The User Guide. Better plants in the palm of your hand. Success by simplicity

Transcription

1 The User Guide Better plants in the palm of your hand. Success by simplicity

2 A solution for every problem. We call NZ home, but we ship the products we make all around the World. At Bluelab, we re dedicated to designing tools, technology and education to change the way tomorrow s world grows plants and food. For more than 30 years, we ve offered our products to growers to conduct measurements in water based solutions and other media environments. We are recognised worldwide as a leader in hand-held meters and control equipment for measuring and controlling factors such as water ph, conductivity and temperature in controlled growing environments. This 2 nd Edition of our Grow Book offers more information on the essentials for plant growth across a wider range of media. This information, combined with our world leading water and soilbased measuring systems, will ensure you obtain optimum plant growth and health. 2

3 Grow your understanding... Then you can grow better plants Whether you re growing plants for food, for business or as a hobby, you need to understand their growing environment. When you understand that environment, you can manage and control it. It s about knowledge Such as the strength of your nutrient solution, and knowing what and when nutritional elements are actually available to your plants. They re areas where accuracy and simplicity matter. That s where Bluelab comes in We help you measure the things you absolutely must know to grow strong, healthy, reliable plants. It s what our testing products are for. We make knowing the essentials easy - so you can have better plants. Contents: Healthy plants don t just happen 5 The basics of plant biology and nutrition 6 The importance of taking ph measurements 9 Conductivity 15 Water quality 21 24/7 Growing 26 Explaining growth media 29 The organic question 35 Looking after your instruments 36 FAQ s 38 Growers Glossary 39 References 41 Writer profiles

4 Welcome Whether you re a seasoned grower, just starting out with your own business or at home system, the team at Bluelab is committed to helping you grow healthy and nutrient-rich plants. With the world population steadily increasing there is an increased pressure to produce more in an area; be that a field, greenhouse or hydroponics system. How can we meet this demand? How can we improve our tried and tested growing practices? Plants have been growing well for millions of years all over the world without any assistance or control. But our world is changing. The composition and nutrient content of our soil is changing and we are constantly learning how we can impact growing conditions to help our plants grow better. This is where the Grow Book comes in. Here we explain some of the important concepts that are major contributors to healthy plant growth in the hope that they may be able to improve your current system. They have been discovered through years of research by scientists all over the world. In particular, we will focus on plant nutrition and how to ensure your plants are getting all the nutrients they need. A lot of this relies on the plants environment and what you feed them, so we will also show you how to efficiently manage your growing system regardless of whether you are growing hydroponically with a soil-less substrate or traditionally. This knowledge is for all growers. Through its leaves, a plant takes in light and carbondioxide (CO 2 ) from the atmosphere. Primarily through its roots, it takes in water and nutrients as ions from the soil or growing environment. It converts light and CO 2 into chemical energy (as sugars), and releases oxygen (O 2 ). The plant then uses these sugars, the water and nutrients for its growth. Just like the human biological system, the growth and development system of a plant is a complex process, which has been refined by nature over generations. Thankfully, scientists have narrowed down some key factors that we can measure in our growing environment and manage to help this system run even more smoothly. We can, in other words, add our knowledge and skills to nature. Shoot system Above ground parts of the plant: Leaves trap energy from sunlight and carbon dioxide (CO 2 ) from the air to create sugars (chemical energy) through a process called photosynthesis Leaves release oxygen (O 2 ) into the air (respiration) Stems provide structure and position leaves so they can collect sunlight. Stems also provide the transport system for nutrients and water to flow from the root zone to the rest of the plant. Root system Below ground parts of the plant: Roots anchor and support the plant in the ground Roots absorb water, oxygen (O 2 ) and nutrients from the soil by the root zone Roots can also output ions to help control the ph of the root zone Sunlight CO 2 Photosynthesis sugars (energy) H 2 O O 2 Fact File When you re managing a growing system, watching and responding appropriately to these key factors will help you grow a successful crop. The key factors to manage: Root zone Absorption of mineral nutrients in the root zone by root cells: H 2 O (Water), K + (Potassium), NO 3 - (Nitrate), Mn 2 + (Manganese) Environment Humidity range, clean air, proper CO 2 /oxygen (O 2 ) ratio, adequate air, circulation, light sunlight or plant lamps, support. Food Sufficient nutrients in the root zone and in an available form for the plant. Temperature Of the soil, media, environment and water Water Sufficient levels, good quality and drainage. ph level Allows uptake of essential ions 5 Bluelab Grow Book bluelab.com 6

