energy. Soil fertility is built by feeding soil organisms by recycling organic matter. This reduces greenhouse gas emissions. Biodiverse systems are also more resilient to draughts and floods because they have higher water holding capacity and hence contribute to adaption to climate change. Navdanya’s study on climate change and organic farming has indicated that organic farming increases carbon absorption by upto 55% and water holding capacity by 10% thus contributing to both mitigation and adaptation to climate change.

Biodiverse organic farms produce more food and higher incomes than industrial monocultures. Mitigating climate change, conserving biodiversity and increasing food security can thus go hand in hand.

Words: Vandana Shiva

There’s just one problem with all this: It’s all a big lie.

Here are the ten biggest lies that have been promoted about S.510 by the U.S. Congress, the food industry giants and the mainstream media:

Lie #1 – Most deaths from food poisoning are caused by fresh produce

Here’s a whopper the mainstream media won’t dare report: Out of the 1,809 people who die in America every year from food-borne pathogens (CDC estimate), only a fraction die from the manufacturer’s contamination of fresh produce. By far the majority of food poisoning is caused by the consumption of spoiled processed foods, dead foods and animal-human transmission of pathogens.

For example, one of the largest food-borne killers according to the CDC is Toxoplasma gondii, a disease that people acquire from cat feces coming into contact with their food, which can happen right in their own homes (http://www.cdc.gov/ncidod/eid/Vol5n…). Salmonella poisoning accounts for 553 deaths a year. As a reference for relative risk, over 42,000 people die each year from road accidents in the USA, meaning driving a car has a roughly 7600% higher chance of killing you than eating fresh produce. (http://www.driveandstayalive.com/in…)

In terms of food-borne illness, many of the deaths come from things like spoiled tomato sauce, spoiled canned foods and spoiled pasteurized milk. S 510, of course, does absolutely nothing to address these food contamination deaths, since those foods are considered “sterilized” at the time of sale.

Lie #2 – Under S.510, the FDA would only recall products it knows to be contaminated

Not true. S.510 merely requires the FDA to have “reason to believe” a food is contaminated. So right there, that means all raw milk will be targeted by the FDA because even without conducting any scientific tests at all, the FDA can say it has “reason to believe” the milk is contaminated merely because it is raw.

In other words, the FDA no longer needs science to outlaw a food product. It merely needs an opinion.

Is this “reason to believe” section really true? Yep, and here’s how it was amended:

SEC. 208. ADMINISTRATIVE DETENTION OF FOOD.

23 (a) IN GENERAL. – Section 304(h)(1)(A) (21 U.S.C.24 334(h)(1)(A)) is amended by

(1) striking ”credible evidence or information indicating” and inserting ”reason to believe”;

(http://frwebgate.access.gpo.gov/cgi…)

In other words, in negotiating this bill, the U.S. Senate removed the requirement that the FDA needed “credible evidence” in order to recall a product and, instead, replaced that with the FDA only needing “reason to believe.”

It is utterly amazing that the U.S. Congress would give the FDA to conduct large-scale product recalls and even imprison people based entirely on what the agency “has reason to believe.”

Last time I checked, the FDA held some pretty bizarre (if not downright moronic) beliefs, including this jaw-dropping whopper: The FDA literally believes that there is no food, no herb, no vitamin or supplement that has any ability to prevent disease of any kind. They don’t even believe limes can prevent scurvy, and you’d have to nutritionally illiterate to believe that.

The FDA believes foods are inert and that all the amazing phytonutrients in those foods (carotenoids, antioxidants, therapeutic fats like omega-3 and so on) are utterly useless for human biology.

This belief, held by the FDA that has now been put in charge of the food supply, is the belief system of an insane government agency that has completely lost touch with reality while abandoning nutritional science.

Lie #3 – They didn’t tell you that nearly 70% of grocery store chickens are contaminated with salmonella every day

Yep, it’s true: Amid all the fear-mongering over salmonella, everybody forgot to notice that the vast majority of fresh chickens sold at grocery stores every single day are widely contaminated with salmonella (http://www.naturalnews.com/028661_c…). Yet S 510 does absolutely nothing to address this. It’s not even mentioned in the bill.

In fact, it is these contaminated chickens that end up cross-contaminating the fresh produce in many kitchens across America. So the so-called “food poisoning” that’s often blamed on spinach or onions often originates with the contaminated chicken meat people bring home and slice on their kitchen cutting boards.

Lie #4 – S.510 will exclude and protect small farmers

The Tester Amendment, which was finally included in S.510, excludes farmers who sell less than $500,000 worth of food each year from the more onerous paperwork and compliance burdens described in the bill. But this dollar amount is not indexed to inflation, meaning that as the U.S. dollar continues to lose value due to the Federal Reserve counterfeiting machine running at full speed (more “quantitative easing,” anyone?), food prices will continue to skyrocket — and this will shift even small family farms into the $500,000 sales range within just a few years.

In fact, a single-family farm with just four people could easily sell $500,000 worth of fresh produce a year right now, even before inflation. Remember, $500,000 is not their profit, but rather the gross sales amount. The profits on that might be only $50,000 or even less.

Furthermore, this $500,000 threshold means that small, successful farms that are doing well and would like to expand will refuse to hire more people or expand their operations. To avoid the tyranny of S 510, small farms will try to stay small, and that means avoiding the kind of business expansion that would create new jobs.

Lie #5 – The FDA needs more power to enforce food safety

The FDA already has the power to effectively recall foods by publicly announcing a product has been found to be contaminated. The FDA already has the power to confiscate “misbranded” products, too, and it could easily use this power to halt the sale of contaminated food items.

But the FDA simply refuses to enforce the laws already on the books and, instead, has sought to expand its power by hyping up the e.coli food scares. The ploy apparently worked: Now in a reaction to the food scare-mongering, the FDA is being handed not just new powers, but more funding, too! And you can bet it will find creative new ways to put this power to work suppressing the health freedoms and food freedoms of the American people.

Lie #6 – Fresh produce is contaminated because of a lack of paperwork

There is no evidence that requiring farms to fill out more paperwork will make their food safer. The real cause of produce contamination is the existence of factory animal farms whose effluent output (huge rivers of cow feces, basically), end up in the water supply, soils and equipment that comes into contact with fresh produce.

The food contamination problem is an UPSTREAM problem where you’ve got to reform the factory animal operations that now dominate the American meat industry. S.510, however, does absolutely nothing to address this. Factory animal farms aren’t even addressed in the bill!

Lie #7 – The American people are dying in droves from unsafe fresh food

The truth is that Americans are dying from processed food laced with toxic chemical additives, not from fresh, raw produce. Partially-hydrogenated oils, white sugar, aspartame, MSG and artificial food colors almost certainly kill far more people than bacterial contaminations.

The American public is also dying from pharmaceuticals — anywhere from 100,000 to 240,000 people a year are killed by FDA-approved drugs (http://www.naturalnews.com/001894.html), most of which have been approved under the guise of blatantly fraudulent science and drug company trickery. The FDA doesn’t seem to mind. In fact, it has been a willful co-conspirator in the scientific fraud carried out by Big Pharma in the name of “medicine.” (http://www.naturalnews.com/027851_h…)

To think that the FDA — the very same agency responsible for the Big Pharma death machine — is now going to “save us” by controlling food safety is highly irrational.

Lie #8 – The FDA just wants to make food “safer”

Actually, the FDA wants to make the food more DEAD. Both the FDA and the USDA are vocal opponents of live food. They think that the only safe food is sterilized food, which is why they’ve supported the fumigation, pasteurization and irradiation efforts that have been pushed over the last few years.

California almond growers, for example, must now either chemically fumigate or pasteurize their almonds before selling them (http://www.naturalnews.com/021776.html). This has destroyed the incomes of U.S. almond farmers and forced U.S. food companies to buy raw almonds from Spain and other countries.

Lie #9 – Food smuggling is a huge problem in America

One of the main sections of S.510 addresses “food smuggling.” Yep — people smuggling food across the country. If you’ve never heard of this problem that’s because it’s not actually a problem.

Not yet anyway.

But there’s a reason why they put this into the bill: Because they’re probably planning on criminalizing fresh produce and then arresting people for transporting broccoli with the “intent to distribute.”

Yep, farmers bringing fresh produce to sell at the weekend farmer’s market could soon be arrested and imprisoned as if they were drug smugglers. Hence the need for the “food smuggling” provisions of S.510.

Soon, we will all have to meet in secret locations just to trade carrots for cash.

Lie #10 – S.510 will make America’s food supply the safest in the world

Actually, even with S.510 in place, America’s food supply is among the most chemically contaminated in the world, second only to China. You can find mercury in the seafood, BPA in the canned soup, yeast extract (MSG) in the “natural” potato chips, and artificial petrochemical coloring agents in children’s foods.

Eating the “Standard American Diet” is probably the single most harmful thing a person can do for their health. It’s the fastest way to get cancer, diabetes and heart disease. Every nation in the world that begins to consume the American diet starts to show record rates of degenerative disease within one generation. This is the “safe food” that the U.S. Senate is now pushing on everyone.

Remember, with S.510, SAFE = DEAD. And the FDA says it wants to keep everybody safe.

Learn more: http://www.naturalnews.com/030587_Senate_Bill_510_Food_Safety.html#ixzz16tPTM4Ew

Article credit: Mike Adams, Natural News.

Stop reading this. Please. Make sure you’ve completely dialed in your grow first. It’s far more important! Perfect your daytime and nighttime temps, keep a tight grip on your relative humidity, maintain optimum light levels, exact your feeding regimen, the works – all of it, get it right first.

The techniques described in this article are NOT for beginners and some of this stuff is nothing short of contentious. (Hmmm, a sure way to peak your interest though, eh?) We’re going to discuss methods of taking your plants to their outer limits and making them go a little bit crazy in the process. So, if you’re coming with us on this journey, buckle up, put on your questioning hat, and hold on to it tightly! Here we go …

Personally, I don’t care for stress, especially that special kind imposed by magazine publication deadlines. But I have to admit, one positive effect these deadlines have is to make me work harder!
So what about plants? We all know that unfavorable growing conditions (e.g. high temperatures and low relative humidity) can stress plants out big time. And if these conditions are severe enough you’re the quality and quantity of your yields will suffer. Invariably badly stressed plants will yield less than plants that have been pampered in every way.
Similar to most things in life, plants stress is not as black and white as you may think. In biology, stress can actually strengthen an organism. Immunity is obtained only from being subjected to an infection which involves suffering followed by growth, resistance and strength. In the human body a muscle cannot grow without being subjected to stress; a broken bone, when it sets properly, binds stronger than it was before and for that reason is very unlikely to break a second time at the same juncture. I’m sure many of you will have heard the phrase “What doesn’t kill you makes you stronger” or “Treat ‘em mean, keep ‘em keen”?  Well to a certain degree there is some truth in these sayings.

So with all this in mind is it at all possible that some forms of mild plant stress can actually improve results? The idea that stress can actually be a positive thing may seem alien to some of you. Why would you purposely want to stress plants? Surely stress should be avoided at all costs, right? Well the answer is “yes” and “no.” Here we explore the realms of stress; types that should be avoided and others which may well help you push your plants from being lazy and complacent into restless and eager producers!

Defining Plant Stress

There are many factors that will cause plants to become stressed, most of which can be grouped into two general categories -
Physical / Mechanical Stress:
Manipulation – Bending or training stems, physically damaging the plant.
Pruning – Removing leaves, stems, flowers or fruits.
Denial – not allowing a certain physical growth factor; e.g. blocking light, preventing pollination

Environmental / Abiotic Stress:
Water – drought, over-watering.
Temperature and Humidity – Cold (chilling and freezing), heat, wet or dry.
Mineral deficiency or toxicity – incorrect fertilization or salinity.
Pests and disease.

Danger Stresses

Temperature
High heat in your indoor garden can create a myriad of problems, the most common of which are tall leggy plants with large intermodal spacing, small fruits and loose flowers, high water usage, lower nutrient tolerance, and if temperatures remain high for long periods the stomata will close, plant growth will slow right down and may even cause severe wilting. Low temperatures are less problematic for indoor growers but can occur and cause slow growth and poor nutrient uptake.

Humidity
Low humidity during hot weather is a common problem that should be monitored and avoided as it will cause elevated transpiration and high water usage, increased susceptibility to over fertilization, leaf roll, stomata closure, and stunting. Periods of very low humidity can also cause wilting. On the flip side, high humidity will invite fungal infection to take hold and will slow the uptake and transport of water and nutrients.

Watering/Irrigation
Consistently irrigating the root zone beyond the plant’s usage capability causes a depletion in oxygen. These anaerobic conditions create a poor environment for root growth, cause poor water and nutrient uptake and favors the development of root diseases. A persistent lack of moisture around the rhizosphere can cause wilting, weakened leaf tissue, permanent root damage and nutrient precipitation in the growing media.

Light intensity
Having the grow lights too close will cause localized high heat and low humidity, this will lead to elevated transpiration and may result in permanent leaf tissue damage. Not having enough light tends to create poor plant growth as low water and nutrient uptake occurs. It most commonly causes elongated stems and large intermodal spacing.

pH
All good growers understand the importance of their nutrient solution’s pH and keep it within the range of 5.5-6.5, thus allowing nutrients to be available for uptake. If the pH swings out of this range for prolonged periods then nutrients that your plants need will be unavailable or  ‘locked out’ which will eventually lead to mineral deficiencies

Nutrient Strength
High nutrient levels can cause permanent damage to your plants.  Symptoms include tough leathery foliage, very dark green growth, leaf curl, poor water uptake and leaf tissue necrosis (death). Low nutrient strength is not so damaging but can also create unwanted characteristics such as soft weak stems and leaf tissue, mineral deficiencies, leggy growth and poor fruit and flower development.

Pests and Disease
Aside from pests physically eating the leaves and causing direct tissue damage, they can also spread disease from plant to plant or make a plant more susceptible to diseases and infections. Plants can usually recover from pest attack if the problem is dealt with quickly but diseases are a little more tricky. Above ground, fungal diseases like powdery mildew or botrytis can be controlled once they have infected the plant but root pathogens, viruses and other forms of invasive diseases are difficult, if not impossible to shift once they have taken hold.

Heard all this before? Okay, well now it’s time to introduce some more concepts that may not be so familiar…

How Can We Use Stress To Our Advantage?

It’s good practice to do all you can for your plants during propagation and their early growth stages because keeping plants healthy during this time is crucial when creating healthy vigorous plants. As plants mature and start producing fruits or flowers, small amounts of stress applied in the right way can actually help to improve the plant’s favorable characteristic. This may be an enhanced flavor, early ripening, elevated resistance to disease or enhanced chemical/medicinal characteristics.
Positive stress techniques are often used in commercial horticulture as a tool for influencing or ‘steering’ plants into a growth habit which the grower desires. Steering plants with mild stresses can influence the plant into shifting its efforts from vegetative growth into fruit or flower production.

Vegetative Steering

Sometimes you want your plants to grow, sometimes you want them to bloom. Most growers are familiar with using their light cycles to steer photoperiod sensitive plants. But this is just the tip of the iceberg. For most cultivated fast growing plants, “mild conditions” play a large role in steering the plant towards a vegetative growth habit. Here are some examples:

Lower nutrient strengths
The idea here is that by using a low nutrient strength you makes it easy for plant to take up water and nutrients through the roots. Obviously, you need to supply enough nutrients so as not to cause any deficiencies or unwanted growth characteristics (stretching/ long internodal distance), so supplying your plants with just above the minimum to reach these requirements will make it ‘easy’ for the plant, less stressful and therefore help keep the plant vegetative.

Wetter Root Zones
By regularly replenishing the growing media or root zone with water and nutrients without allowing dry periods to occur, the grower allows the plant easy access to water and nutrients, helping to steer the plant in a vegetative direction. It’s not good practice to purposefully over water the root zone in an attempt to steer vegetatively – all this will do it drive out vital oxygen and impede root function. The aim is to understand your plants’ (and growing media’s) water requirements and irrigate just before the growing media starts to dry. To implement this technique, drip irrigation systems offer most control. The irrigation strategy employed should be short irrigations with a high frequency. These irrigations should supply a little more than the amount the plants are using, with only a small amount of runoff occurring. By allowing water and nutrients to be constantly available to the plant it minimizes stress and promotes a vegetative growth habit.

