If you haven’t been following along, you might want to take a look at where they started. The flower clusters have been collected and dried. At this point it is suitable for storage, enjoyed by kitties, or in this case, seed collecting. If you look at the dried flowers closely, you can find the seed pods. Here is an example of a catnip seed pod. With a gentle touch, the pod opened, and three tiny seeds emerged. After opening the pods, blowing and shaking to separate the seeds from the chaff, I wound up with a nice pile of seeds, ready for planting. Peace, love and puka shells,

Grubbycup ]]> http://urbangardenmagazine.com/2010/07/catnip-seed-collecting/feed/ 0 http://urbangardenmagazine.com/2010/07/planning-your-grow/ http://urbangardenmagazine.com/2010/07/planning-your-grow/#comments Tue, 13 Jul 2010 01:10:34 +0000 Urban Garden Magazine http://urbangardenmagazine.com/?p=5016 So, you’ve selected where you are going to set up your indoor garden. Now it’s time to spec out exactly what you’re going to need to make it all happen! Your mission, should you choose to accept it, is to provide your plants with all the light they need to grow and bloom, but .. and it’s a big BUT …. you need to maintain your indoor garden’s environment so that it is optimal for plant metabolism.

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.

Jargon Buster

Cation Exchange Capacity – CEC
The ability of a growing media to hold and release positive charged elements (cations). Important nutrient cations include calcium, magnesium, sodium and potassium. Growing media with a low CEC allows cations to be easily leached away whereas growing media with a high CEC withhold cations and act as a long term store.

Air Filled Porosity – AFP
The amount of air space in the growing media.

Water Holding Capacity – WHC
The ability of a growing media to hold and store water.

Coco Fiber (Coir)

What is it? The shredded inner pith of the coconut husk
Where does it come from? Mostly from coconut palms in Sri Lanka and India.
Cost? $13–$50 (3 cu. ft.)
Reusable? Yes
pH: 6.0
CEC: Medium
AFP: Medium
WHC: High
Pros: Naturally contains the beneficial fungus Trichoderma, slowly releases potassium.
Cons: Draws down calcium, easily over-watered.
Irrigation: Manual top-fed, ebb/flow, drip.
Nutrient Requirements: Many growers choose coco coir specific nutrients, others add calcium-magnesium additives.
Usage notes: Coco coir comes in various compressed forms: bricks, bales and slabs. Also available in ready to use loose fill bags.

Coco Chips (Croutons)

What is it? Cube-shaped coconut husk chips
Where does it come from? Mostly from coconut palms in Sri Lanka and India.
How much? Around $65 (3 cu. ft.)
Reusable? Yes
pH: 6.0
CEC: Medium
AFP: High
WHC: Very low
Pros: Naturally contains the beneficial fungus Trichoderma, slowly releases potassium, natural alternative to clay pebbles.
Cons: Tends to float when flooded, needs frequent irrigation.
Irrigation: Ebb/flow, drip
Nutrient Requirements: When using on their own consider incorporating a calcium-magnesium additive to your nutrient regimen.
Usage notes: Excellent for mixing with coco coir fiber to lower the WHC, ideal for using as a mulch on the top of other growing media; excellent for growing orchids.

Vermicrop’s Coco Not

What is it? a soilless medium made from the bark of sustainably harvested redwood trees blended with the fibers of a Kapok fruit
Where does it come from? Mostly California
How much? TBC
Reusable? Yes
pH: Normally 5.5 but increased to a range of 6-7 with oyster flour.
CEC: Low
AFP: Medium
WHC: Low
Pros: Locally made, natural and organic
Cons: Low water retention
Irrigation: Manual top-fed, ebb/flow and DWC
Nutrient Requirements: no special requirements
Usage notes: Does not need to be rinsed but should be fed water only for the first 5-10 days

Perlite

What is it? Superheated and expanded volcanic glass
Where does it come from? Produced worldwide but now mostly in China.
How much? $45 3 cu. ft.)
Reusable? Yes
pH: Neutral
CEC: Low
AFP: High-medium
WHC: Medium
Pros: Lightweight, readily-available, great for rooting cuttings
Cons: Has no buffering qualities, leaches nutrient easily and tends to float when flooded
Irrigation: Manual top-feed, Drip, ebb/flow and aeroponics
Nutrient Requirements: Naturally Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Perlite is available in many grades. 4-12mm is most common for horticulture. Perlite can be used alone or amended into coir, vermiculite, peat moss, or soil mixes to improve aeration/drainage. A 50/50 mix of perlite and vermiculite is ideal for rooting most cuttings.

Vermiculite

What is it? A natural micaceous mineral that expands when heated
Where does it come from? South Africa, China, USA, or Brazil
How much? $40 (3 cu. ft.)
Reusable? Yes
pH: Neutral
CEC: Medium
AFP: Medium-Low
WHC: High
Pros: Lightweight, excellent buffering qualities
Cons: Easily over-watered,
Irrigation: Drip, ebb/flow, and manual top-feed
Nutrient Requirements: Naturally Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Used neat, vermiculite holds too much water for most plants’ needs. Amendment is necessary (see also perlite)

Diatomaceous Earth

What is it? A sedimentary rock made from fossilized remains of diatoms
Where does it come from? Worldwide
How much? $55 (40 litres)
Reusable? Yes
pH: Neutral
CEC: Medium
AFP: High
WHC: Medium-low
Pros: Does not roll, contains silica, sterile (but harbors beneficials well), holds more water than clay pebbles
Cons: Heavy weight; releases sediment
Irrigation: Ebb/flow, drip, DWC, aeroponics
Nutrient Requirements: No special requirements. Diatomite contains silica, which is absorbed into plant tissue and helps improve plant structure and resistance to pests / diseases
Usage notes: Prewash, as sediment may clog drippers. Many growers mix it with hydroton; this makes for improved air / water ratio. Also acts as a good killer of soil dwelling pests.

Sure To Grow

What is it? Recycled polyethylene terepthalate (PET) fibers
Where does it come from? North Carolina (USA)
How much? $60 (9 6”x6” blocks + 3 slabs)
Reusable? Not recommended by the manufacturer
pH: Neutral
CEC: Low
AFP: Medium-High
WHC: High – can hold up to 82% of its total volume when saturated
Pros: Sterile, lightweight, contains no residual particulates, recyclable
Cons: Larger plants will need extra support (i.e., staking / screening)
Irrigation: Top-feed, drip (except waterfarm systems), ebb/flow, DWC, NFT, aeroponics
Nutrient Requirements: Inert medium, suits most hydroponic nutrient solutions.
Usage notes: STG comes in starter cubes, grow blocks, loose-fill cubes, flock, net pot inserts, capillary mats, and starter tray mats.