5 Basics of plant nutrition Knowledge to grow your mind. Just like us, plants need a food source to get what they need to grow. Through photosynthesis they convert energy, but that isn t enough to fully sustain them. They need nutrients. There are 17 essential nutrients that plants need to have a balanced diet, so to speak. Unfortunately, it isn t as simple as giving your crops some nutrients in any old form or amount. There are four main things to consider: 1. The quantities of each nutrient the plant needs for each stage of its life cycle. e.g. fruiting. 2. That all plant species have different nutrient requirements 3. The ratio of nutrients, as the nutrients can interact with eachother and enhance or prevent the plant from absorbing them. 4. Whether the nutrients we add are actually available to the plant! These days, with the wide availability of complete nutrient mixes it is much easier to decide what nutrients to use and in what quantities. However, as with human biology, an unbalanced diet in plants leads to nutrient deficiencies and toxicities. In plants this can be seen through stunted growth and damaged or yellow leaves (Uchida, 2000). The primary method of nutrient uptake is through the roots (carried in by water when dissolved) and due to this, plants can only absorb nutrients in their dissolved form as ions. Managing ph is vital to ensure nutrients remain soluble and available to the plant. The key factor that affects nutrient availability is thankfully one we can control! It is the ph of the root zone environment and of our nutrient solution or fertiliser that we are feeding our plants with. We will be discussing and explaining this in the following pages. Iron deficiency displays in the plant with strong yellowing of leaves and growth shoots between the veins Fact File Essential nutrients Plants need most, if not all, of at least 17 different elements for optimum growth and health. Non-mineral nutrients: Obtained from air and water Carbon (C), hydrogen (H), and oxygen (O). Primary macro-nutrients: Required in the greatest quantities. Building blocks of critical cellular components. Nitrogen (N), phosphorus (P), potassium (K) Secondary macro-nutrients: Also required in large amounts and assist the transport and function of the primary macro-nutrients. Calcium (Ca), magnesium (Mg) and sulphur (S). Micro-nutrients: These are only required in trace amounts, but still just as important! Boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), molybdenum (Mo), nickel (Ni), silicon (Si), and cobalt (Co). The last two mentioned - silicon and cobalt - aren t technically essential nutrients, but when used do improve growth and plant health. What else do plants need to grow? Now we ve established that plants need soluble nutrients in the correct quantities to grow efficiently, what else is needed? Sunlight key reactant for converting energy, through photosynthesis, into a usable form. Oxygen a by-product of photosynthesis, but is also absorbed by the roots as they don t undergo photosynthesis, but still require oxygen. Water carries the soluble nutrient ions from the root zone (close proximity to the root) into the root due to transpiration. The plant roots need to be in a moist environment. Transpiration is the process by which the plant loses water through the leaves by evaporation which pulls more water in through the roots. Temperature the temperature of the environment has an impact on the plants internal temperature and how much water exchange is required to cool it down. This goes hand in hand with the humidity of the environment. Temperature can impact specific nutrient absorption. Humidity is the amount of water present in the atmosphere and how easy it is for the plant to lose water by evaporation. High humidity means that there is a lot of water in the atmosphere so it is hard for the plant to lose water and vice versa. Fact File How do we help keep nutrients soluble and available? Nutrients are commonly separated into at least two parts, A & B, in order to keep certain ions apart, sulphate and calcium. If these two ions are not kept apart they will combine into a form that will precipitate out into an insoluble form. If this happens the ions are no longer available to the plants. Some micro-nutrients also readily precipitate out. This is generally prevented by adding some micronutrients as chelates. Bud Fibrous root Tap root Stem Alternative growing methods; soil-less growing Hydroponics is a type of growing method where nutrients are primarily provided in the water supplied to the plant. Leaf Flower The term originates from the Greek words hydro meaning water and ponos meaning labour or toil, giving a meaning of working water. It follows then that this method uses a nutrient rich solution to directly provide the plants roots with the essential nutrients they need to complete their lifecycle. Extra reading about plant nutrition for the curious grower: Mechanisms and Control of Nutrient Uptake in Plants. Robert Reid and Julie Hayes. Department of Environmental Biology, University of Adelaide. (Reid & Hayes, 2003) 7 Bluelab Grow Book bluelab.com 8

