One of the most appealing aspects of hydroponics for any grower is the ability to recirculate water and nutrients.  Hydroponics can reduce water consumption by up to 80%!  Not to mention the financial savings to be made on nutrients and additives too.

However, recirculating nutrients brings with it additional challenges that the grower must meet in order to maintain maximum production.  So we asked Michael Christian, an expert consultant to the commercial hydroponics industry, to share his insights into recirculating nutrients effectively to achieve high performance plant growth while conserving water and nutrients.

The days of run-to-waste or open irrigation in horticultural operations are numbered.  Not only is pure water an essential resource that is becoming more and more precious as demand increases, but the minerals dissolved in water are also becoming increasingly scarce as they are mined from a finite resource, processed and distributed over long distances. We are quickly approaching the point where they must be recirculated in closed systems.

As food production becomes more localized, horticultural operations in controlled environments are being constructed in and near cities where food is grown short distances from consumers. Produce that is grown for freshness, nutritive value and purity is winning the day for people who care more and more about their health, their family’s health and where and who grows their food.

It is becoming more evident by the size and number of horticultural operations springing up all over the world, that hydroponics is the technique of choice. Why? Because it is not dependent on soil fertility and is therefore not limited by geographic location. Parking lots work well for hydroponic operations, as does hard pan soil and rooms inside buildings.

There are four basics elements of successful nutrient recirculation.  By “successful” I refer to the creation of optimum conditions in the root zone while still enjoying the efficiencies of maximum reuse of water and nutrients.

First, let’s state the common goals in any horticultural operation:

• Create and sustain an environment to generate healthy, vital, fully realized crops on a CONSISTENT basis.
• Avoid CROP LOSS at all costs. Crop loss can be defined as ANY condition or situation that detracts from our first goal. (Aiming for less than 10% crop loss is standard operating procedure in commercial operations.)

In addition, any successful hydroponic growing operation using a closed system (nutrient recirculation) must adhere to these fundamental basics:

• Pure water source
• Balanced nutrient ions/anions (CF)
• Optimum pH
• Plentiful oxygen availability
• Optimum light/temp/humidity/air circulation/CO2

Just to reiterate, if ANY one of these basics is out, plant performance will inevitably suffer.  It really is as simple as that. That’s why it’s important to understand each one individually and then how they operate in unison.  In this article, I’m going to focus on the first of these fundamentals.

To dial in any system is to get a handle on the variables and control them, period. Each one of the basics is a variable that must be managed… as any grower well knows, plant life has a way of beguiling even the most experienced growers. The better the understanding we have of each basic element, the faster we will be able to determine the one that is out and correct it with minimal drop in performance and / or recovery from crop loss.

Water is a universal solvent designed to carry minerals to the ocean and feed life forms on the way. It is hungry and will pick up any element it runs across and dissolve it in itself. It is guaranteed that the water that runs from your tap has a unique cocktail of minerals which may be fine to drink…but in a hydroponic system, it could be the kiss of death. You won’t know until you find out by analysis.

WATER

Water is the heart of a hydroponic system. If you don’t know what’s in your source water and you’re adding nutrients to it in a closed system, AND if plant performance suffers, you won’t have a clue if your water is the problem.  In addition, you will most likely spend a lot of time, money and effort taking ineffective actions to correct it.  This predicament is easy to avoid.  Simply obtain a water sample and get it analyzed. Actually, a simple analysis measuring the mg/l or ppm of, N,P, K, S, Ca, Mg, Cl, Na, Mn, Fe, B, Cu, Zn, Mb, Bicarbs, pH and EC in your water is all you need. If your plants require an EC of 2.0 and your source water is at .7 EC, you have only 1.3 EC “spare room” in which to add actual plant food. The rest is, who knows?  It’s what you don’t know that usually gets you.

All successful recirculating systems have plastic or stainless steel float valves… why? As water is transpired by plants, additional water is required to top up the tank.  Plants uptake more water than nutrients so if additional top-up water is not added to replace transpired water, the nutrient solution becomes more and more concentrated. Not a great situation if you are aiming for high performance. Large, fast growing, annual plants can drink up to a gallon of water a day especially when it’s hot. If it’s REALLY hot, plants will spend all their energy transpiring and NOT feeding which really adds to nutrient imbalance without a float valve.  So use the biggest reservoir you can handle AND a reliable float valve. (Remember that flood and drain systems will require the float valve to be installed at the drain level in the reservoir.)