Rockwool

What is it? Heated basalt rock spun into a fibrous, lightweight material
Where does it come from? Mainly Europe
How much? $80 (9 4”x4” blocks + 3 slabs)
Reusable? No
pH: 8.0
CEC: Low
AFP: Medium
WHC: High
Pros: Lightweight, sterile, recyclable
Cons: Skin irritant, needs pre-treating before use.
Irrigation: Manual top-fed, ebb/flow, drip, DWC, NFT
Nutrient Requirements: Inert medium; requires pre-soaking, suits most hydroponic nutrient solutions.
Usage notes: Presoak with a water and pH Down solution of no less than 5.5 pH. After soaking, allow to drain and irrigate with a suitable nutrient solution before planting. Rockwool comes in starter cubes, plugs, blocks, slabs, mats, and loose-fill (absorbent or repellent granulate).

Clay Pebbles

What is it? Heat-expanded, round-shaped clay pebbles of mixed sizes (8-16mm most commonly used)
Where does it come from? Worldwide, mainly Europe
How much? $70 (100 liters)
Reusable? Yes
pH: Neutral
CEC: Low
AFP: High
WHC: Low
Pros: Difficult to over-water, maintains an excellent air to water ratio when irrigated correctly.
Cons: Bulky, nutrient precipitation on outer surface is common, needs washing before use
Irrigation: ebb/flow, drip, DWC, aeroponics
Nutrient Requirements: Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Spills can be messy. Wash thoroughly before use to remove the small clay particles, this messy sediment may clog pumps and drippers.

Growstones

What is it? Porous rocks made from recycled glass beverage containers received from either the landfill or another source collecting and processing waste glass.
Where does it come from? Santa Fe, NM (USA)
How much? $80 (3.75 cu. ft.)
Reusable? Yes
pH: Neutral
CEC: Low
AFP: High
WHC: Medium-low
Pros: Lightweight; 35% water-holding capacity while maintaining an 85% air-filled porosity; capillary action up to 6″ (15 cm).
Cons: Bulky, needs frequent irrigations.
Irrigation: ebb/flow, DWC, aeroponics.
Nutrient Requirements: Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Wash thoroughly before use to remove small particles. Ideal for using neat or for mixing into coco coir, peat and other growing media.

Peat

What is it? A naturally occuring deposit of partially decomposed vegetation, mainly mosses.
Where does it come from? Peat forms in wetland areas of North America, Ireland, Russia and Northern Europe
How much? Varies
Reusable? Yes
pH: 3.4 to 4.8
CEC: Medium – High
AFP: Medium
WHC: Medium-high
Pros: Readily available,supports beneficials, excellent at holding nutrients and has a good air to water ratio.
Cons: Limited natural resource, extaraction is harmful to the environment, does not re-wet well if left to dry out, naturally acidic.
Irrigation: Manual top-fed, drip
Nutrient Requirements: ‘Soil’ specific nutrients are recommended.
Usage notes: Peat is found in many grow stores in pre-mixed bags or bales. It usually has perlite added for improved drainage, a wetting agent for good re-wetting, and dolomite lime to raise the pH.

SteadyGROW

What is it? Phenolic resin and air
Where does it come from? USA and Canada, out of materials from India
How much? $41 (9 4″x4″ blocks and 3 slabs)
Reusable? Not recommended by manufacturer
pH: 6.0
CEC: Low-medium
AFP: Medium
WHC: High
Pros: No algae growth, sterile
Cons: Reports of phenolic resin’s carcinogenicity by NTP, IARC, and OSHA
Irrigation: Manual top-fed, ebb/flow, DWC, and NFT
Nutrient Requirements: inert medium, suits most hydroponic nutrient solutions.

Usage notes: Comes in two varieties: SteadyGroPro (low water retention) and SteadyGroPro H+ (high water retention)

Water (DWC, NFT)

What is it? Although pebbles may be used to anchor the stem, the plant’s bare roots are in direct contact with an oxygen-rich nutrient solution.
Where does it come from? Good question. Obtain a water analysis.
How much? 0.1 cent per liter for domestic volumes, and 0.03 cents per liter for industrial volumes.
Reusable? Yes (in recalculating systems)
pH: varies; distilled water is 7.0 pH
CEC: N/A
AFP: % of dissolved O2 increases as temperature drops
WHC: N/A
Pros: Readily-available, roots love it when properly aerated and at the correct temperature (64-70F)
Cons: Poor buffering capacity, pH-fickle, may harbor pathogens
Irrigation: DWC, NFT
Nutrient Requirements: inert medium, suits most hydroponic nutrient solutions.
Usage notes: Requires constant aeration to maintain dissolved oxygen levels necessary for healthy roots.

Sand

What is it? a naturally occurring granular material composed of finely divided rock and mineral particles
Where does it come from? Varies
How much? $10-$15 (3 cu/ ft.)
Reusable? Yes
pH: Varies according to its mineral content
CEC: Low
AFP: Low
WHC: Medium
Pros: Cheap, excellent drainage
Cons: heavy, must be irrigated on a schedule for optimal results
Irrigation: manual top-fed, ebb/flow, drip
Nutrient Requirements: Most are inert, some may contain lime. Suits most hydroponic nutrient solutions.
Usage notes: Wash thoroughly before use. Check and correct pH of runoff prior to planting.

Sawdust

What is it? Wood shavings
Where does it come from? Varies, usually as the byproduct of sawmills and retail hardware stores
How much? If you ask nicely, they may give it to you for free!
Reusable? Not recommended
pH: 6.1
CEC: Medium
AFP: Medium-High
WHC: Medium
Pros: Inexpensive, lightweight, biodegradable, harbors beneficials
Cons: pH-fickle, needs frequent irrigations
Irrigation: Manual top-fed, ebb/flow, DWC
Nutrient Requirements: Diligent pH monitoring and adjusting is of the essence. Suits most hydroponic nutrient solutions.
Usage notes: Best used for cycle crops and annuals.

Gravel

What is it? Any loose rock that is larger than 2 mm (0.079 in) in its smallest dimension (about 1/12 of an inch) and no more than 64 mm (2.5 in).
Where does it come from? Worldwide, mostly USA
How much? $12-$15 (3 cu. ft.)
Reusable? Yes
pH: neutral
CEC: Low
AFP: Medium-high
WHC: Low
Pros: Inexpensive, easily-available
Cons: Heavy weight, bulky
Irrigation: Ebb/flow, DWC, Aeroponics
Nutrient Requirements: Mostly inert medium, may contain soluble minerals. Suits most hydroponic nutrient solutions.
Usage notes: Wash thoroughly before use. Gravel is an old school hydroponic substrate.

by Eliab Lozada

“The American print and TV media has never been very good. These days it is horrible. If a person intends to be informed, he must turn to foreign news broadcasts, to Internet sites, to foreign newspapers available on the Internet, or to alternative newspapers that are springing up in various cities. A person who sits in front of Murdoch’s Fox “News” or CNN or who reads the New York Times is simply being brainwashed with propaganda.”