6 ph and its role in nutrient availability The ph controls whether or not the nutrients you add are available for the plant to absorb. Controlling the ph helps ensure that your plant is getting all the nutrients it needs. 0.0 ph 7.0 ph 14.0 ph H + OH + H + OH - H + OH - Another factor to be considered; different plants also have their own preferences for ph values. CASE STUDY: The impact of ph In 2016, The Center for Applied Horticultural Research did a study on the impact of ph on plant growth. As we explained in the previous chapter, the nutrients that the plant takes up are present in their purest and simplest form, as ions. To be available to the plant they will need to be soluble (dissolved in water) and have a positive or negative electrical charge. The ph value that we measure is also based on ions; Hydrogen ions (H + ). The amount of H + present determines the acidity or alkalinity of whatever you are measuring. The ph is a ratio between H + and hydroxyl groups (OH - ). If more hydrogen ions are present, the ph will be acidic (0-7) and if there are less H + relative to OH -, the ph will be alkaline (7-14). The hydrogen and hydroxyl ions, that determine the ph, play an important role in nutrient availability to the plant as they can interact and bind to nutrient ions and make them drop out of solution where the plant is unable to recognise and absorb them. Fact File This causes a lot of nutrient wastage and as they drop out of solution in an insoluble (solid) form, they can cause equipment blockages. Each nutrient ion has a ph range within which it will be soluble (available to the plant). Outside this range the ions could interact or change their chemical form and become unavailable. This is commonly known as nutrient lock-up and is a prominent cause for nutrient deficiencies with nutrients such as iron and molybdenum. Nutrient lock up and precipitation is not an easily reversible process and care must be taken to prevent this from occurring (Paul R. Fisher, 2007). Having soluble nutrient ions at the root zone is essential and dependent on the ph. Controlling the ph so that all your nutrient ions are soluble in your reservoir is then vital for healthy plant growth. Trying to grow without managing the ph can cause nutrient lock up. This is when the nutrients become insoluble and unavailable to the plant, which can cause the following: Slow and stunted growth Leaf, flower and fruit drop Leaf discolouration Root burn Chemical imbalances / Overuse of nutrient solutions Pests and diseases Crop failure What can change the ph of a solution: Water. Most water, except rainwater, tends to be slightly alkali. The carbonates in it work to neutralize the slightly acidic water in your reservoir. As the water in your tank is topped up the ph value will rise. The plants themselves. The plant taking up nutrients or releasing ions into the root zone can affect the ph (Hinsinger, Plassard, Tang & Jaillard, 2003). Your nutrient. Nutrient stock solution is usually slightly acidic and so will lower the ph. They were analysing the effect of ph on plant health and yield across three plant species grown in nutrient solution and mixed-media with fertigation. They compared growing plants in conditions without any control of the ph to growing with a set ph. A wide range of set ph values were used, from 4.5 to 8.5, increasing in 1.0 value increments. Firstly, they found that the different plant species had different optimum ph values where the best quality plants were produced. For example, tomatoes grew best at ph 6.5 and petunias had a 50% growth increase at ph 4.5 than when they were grown at any other ph value. Secondly, they found that even if the ph value of the root zone wasn t the optimum one for that species, the plant would still grow better than if the ph was not controlled. In fact, there was a 44% loss in tomato yield when there was no control of the ph. These findings showed the clear importance of taking regular ph measurements and controlling this in the growth environment to increase and optimise production levels. The full research report can be found by visiting bluelab.com/knowledge-base (Dustin Meador) 9 Bluelab Grow Book bluelab.com 10