With pure, low EC top-up water coming in through the float valve you’ll have no worries.  But if you have source water with a high or unknown EC you can be fairly confident that non-plant food minerals will start to accumulate.  This is because they are not being taken up by the plants. And unwanted or unknown nutrients take up valuable EC… in terms of chemistry, you can bet that there is mischief going on with the precious ion balance that you are trying to achieve with your spare no expense nutrients… plants will only tolerate this situation so long before plant performance suffers. So, TEST YOUR WATER… and avoid all that drama.

If you find your source water to have 40 ppm or more of Cl (chlorides from chlorine) you can off-gas it before adding to your tank or run through an activated charcoal filter. If Calcium and / or Magnesium are high and your water is hard then you will need to use a reverse osmosis (RO) system. Just be sure to run your water through a water softener pre-filter to take out the Ca so your RO membranes last longer. Check with you local garden/hydroponic store… if they are knowledgeable, they’ll have RO units and prefilters in stock. Determine how many gallons per day your plants will be transpiring (say 100) and size one with 25% greater capacity (125) than you need.

Go for a large volume reservoir. Rule of thumb… if you are growing 100 plants and, at their optimum size, they are transpiring half a gallon of water per day, or 50 gallons total, make sure your tank is ten times that (500 gallons). Why? Larger volumes of water stabilize temperature, help nutrient stay in balance longer, and enable the grower to make more subtle adjustments (top-up water added as well as nutrient and pH adjuster) to avoid any spikes in EC or pH that upset ion balance. A good rule of thumb for reservoirs – the bigger, the better.  We have growers with 12,000 plants in their systems running off of 1500 gallon reservoirs who dump their tanks every two or three months with no loss is crop performance. The water in their 1500 gallon reservoir will have been replaced completely with top-up water more than 12 times. This is what you want to aim for. These growers have pure, low EC source water, balanced nutrients, correct pH, large reservoirs, float valves and EC/pH dosers… the ingredients for successful, long term nutrient/water recirculation.

During the life of a plant, as it goes through vegetative growth, flowering and / or fruiting load, different nutrient ions are taken up at different rates. High Nitrogen (N), low Potassium (K) for vegetative growth, and low N, high K for fruiting / flowering growth. Rather than getting anal and freaky and adding all kinds of amendments and extra salts in anticipation of their shifting needs (and perhaps killing them with kindness), go easy! Large reservoirs have enough buffer built in and enough ions to take care of these phases without the balance shifting to detrimental levels and requiring frequent dumps. Particularly if you’re using a nutrient/pH doser (highly recommended), a well balanced nutrient added incrementally to a large volume of pure water will produce phenomenally healthy and robust plants all the way through flowering.

Continue with part 2, where Michael looks at nutrient balance and pH, how they work with pure source water, and how to manage them to steer plant performance.

Everest shares some time-honored heuristics to help beginner growers increase the productivity of their indoor gardens.

1.) Reduce Your Concentration!

Hydroponic growers adjust the pH of their nutrient solution to around 5.8 to 6.2 – this provides the best accessibility to the widest range of nutritional elements.  pH adjuster products are sold in grow stores in concentrated liquid (sometimes powder) form.  However, some growers get lazy and add this stuff neat (undiluted) to their nutrient solution.  This causes nutritional elements to precipitate out of the solution and therefore become unavailable to your plants.  To avoid this, make up a dilute solution of your pH adjusters – 1 part pH adjuster to 100 parts water – and use this instead.  The weakened concentration of your pH up or down will enable you to safely adjust the pH of your nutrient solution without damaging your nutrients!

2.) So Near, So Far …

More light = more yield … but only to a point!  In fact, grow lights can represent a mixed blessing for the indoor gardener.  Sure, they provide the all-important light photons essential for photosynthesis – your plants ain’t growing without them!  But these same lamps also generate a lot of radiant heat!    If your plants grow too close to your lamps they will become too hot and shut down (stop photosynthesizing).  In extreme cases they will scorch and burn and the growth tips will die.  This causes untold stress to your plants and drastically reduces your yields.

On the other hand some growers are overly cautious and raise their grow lights too high, causing their plants to stretch in search of more lumens.  The ongoing aim of every indoor gardener is to get as many growth tips in the “sweet spot” as possible.  This is the area where your plants are just at a safe distance away from your bulbs and receiving maximum light intensity.