- Paul Craig Roberts, Information Clearing House

On May 31st Israeli warships and helicopters surrounded a Turkish ship, called the Mavi Marmara, in international waters. Moments later Israeli commandos stormed the humanitarian aid vessel and brutally shot at least 16 people dead (a figure that has been revised in subsequent reports, without explanation or comment, to only nine dead). At least 30 more crew members aboard the aid ship were wounded. International law defines this act as “piracy.” Israel claims that the crew members on board reacted violently, but nearly all video footage taken on board the Mavi Marmara was confiscated by the Israeli military. Israel then released its own footage of the raid, purportedly showing crew members violently resisting the Israeli soldiers. This footage has since been debunked as fraudulent with citations of key differences between the ship shown on the video and the actual Mavi Marmara.

So what really happened? Well, if you choose to rely on the mainstream media for your McFacts, you may well have received an entirely different happy meal.

Perhaps you are more familiar with those “humanitarian workers” as “armed activists possibly linked to al Qaeda” or “vicious anti-Semites professing pacifism, seeing with hate.” The Calgary Herald even goes as far as to ask, “Was it a peace convoy or a propaganda stunt gone horribly wrong?” We fail to see how an attempt to deliver food and medical supplies to millions of starving people in Gaza amounts to “propaganda.” (And it’s not often Freudian slips are immortalized in print!)

Noam Chomsky wrote on June 8th, “Israel’s pretext for the attack was that the Freedom Flotilla was bringing materials that Hamas could use for bunkers to fire rockets into Israel. The pretext isn’t credible. Israel can easily end the threat of rockets by peaceful means. The background is important. Hamas was designated a major terrorist threat when it won a free election in January 2006. The U.S. and Israel sharply escalated their punishment of Palestinians, now for the crime of voting the wrong way.”

The Gaza Freedom Flotilla consists of several multinational, civilian ships supplying humanitarian aid to the population of the Gaza Strip, which has been under tight siege since 2007. These people are not “terrorists.” Neither are they linked to mythical terrorist organizations. All the aid ships were inspected before departing and were found to contain humanitarian aid only; mostly medical and reconstruction supplies.

Robert Fisk, in his recent column for The Independent, lays out the effectiveness of US/Israeli propaganda:

“On that aid ship,” a Sri Lankan texted me this week, “I had my niece, nephew and his wife on board. Unfortunately Ahmed (20-year-old nephew) got shot in the leg and now treated (sic) under military custody. I will keep you posted.” He did indeed. Within hours, the press was at his family’s home in Australia, demanding to know if Ahmed was a jihadi – or even a potential suicide bomber. Propaganda works, you see.”

These crimes are nothing new for the Israeli military – even though the media will soon choose to forget that they ever took place. For decades, Israel has been hijacking boats in international waters, killing and kidnapping civilians, taking passengers to secret prison/torture chambers, sometimes holding them hostage for years. The UN Human Rights Council has repeatedly condemned Israel for its criminal actions. So you might well ask how Israel assumes it can continue to carry out these crimes with such impunity. Why do the US and Europe continue to provide them with such unrelenting support?

Grassroots movements are emerging across the world to fight for truly fair and balanced news media. These movements are united in their rejection of the mainstream media’s portrayal of global events.

Get your news from more than one source! (Not just Urban Garden Magazine!) Try:

www.culturesofresistance.org
www.informationclearinghouse.info
www.commondreams.org
www.democracynow.org
www.truthdig.com

Okay, we’re going to build an organic, aquaponic living wall in no time at all! Aquaponics means that we feed the fish in a tank, and their poop is pumped up to the plants. The plants feed and filter the nutrient rich water, and the glorious cycle continues. The plants are going to grow in sphagnum moss. It’s very pleasant to work with, and the plants love it! The water from the aquarium provides them with all the high quality organic fertilizer they need.

Supplies:

• Culture tray — 31″ l x 16″ w x 1.5″ h (79 cm x 40 cm x 4 cm)
• Thirty flat-head nuts (4 mm x 16 mm) and bolts
• 6.5 feet (2 m) plastic net
• 2 pounds (0.9 kg) of sphagnum moss
• 6.5 feet (2 m) irrigation pipe – 0.5″ (13 mm)
• A pipe elbow and cap
• 4 adjustable flow emitters
• A submersible aquarium pump – 250 gallons (946 l) per hour
• A complete aquarium
• Twenty small plants in 2 inch (5 cm) pots

Tools:

• A drill and a 0.1575″ (4 mm) drill bit
• 5 gallon (19 l) container
• A screwdriver
• A pair of sharp scissors

Step by step:

Our goal is to install a vertical hydroponic garden above a small fish tank. As already mentioned, besides being a beautiful decorative feature, the plants will act as a water filter for the fish, regularly consuming nitrates and other compounds from the fish droppings. This is the cornerstone principle of ‘aquaponics.’ The plants should maintain an acceptable nitrate level in the water to keep the fish happy without having to replace the aquarium water so frequently.

Set up

First, let’s take a look at the heart of the system: the culture tray, plastic net and sphagnum moss growing media.

The main task is to move water from the fish tank to the top of the vertical wall and arrange it so that the wall is irrigated evenly. We will achieve this using a pump, some irrigation pipe, some dripper holes and emitters. To mount the irrigation pipe, cut a section of pipe roughly the same width as the tray. Connect one end to an elbow joint and the other to a stopper cap. Drill a series of evenly spaced holes in a straight line along the bottom side of the pipe and fix the emitters.

After spacing the emitters, drill four holes into the tray so the emitters can clip into place.

Place the culture tray above the aquarium and secure it to the wall with two mounting brackets. You can also add extra stability with side hooks if you wish.

The irrigation line is now completed. Arrange the pump and pipe so that the pump is at the bottom of the aquarium.

Now it’s time to prepare the substrate. Crumble the sphagnum moss and place it in a watertight container.

After the moss is broken into small pieces, give it a heavy watering, then press it lightly to drain off any excess liquid.

Once the moistened sphagnum moss has changed color and has drunk a large quantity of water, you will notice that it becomes spongy. In fact it almost recovers the elasticity of living sphagnum!

Insert the sphagnum moss into the culture tray and press down on it firmly to remove any lingering excess water.

Continue to push the moss into the tray until it’s uniformly filled.

When the tray is full, press the moss down again. It’s really important to ensure that it’s consistently distributed throughout the tray. The level of the moss should be slightly higher than the edges of the tray—your aim is to have the moss pressed down firmly when you fix the plastic netting in place over the top. After all, you don’t want any moss falling out of the wall into the tank!

Cut a piece of screen, slightly larger than the tray (this will make your life easier,) and lay it on top.