7 Taking ph measurements in different environments: Solution In the nutrient reservoir: If we can have full control of the ph levels here, we can prevent nutrient ions becoming insoluble and unavailable to the plant. In-line with your growing system: Monitoring exactly what your plants are receiving. From the run-off: To ensure that the plants aren t shifting the root zone ph to values which affect nutrient availability. In solution, measurements can be taken using a ph meter, sending a sample to a laboratory or by using test strips (though test strips can be difficult to accurately interpret). Soil Soil is an interesting media to use as it can have a natural ability to prevent the ph from shifting dramatically. This is called buffering (Wang X., Tang C., Mahony S., Baldock J. A., & Butterly C. R., 2014). It also contains microorganisms, decomposing matter and varying moisture levels, all of which can change the ph value. It is beneficial to measure the soil ph prior to planting as well as during growing as different plants thrive in different ph soil values. Knowing what ph value your soil has could have an impact on what you plant or determine any treatment that must be carried out to optimise growth. When growing, it is important to measure the ph at the plant s root zone to prevent damage to the roots (e.g. acid burns) and nutrient ions becoming insoluble. The plant can release ions that can change the ph so careful monitoring is beneficial (Hinsinger et al., 2003). There are four methods to measure the ph in soil: The first method is quick and simple. The first method is quick and simple. The other methods are a lot more labour and time intensive and require taking a ph measurement with a solution ph probe or being sent to a laboratory for analysis. 1. The easiest method is to use a multi-media ph probe directly into the soil by the root zone of the plant. 2. 2:1 Dilution method: Mix 2 parts of distilled water with 1 part of your soil mix. Then wait for the solids to settle and measure the ph of the liquid. 3. Saturated Media Extract (SME): Add distilled water to a sample of your soil until it is saturated (thin film of water on surface), stir and wait at least an hour, drain through a filter to separate liquid and solids and measure the ph of the liquid. 4. Leachate Pour Thru Method: Fill soil container to saturation (so that a few drops of water come out of the bottom of the container) with your normal irrigation water. After container has drained for one hour, place a saucer under the container. Then pour enough distilled water on the surface of the container to get 50 ml (1.5 fluid ounces) of leachate to come out of the bottom of the container. This leachate can then be measured. Soil-less media These types of media are primarily used in contained hydroponics systems. Many different materials are used, such as stone wool, coco coir, perlite and clay pebbles. Accurate measurement of the ph of any of these media is important as the ph level is not a set standard and the medium may require treatment prior to use as a growth medium. For example, the natural ph of stone wool is quite high. This is very important as these media do not have buffering ability to control the ph so ph control during growing will also be required. The methods to measure the ph do vary depending on the structure of the media, but are very similar to measuring the ph of soil with a soil-specific ph probe being the fastest method. The take away message here is that the ph can change very quickly and have a massive impact on your production levels. Therefore, rapid and accurate methods of measuring the ph are essential. What can change the ph of soil: The plant itself. Plants can change the ph of soil or media, and how much can depend on their stage of growth. It can be useful if you ve recorded ph levels through the growing cycle, and have some history to go off in order to know whether the values you see are expected. Applications and types of fertilisers. These can alter the ph significantly. Some fertilisers can make your ph level head in a direction you don t want. Applications of sprays. These can soak into the soil or growing media and change your ph. Soil/media temperature. Soils with high temperatures can have a high concentration of carbon dioxide (CO 2 ). This leads to the production of more carbonic acid, which lowers ph. 11 Bluelab Grow Book bluelab.com 12

8 How can we do this? Recommended range of ph values for commonly grown crops General range for most crops Leafy Greens Optimum ph Range Lettuce Basil Fruiting Crops Tomatoes Chillies Strawberries Flowering Plants Roses Fungi Mushrooms Bluelab ph Pen: Bluelab Soil ph Pen Bluelab Multimedia ph Meter Bluelab Combo Meter Bluelab Combo Meter Plus Handheld device that measures solution for: ph Temperature Handheld device that measures solution or root zone for: ph Temperature Handheld meter that easily measures Root zone ph in soil and substrates ph in solution. 3 in 1 Handheld device that measures solution for: ph Nutrient (Conductivity) Temperature Handheld device with all the features and benefits of the Bluelab Combo Meter. Plus, root zone ph measurement using the included Bluelab Leap ph Probe 13 Bluelab Grow Book bluelab.com 14