Different growers combat this problem in different ways.  All growers should try to move the air in between the tops of their plants and the lamp using an oscillating fan.  Some growers also air-cool or water-cool their grow lights while some put their lights on a mover or spinner.

As well as a light meter, use a thermometer with a remote temperature probe to measure the heat at the tops of your plants.  For many popular indoor crops, the magic number is 82°F (28°C).  What’s the temperature reading at the top of your plants?

3.) Brrrrr!  Using Cold Tap Water!

First off, tap water can contain chlorine and chloramines plus high levels of other minerals (often not in a form that is useful to your plants) and other impurities.  You should always feed your plants with the best quality water you can.  Many professional growers and keen hobbyists take control over their water quality by investing in a water softener and reverse-osmosis water purifier.  Also, you should always make sure that the temperature of your nutrient solution is around 65 – 68°F (18 – 20°C) before feeding it to your plants.  Cold water shocks your plants’ roots and warm water contains drastically lower levels of dissolved oxygen.  If your indoor garden is suffering from high temperatures, using a slightly cooler nutrient solution can help your plants get through until you manage to correct your environment.

4.) Lights++ Environment–

So, you’ve managed to dial in your indoor growing environment with two, three or four lights and you’re growing healthy, happy plants and enjoying regular crops of your favorite veggies all year round.  Great, but don’t make the mistake of thinking you can expand by simply adding more lights!   You need to also consider how this will effect your growing environment.  Firstly, more plants will mean more transpiration, and a need for more CO2.  More lights equals more heat to get rid of.  So if you are thinking of adding more grow lights, make sure you budget for increased air transfer too – you’ll definitely need it!

5.) Unruly Plants

A crucial skill that every indoor gardener needs to learn is how to shape and train their plants so that they make the most of any artificial light source.  You need to let your plants know who’s boss.  Do not grow your plants too large.  Small to medium sized specimens are the way forward for most indoor growers.  Remember, your plants receive exponentially less light the further they are from the lamp.  As most gardeners light their plants from above, a common goal for many indoor growers is for shorter, squatter plants with wide canopies.  Think of a candelabra.  Pruning out the leading growth tip will encourage many types of plants to adopt this formation.

TIP:  If you are growing plants that are sensitive to photoperiod bear in mind that they will not respond immediately when you change your light cycle to induce flowering.  Growers of many plant varieties are often stunned by the amount their plants bolt (or stretch) after changing the day length simulated by their grow lights.  Err on the side of ‘small’ when deciding when to switch your plants from vegetative to flowering mode!

6.) Grow Like A Gardener, Not a Robot

So you think you’ve got your nutrient recipe down and now it’s just a question of making it happen.  But the best growers are always in a state of flux.  They are observing their plants on a daily basis, getting in among them, looking for signs of under / over fertilizing and adjusting their nutrient regimen accordingly.

This is especially important if you are making any chance, whatsoever, to your growing environment.  Improved air exchange or CO2 levels in your indoor garden will cause your plants to grow more vigorously.  The saavy grower observes and recognizes this and increases the strength of his nutrient solution accordingly.

Conversely, if the ambient temperature inside your indoor garden rises above optimum levels (e.g. during the summer months) your plants will inevitably use more water.  You should therefore decrease the strength of your nutrient solution.

7.) Stale Food

Re-circulating your nutrient solution?  Great – you’ll save on precious water resources, not to mention expensive nutrients and additives!  But ask yourself – how often do you really drain your reservoir, then rinse, and replenish with a fresh batch?  Once every week?  Once every two weeks?  Or once every … when you can be bothered?  Younger plants will tolerate less frequent nutrient solution changes than more mature plants.  But if you’re really going to turn on the charm, the time for super frequent nutrient solution changes is during flowering and fruiting.  This is when your plants’ nutrient requirements are at their highest and will benefit most from regular nutrient solution changes.

8.) Poor Propagation

Care early on pays massive dividends later.  Be especially patient and watchful during the propagation stage.  Give your plants time to establish healthy root systems before rushing them into a hydroponics system and flowering them off.  Ensure humidity levels are kept fairly high at 60-80%, especially early on.  This reduces stress on the young plant which, in turn, allows it to focus on that all-important root system.