Fix the net to the rim of the tray by drilling holes in the rim (roughly 4″ (10 cm) apart.) Once all the holes are made, fix the mesh on to the tray with nuts and bolts or, alternatively, some wire.

After attaching the upper edge, fix the sides in the same way. When fixing the net, proceed from the parts that are already fixed as this will give you a better fit. After completing one side, fix the opposite side in place too, stretching out the screen in both directions, horizontally and vertically. The elasticity of the plastic netting can be used to your advantage. Tightening properly will prevent the substrate from collapsing but do not over tighten or the stitches in the netting will tear.

Finally, fix the netting into the bottom edge of the tray—it should be positioned in the same way as the top edge. Once the net is fixed all around the edges of the tray, cut off any excess net from the edges of the tray.

The tray is ready to receive plants!

Figure out how you are going to arrange your plants first. Here we’ve chosen Alocasia (elephant ear), Nephrolepis (fern), Scindapsus (pothos), Ficus pumilla (creeping fig), Chlorophytum (spider plant) and Asparagus.

To prepare the plants, wash off as much existing media from their roots as possible. This can be done by soaking the root-ball of each plant in water and moving it back and forth.

Cut a square in the netting just large enough to insert the root-ball.

Press a hole into the moss by inserting two fingers right down to the bottom of the tray.

The hole is now ready to receive the plant. The only job that remains is to introduce the plants into the tray. Once planted, pack the base of the stem with sphagnum moss to properly secure the plant in place and ensure proper hydration. Repeat this process until all your plants are inserted. Don’t overcrowd the installation—you should think positively and leave room for some growth!

When the installation is finished, straighten the tray and check that all the plants are securely in place.

It’s now time to put the table above the aquarium, fix it to the wall, and connect the irrigation pump! Exciting times indeed! The first watering cycle will serve to re-moisten the moss and ensure that the water is effectively running. All the run-off should make its way back into the aquarium of course!

Now most of the remaining work is up to Mother Nature! The plants should be irrigated a few minutes per day, just long enough to let the water flow from the top to the bottom and back into the aquarium. When water starts to drain from the tray, it means that you have sufficiently watered your plants. It should take around three or four minutes to complete this process.

Maintenance

The water will become slightly orange in color because of the sphagnum moss. To minimize this coloration, you can add some active carbon for aquariums into the sphagnum moss if you wish.

The sphagnum moss is acidic and can affect the pH level of the water. So, to run an aquaponic system properly, the pH should be monitored and maintained at level seven. This is also something that should be considered when choosing the type of fish for your aquarium.

The water temperature should be held in a range of 64°F to 71°F (18°C to 22°C).

Consider using a light foliar spray for your plants once a week to keep them in tip top condition.

Well, we thought enough was enough. So we’ve put together this quick, no-nonsense and impartial guide to understanding how to measure the strength of your nutrient solution so we can all be clear about what we’re talking about – once and for all!

Worldwide, there is one standard parameter for measuring pH, but there are many more for measuring the strength of a nutrient solution. The two major measurements in use today are:

• EC  – Electrical Conductivity
• TDS – Total Dissolved Solids

EC

First, some basic concepts: when we add nutrients to water we create a nutrient solution. The more nutrients we add, the more concentrated the solution, and the more readily it will conduct electricity. So, the electrical conductivity (EC) of your nutrient solution can be seen as a quick and easy measure of how much nutrient is dissolved in it overall. Put another way, measuring the conductivity of a solution means measuring the electrically charged ions. Pure water will not conduct anything, but tap water already contains other minerals, metals and salts so it does conduct a small amount. Remember, it’s always important to measure your source water to see what you’re dealing with.
To measure conductivity we can use an EC meter, also known as a conductivity meter. It has two electrodes that, when dipped in the solution, measure its electrical charge by passing a small charge between them.

What is EC measured in?

Siemens are to “electrical conductivity” what feet or meters are to “length” – it’s the unit of electrical conductance. It’s important to get this distinction really clear in your head right now. EC is the scale (also known as the ‘parameter’) and siemens are the units. When dealing with the very low amounts of conductivity associated with EC in nutrient solutions, the preferred units are mS (millisiemens; one thousandth of a siemen) and µS (microsiemens, one millionth of a siemen) per centimeter.
EC is the most widely accepted measurement for the strength of nutrient solutions, and is the standard in Europe and many other parts of the world. The one notable exception is North America which prefers to use TDS.

TDS

TDS (Total Dissolved Solids) is the preferred scale for measuring the strength of a nutrient solution here in North America. It quantifies the concentration of dissolved solids contained in a solution. TDS is arguably a better parameter for measuring nutrient concentration, since it measures by quantity or weight.  In other words, you can have two glasses of water with equal parts TDS but different EC levels, since one glass may have more or less conductive elements (say salt vs. calcium.)
The problem is that a true TDS measurement is difficult to achieve (and would also defeat the purpose since evaporation is required).  Therefore, if one wants to eliminate the estimating that the conversion factor does, an EC meter is better.  If we lived in a perfect world, and every nutrient company and TDS meter used the same non-linear scale, a TDS meter is preferable.  But since there are so many different variables, an EC meter lends itself to more consistency.

What is TDS measured in?

Once again – make sure you get your head around this – TDS is a scale, or a parameter, just like time, length, temperature and volume. The unit of TDS is ppm (parts per million.) A TDS reading of 50 ppm means there are 50 milligrams of dissolved solids in each liter of water, or 50 mg/l.

How do TDS Meters work?

If EC meters (conductivity meters) work by measuring conductivity in a nutrient solution and expressing this in siemens, how to TDS meters work out how many parts of nutrient there are per million of water? Sorry to break it to you, but the answer is, they don’t.
TDS meters work in actually the same was as EC meters! Both measure the electrical conductivity of the nutrient solution they are dipped in. The difference is in how the information is displayed.
A TDS meter will measure the electrical conductivity, and then use a conversion factor to display the strength of the nutrient solution in ppms. Now here’s the slightly tricky bit. The conversion factor from EC to TDS varies from meter to meter.

Conversion Factors

TDS NaCl

NaCl is a conversion factor based on Sodium Chloride (regular table salt.)
The conversion factor range is 0.47 to 0.5.
Non-linear meters based on NaCl typically use: 0.5 x the EC level (if converting from µS to ppm or mS to ppt) or 500 x the EC level, if converting from mS to ppm.
TDS 442™

442™ or Natural Water™ is a proprietary scale based on properties of naturally occurring fresh water.  The 442™ part is an abbreviation of 40% sodium sulfate, 40% sodium bicarbonate, and 20% sodium chloride.
The conversion factor range is 0.65 to 0.85.
Non-linear meters based on 442™ typically use: 0.7 x the EC level (if converting from µS to ppm or mS to ppt) or 700 x the EC level, if converting from mS to ppm.