9 Electrical Conductivity (EC) Measuring the electrical conductivity is universally recognised as one of the most important measurements to take during growing to optimise plant growth and production, but what is it? The electrical conductivity of nutrient solution is a useful measure of the total available nutrients in the sample. When nutrients (or other salts) dissolve in water, they split into ions. For example, potassium nitrate dissolves into a potassium ion and a nitrate ion. Each ion carries an electrical charge (potassium carries a positive charge, and nitrate a negative charge). These ions are what enables water to conduct electricity. Without ions present, water is not a good conductor. The more ions present, the better water conducts electricity. Only nutrients that are in an ionic form are available to be absorbed by plants. So, measuring the electrical conductivity of the water is a really good way of measuring the strength of your nutrient solution. It doesn t give information about individual nutrients, but gives a useful guide to its overall strength (Bamsey et al., 2012). Just as with ph, different species have different ranges of EC value for optimal growth, but in general if your EC is very low your plant probably doesn t have enough food and if your EC is very high you may run the burning roots or toxic build-ups. However, you must bear in mind that the EC is a general measure of the ions present (Bamsey et al., 2012). It is unable to distinguish or quantify the different types of nutrient ions, such as K + and NH 4+, present in a sample. As we saw, there s one worldwide scale for measuring acidity; ph. For conductivity it is not that simple. The scientific scale most commonly used is millisiemens per centimetre (ms/cm2). In addition, there are at least four other different conductivity scales, or conversion factors, in common use. They are EC, CF, ppm(500) or TDS and ppm(700). Ensure you are aware of which scale your meter is calibrated in, and what scale is used by your nutrient manufacturer. Getting a grip on the different measuring scales What are all the different terms? EC (Electrical Conductivity [1 ms/cm2 = 1 EC] ppm (parts per million) [EC x 700] TDS (Total Dissolved Solids) or DS Dissolved Salts, or MS Measured Salts. Otherwise known as ppm (500).[EC x 500] CF (Conductivity Factor) [EC x 10] They re all related and they re concerned with measuring the same thing using this table shows how to convert from one scale to another. ms/cm 2 (Millisiemen per cm 2 ) EC CF Where is it useful to measure the EC? In the reservoir. This is the solution that will be used to feed the plants and so must have a sufficient nutrient concentration to be able to do this. At the root zone of the plant. The root zone is the region where the plant is able to absorb nutrients from the media around it. Measuring the EC here provides the best representation of the nutrient quantities available to the plant. If you measure away from the root zone, you may obtain the optimum EC value, but the plant cannot absorb nutrients from this location. Conductivity conversion chart ppm 500 (TDS) ppm ms/cm 2 (Millisiemen per cm 2 ) EC CF ppm 500 (TDS) ppm In the run-off. While not in the root zone, it can give a useful approximation, so long as the percentage of run-off is over around 20%. In the water supply. Unless you are using treated water (deionised or reverse osmosis), there is a risk of contaminate ions, that will give a EC value, being present in the water. This would affect your EC value and potentially prevent the optimum quantity of nutrients being present for the plant. 15 Bluelab Grow Book bluelab.com 16

10 How can we do this? NEW COMING SOON Bluelab Truncheon Nutrient Meter: Handheld Meter that measures in solution for: Nutrient (Conductivity) Temperature Bluelab Conductivity Pen: Handheld device that measures solution for: Nutrient (Conductivity) Temperature Bluelab Pulse Meter: Handheld Direct to Mobile 3 in 1 root zone measurements for optimising plant health: Moisture content Nutrient (Conductivity) Temperature How to measure the EC: In-line The simplest method to measure EC is to use a digital EC meter. There are various types which can measure in solution or in different media types. It must be noted that soil is a non-homogenous media type so an EC measurement could vary significantly within a couple of centimeters. There are alternative measurement methods available for soil or soil-less media, but these are more labour, time intensive and may give varied readings. The most commonly used alternative method is the Slurry Method. Take a soil sample and add deionized / RO water until it becomes a thick slurry. Run sufficient slurry through a filter to cover the tip of any EC probe and take the measurement (follow the manufacturers directions). Note: The EC of a slurry tends to be considerably lower than the EC of the solution you are putting in the media. A factor of 10 difference is not uncommon. Bluelab Guardian: Fixed Wall Mounted Monitor that measures and monitors your reservoir 24/7 for: ph Nutrient (Conductivity) Temperature Bluelab in-line Guardian: Fixed Wall Mounted Monitor that measures and monitors your fertigation or irrigation solution 24/7 for: ph Nutrient (Conductivity) Temperature Bluelab Pro Controller: Fixed Wall Mounted Controller that measures, monitors & controls your nutrient solution 24/7 (when used with a Bluelab PeriPod) for: ph Nutrient (Conductivity) Temperature 17 Bluelab Grow Book bluelab.com 18