Warmer Root Zones
Heating the nutrient solution will make it easy for the roots to function and take up water and nutrients easily. Aiming for 70°F (21°C) will help to make it easy for the plant and steer towards vegetative growth.

Low “Dif” – Small Difference in Day and Night Temperatures
The difference between the maximum daytime temperature and minimum nighttime temperature is often referred to as the ‘dif’, and contributes significantly towards your plants’ state of growth. By keeping the dif as small as possible the grower stimulates vegetative growth and keeps the plants short and compact. This is a really crucial technique for all indoor growers to get their heads around as shorter plants tend to yield far more under grow lights. Ideally, to keep plants vegetative and squat you should aim for a dif of no greater than 7°F (4°C). Time to buy that block heater!

Mild Environmental Conditions
To steer plants vegetatively, it’s important that the environment is as stress free as possible; therefore efficient temperature and humidity control are vital. Stress free growing conditions will be created if plants are able to transpire comfortably and create assimilates (sugars) via photosynthesis effectively. This will be achieved if the air temperature and humidity is within the plant’s comfort zone, generally 60-70% relative humidity (RH) with the air temperature between 68-77°F (20-25°C) – these conditions should make it comfortable for the plant to function vegetatively .

Generative Steering

Encouraging plants to flower quickly is a key skill for every indoor grower to acquire. The last thing any of us want are tall, stretching, leggy plants that force us to raise up our grow lights.  To get the most out of grow lights indoor gardeners aim for shorter, compact plants with wide canopies – the best way to harness as much of that precious incident light energy from grow lights as possible. To influence the plant’s speedy shift from a vegetative growth into flower or fruit production (generative growth), most indoor growers cultivating photosensitive plants will alter the light cycle and change out the nutrient solution from a ‘grow’ formula to ‘bloom’, and maybe use a few blooming additives through the cycle. This may meet the plant’s basic requirements  to start producing fruit or flowers, but selectively using mild stresses can not only trigger your plants into generative growth more quickly and efficiently, but it can also help focus your plants, throughout the flowering stage, to drive their efforts into producing copious amounts of flowers and fruits. These generative steering tools include:

Higher Nutrient Strengths
By raising the strength of the nutrient solution you are effectively increasing the concentration of mineral salts around the roots. This situation makes it more difficult for the plant to uptake water. When carefully managed, raising the nutrient strength to just below your plant’s upper tolerance will create a mild stress around the roots and steer the plant towards generative growth. Before undertaking this measure it is important you know your plant’s nutrient tolerance, some species and even different varieties within species will be able to tolerate more nutrient than others. Most importantly, you must have good environmental control to implement this stress technique. If you have problems with low relative humidity (below 50%) or do not have good temperature control, I strongly advise against using high nutrient strength as a steering tool as you will most likely cause problems with over feeding. Only with optimum environmental control can you accomplish generative steering with elevated nutrient strength.

Drier Root Zones
Allowing the growing media to dry slightly between irrigations also causes mild stress. The aim is not to completely restrict the availability of water and certainly not to allow the plant to wilt. The goal is to allow the growing media to dry to a point where the roots are ‘worried’ that water is running out, but not so much as to allow complete dehydration of the root surface. Implementation of this is fairly simple, during veg you water little and often to stimulate vegetative growth so during flower you water larger volumes less frequently. You don’t have to alter the total volume of water given during a day, just the timing of the irrigations. Once aging this technique is most controllable with drip irrigation systems.

Irrigation Start and Stop Times

As well as the frequency of the irrigations, the start and stop time can also be used as a steering tool. During the night your plants still use small amounts of water, this creates a drying back of the growing media during the night cycle. The more the growing media dries overnight, the more of a generative action it has. If the growing media is not drying much during the night it may be because you are irrigating too close to the lights turning off, which is more suited to vegetative growth. Your chosen time to stop and start irrigations will be determined by the growing environment but generally, starting one hour after the lights come on and one hour before they go out will be a good base to start from. If you hand water your plants in veg, say 35 fluid ounces (just over a liter) each day and you get a small amount of runoff, you could change to watering 70 fluid ounces every two days to make your plants more generative.
Word of warning; if the growing media dries too much and does not receive enough nutrient solution to re-saturate it, the nutrient strength in the growing media will start to rise. This will add to steer the plant generatively, but may lead to over fertilization. Always ensure that during the peak irrigations you supply enough solution to re-saturate the growing media and achieve 10-20% runoff.

Colder Root Zones
If you have some degree of control over the temperature of the nutrient solution you can stimulate generative growth by slightly cooling the solution. A drop from 70°F (21°C) down to 65°F (18°C) will make it slightly more difficult for the roots to function, but they will still be more than able to take up water and nutrients effectively. This mild root zone stress will not harm growth, it will just nag at the plant and push it in a generative direction.

Larger Difference in Day and Night Temperatures
Increasing the dif is known to have a positive generative action for most cultivated plants. However, it is not always good for plants that grow large fruits or flowers for the temperature to drop much below 65°F (18°C) as the transportation of assimilates made during the day can be affected by cold nights. If you have moderate day temperatures (75°F/24°C) and cannot achieve your desired dif, you may find it beneficial to raise the day temperatures to enough to keep the plants growing healthily (80°F/26.5°C) in order to enable you to increase the daily dif. To steer plants generatively try to aim for a dif of around 15°F (8°C).
Rapid late evening temperature drops have been used by greenhouse tomato growers for many years as a way of forcing assimilates towards the fruits. A quick fall in air temperature causes the plant to also cool down, but the leaves cool much faster than the fruit. This difference in internal temperature causes a draw of photosynthetic assimilates from the large leaves, which have been working hard to make sugars throughout the day, to be translocated to the fruits to advance growth. These quick pre-night temperature drops are not so difficult to achieve in an indoor garden because when the grow lights switch off, temperature often drops quickly. As long as the temperature falls enough to quickly cool the leaves, and is them maintained at a reduced level, the fruits or flowers can often stay warmer than the leaves for more than an hour. This maybe a mild stress technique you are already employing without realizing it!

Slightly Harsh Environmental Conditions (warmer temperature, lower RH)
One of the most severe stresses you can inflict on a plant is environmental stress. High temperatures coupled with low RH will make it near impossible for most cultivated plants to grow successfully. However, if you have optimum environmental control systems in place, a slight increase in day time temperature combined with a slight decrease in RH can have a significant impact. If, for example, during vegetative growth you are maintaining the day time temperature at 75°F (24°C) with 70% RH, a slight increase for a few hours each day to 80°F (26.5°C) while maintaining the same RH will increase plant metabolism and transpiration rates for short periods creating small periods of mild stress. During these periods the plant is still fairly comfortable and able to function properly but these slightly harsher conditions steers the plant more in the direction of generative growth.

Elevated CO2 levels
Higher CO2 levels in the growing environment increases photosynthetic rate. This in turn creates and provides more assimilates to the developing fruits and flowers. This means better fruit and flower initiation and overall more fruit or flowers on the plant which guides the plant in a generative direction. Dosing CO2 early in the light cycle will have a more generative action as this is when peak growth occurs.

Crop steering techniques are great tools to have in your arsenal when trying to get the most from your plants. When growing vine (indeterminate) tomato varieties or sweet and chili peppers you want to harvest fruits for as much time as possible, generative or vegetative steering techniques can be used to balance the plants into a state of constant production e.g. not too vegetative and not too generative.

When growing short cycle plants like bush (determinate) tomato plants or flowering annuals, the goal is to push the plant from a vegetative direction and force it into a generative state and keep it as generative as possible. This will result in one big flush or fruits or flowers to be harvested in one go. Generative steering techniques are extremely valuable when used in the later stages of a short cycle plants life to help it drive all its efforts into generative production.

Other positive stresses

So, mild stress can be used keep plants growing in your desired direction, but what other stress techniques are out there that may be able to help us achieve better results?

There are many myths that circulate in grower circles about techniques to enhance quality and quantity. One that I would like to quash before we go any further is the stress technique of inserting a nail through the base of the stem. Many times I have heard “This old grower I know says hammering a nail through the stem just before the end of the plant cycle makes the final fruits smell and taste better”. Total BS! Hammering anything into your plant is a sure fire way to majorly stress it out, potentially reduce yield considerably and result in very little change to your end produce. May this myth die a horrible death, much like the hammered plants will.

Topping
Topping is a technique that most growers are familiar with to transform a tall skinny plant into a short, wide bush. Removing the growing tip reduces ‘apical dominance’ which is where the central stem is dominant over other side branches. By removing the growing tip early the plant’s life, many side shoots grow which helps indoor growers create a more even canopy when growing under lights. Removing the growing tip causes some considerable stress to the plant but creates much more productive and controllable plants in the long run.

Thinning
Thinning or complete clearing of bottom growth is a technique often utilized when growing indoors to concentrate the plant’s efforts into producing good quality fruits and flowers that are bathed in light. Stems, leaves and flowering sites that are in complete shade will end up producing very little, so removing them may cause some initial stress in the short term but the plants will benefit from more concentrated growth in the long term. Many growers say that the thinning process, when done in the early stages of the flowering cycle helps to speed up the onset of flower. It may be that the removal of plant material stresses the plant in a generative direction. Fruit thinning is often carried out when growing cucumbers, peppers and even apples. Removal of some of the smaller fruits helps divert energy toward the larger fruits and results in better quality large fruits rather than lots of small ones.

Diverting Energy
When growing sub terrain crops like garlic and potatoes, growers want the plants to put all their efforts into producing those underground delights. To help them do this growers stress the plants by removing the flowering stems when they appear in midsummer. This stops the plants investing energy in fertilizing their flowers and producing seed, and focuses their attention into producing large tubers or bulbs. The picture below show the effect of removing the flowering stalk, aka ‘scape’, from the garlic plants compared to leaving them on. Significant increases in yield can be made using this technique.

Air Pruning
Air pruning roots is another great example of positive stress. It works by allowing the root tip to come into contact with air. During this process the root tip die dies back through dehydration. Although this process is fairly stressful to the root system, it actually enhances it. Once the tip dies it promotes secondary root branching along the length of the root. Once these secondary root tips come into contact with air, they too become air pruned which stimulates more root growth. Much like pinching out the top of the plant to create a bushier plant, allowing the root tip to dry creates a more branched root system within the growing media. Air pruning can be done successfully with rockwool blocks by placing them on a wire rack allowing air to pass underneath them, or with specialized air pruning pots such as ‘Smart Pots’ or ‘Air-Pots’.

Humidity
Plants that are grown for their aromatic qualities can sometimes benefit from brief periods of humidity stress during their final stages of development. As the leaves and flowers reach maturity, a sustained drop in RH can cause the plant to production more essential oils. Apparently this is a defense mechanism to further protect their leaves and flowers from the dry air.

Anecdotal grower reports on positive stress

The following are just “reports” from individual growers – so please take with a pinch of salt!

Give Me Thrips!
One grower we spoke to is now getting consistently better results now that he controls a small population of thrips in his indoor garden! This grower had a dialed in semi-closed garden and was used to getting the same yield time and time again. After a short two week holiday he came back to discover thrips had invaded and many leaves were damaged. He was not surprised when it came to harvest time to find the crop yield was significantly down. However, on the next grow he introduced the predatory insect amblysieus cucumeris in controlled release sachets. He found that by introducing these sachets every four weeks it kept the thrips numbers down to a minimum without having to regularly spray. To his surprise he found the next crop yield was up on his pre invasion average. The next crop he continued with the controlled release sachets to keep the thrips under control and again found his yield to be better than before. Is it possible that the very small amount of thrips feeding from his plants were mildly stressing the plant in such a way that it improved results? Difficult to believe but this grower was convinced.

Problem Plant
A grower had four different 4ft grow tents in one room. Each tent has one big plant in and is harvested every two weeks. That was the theory anyway… all was going well until one problem plant just wouldn’t grow. It was fine two weeks into vegetative growth and then just stopped and the leaves started to curl! At first he thought it was over fertilization, so he ran the nutrient strength much lower, one week passed and still nothing. He then thought it must be over watering so he left it to dry more between irrigations, another ten days passed and still nothing. He noticed some of the roots had started to look slight brown so he disinfected the nutrient solution with an ozone sterilizer. Still the plant looked alive, with green curled leaves but another week passed and it was still not growing!  All his friends told him to stop wasting his time and rip it out and start again but he wanted to fix it. Another two weeks passed with various attempts to fix the problem being unsuccessful until he decided to give the plant a full strength dose of nutrient solution with a ppm of 1200 (2.4mS). Boom! The plant sprung back into life the next day and grew like crazy! This poor stressed plant had been in veg for nearly 8 weeks, when it usually took 2. The long and the short of it is that although this plant did nothing for 6 weeks other than look half dead, it turned around to yield the most he ever got of one plant. Could this be down to its poor stressed out vegetative cycle? Maybe…

Cutting Stress
Another grower took cutting in pots of coir. Rooting times were 12-14 days – at this point he could see roots appearing at the bottom of his pots. On one occasion, four days after taking the cuttings, he was inspecting them when his phone started to ring. He picked it up and got distracted. Ten minutes into the call he remembered that he’d left the propagator lid off. He rushed back to his cuttings and found that many of the larger leaves had started to wilt. He quickly sprayed the lid and put it back on to quickly raise the humidity. The cuttings came back round but he was sure the stress would make the cuttings weak so he took some more as a backup. On the eighth day he checked his stressed cutting and was surprised to find that a few had roots at the bottom already! On the tenth day they all had roots at the bottom. On the next batch he did them as normal and was back to the 12-14 day turnaround, so on the batch after he purposefully took the propagator lid off on the fourth day and waited until most had slightly wilted. Once again the cuttings had visible roots between days eight and ten, as few days earlier than before. He now swears by this technique…

Spicy Stress
This grower loves his mouth to burn, and a few years back grew chilies using an ‘Autopot’ system where a valve tops up a small reservoir of nutrient solution in the bottom of the pot. It was mid July and the plants were in full swing and producing loads of fruits. One particular variety was quite mild and great in salads. One day the grower shuts off the supply valve in order to fill the reservoir with fresh water and nutrients, after filling he forgot to open the valve! An easy mistake to make but he didn’t notice for the whole weekend. Come Monday morning and all the plant were badly wilted but not unrecoverable. He opened the valve and let the plant recover. In the mean time he picked all the ripe chillies and they tasted the same as usual. He though the small developing chilled might abort but they all seem to continue growing. A few weeks later when he picked the ripe chillies the mild ones had developed a much more fierce heat level. It was the chilies that were developing during the drought stress, could it be that the short period of drought increased the spice level of the chilies?? The next set of fruits that came through were back to usual spice level so this grower is convinced that drought can influence spicier fruits.

Cold Roots
During winter, this grower liked to cold shock his roots! He grew in three gallon pots using an organic potting soil with organic liquid nutrients.  During the last three weeks of the flowering cycle he hand watered the plants with water at 55°F (13°C) once a week. He says that these cold irrigations shock the roots and the plant slightly, he does not result in any increase or decrease in yield but it does lead to a definite increase in essential oil production. The mild stress seems to work as a quality and flavor enhancer.

Wilt Shock
One grower finds that by introducing a few periods of drought stress in the last six weeks of his flowering cycle he improves plant vigor and produce quality. His technique is to let his coco coir dry out just to the point where he can see the first signs of the fan leaves wilting. He does this once during week 3, 5 and 7 and finds that the plants come back fighting after each short drought.