A plant that has been “hardened off” for five or six days under a fluorescent veg lamp, for instance, still needs to be introduced to a 1000W metal halide with care.  Raise the metal halide 3-4 foot above the plants until you see the first signs of growth.  Break those babies in slowly.  What is often diagnosed as “transplant shock” is often more due to the shock of an increase in light intensity.

9.) Lack of Oxygen

Dissolved oxygen in your nutrient solution is so important we can’t harp on about it enough.  Oxygen in your nutrients promotes root health and speeds up your plants’ metabolism meaning it can grow faster and bloom copiously!  Lack of oxygen in your nutrients, on the other hand, invites all sorts of problems, the leader of the pack being pythium which can destroy your crop in a matter of days.  You can increase levels of dissolved oxygen in your nutrient solution by bubbling air into it – the smaller the bubbles, the better!

10.) Don’t Be a Dirty Sanchez

What’s that carpet still doing in your indoor garden?  Is that decomposing plant matter in the corner over there?  Still not got rid of that bag of old root balls from last crop?  Get a grip on your garden!  Clean as you go.  Keep it as spotless as possible.  Filter all air vents.  Think of your indoor garden as a laboratory and you won’t go far wrong.  The cleaner your growing environment, the fewer viruses your plants have to fight; the more energy your plants can put into their primary mission – growing and blooming!  Cleaning sounds boring, and it is.  But how boring is 10% more yield?  Nuff said.

All sounds rather slick, right? After all, the key to huge harvests is providing a whole spectrum of optimum conditions for your plants – like a series of links in a chain. However, there’s one thing missing from this garden – an essential building block of the sort of harvests your plants want to give you. MICROBES.

Beneficial Microbes

Microbes may be small, but they’re taking off in a big way as indoor gardeners discover new ways to harness the benefits they bring. And leading the pack is John Perrino of Vermicrop Organics, California.  He’s taken some time out from his crazy microbial world to explain what microbes are, what they do, and how we urban gardeners can use them to take our gardens to the next level.

Perhaps I shouldn’t attempt to summarize everything in the first sentence, but here goes: Beneficial microbes increase the efficiency of your nutrients. Put another way, microbes allow your plants to feed more. Even the highest quality nutrients can be made more efficient through microbiology, thus increasing growth, vigor, sugars and yields. Ok, so now you know what beneficial microbes are basically about – but let’s look a bit deeper!

The basic application of beneficial microbiology in soil and hydroponic gardening is simple, really. It kind of falls under the same concept as the food chain. When a plant’s root system has a well-rounded colony of micro-organisms, it has billions of microbes doing a wide range of jobs. Some microbes consume nutrients; some microbes consume the microbes that have consumed the nutrients, thus breaking the nutrients down into a smaller form. This allows the nutrient to be absorbed by the plant more efficiently. Other microbes defend against unbeneficial microbes and keep the plant’s natural defense system at its peak performance level. Each microbe exudes different types of enzymes, proteins, acids and other essential elements. These are the elements needed to break down trace minerals, micro nutrients, and macro nutrients making them immediately available as a food source to the plant. All this really means is an explosive increase in root mass, which equals increased nutrient uptake, which equals bigger yields!!!

So if these beneficial microbes are the building block to a robust and vigorous garden, how do we get them there in the first place? Remember, these little guys are living entities. So the best way to increase the levels of microbes in your gardening system is a fresh brewed, microbial rich solution. We are talking about Actively Aerated Microbial Extracts (AAME). Now, don’t switch off on me just because I’m using acronyms already. I’m telling you that AAMEs are going to change your life!  So listen up!

So What’s Brewing?

Actively Aerated Microbial Tea

Like I said, these little guys are LIVING so they’re going to need feeding. The idea behind AAME is to take an organic material that is high in beneficial aerobic microbes and add essential food sources to raise certain levels of each type of beneficial micro-organism. To get things to multiply, dissolved air and a food source in an aqueous environment is needed. But you have to create the right conditions for these little fellas to multiply at the rates we want – using water straight from the tap is a no-no (because of chlorine levels); reverse osmosis or de-chlorinated water at the perfect temperature and the right type of food sources will allow microbes to multiply at extremely rapid rates.