11 EC in Soil/Soil-less media Factors that can affect EC (nutrient) levels in soil (United States Department of Agriculture, 2014): Uptake of nutrients by the plant: This will generally decrease the nutrient ions present in solution and decrease the EC. However, the plant may release other ions into solution which would increase the EC. The growth medium: Some mediums can release ions, generally by breaking down, which raises the EC measurement. Conversely, they can sequester nutrients and prevent them from conducting electricity and being measured. Reactions between ions: Some ions can easily react with each other and form an insoluble complex that is no longer able to conduct electricity. A common example of this is the precipitation of calcium sulphate complexes. Change in water concentrations: High environmental temperatures causing evaporation or high transpiration rates that result in a more concentrated nutrient solution. For example, on a hot day, plants will take up more water than nutrients - so the nutrient level, or conductivity, will rise. If salt levels get too high, the internal osmotic system will reverse and the plants will dehydrate. Type of soil: As we will see later on, some soils are able to retain nutrient ions and stop them from moving freely in solution and conducting electricity. If you have soil components that behave like this, like clay, your EC value may not represent all the ions present and be lower than it should be. Recommended range of solution EC values for commonly grown hydroponic crops Leafy Greens Lettuce Basil Fruiting Crops Tomatoes Chillies Strawberries Flowering Plants Roses Optimum EC Range It is important to note that when the plants are young the EC values used should be very low and slowly increase along with the plant size. These changes can happen quite rapidly so regular measurements are preferable. It is easier to prevent a nutrient imbalance issue than correct one. Remember EC measurement in or from media will generally be considerably lower than the EC used in solutions. Fact File Measuring organic nutrients Often when growers are using organic nutrients they believe they cannot quantify the available nutrient or nutrient levels using the conductivity of their solution due to often obtaining a low reading. However, this is not the case. A low reading still means that that there is a low level of nutrients is available to the plants. This may be because the organic nutrients haven t yet been broken down into an available form, or that they have already been taken up by the plants. Either way, it does indicate the current level of available nutrients. Remember that the EC is a general measure and that there is no way of knowing whether there is a balanced nutrient composition present. 19 Bluelab Grow Book

12 Water quality The quality and contents of your water is paramount in any growing system. Water can contain contaminants that limit irrigation flow, plant nutrients and the efficacy of water treatment to control pathogens. The assumption that whatever water you use is beneficial to your crops health can be a dangerous one. In 2012, Meador et al. quantified the levels of physical, chemical and microbial contaminants in a survey of commercial horticultural operations. This study emphasized the importance of on-farm monitoring of water quality and provides several guidelines to improve irrigation management. Pure water (H 2 O), is composed of equal parts the hydrogen ion (H + ) and hydroxyl ion (OH - ) and nothing else. A balance of H + and OH - produces a neutral ph of 7. Pure water contains no other minerals, microbes, pathogens or other contaminants. Monitoring water quality can help determine how pure your water is, meaning how close it measures to ph 7 and an EC value of zero or very close to zero. In our world today there are few sources of pure water, therefore growers should establish a water monitoring and treatment program that enhances the ability of water to hydrate and transport essential minerals and plant available nutrients to the plant. Irrigation management can be improved with an awareness of its contents, to determine the level of treatment needed and help you prevent problems further on. Thus, pure water is used as a reference point in growing systems because there are no contaminants interfering with water treatment and has nothing present that could be detrimental to the plant growth or to the performance of any of the added nutrients. Why is using pure source water preferable? No waste ions present that could disrupt the optimum nutrient ratios once a nutrient mix is added. Having waste ions like sodium present in the source water will limit plant uptake of essential nutrients like potassium. If additional fertiliser is added without removing the sodium in the water, it could result in toxic EC levels due to excess of salts and nutrients which results in health issues within the plant. No physical, chemical or biological contaminants that could react with added nutrients and result in an insoluble precipitate that is unavailable to the plant and then block or damage equipment. No elements that could harm biological treatments, such as beneficial microbes present in growth media or other biological control organisms that may be part of an integrated pest management program (IPM). No pathogens present, or insoluble matter that can interfere with water disinfection treatments. No unwanted salts that could cause problems for plants, e.g. sodium chloride. Source water is the water we have available to use for irrigation. The quality of the source water can effect the delivery and solubility of fertilisers and availability of added nutrients to provide crop fertilisation. Issues caused by excess ion levels in source water: Iron: Can quickly oxidise to rust and cause damage to system equipment. Once oxidised it is no use as a nutrient. Iron is commonly found in bore or ground water and if present in high quantities will turn brown after several hours once exposed to air. Nitrogen: Causes excessive growth, but delays maturity of the crop and so can delay harvesting. The best system to optimise growth is one we can fully control. Within this is the control of the water we use and knowledge of everything in it. Common characteristics of untreated water: Water hardness: This is water with a high mineral content, commonly from excessive quantities of calcium and magnesium that has dissociated from bicarbonate (HCO 3- ) complexes (S. M. Deshpande & Aher, 2012). This causes nutrient ratio imbalances when adding set nutrient mixes to then feed crops. The presence of calcium increases the risk of the white precipitate of calcium sulphate forming (CaSO 4 ), which can then cause equipment blockages. It is possible to get nutrient mixes for hard water, but unless you know the exact concentration of excess elements present this isn t a fail-proof solution. Salinity: The quantity of salts, such as sodium chloride (NaCl), carbonate (CO 3 2- ) and bicarbonate (HCO 3- ) complexes, in the soil or water that can have a detrimental impact on the availability of water to the crop and result them becoming dehydrated (Ayers, 1976). While some of these are essential plant nutrients, excess will disrupt the nutrient ratios and result in toxicity. However, this does mean that measuring the EC of your source water will give an idea about the total salt concentration already present. So, if the EC of your source water seems quite high you may have an issue with salinity. If the salinity of your water, (or even soil) is an issue, your crop can have a drought like appearance ( Bicarbonate bad guy in Western soil, water, 1998). Alkalinity: A measure of the quantity of bicarbonates (HCO 3- ) present in source water. Bicarbonates are an alkaline compound and cause the ph value to rise (S. M. Deshpande & Aher, 2012). This can be remedied by adding acid, however, when present in large amounts it is a very effective chemical buffer and can make it very difficult to shift the ph to the optimum level for nutrient availability. If you are noticing that your ph value requires a large quantity of a ph down adjuster agent and then rapidly decreases, you may have an issue with alkalinity. Another issue caused by bicarbonates is that they often cause blockages in system equipment. Due to this, adding water with a high alkalinity can create many additional challenges for the grower. 21 Bluelab Grow Book bluelab.com 22