A Final Repetitious Word of Warning

There’s plenty of food for thought in this article. And perhaps that’s the best thing to do. THINK about it. Before we all get instantly carried away the notion that stress can be good please read and heed this final word of warning:
PURPOSEFULLY CAUSING PLANT STRESS IN AN ATTEMPT TO IMPROVE RESULTS WILL NOT MASK OTHER GROWING INADEQUACIES SUCH AS POOR ENVIRONMNETAL CONTROL OR NUTRITIONAL DISORDERS!
If you want to have a play with positive stress techniques you should do so in a controlled fashion where all aspects of your grow are completely dialed in. Only then will you know if what you are doing is positively or negatively affecting your plants. It is one thing to mildly stress a healthy plant, but to stress an already stressed plant could lead to disaster!
If you have any experiences involving plant stress (whether you caused them intentionally or otherwise) be sure to tell us about it by emailing:  rant@urbangardenmagazine.com

WORDS: Dr. Garibaldi

Borlaug grew up in a remote corner of rural Iowa – a place with twelve- grade one-room schools from which most youngsters dropped out by the eighth grade, a place with one car, no telephones, no electricity, but the Iowa Corn Song ,3 proudly sung like the Star-Spangled Banner at the start of every school day:

There was no future, other than growing corn, but “Norm Boy’s” grandfather had another vision, and inculcated the boy with a determination to obtain a higher education. He arrived at the University of Minnesota at age 20, “as a student athlete [whose] ability to do university work was questioned” 4 but left years later clutching a Ph.D in plant pathology,.

Assigned during World War II to Dupont, where he helped to develop DDT as part of the war effort, Borlaug was offered the sky, but given the choice between Dupont and sub-subsistence science for sub-subsistence Mexican farmers, he chose the. latter, working. with the Rockefeller Foundation, in a project to stave off a looming food crisis in overpopulated Mexico.5

THE AGRICULTURAL END OF FOOD PRODUCTION USES STAGGERING AMOUNTS OF WATER. AS AN ILLUSTRATION, HERE’S A RECIPE FOR A QUARTER-POUND CHEESEBURGER

The project goal was to breed strains of wheat that could withstand adverse climates, survive wheat’s fungal diseases, and produce prodigiously on dwarf plants, then convince tradition-bound farmers to adopt forthwith the new hybrids and the technology that accompanied them.. It was a race against time, and an extraordinarily demanding task in the pre-DNA era. Borlaug set up field operations in two locations with disparate climates and growing seasons so he could have plants accustomed to multiple climates, and could grow two generations of seedlings each year.

Borlaug shortly achieved his goal, and Mexico’s food crisis was over in a decade. On to Asia, where the same thing was happening: overpopulation, courtesy of modern medicine.. India was home to some of the poorest people in the world. Famine was widely forecast for the mid-seventies. It was the era of Ehrlich’s Population Bomb. Stanford professor Ehrlich was an icon for the rising environmental movement, but overnight, stubborn farm boy Borlaug appeared to prove him wrong. In a few short years, the Green Revolution turned a land of undernourished millions into the second largest wheat producer in the world. Borlaug became the hero of millions of peasants, and also of those who spoke for unlimited growth, and in the next twenty years The Population Bomb disappeared from the environmentalist lexicon, leaving the population boom unquestioned.

The Green Revolution, which was to go on producing wonder strains for other crops and other countries, had three central parts. The other two were irrigation and chemical fertilizer. These changed agriculture fundamentally, from a primarily solar-energy craft dependent upon local weather and soil conditions, to a fossil-fuel technology designed to force the land to produce mightily regardless of its natural limitations. Borlaug, summarizing in his Nobel lecture, warned that the new hybrids had not resulted in major yield improvements without both irrigation and “a strong responsiveness and high efficiency in the use of heavy doses of fertilizers.”6 Plentiful water, plentiful chemical fertilizer – that’s the secret to how in the last half century India – and California – turned arid lands almost instantly into wildly productive garden baskets. It may not be a sustainable solution, but at the time, the world needed a quick fix.

In his Nobel lecture, Borlaug talked proudly about how the new practices had given near-starving subsistence farmers surpluses they could sell, the money to buy oil-driven water pumps and tractors, and the influence to insist upon doors opening to the broader world. If you’ll permit me a broad brush, the Green Revolution had doubled and tripled grain production for multi-millions who had been on the brink of starvation, but turned locally self-sustaining agriculture into hydroponics. And it turned subsistence farmers, dependent on the whims of the soil, sun and rain, into small-time contractors dependent on the whims of the discount rate, the commodities markets and the petrochemical industry.

It weakened their umbilical cord to Mother Earth, and eased a process in which millions would find themselves drawn to seek their fortunes in the cities, providing cheap labor to run the Indochinese economic machine. But those were events far in the future when Borlaug performed his magic, and it’s hard to quibble when several hundred million people are about to die of starvation..

The agricultural end of food production uses staggering amounts of water. As an illustration, here’s the author’s recipe for a quarter-pound cheeseburger:

Ingredient /Water used in production

Lettuce (1/4 cup)…………………………0.8 gal

Bun (2 bread slices equiv) …………………….. 22.0 gal

Tomato (1 oz paste equiv) ……………………. 6.1 gal

Cheese (1 oz.)……………………………………… 58.3 gal

Ground beef (4 oz) ………………………………..641.2 gal

TOTAL………………………………… 728.4 gal

8-oz. Glass of milk……………………… 50.0 gal 7

The reason water consumption for meat and dairy products is so much higher than for vegetables and grain, is that, very approximately, it takes two pounds of grain to produce a pound of chicken, five pounds to produce a pound of pork, and ten pounds to produce a pound of beef.

The Green Revolution doubled the world’s irrigated acreage from 346 million acres to 690 million acres, and increased by a factor of nearly five its consumption of chemical fertilizer .8 Where does all the irrigation water come from? Wells, largely; as the World Bank has pointed out, groundwater comprises 97% of the world’s accessible freshwater reserves.9

Wells are a classic case of Garrett Hardin’s “tragedy of the commons” 10 – if the aquifer is shared by multiple individuals or multiple villages and there are no rules on how much anyone can use, then the users are individually, although not collectively, better off if they use as much as they want until the wells all run dry. So unless everyone follows the Golden Rule or there is an elaborate legal “groundwater management plan,” controlling how much everyone gets, the wells DO run dry. The first thing you need to begin fair and sustainable allocation of groundwater supplies is records of pumping from wells. They don’t exist. And farmers everywhere, from the one-acre plots of North China to the 1000-acre ranches of California, rebel against interference with their freedom. Even if there were the will and the way to adopt rational groundwater management programs around the world, the task would take many decades to accomplish – unless another farm-boy-savior-scientist comes down from the sky, to whom the farmers and bureaucrats can relate.

So where does that leave us? The United States is in a relatively good position because only one fifth of its grain production comes from irrigated land, but the figure is three fifths in India and four fifths in China.11 The world-wide picture is bleak:

* The annual overdraft from the U.S. Ogallala Aquifer, producing cattle and grain in quantity, is said to be about equal to total yearly flow of the Colorado River.12 It was declared by the USDA over a decade ago to be “near depletion,” with Texas having already lost 1.4 million acres of irrigated land and the irrigated land supported by the aquifer expected to be reduced 50% by2030, an acreage accounting for roughly 10% of US grain production.

* In China, the world’s greatest grain producer,13 pumping from a fossil aquifer in the North China Plain is relied upon to produce half the nation’s wheat and a third of its corn, approximately 40 million tons per year or 10% of the nation’s grain production; 14.

* Northern India is also overdrawing its groundwater supplies to maintain grain production. Although the overdraft is apparently much less severe than in China or the United States, nonetheless, if the current level of unsustainable groundwater overdraft continues, government experts have concluded that “India could face severe water shortages.”15

* Lester Brown, founder of the Worldwatch Institute, reports that fifteen nations containing half the world’s population, rely on groundwater overdraft for irrigation.16

These practices cannot go on for long, and in this writer’s opinion, water development and conservation are unlikely to come to the rescue. large surface reservoirs and desalinization are unlikely to save the day, because these projects do not ordinarily pay for themselves and for the foreseeable future governments are unlikely to be in a position to subsidize multi-billion-dollar investments in concrete and steel to feed the poor. As for water use efficiency, it might theoretically permit savings of anywhere from 10-40%, but implementation and enforcement have all the hurdles of groundwater management plans, plus the additional hurdle that tens of millions of farmers were taught decades ago that plentiful water was essential to high yields. Changes may occur, but they will most likely be incremental and slow. So dropping grain production appears inevitable in the US and China, and likely in much of the rest of the world, in the absence of major increases in acreage and/or yield per acre.

As for increased acreage, there is general agreement that the acreages have been at best essentially “flat” for decades17 and in any event it is hard to envision major investments being made in land development to feed the undernourished and virtually destitute bottom seventh of our population when the same land could be used, if at all, to produce beef or biofuels for the top seventh.

Yields? They are still increasing at approximately 1% per year, not enough to keep up with population increase; in fact, world per capita grain production peaked in 1986.18 Steady 1% per year yield increases cannot, of course, solve the problem of exhaustion of fossil aquifers, likely to occur close to the same time as exhaustion of the oil supply. There are disputes as to whether or how long genetic tinkering can continue to improve yields. Eventually we have to hit the maximum efficiency at which photosynthesis can occur, but there are radically different educated views as to how close we are.19

In Lester Brown’s view, “Unless population growth can be slowed quickly, there may not be a humane solution to the emerging world water shortage.”20 The statistics appear to show that he should have said population growth must be “reversed quickly,” rather than merely “slowed quickly.”

So when the aquifers run dry, a return to the days when agriculture was limited to natural precipitation, is inevitable. This means, on top of the present inability of yield increases to keep up with population increases, a relatively abrupt loss of at least 10% of production.

What about the fertilizer? That comes from mining operations, too. That is literally true of phosphorus, although it wasn’t before we came along. There are more phosphorus-rich bones walking the face of the earth than ever before in geological history; humanity is hoofing it around with 5 billion kg or 11 billion pounds of phosphorus ,21 which comes from mines,22 – NONE of it recycled. This has happened only since half of us moved to the cities, taking our personal wastes with us; petrochemical fertilizers replaced natural ones; and community sewers were invented. Mama Nature can’t afford this kind of progress for long.

In fact, the world phosphorus reserves are expected to be depleted within 25 to 70 years, depending upon where you are. Humanity will apparently go extinct for lack of phosphorus within a century unless we resume recycling,.23 This writer is unaware of any government plans anywhere, to do so.

And phosphorus isn’t the perceived serious problem. Nitrogen is. We have a reasonable amount of nitrogen in the air for the present, but the nitrogen has to be processed into ammonium nitrate or something comparable with a high energy input, and the starting material is natural gas, 5 % of which globally is used for production of nitrogen fertilizers.24 There are presently no alternatives. Natural gas accounts for 90% of the cost of nitrogen fertilizer, so the cost of the latter is pretty much proportional to the cost of the former.25 When the petroleum supply starts to go, fertilizer prices will spiral upward.

Of course nitrogen fertilizer can also be produced by nitrogen-fixing legumes, but that necessitates alternating between nitrogen-fixers and market crops. In his Nobel lecture Borlaug spoke of a dream of nitrogen-fixing grains being introduced in 1990 that would free peasant farmers from the need to purchase chemical fertilizers, but then, he said, he would wake up, disillusioned. It was only a dream. 35 years and 3 billion more people later, he would have to tell the New York Times, “This is a basic problem, to feed 6.6 billion people. Without chemical fertilizer, forget it. The game is over.”26

So at present, grain yield is not keeping up with the population, and things will get worse as fertilizer and water become expensive and scarce. Will a large part of the population die when they are curtailed? Not necessarily, because of how we allocate the use of the grain we produce.

To see the whole picture, we need to understand a little about the grain market, which is the dominant food market.. There are at this time three competing demands for the commodity: food (i.e. direct consumption by people), fodder, and fuel. Before fuel became part of the mix, the division between food and fodder was 60:40, with the “fodder” component capable if used as food, of providing the caloric needs of 3.5 billion people.27 But we are squandering the 40% “cushion.”

The mix in 2008 was said by Worldwatch Institute to be 47% food, 35% fodder, 18% fuel. The 18% figure may not be a 2010 reality, but no one claims less than 9%, and use of grain for bioalcohol is projected to double in the next decade.28 The 18% that we burn or apparently will burn is more than sufficient to fill the stomachs of the record 1 billion people who are undernourished today. Does it give you a warm and fuzzy feeling that we burn the grain that is sufficient to eliminate world hunger? Me neither. And If we engaged in a modest conservation program in our gasoline use and gave the saved grain to the hungry, no one would have to go hungry, at least for the moment The feed use is increasingly for beef, and the fuel use is primarily bioethanol – an attempt to use the “cushion” in world grain production to let the middle class, particularly in the

US and China, indulge in quarter-pounders and gas guzzlers for a few more years, while the poor’s burgeoning undernourished try to maintain themselves on an ever-slimmer portion of the grain production.

Feed and fuel compete with food not only for consumers, but for land. The EU has adopted a policy requiring 17% of its farmland to be devoted to biofuels in place of food.29 Land from Brazilian deforestation (which of course many of us would rather see not at all) could produce grain for food, could support range cattle, or could produce sugar cane (or grain) for ethanol. Not surprisingly, biofuel and beef are Brazil’s primary products from destruction of the rainforest.30 Food comes out as a poor third in competition with feed and fuel both for grain and for land. No wonder there were riots over bread in 2008.

“THE MIX IN 2008 WAS 47% FOOD, 35% FODDER, 18% FUEL. THE 18% THAT WE BURN IS MORE THAN SUFFICIENT TO FILL THE STOMACHS OF THE RECORD 1 BILLION PEOPLE WHO ARE UNDERNOURISHED TODAY. DOES IT GIVE YOU A WARM AND FUZZY FEELING THAT WE BURN THE GRAIN THAT IS SUFFICIENT TO ELIMINATE WORLD HUNGER?”

And we have hardly looked at the inevitable consequences of an agriculture dependent for more than half its productivity on fossil fuels, outside the control of one-acre farmers in the Third World or even of thousand-acre farmers in the US. Two of the simpler ties between fossil fuels and food are the costs of fertilizer and water for a typical Third World one-acre farm. With most of the cost of fertilizer(although varying widely year-to-year and place-to-place, $100/acre is a reasonable figure) coming from the cost of natural gas, its cost is going to go up rapidly as oil runs out and (if it happens at all) as the world starts to do something about global warming. And the cost of gasoline at $3/gallon for pumping the water from an -all-too-typical 500-foot-deep well sufficient to irrigate an acre for a year is about $200.31 So rising fossil fuel costs are likely on the near term to drive up fertilizer and water coss by hundreds of dollars per acre The Ogallala-Aquifer farmer may be able to “pass the cost along to the consumer”(Brace yourselves, Americans!), but the farmer in India or China or Bangladesh has mostly to pass the cost on to herself. Where will it come from? Less fertilizer, less water, less food, with one billion people hungry already. These are of course just illustrative costs, but he writer suspects they are more accurate than the assumptions made by the U.N. Food and Agricultural Organization in its food supply projections for the next decade, that the international community will invest $200 billion per year for technological improvements in agriculture, that oil production will meet demand and that its costs will hardly budge.32 So even if the world can produce enough food, most folks may soon be unable to pay for enough.

The story of how we got here is complex – a confluence of population boom, oil boom and bust, the tragedy of the commons, misallocation of resources between rich and poor, the almost-deliberate blindness of America to the consequences of biofuel production -. the list goes on. There is an ongoing academic argument about whether the plight of the poor is one of inequitable distribution “or” population, but it is quite clear at this point that the answer is “Both.” There is also a sociological factor – the separation of people from the land, which has allowed us to “commoditize” land, to block the recycling of phosphorus and nitrogen, to separate sustenance from daily life, to warehouse in China’s cities the millions who had recently been attached for millenia to the cycles of sun and rain and soil. Out of sight, out of mind. We will not treat the earth sustainably when we do not see it and feel it in our daily lives and know directly that what surrounds us is what keeps us and our descendants alive and healthy.

There are too many of us to go “back to the land,” but we must preserve the connection. In coming decades necessity will dictate that everyone produce their own food wherever and however they can, but more important, we must reconnect ourselves to the earth we have abused. You who put aside a little corner of your urban homestead where things green can flourish are preserving the connection as best you can, and must teach others to do likewise. You are preserving an essential thread to our past, which will, if we are lucky, allow us to have a future.