TDS KCl

KCl is a conversion factor based on Potassium Chloride.
The conversion factor range is 0.5 to 0.57.
Non-linear meters based on KCl typically use: 0.55 x the EC level if converting from µS to ppm or mS to ppt) or 700 x the EC level, if converting from mS to ppm.

TDS 640

A less popular conversion factor.
The conversion factor range is 0.64 to 0.67.
Non-linear meters based on 640 typically use: 0.64 x the EC level if converting from µS to ppm or mS to ppt) or 640 x the EC level, if converting from mS to ppm.

Yes, four different possible conversion factors means that four different meters that give measurements in ppm may all give different readings from the same solution! However, all EC meters should give the same reading in the same solution as there’s no conversion factor necessary.
I know, I know … TDS sounds like a confusing thing – but it’s really just a measure of the total ions in solution. For every gallon of water you have X mg’s of stuff in it. If one of your friends starts talking about their nutrient solution in terms of TDS, be sure to find out what scale they are using. Many growers, especially in Europe, in an effort to avoid confusion, use EC. If you are still confused, contact the manufacturer of your nutrients and find out what they recommend. Remember to ask them what TDS scale they use if they give you dosages in terms of ppm.
Likewise, if you are working with a TDS meter that only has a ppm display, remember you need to be sure of the conversion factor being used. TDS comes into its own when you need to measure individual elements in applications such as nutrient and water quality, tissue analysis results and soil analysis. Results from these laboratory tests will give individual elemental readings in ppm or mg/l. Remember, a TDS meter will only give you an approximation of the overall nutrient concentration, based on the conversation factor used.
Below is a table to show the relationship between the various methods of displaying the strength of a nutrient solution.

Jargon Buster

• EC = Electrical Conductivity
• TDS = Total Dissolved Solids
• PPM = Parts Per Million
PPT = Parts Per Thousand
• µS (or µS/cm) = micro-Siemens (one millionth of a siemen.)
• mS (or mS/cm) = milli-Siemens (one thousandth of a siemen.)
• NaCl = Sodium Chloride (EC-to-TDS conversion – EC x 0.5)
• KCl = Potassium Chloride (EC-to-TDS conversion EC x 0.55)
• 442 = 442 Natural Water™ (EC-to-TDS EC x 0.7)  (The “442” is an abbreviation for 40% sodium sulfate, 40% sodium bicarbonate and 20% sodium chloride.)

Making Sense of your Meter

Here are some popular TDS meters along with their conversion factors, where applicable.

Towards A Clearer World

There is a drive towards some standardization in the hydroponics industry to create less head work for all concerned. Nutrient manfacturers, if you specify dosage with in ppms, please also state what TDS scale you are using. This includes calibration fluid!

by Everest Fernandez

1. Insulation

The better your indoor garden is insulated, the easier it will be to grow in it. Many indoor gardens suffer from excessive heat problems, especially during the summer months when ambient temperatures are considerably warmer. High temperatures can slow plant metabolism and stress your plants causing them to respond in unfavorable ways. This isn’t just a euphemism for death either. Many culinary herbs and lettuces will ‘bolt’ into premature flower and seed production if they are forced to endure prolonged high temperatures. Similarly, if nighttime temperatures drop too low this invariably stunts growth and bloom. Cold, poorly insulated rooms cause very slow growth, poor water and nutrient uptake, and low temperatures can cause further undesired changes in your plants – e.g. chili peppers will fruit prematurely if nighttime temperatures drop below 65°F (18°C). So remember, the better a potential grow space is insulated, the greater the “base level” of protection from extremes in ambient temperature and the less money and effort you will have to invest into controlling temperatures in your indoor garden. Is it really worth all the energy, money and time investing in a state-of-the-art cooling system to chill your grow lights in a ramshackle loft apartment in Los Angeles, or will it simply be cheaper and easier in the long-run just to move to somewhere more suitable? Now’s the time to ask yourself these questions!
Take a moment to think about the general characteristics of your house or apartment. What is it made of? Wood, stone, brick, concrete? How thick are the walls? What type of insulation has been used? Not sure? Ask yourself these questions: Does your home already get too hot in the summer, and is it a pain to keep warm during the winter? In either case – not a good sign! What about your indoor garden’s location within your home? Is it in a room at the top of the house that has an external wall facing the sun all day? Or is it cool and shady? Hopefully you’ll be nodding at the latter.
Insulation is measured by its R value. The higher the R value, the more effective the insulation. Some of the best insulation materials are:

• Blown in Cellulose Insulation – R3.70 per inch
• Fiberglass Insulation – R3.14 per inch
• Expanded Polystyrene – R4.00 per inch

Many growers report their greatest successes from gardens located in a cellar or basement. And there is a good reason for this – the amazing insulation qualities of the earth! So whether you are storing wine or growing food to accompany it, a basement can be ideal. (Just don’t do both at the same time!) Basements can be subject to high humidity, so you may also need to invest in a dehumdifier. Their subterranean location can make getting rid of spent nutrient solution more tricky than usual.

2. Ceiling Height

Look up. What do you see? Hopefully it’s a ceiling high above you, well out of reach. 8 ft ceilings are okay. 10 ft or more is a godsend for any indoor gardener – that extra air volume makes your life so much easier, believe. Not only do you have more height to grow climbing varieties of tomato, peas and beans but, once again, you will find your temperatures and CO2 levels far easier to maintain and control. Additional ceiling clearance means that you also have the option of raising the height of your grow trays so that your garden is easier to work in, with the additional benefit of making drainage / nutrient return easier to manage using plain old fashioned gravity alone.

3. Water

Your plants want a lot of things – some of them desirable, some of them essential. One thing they can’t possibly go without is water! Prior research into the water quality of the area will be useful. Generally, the softer the water the easier it is to grow with. Hard water can still be used to produce productive crops but a lot of growers now use RO machines to remove the carbonates and other contaminants. Indoor gardeners commonly use a large container such as a rain collection barrel to mix and store their nutrient solutions – often referred to as a reservoir or ‘res.’ Ideally this should be kept in an adjacent room so that your nutrient solution is not subject to the temperature changes in the growing area itself. Think about where you are going to store your nutrient solution and its location relative to your nearest water source. Running hoses across landings or up and down stairs is a pain and invariably leads to leaks and spillages. I’ve lost count of the amount of times a hose end has flopped itself out of a res, spewing water all over the floor. It’s a nightmare scenario! Filling up your res is a regular chore, so make your life as easy as possible with sensible planning and, ideally, a dedicated tap right above it. The less hose pipe in your life, the better! (My wife hates seeing hose pipe running from room to room!)