13 What types of source water are available? There are a number of sources of water for use in hydroponics. All have advantages and disadvantages and growers need to be aware of them. There are three main divisions of naturally occurring water supplies: rainwater, surface water, and ground water. In addition, domestic water supplies (tap water) are frequently used. Rain water This is often the best water to use for crop irrigation. The natural water cycle (evaporation, condensation, then rainfall) results in quite pure water with only traces of minerals, due to reactions with atmospheric gases. Collection from roof structures can add contaminants such as lead (from paints) and asbestos, so caution may be required. Groundwater (springs, wells and bores) Groundwater can be extremely good for crop irrigation and horticulture. It may be high in dissolved minerals such as calcium carbonate, especially if limestone is present. The ph may be higher as a result. Analysis is advisable to quantify the levels of minerals existing in the water and to ensure the levels of salt (sodium chloride) are adequately low. Groundwater can also be contaminated from material leaching into it from surface activities such as waste disposal, farming or industrial activities, so caution is advised if this is suspected in surrounding areas. Domestic water supplies (tap water) Water directly from the tap can be very variable depending on the origin of the water and how it has been treated. Normally, this water will have been purified through filtration or desalination, and had elements such as chlorine or chloramine added to neutralise pathogens. These elements can slow growth and negatively impact microbes present in the growing environment. Fact File If your source water quality isn t up to standard you may want to treat it through the following techniques: Deionised water: The removal of all charged ions through the use of ion exchange membranes. This method won t remove pathogens or microbes from your water. Reverse osmosis (RO) water: This method uses a semipermeable membrane to remove ions, molecules and larger particles to purify water. It cannot remove pathogens or microbes, but is an effective way of removing excess or unwanted nutrients and elements. Ultra-violet (UV) light treatment: UV light acts as a chemical free disinfecting agent to effectively remove microorganisms (such as bacteria, viruses and pathogens) from water supplies as they can have a negative effect on the health of humans and crops. It doesn t remove ions or other contaminating particles and is only effective if the water appears clear. There are other methods of water purification, but as many result in unsustainable by-products, the methods above are the preferred and most commonly used ones. Recirculated or recycled water: In most cases the purer your source water, the less treatment will be required to provide optimal plant health. The benefits of pure water are due to decreased contaminants, unwanted minerals and nutrient lockout. Furthermore, if growing in soil, where the microbial community is vitally important, the addition of contaminated water could harm it and affect the utilisation of organic matter. Contaminated water often results in a chain effect that decreases the amount of nutrients present in the soil that are available for beneficial microorganisms or plant growth. No matter what type of source water you use, the experts all agree that monitoring is the key to determine the level of contaminates and provide treatment to remedy poor growing conditions. Regularly monitor the EC and ph of your source water to determine the starting point for your plant nutrition and water treatment systems. The closer the EC value of the source water is to zero and the ph value to 7.0, the better conditioned your water is to carry nutrients from fertilisers and other enhancements designed to improve plant heath. Plants are significantly more sensitive to water quality than humans and have different requirements. Just because water is suitable for our consumption doesn t mean it will be for your crops. 23 Bluelab Grow Book bluelab.com 24