But it’s a slim thread.

It didn’t need to be this way. Norman Borlaug, far from viewing himself as the man who proved the doomsayers wrong, knew what was coming if we didn’t take care. In his Nobel lecture he described the Green Revolution as giving the world a “breathing space” until the year 2000, but then referred to an “impending doom” imposed upon us by the “Population Monster ,” and told his audience that”the frightening power of human reproduction must also be curbed; otherwise the success of the green revolution will be ephemeral only.”

Dr. Borlaug said in his lecture that whether and how we deal with the population problem is a”test of the validity of “sapiens” as a species epithet.” We have so far failed the test and squandered the thirty years he gave us. But the substantial fraction of the grain crop not used directly as food can, if we act quickly, allow us without famine to put ourselves on a sustainable population track, one recognizing that we don’t presently feed ourselves and that on the present track, things will get much worse. And of course no technical fixes can give the bottom seventh of the world population the wherewithal to pay for what they eat, so the looming food crisis will not just be fixed with a theoretical food supply for which they cannot pay. These things must happen. Is that likely? Probably not, given past history. But it is necessary.

Once again we 6.9 billion people are on our own, without leaders or guidance. But we know what we must do, as individuals and nations: we must avoid gasohol and beef, because we cannot take food from the mouths of the hungry; we must manage and conserve our diminishing water supplies, we must work to eliminate abject poverty so that people can pay for what they eat and we must begin to decrease our numbers by limiting ourselves to one child per family.33 There is no evidence that we can avoid famine otherwise. The Green Revolution was a one shot deal, because we cannot again double irrigated acreage or multipy use of chemical fertilizers by five; and because the Green Revolution was a program of the oil age, which is fast departing. Modest crop-yield increases may keep up with population growth for a while (although they haven’t for 25 years), but all indications are that the prices of what food there is will rapidly climb above the budgets of billions of us.

“Norm Boy,” the Iowa farm kid, died last year. He was 95.

………………………………….

The writer is a California-licensed attorney currently residing in Massachusetts. He has had professional experience trying without success to implement groundwater management in California’s vast agricultural San Joaquin Valley. Research and writing were supported by Urban Garden Magazine, which reserves copyright and all other republishing rights except the right to online submissions by the author. He wishes to thank Patricia Lemon and David Steele for invaluable editorial assistance.

1. This article will be published by Urban Garden Magazine in mid-August.
2. Bruce Alberts, President, NationalAcademy of Sciences
3. For the full lyrics, see http://www.netstate.com/states/symb/song/ia_corn_song.htmor http://iowareunionclub.com/iowacornsong.aspx
4. Mark Yudof, President, University of Minnesota.
5. Biographical information from Vietmeyer, Borlaug, Volume 1 (2004), unless otherwise indicated..
6. Dr. Borlaug’s Nobel lecture: http://nobelprize.org/nobel_prizes/peace/laureates/1970/borlaug-lecture.html
7. See Dr. Thomas Stein, sakia.org, 2007, http://www.sakia.org/cms/fileadmin/content/irrig/general/stein_2007_water_use_charts-units_converted.pdf for a general compilation of different foods and their water needs for production, together with a link for explanations as to how these were determined.
8. See chart, Global Education Project, Food and Soil, http://www.theglobaleducationproject.org:80/earth/food-and-soil.php. A hectare, a 100-meter square, is 2.2 acres. Spend an hour studying these charts, and you will know more than the average Ph.D. about modern agriculture.
9. World Bank, Groundwater, http://web.worldbank.org/WBSITE/EXTERNAL/TOPICS/EXTWAT/0,,contentMDK:21633297~menuPK:4620525~pagePK:148956~piPK:216618~theSitePK:4602123,00.html.
10. (Garrett Hardin, 1968 paper published in the journal SCIENCE (162:12431248). If you aren’t familiar with it, read it, and then go for a vacation and meditate on it for a week.
11. Lester Brown, Aquifer Depletion, 2006, http://www.eoearth.org/article/Aquifer_depletion
12. Patricia Muir, http://people.oregonstate.edu/~muirp/waterlim.htm
13. UN Food and Agricultural Organization (FAO), Agricultural Outlook 20102019 (2010)
14. Lin Shujuan, China’s water deficit ‘will create food shortage’, Science and Development Network, 2007, http://www.scidev.net/en/news/china-s-water-deficit-will-create-food-shortage-.html; and Lester Brown, WATER DEFICITS GROWING IN MANY COUNTRIES: Water Shortages May Cause Food Shortages, http://www.greatlakesdirectory.org:80/zarticles/080902_water_shortages.htm.
15. T. V. Padma, Thirsty Indian farming depleting water resources, Science and Development Network, http://www.scidev.net/en/news/thirsty-indian-farming-depleting-water-resources.html, quoting scientists from NASA and also citing the Indian Ministry of Water Resources..
16. http://www.eoearth.org/article/Aquifer_depletion,
17. See e.g. the graphs shown in Staniford’s article cited below.
18. Patricia Muir, http://people.oregonstate.edu/~muirp/waterlim.htm
19. Stuart Staniford, Food to 2050, The Oil Drum, http://www.theoildrum.com/node/3702, discussing both sides of the dispute. See also Grain Production, http://www.whole-systems.org/grain.html, and Science’s February, 2010 issue devoted to food security. http://www.sciencemag.org/cgi/content/full/327/5967/812
20. Lester Brown, WATER DEFICITS GROWING IN MANY COUNTRIES: Water Shortages May Cause Food Shortages, above.
21. http://www.random-science-tools.com/chemistry/chemical_comp_of_body.htm
22. UN Food and Agricultural Organization (FAO), Current world fertilizer trends and outlook to 2011/12, Table 4, ftp://ftp.fao.org/agl/agll/docs/cwfto11.pdf
23. For a recent and very readable discussion of the phosphorus situation, see D.A. Vaccari, Phosphorus: A Looming Crisis, Scientific American June 2009, www.ScientifiAmerican.com.
24. Wikipedia, Fertilizers, http://en.wikipedia.org/wiki/Fertilizer.
25. GAO, Domestic Nitrogen Fertilizer Production Depends on Natural Gas Availability and Prices, 2003, http://www.gao.gov/new.items/d031148.pdf.
26. K. Bradsher and A. Martin, The Food Chain: Shortages Threaten Farmers’ Key Tool: Fertilizer, New York Times, http://bigteaparty.com/fertilizer-soaring-foodprices-key-to-health-bad-for-environment/
27. United Nations Environment Program (UNEP), Food from Animal Feed, World Food Supply, http://www.grida.no/publications/rr/food-crisis/page/3565.aspx). R. Segelkin, US could feed 800 million people with grain that livestock eat, Cornell ecologist advises animal scientists, Cornell University Science News, 1997, http://www.news.cornell.edu/releases/aug97/livestock.hrs.html.
28. Worldwatch Institute, Vital Signs, Grain Harvest Sets Record, But Supplies Still Tight, 2009, http://www.worldwatch.org/vs2009.. The UN Food and Agricultural Organization says the figure is only 9% for biofuels at this time, but also says that the amount of grain being turned to alcohol will double in the next decade. OECD-FAO, Agricultural Outlook 2010-2019. So if 18% isn’t correct today, then it is likely to be correct in a decade…
29. X. Navarro, The European Commission says no to reviewing biofuel percentage goal, http://green.autoblog.com/2008/04/15/the-european-commissionsays-no-to-reviewing-biofuel-percentage/
30. OECD-FAO, Agricultural Outlook 2010-2019.
31. 1 gallon [U.S.] of automotive gasoline = 97,181,192.2530305 foot pounds. 1 acre pumping from 500 ft.: 3 acre-feet of water = 975,000 gal water x8 lbs/gal x 500 ft = 3,900,000,000 ft lbs/ 97,181,192.2530305 ft lbs/gal gasoline = 40.131 gal x $3/gal = $120, assuming a 100% efficient pump, or $200 assuming a 60% efficient pump.
32. OECD-FAO, Agricultural Outlook 2010-2019
33. There is a time lag of 30-40 years built into any population policy based upon birth control, because a rapidly-growing population over-represents the age group under reproductive age. Consequently, a “ZPG” birth rate does not result in ZPG for decades. Moreover, the water and energy problems imply that an overall population reduction is necessary.

By Nicholas C. Arguimbau
31 July, 2010
Countercurrents.org

Here’s our guide to setting up a basic, conventionally ventilated indoor garden on a budget. We’re going to show the different ventilation requirements for a 2 light and a 6 light grow in the same space.

Big rooms need lots of lights with a high-powered ventilation system whereas small rooms will only need a few lights with a low powered ventilation system. All sounds like simple stuff, doesn’t it? But how do you work out exactly what your room needs? Here’s what you need to consider:

Size

All of the equipment your new indoor garden will need comes down to the size of the room. So, the first thing you need to do is accurately measure it. You will need the length, width and height of the room.
The example shown has the dimensions of:
Length x Width x Height
24ft (7.2m) x 12ft (3.65m) x 8.2ft (2.5m)

Now before we get carried away filling this room with lights and fans, you have to consider the budget and ability of the grower undertaking this new project. A confident and experienced grower may well fill the whole room, but let’s not bite off more than we can chew. First, let’s create a smaller room within the larger room by sectioning off the back portion to give a working room size that is more suited to a beginner.
Length x Width x Height
12ft (3.65m) x 8ft (2.4m) x 8.2ft (2.5m)

You might well be asking, “What are the benefits of sectioning off the room? Why can’t I just hang the lights in the corner?” Well, by creating a room within a room you gain better control of the environment. With the sectioned off area you make the best use of the available light by having walls lined with reflective sheeting – this creates a bright well-lit environment for productive growth.

You can use various materials to section off the room but the better insulated, the better. A well insulated room will immediately lend itself to far easier environmental control.

If you have no interest in building your own indoor garden, or you’re not too confident with your DIY skills then don’t worry, help is at hand. You can purchase purpose-built indoor grow tents – highly recommended for all levels of grower! These come in many sizes, with one bound to suit your requirements, and it makes hanging lights, fans and filters a sinch.

Lighting

Now you know the size of the room you’re working with you can calculate how best to illuminate it. The most widely used light source for indoor gardens is high intensity discharge (HID). They are widely available, competitively priced and produce consistent results. Two types of lamps are able to run in HID systems; High Pressure Sodium (HPS) and Metal Halide (MH).
HID lighting systems are available in many different sizes, but the most commonly used for indoor growing are 1000W, 600W and 400W. Each size light is suitable for a defined amount of floor space:

1000W = 4-5ft (1.2-1.55m)
600W = 4-3.3ft (1.2-1m)
400W = 3.3-2.5ft (1-0.75m)

One thing to bear in mind is that the more powerful the light, the further away from the tops of the plants it needs to be. This means that if you have a low ceiling height, you should consider using lower wattage lights. The example room has an 8.2ft (2.5m) ceiling height so we can use the 1000W lights, as long as the plans don’t get bigger than 5ft (1.5m) which is fine for most plants. Indoor plants want to be short and wide to make the most of the light available. The distance between the light and the canopy that most growers follow are:

1000W = 39-31 inches (100cm-80cm)
600W = 31-24 inches (80-60cm)
400W = 24-16 inches (60-40cm)

Please bear in mind that the above information is for horizontally mounted lamps in normal open or closed reflectors. If you are using parabolic reflectors with vertically mounted lamps or air-cooled reflectors you can allow the light to be closer to the plants as there is less direct radiant heat.

So the floor space available in our room is 12ft (3.65m) x 8ft (2.4m). You could try and squeeze as many lights as possible into this room, but as well as being productive, you want to try and make your room easy and comfort- able to work in. To do this you will need adequate access around your plants to make maintenance and inspections easy. Approximately 2ft (0.66m) around your plants is a good working area. Elderly or disabled growers may opt for considerably more space than this. In our first example we’re using 2 x 1000W lights.

If you want to make life difficult for yourself, you could fit a maximum of 6 x 1000W lights. In order to make this room work you would need to choose a growing system or technique that allows you to move the plants to gain access around the garden. This might be achieved by growing in pots/containers or movable beds.

Ventilation

Ventilation in your indoor garden comprises of two main factors: the removal of hot waste (CO2 depleted) air and the input of fresh cooler air. Hot waste air is removed actively using an inline fan, AKA the extractor fan. Fresh cooler air can either be drawn in passively through vents or pushed in actively using another inline fan AKA the intake fan.
Now we know the size of the room, and the amount if light being used, we can now work out the ventilation requirements. In North America most inline fans are rated in Cubic Feet per Minute (CFM), whereas in Europe they are usually rated in cubic meters per hour (m3/hr).

The Extractor Fan

Firstly, we’ll work out what size extractor fan is needed. There are many ways to work out what size extractor is needed for a particular sized room, some equations are more accurate, others are overly complicated – the following method is very popular and straight forward and has served many growers well.

Required extractor fan size in CFM= Volume of active growing area (ft) x 1.25
Required extractor fan size in m3/hr= (Volume of active growing area (m) x 60) x 1.25

When we say the volume of the active growing area we mean the volume occupied by the lights and plants. To work out the volume simply multiply the length x width x height. In our example with 2 x 1000W lights this is 4ft (1.2m) x 8ft (2.4m) x 8.2ft (2.5m), which gives the volume of the active growing area of 262.4 cubic ft (7.2m3).

Once you have your volume, you need to multiply it by the amount of air changes needed per unit of time. For the majority of indoor gardens without AC or supplementary Co2, the rule of thumb is one air change per minute. For the CFM equation there is no need to multiply it as we already have the total volume in cubic ft which is needed to be changed every minute. For m3/hr equation we need to multiply the volume by 60 to step it up to the amount of air changes needed per hour.

Lastly, when using a carbon filter attached to the extractor fan we expect a drop in fan efficiency of approximately 25%. This figure is not fixed; it depends on the make and age of the filter and the length and course of ducting between the fan and filter and many more interesting factors that we won’t bore you with here. To step up this efficiency drop of 25% simply multiply by 1.25.

If we run this equation through our example indoor garden it gives us;
Required Fan size (CFM) = (Volume of Active Growing Area) x 1.25
(4 x 8 x 8.2) x 1.25 = 328 CFM

Required Fan size (m3/hr) = (Volume of Active Growing Area x 60) x 1.25
(1.2 x 2.4 x 2.5) x 60 = 432.
432 x 1.25 = 540 m3/hr

This final figure is the minimum size extractor needed. If the garden is in a very well insulted location such as a basement using this figure should be fine. If the garden is located in a very sun-exposed location such as an upstairs bedroom or attic then the extractor size may need to be increased by approximately 25%. More often than not, you will have to match your required extractor size to the nearest size avail- able. In this instance the nearest widely available inline fan size is a 6” (150mm) 390CFM (660 m3/hr) extractor.

Interestingly, if we work though the equation for the same room with 6 x 1000W lights it will give very a different answer;

Required Fan size (CFM) =  (Room volume) x 1.25
(12 x 8 x 8.2) x 1.25 = 984 CFM

Required Fan size (m3/hr) =  (Room volume x 60) x 1.25
(3.65 x 2.4 x 2.5) x 60 = 1314
1314 x 1.25 = 1643 m3/hr

In this indoor garden the nearest widely available fan size available is a 12” (315mm) 1000CFM (1700 m3/hr) extractor.

Oversized Fans

Many growers think ‘bigger is better’ when it comes to extraction but this is not always the case. By extracting air from the garden you’re removing the heat, but you’re also removing the hu- midity. This means that an oversized ex- tractor fan can often cause low relative humidity, which will create an onslaught of negative effects that will lead to poor plant growth.

‘Summer sized fans’ are also not always the answer to a warm indoor garden. There comes a point where it doesn’t matter how much air your extracting, if your incoming air is warm your room will stay warm. If you can’t keep the heat down and you’re changing the air in your garden more than three times a minute, you need to consider installing air conditioning or using air-cooled or water-cooled grow lights.

Fresh Air

As mentioned earlier, we need to get fresh air into the garden. This can be done using two methods:

1. By making passive vents (basically holes) through which fresh air can be drawn in.
2. By installing active inline fans that push fresh air into the garden.