4. Drainage

It’s not just about getting water into your indoor garden. What about getting it out? Is there an easy way to drain your spent nutrient solution? Once again, it’s all about making life easy for yourselves! Most growers use a submersible pump and hose to drain their reservoirs. Some growers recycle their spent nutrient solution by using it on their outdoor gardens too.

5. Ventilation / Windows

Unless you are growing in a sealed room with AC and CO2 supplementation, you are going to need to install some sort of ventilation in order to keep on top of temperature, humidity and CO2 levels in your indoor garden. Many novice growers grossly underestimate their ventilation requirements. Remember, all that hot, CO2-depleted air needs to go somewhere. And then it needs to be replaced with cool, clean, fresh air of course! Simply pumping air out of your grow tent back, for example, into the same room it’s situated in does not count as adequate ventilation. We need to transport the old air well away, and keep the fresh air … well fresh!
Think of your ventilation in terms of input and output. In order to maximize your control over your indoor garden’s environment you should always spec the size of your output (aka extraction) inline fans bigger than your input. More air being pumped out than being pumped in creates a ‘negative pressure’ which ensures zero air and odor leaks and also increases the efficiency of your input fans. If you are using carbon filters with your input or output fans, remember to take into account their diminishing effect on their respective fan – often a 25% reduction factor is used but depending on the make and age of the filter it could be anywhere between a 10 – 30% reduction.
Extraction has the most positive effect on reducing temperature when it is removing air from the top of a room – as hot air rises. Ideally it should be vented out of the property to the outside world. As far as intakes are concerned, be aware of where you are taking your air from. Drawing ice-cold air direct from sub-zero temperatures outdoors and blowing it directly on your plants is not clever. It’s a far better option to draw air from a cool room in your home instead. Be sure to use a bug screen on all air intakes. Yes, you will have to spec up your fan by 10-30% to counter the increased air resistance, but at least you won’t be drawing bugs, mold spores and pollens into your indoor garden!

Size and Accessibility

Remember, you need space to work and get around in your garden. Ideally you should be able to access your growing area from all sides, allowing you to inspect all your plants with the same level of care and precision. Overfilling your garden, however tempting, will quickly turn maintenance into an onerous, back breaking exercise. Remember, your hobby should be a pleasure, and not a chore!

Pest Protection

All carpet should be removed from any space where you are planning to grow as it can harbor no end of pests and pathogens. If removing the carpet is not an option, you can lay down protective plastic sheeting. Remember, your indoor garden should be as easy as possible to keep squeaky clean. A laminate floor that is easy to mop is ideal. Air intakes should use a bug screen so that you don’t inadvertently suck bugs into your garden.

Next issue: Electrical Safety in your indoor garden – so important, we need to tackle this subject on its own!

DESIGNING A HYBRID AERO-FOG-SWC SYSTEM

This system irrigates each plant in three different ways, yet it’s blissfully simple. It’s essentially a modular re-circulating system which incorporates: shallow water culture (SWC) aeroponics misters and aeroponic foggers.

Each plant gets the VIP treatment, basking in a 20 gallon Rubbermaid container! Wow! There are 70 plant containers in total. They are all joined together via ¾” tubing. Nutrient solution is pumped from an underground 55 gallon reservoir with a 1546 gallon per hour pump to the middle of each container. Within each container there’s a large ¾” flexible PVC irrigation ring with 3 x 180° misting nozzles ready to rumble. When the misters are on, the container gets filled with small droplets of nutrient solution, the droplets that don’t get absorbed by the roots fall to fill the bottom of the containers. As the container fills past 2.5 gallons, the solution reaches an overflow tube, from here it returns through ¾” PVC pipe back to the main reservoir.

After running a few tests Devin adjusted the return pipe to the reservoir to make it a more direct return. The foggers are set to spray for almost 7 minutes on and off for 4 minutes. This timing is deliberately adjusted so that sometimes there is only fog, sometimes fog and sprinklers, and sometimes sprinklers half the time and fog half the time. The timers are set so that different watering techniques are activated at different times in different combinations. The logic is the plant won’t get too used to anything and it also allows the root zone to dry a little, encouraging the root hairs to go in search for food. This makes the roots very tenacious, white, and strong.

As soon as the solution returns back to the 55 gallon from the overflow the system kicks back on. The return takes almost 4 minutes. When spraying the roots, the solution comes from the 55 gal reservoir, and it takes just 7 minutes to empty the 55 gal. This is the maximum watering duration that Devin feels he can achieve without getting a bigger reservoir.

In the bottom of each container is a 4” air stone, these are connected to 4 x 750psi air compressors to infuse the 2.5 gallons of nutrient solution with oxygen rich bubbles. Sounds just like an interesting re-circulating system right? Well here is the secret to this high yielding system…

Each container has an aeroponic fogger floating just under the surface of the nutrient solution. Each fogger has three disks. These foggers are on a 5 minute on, 5 minute off cycle to create an extremely fine mist or ‘fog’ with a particle size of 3-5 microns! Such a fine fog of nutrient solution creates supercharged roots with an abundance of fine root hairs. These root hairs can take up water and nutrients at a rapid rate creating explosive plant growth. This technique of utilizing ultra sonic foggers to deliver a nutrient fog to the roots has been recently dubbed ‘Fogponics’, although officially it falls under the banner of aeroponic cultivation.

AEROPONIC FOGGERS

Aeroponic foggers come in various shapes and sizes but all utilize the same technology. They work by sending ultrasonic frequencies to ceramic disks which sit just below the surface of the water. These ultrasonic frequencies vibrate the disk which oscillates the water above creating an ultra fine fog. This fog has such a small particle size that it feels dry to the touch yet it can easily penetrate roots without totally saturating them.

CHALLENGES

1) Foggers

The main drawback of using most foggers with nutrient solutions is they can become clogged very quickly with nutrient precipitate. Even using foggers in hard water alone can cause a quick build up of lime scale, let alone adding mineral salts to the mix, so how does this extreme aeroponic system get around this?

Through trial and error and with some help from Ryan Clout at Sunflower Supply and the online garden forums, these crazy cats found a solution. Devin located a company online selling Teflon coated disks that are longer lasting and keep residues from building up on the disk surface. This drastically prolongs the life of the foggers reducing the need for constant cleaning and frequent replacements.

As mentioned previously, the foggers need to be just below the surface of the water in order to emit the ultra-fine fog. To enable the water level in the container to rise and fall while still allowing the fogger work it became clear that the fogger would have to float. So armed with a tiny budget and a trip to the dollar store, the floats for the foggers were created from play snorkels and net cups for only a dollar for each fogger!

2) Solution Temperature

While in operation, the foggers generate a significant amount of heat that gets soaked up into the nutrient solution. Even with the solution circulating from a large reservoir around all the containers, the temperature of the solution in the bottom of the containers was quickly rising to beyond 75°F. Ideally the nutrient solution should be around 65°F for optimal levels of dissolved oxygen and nutrient uptake. This was a tough nut to crack. The way forward was to cool the nutrient solution and, being and inventive bunch of growers, they decided to make their very own homemade water chiller.