Beneficial Bacteria

There are three basic groups of beneficial micro-organisms (take note there are tens of thousands of individual types of each microbe in each group). The first to be addressed is beneficial bacteria, the smallest of the three groups. They attach to your root system and feed on unavailable nutrients in and around the root web. Once a bacterium has consumed a nutrient (food), the nutrient is then immobilized (locked inside of the bacteria’s cell wall).  Here the nutrient is broken down with a mixture of different proteins and enzymes. The only way that the nutrients can be unlocked (mineralized) and up-taken by the plant is if the bacteria dies and/or is consumed by a competing micro-organism. Once this process occurs, the nutrients are released in their mineralized form and are immediately absorbed by the plant.

Fungi

Fungi, the second group of beneficial micro-organisms, are much like bacteria in the sense that they too find and immobilize unavailable nutrients. Unlike bacteria, fungi find their nutrients in a completely different way. Fungi live in and around your root web, and grow miniscule root-like strands called “hyphae”; these strands can stretch for many feet. The hyphae stretch throughout the network of the plant’s root system, usually ending on an attachment site on the root. The nutrients are then distributed in a number of different ways. Immobilized nutrients are locked up within the cell walls of the hyphae until the fungal microbe dies and/or is consumed by a competing micro-organism. The nutrients then get mineralized and passed off to the plant as an “easy to absorb” food source. Other fungi trade exudates (carbohydrates, sugars and proteins made by plants and excreted by roots) for water and nutrients; these fungal organisms are known as mycorrhizae. Mycorrhizae work in a symbiotic relationship with the plant’s roots: the fungi brings nutrients and water back to the plant’s roots in exchange for exudates collected from the roots. It’s a win-win situation. The plant then becomes somewhat dependent on the fungi and the fungi cannot live without the exudates from the plant. Through this relationship, many different nutrients are mineralized and absorbed immediately by the plant.

Protozoa

The third type of beneficial micro-organism is the protozoa. Protozoa microbes can be up to 100 times the size of bacteria and fungi. The protozoa feed on mostly bacteria and fungi (protozoas can eat up to 10,000 bacteria a day). When the protozoa consume bacteria or fungi, they mineralize any of the nutrients that were immobilized in the bacteria or fungi. This unlocks any nutrients that have been locked up in the bacteria and fungi. They are then absorbed rapidly as a food source to the plant. Protozoa are at the top of the food chain in the beneficial microbe world. This means there always needs to be a food source, otherwise protozoa will die. Luckily, as the protozoa consume the microbes they consume small bits of organic matter that are processed and exuded as food sources for bacteria and fungi. This helps keep fungal and bacterial populations sustained when conditions are right. If fungal and bacterial populations diminish, protozoa will start to eat their own and eventually die. This is why it is important to replenish microbe populations with a balanced array of beneficial micro-organisms, keeping the food chain in balance and allowing optimal performance.

The only way to get an extremely high multiplication of micro-organisms is through a fresh extracted AAME. Unfortunately, Actively Aerated Microbial Extracts are not available as an ‘off-the-shelf’ product.  To solve this issue, an on-site extraction process with a culture of biology is necessary. This process can multiply the culture of aerobic micro-organisms over 9 billion times in a 24 hour period. When an AAME is used as a foliar spray and as a root inoculant, it will raise the number of micro-organisms that work together in a symbiotic relationship with the plant to increase vigor and yield. With a high diversity of beneficial micro-organisms, plants receive a wide array of the micro-organisms that exude humic, fulvic, amino acids and proteins. These micro-organisms and their exudates aid in immobilization and mineralization of trace elements, micro and macro nutrients.  Microbes have been around for millions of years and now we have the technology to put them to use in our gardens.

Microbe Tea – Q&A

You say actively aerated microbial extracts aren’t available ‘off-the-shelf’ – so once I’ve brewed the tea do I need to use it straight away?
No – think of it like milk. It will last for 12-24 hours if stored at room temperature, or 7-10 days in the refrigerator. Use the smell test. It should have an earthy and fresh aroma if it’s good. Smells damn awful when it’s gone bad!

How much microbial extract brew is good for my plants?
For Soil: Dilute with water at a rate of 75 ml to gallon (1:50). Apply this solution directly to your soil over the root zone.
For Hydro: Use the same dilution ratio but reintroduce more microbial tea solution to your nutrient solution every 7-10 days.

Can I use boiled tap water to make the microbial tea?
No, boiling won’t cut it. You must use non-chlorinated or Reverse Osmosis filtered water. Reverse osmosis machines are more affordable than you think. Check out the Small Boy made by Hydro-Logic.

What do you think about using microbes in your garden? Do you have any tips, tricks or stories to share?