When using passive vents you have to ensure there is adequate fresh air outside the growing area. It’s no good if you’re pulling in stale or warm air. This means you may need to have a window open so fresh air can be drawn in from outside and into the indoor garden. As a rule of thumb, the passive vents should be two to three times the size of the surface area of the extractor fan outlet. This means if the extractor has a 6” (150mm) spigot size, the garden will need 2-3 x 6” holes or rectangular vents with and equal surface area. When installing passive vents always have the extractor fan at the opposite end of the room. It’s better to have oversized passive vents than undersized. If the vents are too small, the extractor fan will struggle to pull in sufficient quantities of fresh air.

Indoor gardens with active intake fans often run more efficiently than those with passive vents. By pushing in fresh air you not putting as much strain on the extractor fan and you also get to choose where to pull the fresh air from. During the cooler winter months its best practice not to pump in very cold air, so a lot of growers pull slightly warmer air from inside their home. If it’s a room you spend time in, like your bedroom or living room, it will also have the added benefit of the air being slightly higher in Co2. During the summer months its best to pull fresh cooler air in directly from outside as air from inside you house is likely to be warmer. Whenever you pull air straight from outside it’s best to use an intake filter or ‘bug screen’ to limit the possibility of sucking in pests.
The golden rule when installing an intake fan is to make sure you’re blowing in less air than is being removed by the extractor. This creates a ‘negative pressure’ and ensures that all the air exits through the carbon filter. If you input more air than the extractor can remove the air will start to build up and cause a ‘positive pressure’ forcing untreated air out of the garden.
When selecting an intake fan it should have a maximum capacity that is 10-20% lower than the actual output of the extractor. This will maintain adequate negative pressure while not putting too much strain on the extractor and intake fans.
To work out the intake fan size we will need to take the extractor fan size and apply an estimated reduction for the carbon filter- 25%. If our target for the intake fan is 15% less air than the exhaust we need to multiply the reduced output by 0.85. Below is a work through of how to size up the intake fan for both or the example rooms.

2 light room:

Extractor size – 390 CFM (660 m3/hr)
Estimated extractor power with carbon filter – 390 x 0.75 = 292.5
Reduction to ensure negative pressure = 292.5 x 0.85 = Intake Fan Size 249 CFM (420 m3/hr)

6 light room:

Extractor size – 1000 CFM (1700 m3/hr)
Estimated extractor power with carbon filter – 1000 x 0.75 = 750
Reduction to ensure negative pressure = 750 x 0.85 = Intake Fan Size 638 CFM (1084 m3/hr)

When installing the intake fan, make sure the extractor is at the opposite end of the garden. It’s a good idea to split the intake air with a solid ‘T’ or ‘Y’ piece so that the cooler fresh air is distributed evenly. Using air socks or longer lengths of ducting with holes in is a good way of evenly distributing the incoming fresh air.
One last factor to consider is that inline fans are better at pushing than pulling air through ducting. This means than when positioning your intake fan, it’s better to place it nearer the source of fresh air and push it towards the indoor garden. To make the air reach the garden efficiently, make sure the duct runs are as smooth and straight as possible.

Air Movement

Moving the air within the garden is of utmost importance. A light breeze moving air over the plants’ leaves refreshes the CO2 depleted air, gets rid of heat and humidity and encourages transpiration. The area of an indoor garden where most unwanted heat will accumulate is between the lights and the canopy, so it’s absolutely crucial that this air is removed to avoid heat build up. To achieve good air movement between the lights and the canopy you can install fixed or oscillating air circulation fans. These can be wall mounted or floor standing and should be powerful enough to mix the air well, while not causing the plants to be blown too vigorously. You want to move the air, not your plants! If you point strong air circulators straight at your plants the air will move past the leaves so quickly that it will strip away the humidity surrounding the leaf and encourage rapid transpiration. This leads to the leaves losing water rapidly and can cause them to appear burnt at the edges crispy to touch; this is known as ‘wind burn’. If you need to enhance the air movement around your plants, it’s a good idea to point air circulators towards walls rather than directly at the plants to mix the air adequately while not causing the plants to be flapping around in turbulent wind.

Equipment location

To avoid unnecessary heat transfer, any equipment that generates heat should to be stored outside the garden. Most notably, the power packs (aka ballasts) that can get quite warm need to be situated outside the garden on a shelf or any non flammable surface. Having them outside the room also is best practice for electrical safety as they won’t be operating in a warm and humid environment and will not have risks of stray foliar sprays landing on them or accidental splashes of nutrient solution.
Nutrient solution will also benefit from staying outside the garden. Your reservoir will quickly heat up under the direct light from your grow lights so its best practice to locate your reservoir outside the garden.

Any liquid nutrients and additives should not be stored in hot or cold environments. It’s best to consult the packaging and see what the best environment is for your products but most appreciate a constant moderate temperature. This should again be outside your garden.

Summary

Following the above principles you can construct your- self a great, budget indoor garden, suited around you, while creating the ideal environment for your plants. All you need to do after this is choose a method to grow your plants whether it’s growing passively in plant pots, or using an active hydroponics system such as an Ebb and Flow, Drip, or NFT – all will flourish in your well planned indoor garden.

NEXT TIME:
We will be looking at selecting the best growing system to suit the needs of you and your garden and using fan speed and environmental controllers.

Have you ever been given this odd-sounding advice? Even when we are encouraged to try and understand how plants work, our inherent tendency to personify the natural world is inescapable. Growers often like to draw parallels between humans and plants, after all, there’s no doubt that plants are marvelous, highly specialized and well-adapted organisms. You might even go as far to say they are “intelligent.” But let’s be honest here. Plants are totally different from us, especially in the way they react and respond to their environment. However, if we can get our heads around the world from a plant’s perspective, we become what is commonly referred to as “green-fingered.” We become … better growers.

Have you ever wondered how plants “feel” humidity? An understanding of what humidity is, what it means to plants, and how you can manage it in your indoor garden will help you and your plants stay happy all year round.
The humidity of the air is basically the amount of water in the air. Water can only truly stay in the air when it is the invisible gas – water vapor. Small droplets of water in air, such as fog or mist, are not water vapor; they are simply larger particles of water temporarily suspended in the air that are ready to be turned into water vapor by evaporation.

Temperature plays an important role when it comes to humidity. The warmer the air, the more water vapor it can hold. This means the maximum amount of water that air can hold is directly related to the temperature of the air. As the amount of water air can hold constantly changes with temperature it is difficult to pin an absolute or fixed amount of water that can be held by air. So what’s the best way to quantify humidity if the goal posts are changing all the time? The answer is something called Relative Humidity (RH) – this is a measure in terms of percentage, of the water vapor in the air compared to the total amount of water vapor that the air could potentially hold at a given temperature.

Why is RH so important?

As growers we measure the RH of our gardens using digital or analogue hygrometers. These readings are very important because RH has a direct effect on the plant’s ability to transpire and therefore grow. Generally, plants do not like to lose lots of water through transpiration. Plants have some degree of control of their rate of transpiration through management of their stomata but the general rule is the drier the air, the more plants will transpire.
Now let’s move on to the idea of “pressure” – this is an important concept to grasp when it comes to understanding a plant’s response to humidity. All gasses in the air exert a pressure. The more water vapor in the air the greater the vapor pressure. This means that in high RH conditions there is a greater vapor pressure being exerted on plants than in low RH conditions. High vapor pressure can be thought of as a force in the air pushing on the plants from all directions. This pressure is exerted onto the leaves by the high concentration of water vapor in the air making it harder for the plant to ‘push back’ by losing water into the air by transpiration. This is why with high RH plants transpire less. Conversely, in environments with low RH, only a small amount of pressure is exerted on the plants’ leaves, making it easy for them to lose water into the air.

What is Vapor Pressure Deficit (VPD)?

VPD can be defined as the difference (or deficit) between the pressure exerted by water vapor that could be held in saturated air (100% RH) and the pressure exerted by the water vapor that is actually held in the air being measured.
The VPD is currently regarded of how plants really ‘feel’ and react to the humidity in the growing environment. From a plant’s perspective the VPD is the difference between the vapor pressure inside the leaf compared to the vapor pressure of the air. If we look at it with an RH hat on; the water in the leaf and the water and air mixture leaving the stomata is (more often than not) completely saturated -100% RH. If the air outside the leaf is less than 100% RH there is potential for water vapor to enter the air because gasses and liquids like to move from areas of high concentration (in this example the leaf) into areas of lower concentration (the air). So, in terms of growing plants, the VPD can be thought of as the shortage of vapor pressure in the air compared to within the leaf itself.

Another way of thinking about VPD is the atmospheric demand for water or the ‘drying power’ of the air. VPD is usually measured in pressure units, most commonly millibars or kilopascals, and is essentially a combination of temperature and relative humidity in a single value. VPD values run in the opposite way to RH vales, so when RH is high VPD is low. The higher the VPD value, the greater the potential the air has for sucking moisture out of the plant.
As mentioned above, VPD provides a more accurate picture of how plants feel their environment in relation to temperature and humidity which gives us growers a better platform for environmental control. The only problem with VPD is it’s difficult to determine accurately because you need to know the leaf temperature. This is quite a complex issue as leaf temperature can vary from leaf to leaf depending on many factors such as if a leaf is in direct light, partial shade or full shade. The most practical approach that most environmental control companies use to assess VPD is to take measurements of air temperature within the crop canopy. For humidity control purposes it’s not necessary to measure the actual leaf VPD to within strict guidelines, what we want is to gain insight into is how the current temperature and humidity surrounding the crop is affecting the plants. A well positioned sensor measuring the air temperature and humidity close to, or just below, the crop canopy is adequate for providing a good indication of actual leaf conditions.

Managing Humidity

Managing the humidity in your indoor garden is essential to keep plants happy and transpiring at a healthy rate. Transpiration is very important for healthy plant growth because the evaporation of water vapor from the leaf into the air actively cools the leaf tissue. The temperature of a healthy transpiring leaf can be up to 2-6°C lower than a non-transpiring leaf, this may seem like a big temperature difference but to put it into perspective around 90% of a healthy plant’s water uptake is transpired while only around 10% is used for growth. This shows just how important it is to try and control your plants environment to encourage healthy transpiration and therefore healthy growth.
So what should you aim to keep your humidity at? Many growers say a RH of 70% is good for vegetative growth and 50% is good for generative (fruiting /flowering) growth. This advice can be followed with some degree of success but it’s not the whole story as it fails to take into account the air temperature.

Humidification systems to increase RH.

Table 1 shows the VPD in millibars at various air temperatures and relative humidity. Most cultivated plants grow well at VPDs between 8 and 10, so this is the green shaded area. Please note that the ideal VPD range varies for different types of plants and the stage of growth. The blue shaded are on the right indicates humidification is needed where the red shaded area on the left indicates dehumidification is needed.

By looking at this example we can see that at 70% RH the temperate should be between 72-79°F (22-26°C) to maintain healthy VPDs. If your growing environment runs on the warm side during summer, like many indoor growers, a RH of 75% should be maintained for temperatures between 79-84°F (26-29°C.)

The problem with running a high relative humidity when growing indoors it that fungal diseases can become an issue and carbon filters become less effective. It is commonly stated that above 60% RH the absorption efficiency drops and above 85% most carbon filters will stop working altogether. For this reason it is good practice to run your RH between 60-70% with the upper temperature limit depending on your crop’s ideal VPD range, in the example it would be 64-79°F (18-26°C.)

The table also shows that if your temperature is above 72°F (22°C), 50% RH becomes critically low and should generally be avoided to minimize plant stress.
Please understand that by presenting this information we do not want you to go to your indoor gardens and run your growing environment to within strict VPD values. What’s important to take from this is that VPD can help you provide a better indication of how much moisture the air wants to pull from your plants than RH can.
If you want to work out for yourself the VPD of your plants leaves you can follow the steps below:

1. Measure the leaf temperature and look up the vapor pressure at 100% RH on table 2 below.
2. Measure the air temperature and relative humidity and look up the nearest vapor pressure figure on table 2.
3. Subtract the air vapor pressure from the leaf vapor pressure

Example:
Leaf Temperature = 24°C (100% RH)     Leaf VP: 29.8
Air Temperature = 25°C @ 60% RH     Air VP:     19.0
VPD=     10.8

Humidity’s Effect on Plants

Plants cope with changing humidity by adjusting the stomata on the leaves. Stomata open wider as VPD decreases (high RH) and they begin to close as VPD increases (low RH). Stomata begin to close in response to low RH to prevent excessive water loss and eventually wilting but this closure also affects the rate of photosynthesis because CO2 is absorbed through the stomata openings. Consistently low RH will often cause very slow growth or even stunting. Humidity therefore indirectly affects the rate of photosynthesis so at higher humidity levels the stomata are open allowing co2 to be absorbed.

Leaf roll on Thai basil- Localized humidity stress causes by the lights being too close.

When humidity gets too low plants will really struggle to grow. In response to high VPD plants will try to stop the excessive water loss from their leaves by trying to avoid light hitting the surface of the leaf. They do this by rolling the leaf inwards from the margins to form tube like structures in an attempt to expose less of the leaf surface to the light, as shown in the photo.

For most plants, growth tends to be improved at high RH but excessive humidity can also encourage some unfavorable growth attributes. Low VPD causes low transpiration which limits the transport of minerals, particularly calcium as it moves in the transpiration stream of the plant – the xylem.  If VPD is very low (95-100% RH) and the plants are unable to transpire any water into the air, pressure within the plant starts to build up. When this is coupled with a wet root zone, which creates high root pressure, it combines to create excessive pressure within the plant which can lead to water being forced out of leaves at their edges in a process called guttation. Some plants have modified stomata at their leaf edges called hydathodes which are specially adapted to allow guttation to occur. Guttation can be spotted when the edges of leaves have small water droplets on, most evident in early morning or just after the lights have come on. If you see leaves that appear burnt at the edges or have white crystalline circular deposits at the edges it could be evidence that guttation has occurred.

Guttation on tomato plants caused by high RH and wet coco coir.

Powdery Mildew from poor humidity control.

Most growers are well aware that with high humidity comes and increased risk of fungal diseases. Water droplets can form on leaves when water vapor condenses out of the air as temperature drops, providing the perfect breeding ground for diseases like botrytis and powdery mildew. If humidity remains high it further promotes the growth of fungal diseases. The water droplet exuded through guttation also creates the perfect environment for fungal spores to germinate inviting disease to take hold.

Quick reference chart:

So hopefully now you are not just ‘thinking like a plant’ – you’re ‘feeling it’ too!

Next time, part two of Plantworks will be looking at foliar spraying and how plants absorb nutrients into their leaves.

As we’ve learned in part 1 and part 2, in order to grow successfully in a hydroponic system, there are certain basics that always need to be kept in check: otherwise, plant performance inevitably suffers. After covering source water, nutrient and pH, world-renowned hydroponics expert Michael Christan breaks down the final ingredients of a healthy indoor growing environment: oxygen, light, temperature, humidity, air circulation and CO2.

Photos courtesy of AmHydro.

The 5 basics of recirculation and plant performance:

1. Pure source water
2. Balanced nutrient ions/anions (EC)
3. Optimum pH
4. Plentiful oxygen availability
5. Optimum light/temp/humidity/air circulation/CO2

The Importance of Oxygen

It’s obvious that loose, friable soil with organic matter and thriving microbes grows plants much better than tight, clay soil devoid of organic matter. The primary missing ingredient in the latter is air (oxygen) availability.

The air we breathe is composed of gasses: 78% nitrogen (N2), 21% oxygen (02), 0.9% argon (Ar) and 0.03% carbon dioxide (CO2). The one we’re focusing on in this article is oxygen. The action of microbes on organic matter in a loose soil produces air pockets as organic matter is mineralized. These oxygen pockets are crucial to the survival and rapid colonization of healthy microbial populations. When the organic matter in the soil is fully consumed by the microbes and plants have consumed all the minerals, oxygen becomes depleted and, if more organic matter is not reapplied, plant performance slows and pathogenic (anaerobic) microbes can colonize. This condition is best avoided.