Using an old freezer (2ftx2ftx4ft) as the cooling chamber the crew drilled two ¾” holes through the casing, one near the top and one near the bottom. The cooling mechanism was created by constructing a coil made from 25ft of aluminum tubing. This fitted perfectly into a five gallon bucket which had a drilled hole at the top and bottom. This allowed the ends of the coil to come through. Then, they fed a ½” hose into each of the holes in the freezer, used silicone to seal the holes, and connected them to the coil lines. After making sure the hose and coil were watertight, they used non-toxic propylene glycol antifreeze to fill the five gallon bucket and popped a lid on it.

This homemade chiller is located next to the underground 55 gallon reservoir with the upper ½” hose connected to a pump in the bottom of the reservoir and the lower hose draining the chilled solution back into to the reservoir. This constant flow of nutrient solution being pushed through the chiller created a constant nutrient solution temperature in the reservoir of 60°F, with the containers stabilizing at 70°F, keeping the heat emitted by the foggers under control.

3) Environment

Being in the heart of Southern Oregon, air temperature during summer is also an issue for this aeroponic set-up. The roots are particularly susceptible to extremes in temperature as there is no growing media to act as insulation. On a nice sunny day, an outside temperature of 75°F can easily create up to 100°F in the greenhouse and that’s with the 24 inch ventilation fan and both 24 inch passive shutter inlets open! To keep temperature down on hot days a 25,000 BTU air conditioner was incorporated. It also doubles up as a heater for those cold nights in winter.

SYSTEM ENHANCEMENT

The secret to the system is the hybridizing of SWC, aero-sprayers, and the ultra fine fog creating by the foggers. Studies in the late 90s by NASA have shown that solely using ultra sonic foggers to feed plant roots creates a disproportionate amount of root hair with significantly less lateral root growth, making ‘fogponics’ less suitable for prolonged plant growth – i.e. bringing plants to full maturity. By combining the two aeroponic techniques of fogging and misting upper root zone and utilizing SWC to supply water, dissolved oxygen and nutrients to the lower branching roots, they have achieved the best of both worlds.

One key aspect of this hybrid system that Devin is keen on maintaining is a high beneficial microbe count, particularly predatory nematodes, in the growing media and nutrient solution. The beneficial nematodes are an excellent predator of fungus and bacteria, which Devin is sure will help keep the system clean.

To provide a good home for the microbes to hang out and breed, they have come up with a media mix for the net pots of 5 parts Hydroton to 1 part ‘loose fill’ Sure To Grow. Devin and the crew feel that this mix provides them with the ideal surface area for the microbes to stay happy.

To inoculate the system with tons of beneficial microbes they brew their very own worm compost tea!

DEVIN’S WORM COMPOST TEA

Step 1: To 16 gallons of reverse osmosis water, add 1 fluid oz (28.5ml) of fulvic acid and 1 oz of brewers’ yeast (used for home brewing beer and wine).

Step 2: Add 2.1 fluid oz (60ml) of Humboldt Honey Hydro ES to provide food and energy for the microbes.

Step 3: Add 4 teaspoons (20ml) of Cutting Edge Solutions’ calcium carbonate, the microbes to love it!

Step 4: Take 15” x 23”brew craft fine screen mesh bag and add 2.5 pounds of worm castings.

Step 5: Add and air stone (attached to an air pump) to the mix.

Step 6: Steep the worm casting bag in to solution for 72 hours.

Step 7: Remove the bag, give it a few squeezes and let the solution brew for another 12 hours.

Step 8: Prepare the nutrient solution, Devin uses Cutting Edge 3 part formula.

Step 9: Add the 16 gallons of fresh worm tea to 300 gallons of nutrient solution.

Using this technique the crew manage to brew a full 16 gallons for $15! With this fresh brew of beneficial microbes Devin says you can’t add too much. They even spray the mix on the plants in vegetative growth stage which they have found works best neat or at a minimum dose of 1 part tea to 5 parts water.

Using a plant viable form of calcium carbonate really works wonders. Microbes like to have some kind of nutritional buffer, whether it’s a little bit of potassium or even phosphorus, they just need some kind of mineral to feed off. Devin noticed that his nematode population is 10-15% higher when he used calcium carbonate. He used Cutting Edge Solutions’ calcium carbonate – once you open it you really must use within eight weeks, otherwise it can get susceptible to mold.

Using this concentrated homemade worm-tea the growers find they only need to use ½ to ¾ strength nutrient solution! The main reason is that the worm-tea contains a huge population of predatory nematodes and protozoa (single celled organisms that are found across several kingdoms). They are non algal, and non fungal (such as amoebaes, ciliates, and flagellates) and are the number one predators to bacteria and fungi alike. These little worm-like parasites are nasty little buggers. They are heterotrophic which means they cannot produce their own food. Instead they hunt bacteria and fungi while remaining harmless to you and your plants. They locate and shred apart the fungal mycelia and bodies of bacterial organisms which then provide plant available nutrients and minerals to the root system. It’s a beautiful circle!

Freshly brewed, actively-aerated compost tea and compost tea brewing machines with ready-to-use brewing kits are also available from several companies.

We recommend you check out:

• Vermi-T from Vermicrop Organics
• Progress Earth
• Nature Technologies International
• Bountea

To complete the beneficial microbe mix, they add other beneficial liquid additives. These include Canna’s Cannazyme and Botanicare’s Aquashield. Also, check out Sub Culture B from General Hydroponics.

Every two weeks they change out the nutrient solution for a fresh batch. To empty the system all they need to do is open up three taps – this allows the solution to run out through pipe work onto an outdoor vegetable plot, putting even the ‘waste’ nutrient to good use. To fill the whole system they prepare a 300 gallon reservoir which pumps the fresh solution to each container.

Devin has extensive hydroponic experience with flood and drain tables, drain to waste systems, Deep Water Culture, aeroponics, soilless and soil yet finds this hybrid shallow water culture/aeroponic/fogponic system the most sanitary, easier to clean with the least amount of nutritional and pest problems.

To provide support for the plants they use tomato cages fitted into the exterior of the net pots. This offers great support and allows the branches to be trained out, which in turn enables the plant access to more light, better support, more growth and more fruit!!!!

The assemblage of all these high yielding methods with a few tweaks has provided Devin and his crew an affordable homemade system that that they can literally (and physically) grow trees in!

WHAT DO YOU THINK OF THIS

SYSTEM? ARE THESE GUYS DESTINED FOR GREATNESS OR WHAT?

Special thanks to Ryan at Sunflower Supplies (www.sunflowersupplies.com) for his help with the ultrasonic foggers!