In media-based recirculating systems, the O2 is in the media: e.g. rockwool, perlite, grow rocks. Plentiful air space is available even after water is drained from the media. Roots thrive in O2-rich pockets. They are able to produce prolific root systems and plentiful root hairs to increase surface area to better absorb available ions. This is the best reason for using media with porosity. Of course, flood and drain systems suck fresh air into the media when it drains, which is why it’s such a great irrigation system.

In water-based recirculating systems, NFT, DFT and Aeroponics, O2 availability is intrinsic to the design of the system. NFT is a flat-bottomed tube with a shallow nutrient stream moving slowly, keeping root hairs moist and absorbing O2 (see “NFT Gro-Tanks,” UGM009). Aeroponics is misting droplets of water, increasing the surface area many-fold for roots to grow prolific root hairs for ion absorption. It supersaturates the solution with O2. DFT uses air pumps and water temp to keep roots bubbled with 02 and oxygen rich.

The heart of a media-based or water-based recirculating system is the nutrient reservoir. This too requires oxygenation, especially when water temperatures rise. The use of air pumps and air stones on smaller reservoirs and pump-powered eductors (venturis) on larger reservoirs make a big difference in pathogen suppression (nasty fungi and bacteria don’t like O2). This agitation drives ethylene gas from the solution and increases the longevity of the nutrient. Be sure that, if there are reservoir lids, there’s room for air exchange with ambient air in the room or greenhouse. Many commercial growers use fresh outside air in their eductors to keep the nutrient solution optimum.

Dissolved Oxygen (DO) can be measured to determine solubility of oxygen in fresh water. Fresh water at 72°F (22°C) has a DO of 8.7 ppm; at 82°F (28°C) it drops to 8.1 ppm. Salt solutions are lower. As a rule of thumb, every increase of 1ppm in DO is equivalent to an 11°F (12°C) temp drop. The cooler the temp, the higher the DO. You don’t want cold water on plant roots, though. You want 72°F (22°C) water at your roots for most plants.

When we measured DO in our greenhouse reservoirs, we found that a 74°F (23°C) nutrient tank at an EC of 2 had a DO of 6.3 ppm (low because of salts and sitting still). When we turned on an eductor (venturi), which we do in ALL reservoirs, we received a reading of 7.6 ppm. BIG difference. That’s an increase of 1.3 ppm without changing temperature.

Then we add an in-line Mazzei injector in between the tank and the feeder pipe, which raises DO to 8.3 ppm. By the time the water had run down the NFT channel and 18 plants had their way with the O2, with some off-gassing occurring, there was an 8.1 ppm DO left in the nutrient solution going back to the reservoir. That’s what we’re after! Plants thrive at those DO levels. Makes ALL the difference.

Be careful: as water temperatures of salt solutions increase, you must mitigate by adding O2 in the reservoir as well as directly on the roots. If you can’t get the DO level up by mechanical means, then you will most likely require a water chiller, which is expensive but sometimes imperative. If you cannot bring water temps down or increase DO in the nutrient solution, your next action will be disease suppression or inoculating roots with beneficials to out-compete the pathogens that thrive in high temp, low DO water. If you do get a DO meter, get a good one. We use an Extech Model 407510.

Light

Photosynthetically Active Radiation (PAR) light is a fancy term for the wavelengths plants use to vibrate chloroplasts to power the engine of photosynthesis, a vaguely understood process in my opinion. It is said that PAR light is in the 400 to 700 nanometer wavelength range. No big deal if you’re outside or in a well-lit greenhouse. But if you are growing under HID light or using it as a supplement, it certainly is.

Color temperatures of lamps are measured in degrees Kelvin from a color rendering index (CRI). The blue/white side of the spectrum has higher Kelvin temp: 6000K-8000K (MH lamps). The yellow/red side of the spectrum has lower Kelvin temperature: 3000K (HPS lamps). As a rule, the higher the Kelvin temp, the more vegetative the growth. The lower Kelvin temps are used for supplemental and/or flowering light. Different bulbs have different combinations or blends of gasses for better PAR value. Plants can be finicky and prefer one blend of light more than another. Trial and error, sometimes, is the only way to find out what your plants really like.

High Intensity Discharge (HID) lamps produce light when the gases inside the fused alumina tube are heated to the point of evaporation by high voltage electricity. This process forces the metal gasses to throw off a barrage of photons partly in the PAR range. As the bulb burns over time, the metal gasses slowly change form and degrade out of the PAR range. It is not obvious, but plant performance can suffer from lack of the PAR light when there is no shortage of photons to the naked eye. To look at light as a possible limiting factor, keep track of the hours your bulbs have been burning. If you are over the recommended burn range as stated by the manufacturer, that could be what’s compromising your system. Rule of thumb with HPS bulbs is to replace them every 12 months, and MH bulbs every 9 months, with HPS burning 12 hour days, MH burning 18 hour days.

Outside it’s obvious what limits light, like trees. But in greenhouses, if the glazing is dirty, that’s a big deal and that situation just creeps up on you. Depending on what you’re growing and what time of year it is, a dirty film can cut out as much as 30% of available light. If you are using an 85% transmission film and have 30% attributed to dirt, that’s 55%, basically shade cloth. In situations where there is too much light and plants are unable to cope with the leaf temperatures or solar radiation, a white or metallic shade cloth is preferable to black, as black can radiate heat back down on the plant canopy. A simple mistake easily avoided by many growers in double poly greenhouses is that the inflation fan is pulling inside air in between the films, thereby creating moisture that blocks light. You can tell by the droplets in between the films, or a haze. It is always recommended to use outside air for inflation. Of course, all of this is dependent on location, latitude, geography, plant in cultivation and skill/experience of the grower. We cannot cover all those variables in a brief article.

Temperature

Plant response to temperature is pretty obvious. It’s visible. Plants stop growing when root temps hit 58°F (14°C). Air temp can actually be cooler than 58°F, but when roots are cool, growth slows and stops even when air temp increases. When temps are too high, say 95°F (35°C) plus, depending on RH, air flow, light, kind, size, and age of a plant, they may stop feeding and spend their energy evaporating water from their stomata to cool down. Temperature must be managed to keep plants transpiring and active in the sweet spot.

Most temp controllers are effective, turning on fans for increased air exchanges, but when temps are too hot outside, air conditioners must be used. As a variable, though, temperature control is straightforward. It’s common knowledge that insects like very consistent temperatures and no air movement. Find which temperatures are your best high and low, and vary them morning, daytime and night. Keep an inhospitable environment for the pests without sacrificing plant performance: another dance to master.

Humidity

The two ways of explaining humidity are relative humidity (RH) and vapor pressure deficit (VPD). Most people are familiar with RH and use hygrometers so, for the purposes of this article, I will use RH.

In my experience, this is the one variable that most growers need to be more aware of. The dance between temp/humidity directly affects transpiration rates as poor transpiration opens the plant organism to disease and mineral deficiencies.

RH is the amount of water vapor present in the air expressed as a % of the amount needed for saturation at the same temperature. Here’s what that means: if the humidity is too high, e.g. 95% at 75°F, plants cannot transpire or evaporate enough water to pull minerals up the vascular system even with stomata wide open. This usually results in calcium (Ca) deficiency (remember, Ca is a non-mobile element and must be constantly supplied to growing tips) and plant stress, which increases their vulnerability to fungal intrusion.

If humidity is too low, 50% at 75°F, stomata will open in an attempt to evaporate water because of the low pressure around the leaf, but then close up to conserve cell pressure in the leaf. Plants stress as they cannot take in CO2 with closed stomata and growth stops as the plant is just trying to survive without going into wilt (i.e. loss of leaf turgidity from which it’s difficult to recover). Again the plant is vulnerable to disease and insects. These two extremes points will create a high probability of crop loss.

As a rule, at 75°F (24°C), if RH is below 60% you must add moisture to get to 75% (which is ideal), but stay below 85% to avoid stress and disease. At 85°F (29°C), if RH is below 70% you must add moisture to get to 80% (which is ideal), but stay below 90% to avoid stress and disease. As temperature rises, air holds less moisture. Steer your plants within these parameters for optimum plant performance.

When RH is too low, use a fogger or humidifier coupled with outside air exchanges. When outside air is too warm and dry, you will have to use some form of air conditioner (if that is the only way) to drop the temperature to increase the moisture-holding capacity of the air.

When RH is too high, raise temperature to reduce moisture saturation of air coupled with outside air exchanges. If outside air has too high of an RH, you will need a dehumidifier to pull water out of the air.

Transpiration is king. Monitoring transpiration rates and keeping them optimum with temp/RH manipulation is crucial. If you are outside of the temp/RH safe zones and don’t use some mechanical method of bringing them under control, you will always be fighting the results of that variable being unchecked. This is where high quality environmental controllers come in handy

You can buy the most expensive nutrients, goodies and gadgets available to grow your crop, but if your plants are unable to transpire and you don’t know that, you had best learn quickly or get a day job

Air Circulation and CO2

No matter what kind of controlled environment you’re running, greenhouse or greenroom, air circulation is another key component that is often overlooked until mildew takes out your crop or your plants starve from lack of CO2. The great outdoors takes care of all this, but inside you have to provide the controls or fall prey to what you didn’t know you didn’t know.

Rule of thumb: 60 air exchanges per hour. Not only do you need to flutter your plants with gentle breezes from an oscillating fan or horizontal air flow (HAF) fans in a greenhouse, but you must freshen the air with air exchanges from outside, taking advantage of the 385 ppm ambient CO2. The raw materials that PAR light makes into carbohydrates are CO2 and H2O. CO2 furnishes the carbon and oxygen, while water furnishes the hydrogen for the carbohydrate (CH2O).

If air exchanges are frequent, 385 ppm CO2 is plenty unless you’re looking to accelerate growth by enriching your space with higher levels to, say, 1500 ppm CO2. Even if you are adding CO2, you still must exchange air. There are numerous ways to provide CO2: chemical reactions, gas bottles, gas generators and a variety of controllers and monitors depending on the size of the operation. For the purpose of this article, you just need to know that it is a basic component of the indoor growing environment, and be mindful that it’s always available. Without CO2, plants will not grow.

One of my teachers, Grenville Stocker in NZ, took me into one of his client’s lettuce/herb greenhouses and asked me, “Would you get a chair, sit down, read a book or hang out in here all day?” Actually, it was way too moist, not enough air movement, my shirt was sticky, and it was uncomfortably warm. I said, “No way.” He remarked, “How do you think those plants feel? The same way, I reckon, except they can’t leave.” Then he showed me powdery mildew in certain areas, a thrip infestation and tip burn in some of the lettuces. The plants did not look vital, they looked stressed. I noticed the HAF fans were down, because of a blown breaker that the grower had been meaning to fix for a week. He had an RH monitor but no controller to check humidity and spill air or add heat … AND he was doing only 1 air exchange per hour because it was cold outside. He wanted to keep temps up inside without turning on the heat, which would cost him money. I looked at the RH: it was 95%. Temp was 80°F but it felt like 90°F because of the humidity. His client was too busy to pay attention or take coaching, and he wasn’t even there. Grenville always tested me; he’d say, “What’s wrong with this picture?” Then he would point out a basic that was obvious once I saw it. Most problems were easy to correct once distinguished.

I found out later the grower lost 50% of his crop and the other 50% was barely marketable. Had he kept HAF fans working, increased his air exchanges and turned up the heat to drive off the humidity with the help of a controller, he would not have had crop and financial loss. Just that one error cost him a market: he couldn’t deliver, so a competitor moved in. The point I’m making is: don’t leave your plants in an environment you can’t handle being in yourself. Use meters and controllers, but always keep them honest by paying attention to what your skin says.

All the variables of light, temperature, humidity, air circulation and CO2 must dance together in a harmony that you must monitor and control to be successful and avoid crop loss. If you cannot distinguish which variable is out, you will be guessing what the problem is and perhaps taking actions that are detrimental. Next time a problem arises (which inevitably will happen) and you’re scratching your head as to what to do, go through this list and check off each one that you KNOW is in tolerance. These 5 basics could be what you didn’t know you didn’t know. Now that you do, dissect them and become competent with each one:

The 5 basics of recirculation and plant performance:

1. Pure source water
2. Balanced nutrient ions/anions (EC)
3. Optimum pH
4. Plentiful oxygen availability
5. Optimum light/temp/humidity/air circulation/CO2

For the content and experiences that allowed me to write these articles, I’d like to thank my teachers, Grenville Stocker (Stocker Hort), Jeff Broad (AutoGrow), Genaro Calabrese (ex partner), Grant Creevey (Accent Hydro) and all our clients and associates for sharing and being open to “figuring it out.” Controlled environment plant cultivation is infinitely beguiling; I am always learning a greater respect for being part of that process. Genaro’s motto: “Every plant, every day.”

Good luck and good growing.

Michael Christian, the president of American Hydroponics since 1984, is a hydroponic system designer and consultant to commercial growers worldwide.

Rockwool is a mainstay of commercial hydroponic growers – and for good reason. It takes up a minimal footprint and, when used correctly, yields like crazy. We asked Dr Lynette Morgan, a world authority on hydroponic vegetable production, to give us some expert advice on growing tomatoes in rockwool. There’s LOTS to be learned here as Dr Morgan takes us through how to develop irrigation strategies for your particular growing environment.

Rockwool, also known as stone wool or mineral wool, is the most widely used substrate for the commercial production of hydroponic tomatoes. It is also a great tool for smaller growers who can benefit just as much from its use in a range of different systems and situations. While rockwool is relatively easy to set up and use, it does require some monitoring and irrigation adjustment to make the best of its ability to hold high levels of moisture and aeration at the same time.

Rockwool originally started as a thermal insulation material in the construction industry: its lightweight but highly aerated nature helps keep heat in buildings, while being easy to handle, cut and install. However, towards the end of the 1960s, trials were carried out in Denmark to test the possibility of using stone wool as a substrate for plants. Things went well and since then rockwool as a growing media has seen some continuing development of the substrate and the tools used to manage it.

Rockwool comes in a range of sizes from propagation cubes to large slabs and even a granulated product.

Rockwool is manufactured by melting basaltic rock and spinning this molten mix into thin fibers which are then cooled by a stream of air. Although rockwool is a man-made substrate it is essentially made from rock and considered by many to be a natural product. Grodan dominates the rockwool market world-wide and is the most common brand used by large and small hydroponic growers alike. Grodan rockwool is highly advanced and is not a single product – growers can select from a number of different Grodan rockwool types such as `Grotop Master,’ `Grotop Master dry,’ and `Grotop Expert,’ all of which have slightly different properties and uses. `Grotop Master Dry,’ for example, maintains a slightly drier root zone and is used by tomato growers to steer crops away from overly vegetative growth. `Grodan Classic’ is used for multi-year use, while `Grotop Expert’ is designed for ultra quick root growth and development. Along with these product differences, rockwool of many brands comes in a huge range of sizes from tiny propagation plugs for seeds to larger cubes for cuttings, mega sized cubes for large plants, a wide range of slab sizes, and as a granulated product as well.

Setting up to grow with rockwool

1. Sit the rockwool down

Whether you are using the standard rockwool growing slabs, large cubes, or even pots of granulated rockwool, basic preparation is important. Slabs and cubes in particular need to be on a flat, even surface as any indentations will cause the material to sink and create pockets of unwanted moisture. Next, realizing that nutrient solution will be draining from holes cut in the slab’s plastic wrapper or from the base of cubes, some consideration for drainage of this solution away from the slab is important. There is no point in having well placed and made drainage holes if the solution can’t be channeled away from the slab and the material ends up sitting in a pool of stagnant waste nutrient. Many small hydroponic systems on the market these days designed for use with rockwool have trays and channels designed to do just this and these are a good choice for inexperienced growers.