Healthy plant growth depends on properly synthesizing the perfect environment for your fruits, veggies and decorative plants. And just as correcting the pH level in soil or water can help a plant thrive, an incorrect pH level can lead to disease or potential death.

What is pH?

PH is the abbreviation for ‘potential of hydrogen’ which indicates a substance’s acid or alkaline (base) properties. The standard pH scale (occasionally referred to as the acidity or alkalinity scale) goes from 0 to 14, although it is possible to exceed these levels. The higher the pH, the more base or alkaline a substance is. The lower the pH, the more acidic it is. And a pH level of 7.0 is of neutral acidity and alkalinity.

A note to all you beginning gardeners: “Acid” often has a dangerous connotation, but a substance that is too alkaline can be just as dangerous for people and plants.  Did you know that bleach has a pH level of 12.0 to 12.6?

How can you measure pH?

Although it is impossible to visually determine the pH level of a liquid, the pH of soil will often affect its color. A greener shade of soil is typically more alkaline, while a yellow or orange tinted soil tends to be more acidic. Soil pH can be measured with a pH test kit or a meter that is specifically designed for soil testing.

The pH level of a liquid can be measured using reagents incorporated into paper strips or liquid drops or with a digital pH meter. Reagent testing strips and drops incorporate color-matching techniques.  While they are initially inexpensive, they will ultimately cost more than a pH meter.  More importantly, strips and drops have a shelf life, do not provide pinpoint accuracy, and the color matching is open to interpretation. For example, most strips will show an increase of pH levels by increments of 0.5. Therefore, when using a pH strip, the difference between pH 7.0 and pH 8.0 will only be two different shades of pink. And what about the roughly 7% of males in the United States that are color blind? A digital pH meter, on the other hand, provides a pH level display screen, so there is no interpretation required: a user simply inserts the meter into a solution and views the digital reading.

It is important to note that soil and liquid pH meters have very different probes and should always be used accordingly. Make sure you have the right one for your needs.

How do pH meters work?

Even though there are a variety of pH probe types, ranging from inexpensive handhelds to laboratory models that cost tens of thousands of dollars, the most common pH meters incorporate a glass sensor and a reference tube. The pH probe measures the activity of hydrogen ions by generating a small amount of voltage across the sensor and the reference tube. The meter then converts that voltage to a pH value and displays it on a digital screen.

Also, many digital pH meters have a built-in thermometer that automatically adjusts for any discrepancies off the baseline of 77ºF (25oC). This function is called automatic temperature compensation (ATC).

What is calibration and why is it necessary?

Calibration is akin to tuning, and just as a musical instrument must be tuned from time-to-time, a scientific instrument must be properly calibrated to achieve accurate test results.

While some humans may have perfect pitch and can tune a musical instrument without the use of a tuner, the only certain way to determine if a pH meter is calibrated properly is by comparing it to a laboratory-certified standard reference point, more commonly known as a ‘buffer solution.’ Buffer solutions are liquid, but can also be purchased in powder form and mixed with distilled or deionized water to create a fresh batch each time.

Any scientific instrument should be calibrated as close as possible to the level that will be tested. If testing a range, then the meter should be calibrated in the middle of that range. For example, if testing an acidic solution, a pH meter should be calibrated to pH 4.0 to achieve the most accurate results. Most waters fall into the range of pH 6.0 to pH 8.0. Therefore, to test the pH of water, calibrating your meter to pH 7.0 will suffice. The three most common pH levels for calibration are 4.0, 7.0 and 10.0. These points cover the pH range of 0 to 14, but other values are available.

A pH meter will require single-, two-, or three-point calibration for accurate results. Some meters can be calibrated to a single point, but the manufacturer will recommend at least two points for optimum testing. The differences will depend on the technology of the meter and the type of sensor it uses.

Once you have a pH buffer solution, calibrating a pH meter is typically a simple process.

A pH meter, whether analog (a needle points to the pH level) or dialog (displays the pH level as a number on the screen), will incorporate either analog or digital calibration. Analog calibration is done by using a small screwdriver to adjust the reading until it matches the value of the buffer solution. Digital calibration is done by pressing up and down buttons until the reading matches the value of the buffer solution. A digital pH meter can have analog calibration.

Some meters also offer automatic calibration, in which case the meter will automatically recognize the value of the buffer solution and calibrate itself to that value. This is by far the simplest method of calibration, but it is important that these meters also have manual calibration for fine tuning and/or troubleshooting.

Many brands of pH meters are factory calibrated and ready to use right out of the box. However, the factory calibration should only be considered a convenience for a few uses; the calibration could shift during shipping, and it’s also possible that the factory calibration may not be ideal for your needs. And as mentioned above, all pH meters will need to be recalibrated at some point.

Regardless of what method of calibration your meter employs, always carefully read your meter’s instructions and perform calibration according to the manufacturer’s recommendations.

For best results, a pH meter should be calibrated:

• With regular use—at least once per week
• If not used—at least once per month
• If you think the readings are incorrect
• If testing aggressive liquids (very acid or basic liquids)
• If testing a wide range of liquids (going back and forth between acids and bases)
• Whenever the sensor is replaced

How should a pH meter be properly cared for?

Although there are general maintenance techniques for pH meters, each brand and model will have its own requirements. Always follow the directions for your meter and you will enjoy it for a longer time, with fewer issues.

In addition to frequent calibration, properly maintaining the pH sensor will ensure a longer life and more accurate results. Many pH meters incorporate glass sensors and reference tubes that must be stored in specially formulated solutions. If using a handheld meter, the storage solution will often be in the meter’s cap. Don’t spill this solution … you need it! For most pH sensors, it’s critical that the sensor be stored wet in the appropriate solution.

To clean most pH sensors, rinse in distilled or deionized water. Shake off any excess water and return the sensor to its storage solution.

The majority of pH sensors have a lifespan of approximately 1–2 years. If you are experiencing erratic readings and having difficulty calibrating, it may be time to replace the sensor (or your meter, if the meter doesn’t have a replaceable sensor).

Tips and tricks

• Always read the instruction manual prior to use. Sure, the instructions may be boring, but they’ll answer your questions, and those answers will protect your investment
• Always be sure your pH meter is properly calibrated
• If your handheld meter includes a storage solution in the cap, store the meter upright for more effective saturation
• Never touch a sensor electrode or reference cell with your fingers: skin oils will affect readings and can permanently damage a pH sensor
• Always lightly swirl a meter in the water or solution to dislodge any trapped air bubbles
• Never store a pH meter in high heat or humidity
• Never store a pH sensor in distilled water
• A pH meter is a sensitive scientific instrument and should always be treated as such

By Rob Samborn

Rob Samborn is Director of Sales and Marketing for HM Digital, Inc., a manufacturer of water testing instruments, including pH and TDS (aka nutrient) meters.