2. Settle the rockwool in

Rockwool, whether it is slabs, small propagation blocks, or large growing cubes, needs to be prepared correctly by fully wetting the substrate before use. Some growers like to adjust the pH of their water to 5.5 before wetting up rockwool, but generally for small systems it’s not necessary with good quality brands (unless you have a very `hard’ water supply in which case acidification of the water before making up any nutrients would be a good idea). The rockwool should be fully saturated so that all of the material is wetted and then left to drain. Some growers pour water into the rockwool slab before the drainage holes have been cut to make sure everything has had a good drenching, while others just pour water on or run the irrigation long enough for saturation to take place.

3. Remember the holes

Rockwool slabs need drainage – holes or slits should be cut in the plastic sleeve the material comes in. Several cuts are required along the base of the slab. Granulated rockwool should be placed into containers or pots with plenty of drainage holes in the base.

4. Irrigation programs

The most common way of applying nutrient to rockwool slabs or large blocks is with the use of dippers. A simple drip irrigation system should use a dripper with a capacity of 2 litres/hour, with one dripper per plant. Because a standard rockwool slab may hold four tomato plants, four drippers per slab are required, which also means that if any one dripper becomes clogged, the entire slab will still be getting enough irrigation until the problem is fixed.

Developing an Irrigation Strategy for Rockwool – The Moisture Gradient

Rockwool is the most widely used substrate for hydroponic tomato production.

The irrigation program for any hydroponic plant is vital for successful growth, development and optimal yields. The most common problem experienced by smaller or new growers is over watering, and usually the grower is totally unaware that it is their irrigation program causing problems with plant growth. Flushing vast amounts of nutrient solution through the root zone in a substrate-based system often equates to plant murder – more is not necessarily better when it comes to nutrient application. This type of mistake is easy to make. After all, many new growers get enthused about hydroponics after seeing a well-run NFT or other solution culture system and assume that plants are more than happy to grow and thrive in a flooded root zone environment. However, solution culture and substrate systems are completely different and need to be managed in different ways for the plants to get the optimal root zone conditions they need. In NFT the roots should never be flooded: they sit in a very thin film of nutrient flow (2-3 mm or about 0.1″ deep), hence the roots have moisture at the base of the root system, but many of the other roots are sitting up in the moist air, accessing all the oxygen they need without being submerged. In a rockwool slab the plants are in a similar situation – at the base of the slab there is plentiful moisture, usually at media saturation levels, while in the upper layers of the rockwool slab the roots are in drier conditions and hence have access to plenty of aeration and oxygen for root uptake and respiration. It is this moisture gradient from the top to the bottom of the rockwool material that makes it such a good substrate. At the same time, growers who are not aware of this property can make the mistake of thinking the rockwool is too dry on the surface and over-irrigate their plants despite having plenty of nutrient solution being held deep down in the root system. Rockwool growing media, when being irrigated correctly, should not sit in a pool of nutrient and be completely saturated from top to bottom like a sponge. It is essential that the rockwool is allowed to completely drain so that excess nutrient leaves the slab or cube under the pull of gravity after being applied– in doing so, fresh air is drawn into the top layers of the material, providing fresh oxygenation for the root zone. By allowing the rockwool material to drain freely, over-watering becomes more difficult, although vast amounts of nutrient drainage from the base of rockwool slabs or cubes is not an ideal situation either.

Setting up an Irrigation Program

Obviously the amount of nutrient required is going to depend on factors such as the size of the plant, the growing conditions, light, temperature and, in particular, humidity, which drives plant transpiration and water uptake. So the irrigation program is going to change as the plants develop. Also an irrigation program needs to be developed and adjusted by each grower for their particular system, environment, and set up and this has to be monitored and adjusted as required. Just following guidelines for the amount of nutrient to apply at certain times will eventually lead to over or under-watering, as each plant and situation is different when it comes to nutrient and water requirements.

Commercial hydroponic rockwool growers have some good tools for fine-tuning their irrigation. The Grodan water content meter allows growers to measure the water content, EC and temperature in the rockwool slab root zone using hand-held meters or a continuous monitoring system hooked up to the computerized irrigation program. However, these sorts of high-tech tools are not often used by smaller growers and a successful irrigation strategy can be put together with just observation, some innovation, and a little time.

Remember the Moisture Gradient

Rockwool propagation cubes and slabs are designed to be used together to minimize root disturbance. Excellent moisture holding capacity and good aeration of the root zone are features of rockwool substrates.

Irrigation of rockwool is a little different to other solid substrates because of the way the material is manufactured to have just the right degree of moisture gradient, and because it does give quite a limited root zone for plants that eventually grow fairly large. For this reason, rockwool is best irrigated with short, frequent applications of nutrient, with just enough at each irrigation for the rockwool to reach ‘field capacity’. Field capacity is a term that means the substrate has drained fully but is still holding a good level of moisture for the plant roots to access until the next irrigation. At each irrigation, there should be some drainage from the rockwool material. However, this doesn’t need to be excessive. Even in closed systems where the drainage solution is being collected and reused, it pays not to over-water and not to run the irrigation continuously. Having around 10-15% of the nutrient solution fed to the plants, drain from the slab at each irrigation is considered to be optimal. This amount of drainage of solution flushes fresh nutrient solution right through the slab without too much wastage and usually keeps the EC in the slab fairly stable.

When rockwool is irrigated and allowed to drain naturally, it will then contain 80% nutrient solution, 15% air pore space and 5% rockwool fibers. A typical rockwool tomato growing slab actually holds around four gallons (about 15 liters) of nutrient solution immediately after irrigation, despite the drainage holes allowing free drainage of excess solution. Four gallons is a good reserve of moisture for four plants, so drying down to wilting point could take a long period of time for small plants.

How much solution should be given at each irrigation?

Having a drainage collection tray or channel under each slab allows growers to see how much drainage they are getting after each irrigation (even if this has to be poured off and measured in a jug) and the irrigation program can be increased or decreased to keep this at the 10-15% level. By doing this, the amount of solution to be given at each irrigation can be worked through and adjusted as the plants grow. Keep cutting back the irrigation amount until only 10-15% of the solution volume applied drains from the slab, and then the amount of irrigation has been fully adjusted for.

How often should nutrient be applied?

Rockwool needs small frequent irrigations, particularly under hot or low humidity conditions when the plants are taking up a lot of water. However, the frequency of irrigation can be as low as once per day (or every other day) for small plants under cool conditions, to over 10 times a day for large plants in a hot or dry environment. It can be hard to judge just how much moisture the rockwool material may be holding at any one time to determine when to irrigate. Smaller propagation blocks and even larger cubes can be gently picked up – the weight will soon tell you if the cube is saturated (it will be comparatively heavy and moisture will drip from the wet base), or whether it has dried out considerably, in which case it will feel very light (compare an unused dry cube to one in use). Rockwool is an unusual material in that, even when the slab has lost 50% of its moisture to plant uptake, the plants are still able to very easily keep extracting water until the slab is almost completely dry – so plants in rockwool can’t get water stressed until the rockwool is almost completely dry, by which time the cube or slab has become much lighter in weight. For granulated rockwool in pots or containers, a similar method can be used, either by gently lifting the pot to see what the weight might be (a light pot is a dry pot) or by a light tap or kick: if the pot moves, the rockwool has become quite light and potentially too dry.

Another method to try and gauge the moisture status of the rockwool and how often to irrigate is to carefully remove a small piece of the wrapper plastic and examine the moisture gradient of the slab from top to bottom. Like all growing media, moisture in rockwool can be gauged manually. Lightly touching or pressing the rockwool at the base of the slab will soon determine if there is still a good level of nutrient held in the base of the slab or whether it has become too dry. The top and middle layers of the slab should always appear drier than the base where the reservoir of moisture is naturally held, so only the base of the slab should be checked. Even if the top of the slab appears to be dry, this is not important as the moisture gradient has been designed to give these sorts of root zone conditions – only ensure the base of the slab has sufficient moisture.

This process of working out how much moisture is still in the rockwool material is not something that needs to be done for long. Growers will soon become quite skilled at working out their frequency and amount of irrigation for each stage of plant growth and may only need to do this for their first crop provided growing conditions remain stable. Other times when it might be important to have a quick check of the amount of solution drainage or amount of moisture in the slab is when conditions suddenly change – addition of more grow lamps, sudden changes in temperature or humidity, or rapid growth spurts can all change the irrigation requirements of the plants.

Generally, good brands of rockwool are quite forgiving compared to other substrates – the material is naturally well aerated and doesn’t suffer the compaction issues that some substrates do during the life of the crop. It does hold high levels of moisture, so the chance of drying out is not as severe as it might be with other substrates and being sterile gives young plants, seedlings and cuttings an advantage as well. The irrigation program and water holding capacity of the substrate depends on the fiber density and arrangement, which can differ from brand to brand.

More Advanced Irrigation Practices

With tomatoes and similar crops, growers have the option of using the EC and moisture content of the rockwool slab to help ’steer’ the plants into either more vegetative or ‘generative/reproductive’ growth, depending on what is required. Drying the slab back between irrigations and allowing the EC in the root zone to increase pushes tomato plants into a more generative or reproductive state with less leaf growth and more assimilate being directed into the fruit. A higher level of moisture maintained in the rockwool and a lower EC pushes the plants towards more lush vegetative growth. Skillful growers use these techniques to direct their crop and control leaf, flower and fruit growth at different times, and rockwool is a great substrate for this sort of control via the root zone.

Other Rockwool Tips

EC Levels and Management

Checking the EC in the root zone is important with rockwool just as it is with any media. The EC of the nutrient solution in the growing substrate changes as plants extract different ratios of water and nutrients from the root zone. The EC in the drainage solution coming from the base of the rockwool cubes or slabs is the best indication of the EC the plants are actually experiencing in the root zone. As a general rule, the EC in the drainage solution should be the same as or only slightly higher than that applied to the plants in the feed solution. If the EC is becoming much higher in the drainage than what was fed to the plants, then the EC in the feed solution should be dropped back – this is common under hot growing conditions when the plants might be taking up far more water than nutrients, hence concentrating the nutrient solution.

Rockwool Reuse

Rockwool for tomato crops can be reused – some commercial growers get many successive crops from rockwool slabs by steaming these after the plants have been removed and then replanting. Smaller growers can also do this – a few slabs can be heat treated by pouring hot water through them. Solarization is also possible, as is using chemical disinfectants, although care should be taken to rinse the rockwool well with plenty of water after using these. Commercial Grodan users have the option of the Grodan recycling service, which picks up the used slabs and recycles them into new product. However, smaller growers with just a few slabs of used rockwool can recycle the material by shredding it and reusing it as a growing media, as a component of potting mixes, or by incorporating it into outside soils and gardens.

Real World Rockwool Q&A

Q: What pH should I adjust the nutrient solution to and how do I monitor and adjust accordingly? For instance, keeping the tank pH at 5.8 and the run-off at 6.0 is perfect, but what happens if the pH starts to come back higher or lower than expected? What could / does this mean? And what should be done to correct it? How much should a grower raise or lower the pH of the tank with pH adjusters – when does a situation become ‘too extreme’ to use pH adjusters?

A: There are many factors that affect pH in the nutrient: some are normal like plant uptake and nutrient formulation salts (NH4 in particular), and some are not so good, like root disease. Water plays a big role and can range from very hard to very soft and hence needs to be handled differently depending on what a specific grower is dealing with. Chemicals for pH adjustment are also a huge topic! The nutrient solution pH is usually optimal at around 5.8 – 6.0 for commercial tomatoes; however, for small systems pH in the range of 5.5 – 6.8 is usually fine and having tight control at 5.8 is not necessary. The main problem with pH is with growers who might have a `hard’ water source, which is highly alkaline. In that case, acidifying the water with acid (nitric or phosphoric) before making up any nutrient will give better and longer term control of pH swings (in any growing media). pH should not need to be raised in most situations unless the water supply is very acid: in that case, potassium hydroxide should be used.

Q: I understand that rockwool can be prone to salt build-up if you don’t know what you’re doing like the commercial guys. Most hobby rockwool growers I have talked to flush either one day a week, throughout the whole grow and bloom cycle, or when they dump the res. (They will commonly give their plants 24 hours of either very low nutrient solution (if so, what EC?) or pure water, or even pure water with a product like GH Flora Kleen. What do you think of these flushing techniques? Do you have any better advice?

A: Rockwool is actually one of the better media for preventing salt build up as it tends to be drip irrigated from above and not bottom watered like with ebb and flow. Flushing is another subject that really needs a whole article to cover the theory, practice and problems with it. Flushing with straight water after a plant has been sitting at normal or high EC is not recommended: it causes the plant cells to suddenly take up huge volumes of water (because the osmotic pressure has been dropped in the root zone). This can cause cells to burst and create major physiological problems – splitting of tomato fruit is one common one; many other fruits and vegetables do the same. Even low strength nutrient can do this. Any changes in EC in the root zone should be done slowly (i.e over days), so a gradual dropping back of the EC over a few days should be done rather than flushing with water. Or better still, don’t let EC build up in the first place!

Q: What is the disadvantage of watering rockwool for a minute and getting 50% run-off in a closed system with adequate drainage, as opposed to watering for a minute and getting, say, 15% runoff? If you are only achieving 15% run off, is it not the case that the rockwool is already fully saturated and any additional runoff will just wash out the excess salts more thoroughly? In short, how difficult is it to over-water rockwool? I also can’t see what the problem would be for the plant if more run-off was created unless, of course, you were irrigating for several minutes to achieve this much run off, but even then surely the plant won’t feel any effect having its roots flooded for, say, 10 minutes, then allowed to drain freely?

A: Rockwool is a media which has been specifically designed for commercial growers who aim to have the recommended 10-15% run-off with the slabs spending as little time as possible at saturation levels – when doing this, the structure of the rockwool has been manufactured so that the root zone will remain at the correct moisture status which is why it is recommended. Also, with rockwool systems, the feed nutrient should be applied so that ‘excess salts’ don’t occur and therefore don’t need continual flushing. If the EC is getting high in the drainage solution, drop it back in the feed solution and/or increase the frequency of short irrigations. Rockwool, like any media, can be over-watered if flooded and is best kept below the saturation level for balanced growth.

Q. What’s the scientific explanation behind the influence that irrigation strategies have (or, to be more precise, the levels of moisture in the root zone) on generative / vegetative growth? Is this peculiar to tomatoes or is it applicable to other species?

A. Crop ’steering’ as it’s called is a technique used by commercial growers to manipulate the natural growth pattern of the plant. It’s widely used by skilled growers of tomato crops, but also on capsicum and many other plants as well. It’s quite a complex topic as there are a number of tools a grower can use in a controlled environment to direct the growth of the crop – commercial growers will use a combination of DIFs (day/night temperature differentials), EC, CO2, moisture control in the root zone and directional heating (i.e. directing heat towards the fruit or tops of the plants) to manipulate the growth of the plant. Different techniques force the plant to send the assimilate produced in the leaves into flowers/fruits when required or direct the plant back to some more vegetative growth if that was what was required. Various temperature techniques are sometimes used to keep seedlings or older plants as short and compact as possible (i.e. prevent stem elongation) and to get the plant to hold back on the production of overly large, succulent leaves. Commercial tomato growers use tools such as measurement of stem diameter to determine if their plants are getting overly vegetative or too generative at certain times of the year. The basic scientific explanation of why this works is that when a flowing plant encounters ’stressful’ conditions such a drying back of the root zone, high EC, high light and temperatures, it triggers a response – the plant wants to hurry up and flower, and to set seed to make sure it reproduces before the harsh conditions can kill it. We sometimes see this effect on lettuces which, under high light, temperature and moisture stress, can flower (or bolt) while the plant is still only a seedling and far from maturity. A plant with plenty of moisture under no particular stress is happy to go on producing a lot of large leaves with no hurry to set fruit and seed, which is great for vegetative crops such as lettuce but not so much with fruiting crops like tomatoes and capsicums. The ‘controlled stress’ commercial growers use to direct plants into more generative growth is often via the root zone because with Grodan rockwool very precise control of moisture content in the substrate can be controlled – particularly with the use of the Grodan moisture meter. And in hydroponics, control over EC is also fairly easy and precise. For this reason, Grodan Rockwool has different products for growers who might need to steer their crops towards more generative growth by having a drier root zone. It makes it much easier for the grower to then restrict irrigation and moisture levels in the root zone to steer the plants towards more generative growth and generally the technique is very effective. However, commercial growers use high tech tools likes moisture meters linked to their computerized irrigation program so that the crop is not at risk of being damaged by delaying irrigation to long. Smaller growers can certainly use similar techniques and allow the rockwool to run a little drier between irrigations and keep their nutrient run off to an absolute minimum if their plants are getting a bit too vegetative. Running a lot of nutrient through the rockwool on a frequent basis means the slabs or media are at saturation for much longer, and that favours vegetative growth (although we should also remember a lot of other factors, such as the growing environment, play in a role in the vegetative/generative balance as well).

Dr Lynette Morgan holds a B.Hort.Tech(Hons) degree and a PhD in hydroponic greenhouse production from Massey University in New Zealand. Her PhD thesis focused on hydroponic tomato production in both NFT and media systems and improvement of fruit quality aspects. Now a partner in SUNTEC International Hydroponic Consultants, Lynette is involved in many aspects of hydroponic production, including remote and on-site consultancy services for new and existing commercial greenhouse growers worldwide as well as research trials and product development for manufacturers of hydroponic products. Lynette is also the author of 5 hydroponic technical books: Hydroponic Lettuce Production, Hydroponic Capsicum Production, Fresh Culinary Herb Production, Hydroponic Strawberry Production and her latest release, Hydroponic Tomato Crop Production.

The basics – What is NFT?

NFT stands for Nutrient Film Technique. With this hydroponic system, plants grow in a purpose-built sloping channel with a fall of 1:40–1:50. Nutrient solution is pumped from a reservoir onto the channel where it passes over the plants’ roots and finally returns back to the reservoir. The roots on the channel develop to form a mat, which is partially in the shallow film of re-circulated nutrient solution, and partially above it. Utilizing this technique, the root mat growing in the nutrient film is supplied with essential water and nutrients, and the root mat above the film remain sufficiently moist with an abundance of oxygen.

The NFT system was developed between the 1960s and ’70s by Dr. Allen Cooper at the Glasshouse Crops Institute in the UK. In the early days, the growing channels were made in concrete floors. Today, growing channels are made from plastic and are often referred to as “trays” or “gullies.”

Why choose NFT?

Other than supplying your plants with the ideal root environment, NFT systems are incredibly efficient and environmentally friendly. The nutrient solution is recirculated for long periods: in some commercial applications, for many months. This continual recycling of the solution makes the most out of the water and nutrients you’re supplying. NFT systems also use very little growing media: just the small amount of substrate the plant is propagated in. This means that after each crop all you have to dispose of is a mat of roots, which easily biodegrades.

NFT Gro-Tanks

The system I will be demonstrating is called a Gro-Tank and is manufactured in the UK by Nutriculture.

The Gro-Tank is great for small-scale production as it has a wide top tray for the roots to grow on, with the reservoir directly beneath it spanning its whole length. A small submersible pump in the reservoir delivers nutrient solution to the tray above, which flows down the tray and back into the reservoir. This compact, self-contained design eliminates the need for lots of pipe work and is very low to the floor, making best use of the height available for tall/vining plants.

I have used the Gro-Tanks for many types of crops, including lettuce, basil, watercress, coriander, parsley, rocket, chard, chives, tomatoes, peppers, chillies, strawberries, cantaloupe melons, cape gooseberries, and many more. The diary below shows one of my NFT grows with cucumbers. I hope you enjoy…

Equipment

1 x heated greenhouse
1 x heated propagator
5 x starter plugs
5 x 4” rockwool blocks
1 x 604 Nutriculture Gro-Tank: 5ft x 1.5ft (153cm x 49cm) tray with 16 gallon (60L) reservior
1 x submersible adjustable pump
1 x submersible water heater
Spreader mat (capillary matting)
4 x roller hooks (plant supports)
Vine clips
Liquid nutrients and growth supplements

January 18th – Germination

I’m growing a cucumber variety called Carmen, which is an all-female F1 hybrid variety. The majority of cucumber varieties produce both male and female flowers; all we are interested in are the female flowers, as these develop cucumber fruit. This all-female (parthenocarpic) variety will develop a seedless fruit without the need for pollination. I found Carmen great last year for greenhouse growing as you don’t have to pick male flowers off and it produces large, full fruits.

I planted the seeds in starter plugs pre-soaked with a low-strength nutrient solution (EC 1.2) designed for seedlings and cuttings, and a liquid beneficial microbe additive. These were placed in a heated propagator and germination was fast!

Shown here is one cucumber seedling 8 days after planting. At this point they were transplanted into 4” rockwool blocks.

January 31st – Propagation

Considering it’s been 21 days since I planted the seeds, I’m happy with the way they’re progressing. They are now being watered with nutrient solution (EC 1.4, pH 5.8) every 2-3 days. The roots are doing really well and can be seen on the top of the block.

Without the block covers, algae would be taking over and the roots would not be growing so well on the surface. The natural light entering the greenhouse is being supplemented with 220W fluorescent strip lights. These plants should be ready for their NFT system in about 1 week.

February 4th – Growing on

The plants now need nutrient solution every day and the roots are clearly visible all over the bottom of the block. I also have increased the EC to 1.6. They will need to be planted in the next few days.

February 5th – Setting up

These cucumber plants are now 26 days old and are ready to go onto their final system, which will be an NFT Gro-Tank.

The most important thing about getting plants ready for NFT systems is to ensure they are well-established and have a mass of healthy white roots. Without this mass of roots inside the rockwool block, the plant will not be able to cope with the continuous irrigation of the NFT system. These plants have been propagated using an air pruning technique (see “Power Propagation” UGM0005) to ensure the rockwool block is packed full of roots.

This is the Gro-tank I will be using (below). It is called a 604. Nutriculture, which makes the system, also makes 5 other size variations to suit any grow area. The top tray is where the plants are placed and the reservoir underneath stores 16 gallons (60L) of nutrient solution.

The Gro-Tank has one delivery tube where the nutrient solution is pumped onto the tray using a small submersible pump with an adjustable output:

To ensure an even distribution of nutrient solution on the tray, I use capillary matting, aka “spreader mat.” The system manufacturers recommend using spreader mat and supply it with the system. One layer is enough. After laying it out, I fill the reservoir with water that has been standing in a storage tank for a few days: this allows some chlorine to be evaporated and, more importantly, allows the temperature to rise. Tap water in February in the North of England usually comes out ice cold and will seriously stress plants if used.

Once the tank is filled I turned the pump on and slow the output down so the solution lands in the middle of the first diamond. This provides a flow rate of approximately 1 quart (1L) per minute. Recommended flow rate for NFT systems can be anywhere between 13.5oz to 2 quarts (400ml to 2L) per minute. Determining flow rate in NFT systems usually depends on channel length; if you have very long channel lengths you will need larger flow rates. You could probably write a thesis on other variables that will determine the required flow rate for NFT, but I find that as long as nutrient solution flows as a shallow film and does not “puddle,” the plants grow well.

After a few minutes of the pump running, the spreader mat wets throughout the tray. I always run the pump and observe the way the water is flowing down the tray. I have found from experience that if the Gro-Tank is not placed on a level floor then some areas of the tray will develop puddles and other parts will remain dry. Leveling out the tank with thin pieces of plywood usually sorts out an uneven floor. Luckily, the floor is fine and I’m happy to “go with the flow.”

Now that I know the flow down the tray is perfect, I cut out the planting holes in the corriboard cover. Corriboard is twin-walled, semi-rigid plastic sheeting. It prevents any light from reaching the roots and can help provide a bit of support for the plants. I’m planting 4 plants in the Gro-Tank, so I cut the holes accordingly.

Providing support for large plants is very important. To support my cucumber plants I use roller hooks, which are a spool of string on a wheel attached to a support hook. The vines are trained up the string with the help of plastic vine clips. When they grow tall enough to reach the wheel, string is let out, which lowers the vine. This support hook is then moved along so the excess vine at the bottom rests on the corriboard. Using this technique, one of my cucumber plants last year was 49 feet (15m) long!

Another popular way to support plants on NFT systems is using netting, which is stretched out horizontally on a frame above the plants so that when they grow into it they are supported by the net.

Before planting onto the tray I remove the plastic wrapper from around the block. When I was learning how to grow using NFT systems I was told by a more experience grower at the time to “leave the wrapper on, otherwise the block will fall apart.” After a few crops I decided to experiment so I slid the wrapper up the block exposing the bottom third. This helped with initial establishment and root growth from the block, which I believed was a factor in achieving a more successful crop. The next crop I decided to risk it and remove the wrapper completely and, instead of the block falling apart, I got quicker establishment and a much better root mat. The block lasted the whole season, staying completely intact. Not surprisingly, I don’t follow this grower’s advice anymore.

Once the roller hooks are in place, I tie the string around the rockwool blocks and place them into position:

The positioning of the blocks on the tray is fairly important: I find staggering the plants works best. This allows the nutrient solution to flow uninterrupted through the mid-section of the tray, which helps once the root mat has built up. I also find that positioning the blocks so that the solution can flow through the grooves on the bottom of the block helps with establishment.

Then I place the corriboard and black and white sheeting back on the tray and lower the plants into their pre-cut holes. I cut the black and white with an X so the folds can be repositioned over the top of the block to cover it and prevent algae growth.

Now that the plants are in their system, I add a “grow” nutrient to the water in the reservoir at an EC of 1.6 and a pH of 5.8. I also add a strong dose of beneficial microbes to the mix to aid with root growth and disease prevention.

I put a submersible water heater in the tank and set the thermostat to 64°F (18°C). I also plugged in the pump, which I will now leave alone to run 24/7. Some growers plug their NFT pumps into a segmental or interval timer. This “pulse feeding” is not the strategy Dr. Allen Cooper conceived when he developed NFT, but some people growing plants with more sensitive root systems or who use large propagation blocks find it helps. It’s very important when implementing pulse feeding that the root mat never approaches a dry state. I have contacted Nutriculture about pulse feeding, and they only recommend that the pump is run 24/7.

These cucumber plants should settle in and start growing vigorously in the next few days. Hopefully I should be picking my first fruits in no time.

February 14th – Vegetative Progress

In 11 days these cucumbers on the NFT Gro-Tank have more than doubled in height and they are establishing well into their system. I have attached them to the string using plastic vine clips, which clip onto the string and hold the vine in place.

I have been routinely checking the nutrient solution pH and EC every 1-2 days. The pH was rising by 0.2 points every 2-3 days. As the pH reached 6.2-6.4, I added phosphoric acid to bring it back to 5.6-5.8. I like to let the pH drift a bit rather than keeping it within a tight range: as long as it doesn’t go higher than 6.5 or lower than 5.5, I’m not worried.

Usually I find the nutrient strength stays stable or increases slightly as the water level drops, but over the past 11 days the plants have used approximately 4 gallons (15L) of nutrient solution and the EC has dropped to 1.2. This is an indication that the plants are hungry, so I top up the reservoir with water and increase the nutrient strength to an EC of 1.8. Whenever I add anything to the tank I disconnect the delivery tube from the tray and submerse a larger 265 gallons/hour (1000L/hour) pump in the reservoir to mix the solution. Once the nutrient solution is corrected, I reconnect the delivery tube.

I always estimate how much water I add back to the tank and take a mental note. Once I know I’ve added back roughly the same volume as the tank holds (16 gallons / 60L) I will consider running the reservoir down to half full, emptying the tank, and refilling it with fresh water and nutrient solution.

Many growers change out the nutrient solution every week, regardless of how much the plants are using. I find this a bit unnecessary and like to base my solution change-outs on how the plants are using it.

The pictures below show how well the roots are extending from the rockwool blocks. Soon there will be a thick mat of roots all over the tray:

February 25th – Flowers and Fruits

It always amazes me how fast plants grow in a productive environment using hydroponic systems, but cucumbers are a whole other ball game. In 11 days they have more than tripled in size and burst into flower. One fruit is already quiet large and will be ready in a few days.

They have also started sending out tendrils and growing side shoots. I remove both but keep a few side shoots for cutting material and put them in my aeroponic propagator.

The greenhouse environment is pretty easy to maintain this time of year. The heating keeps the night-time temperature around 64°F (18°C) and the top vents ensure the day temp does not exceed 77°F (25°C). I have 2 centrifugal humidifiers running to keep the relative humidity between 60-70%.

The plants are now using 1.5-2 gallons (6-8L) of nutrient solution per day and I make sure I top up the reservoir frequently. It’s better to have a full tank as it provides a better buffer for changes in pH and EC. The plants seem happy with the nutrients at 1.8 EC so I’ll leave things be.

One thing I love about NFT is that you don’t have to think about irrigations. The pump is on a slow trickle, and that’s all that matters.

The cucumber fruit develops behind the un-pollinated female flower.

February 27th – Nutrient tweaking

We have had a few warmer, brighter days recently and the plants are loving it. The first large fruit is growing well but is showing signs that I need to tweak the nutrient slightly. You may notice in the picture below that the bottom of the cucumber is slightly more bulbous than the top. The leaves of the plants are also showing a faint yellowing (chlorosis) around the edges. This is a sign that the plant requires more potassium.

To increase the potassium in the solution I add a blooming additive high in potassium and phosphorus at the rate of 1 ml per L. Before adding this I top up the tank with water, add the PK booster, then add more base nutrient to bring it back to 1.8.

You may also notice some loose vermiculite on the tank and floor. I have introduced the predatory insects Phytoseiulus persimilis, which come in a vermiculite carrier. I noticed a small outbreak of spider mite on some peppers on the other side of the greenhouse, so as a precaution I sprayed all the plants in the greenhouse with a natural-contact insecticide that works by suffocation, not chemicals. A few days after spraying, I introduced the predators to clean up any lingering spider mites. I will now introduce a bottle of 2000 Phytoseiulus persimilis every 4 weeks throughout the greenhouse and keep spraying to a minimum.

February 29th – Roots going mad

The roots are really growing well now and starting to develop to form a mat in places. I like to regularly inspect the roots in the NFT system, mainly because you don’t get to do it with other systems!

March 3rd – Plant Training

The plants have now reached the full height of the greenhouse so I let out a small amount of string and lower the vines.

Once I have lowered these a few times I will move the roller hooks clockwise around the Gro-Tank. The stems rest on top of the corriboard. I started using this training technique with my tomatoes and tried it with cucumbers. I find it works pretty well but most commercial growers implement an umbrella training system. I have yet to try it but will get around to it one day.

March 11th – New plants!

The side shoots I took off 2 weeks ago are now rooted plants and are ready for transplanting.

I have to say, aeroponic propagators are great. I have one running continuously in the corner of my greenhouse and just put shoots in and forget about them. 1-2 weeks later you have cuttings. Can’t get any easier.

March 14th – The Bumper Crop

The plants have definitely responded well to the PK booster. The leaves are now dark green all over and the fruits have developed to be large, full and evenly shaped. Some are slightly curved but it adds to the character!

I’ve had 3 cucumbers off the plants so far, but today I picked 6 ripe fruits in one go. From here on out I guarantee I will have so many cucumbers that I will make myself and all my friends sick of the sight of them!

March 26th – Growing on

The cucumbers have been growing well and are now producing ripe fruit at a steady rate of two to three cucumbers every four days. They could try and produce more but I remove developing fruits once there are more than 4 developing on each vine. If there is a high fruit load on the plant, developing fruits will abort. The weather is starting to warm up and the greenhouse is now thriving from the increased day lengths and light intensity. Bring on summer!

Looking Ahead

Recognizing the environmental conditions and adjusting the nutrient solution is part of my ongoing management strategy for recirculating systems. As warmer weather comes along in May and June I will certainly see the EC rising every few days in the reservoir. As this starts to happen I will dilute the EC slightly to around 1.6.to compensate.

Water uptake will certainly go up too so I will have to make sure I regularly top up the reservoir once a day. I also make sure I service my pump every 2 months. This is fairly quick and easy to do and will give me peace of mind that it’s in good working order.

Interested in NFT and want to learn more? If you missed Everest’s introduction to NFT and grower’s tips in UGM0009, check it out here!