14 When should we test our water? Before adding any nutrient: Nutrients are expensive and we don t want to add any that are already there and risk them precipitating out of solution or having toxic effects on our plants. We want to maintain our optimum nutrient ratios. Also, knowing if our water has a high level of alkalinity can make life a lot easier when trying to adjust the ph further on. If growing hydroponically, you will be able to examine your nutrient solution after it has run through your system, but do note that this will not be assessing the quality of just your water. Testing: While sending a sample to a laboratory for full elemental analysis is the best way to determine what is in your source water, this is expensive and time consuming. Testing your source water should be a regular process so here are some basic measurements you can take at home to monitor your water quality. ph: Ideally your source water should have a ph of 7. As previously mentioned, the presence of contaminants such as bicarbonates will cause the ph to rise and be alkaline so measuring the ph can be an indicator for the possible presence of these. Electrical Conductivity: Pure water doesn t have any components that are able to conduct electricity so the ideal source water will have an EC value of zero. By measuring your EC, you can get an idea of the quantity of ionic nutrients, elements or heavy metals present that could disrupt your carefully calibrated growing system. However, even with an EC reading of zero, non-ionic contaminants could be present and cause issues. What does the water look like? Is it clear, or cloudy? Clear water can be deceptive as it appears free of contaminants, but these may simply not be visible and it should still be tested. Cloudy water contains insoluble particles that can block your equipment and may also contain unwanted contaminants. 24/7 Growing While growing plants may seem like a complicated task, this section should reassure you that you can successfully set up and grow crops without having to spend all your time in the garden. Automation can have a great impact on the success of the growing system. Automating nutrient preparation and maintenance provides more consistent nutrient composition over time, and facilitates better plant growth. Constant monitoring and correction means that nutrient solution values are stable 24/7. It saves time, meaning there is more time to check plants for disease, pests, and overall health or to get away from it for a while. Efficiently controlling how much nutrient and water is provided to the crops and eliminating mistakes when preparing nutrients manually means expensive nutrients are not wasted and water use is reduced. It gives peace of mind. Knowing the system is monitoring and controlling growing conditions 24/7 and being able to monitor it when off-site allows the grower to escape the growing operation, while still knowing that all is well. Nutrient The key nutrient parameters that can be automatically controlled are EC, ph and temperature. Controlling EC means that sufficient nutrients are provided at all times, and maintaining the correct ph ensures that the nutrients are available to the plants. Having an automated system dosing nutrients only as required instead of manually dosing larger quantities means nutrients are fresher, and there is less chance of the nutrient elements precipitating out of solution over time. Environment Other environmental conditions that can be controlled are air temperature, humidity, light levels and carbon dioxide (CO 2 ) levels. Temperature extremes can slow growth if too cold or place the plant under heat stress if too warm. Humidity: The humidity in the growing environment plays a huge role in the rate of water and nutrient uptake by the plant, and therefore, the rate of growth. Temperature: With humidity, temperature plays a big role in water and nutrient uptake rates, and affects growth rates directly. Keeping environmental temperatures within an optimum range maximises growth rates. Carbon dioxide: Carbon dioxide (CO 2 ) is an essential component of photosynthesis, and the main source of carbon for the plant. It is taken in through the plants stomata. Augmenting the atmospheric CO 2 level can increase growth rates in some plants. Irrigation: Control of irrigation can also be automated, based on time (especially in artificial light situations) or light intensity (in natural light conditions). 25 Bluelab Grow Book If temperature is maintained within the range that is ideal for the crop, growth rates can be maintained during cold periods, and the problems caused by warmer nutrient temperatures, such as reduced dissolved oxygen levels and root diseases can be avoided. bluelab.com 26

15 Automation equipment Nutrient automation equipment usually consists of a controller, which monitors the nutrient EC and ph values (sometimes the temperature as well) and a doser, which, when triggered by the controller, doses nutrient stock solutions and ph adjuster to bring the nutrient solution to the required levels. A typical doser has three pumps (part A and part B plus ph), as most commercial nutrients are two-part nutrients but some controllers and dosers have the ability to dose multiple nutrient parts and additives in order to change the nutrient mix over the growing cycle of the crop. Fact File How can we easily automate our system? Monitoring equipment: Bluelab Guardian Monitor: Continuously measures the conductivity, temperature and ph of your reservoir using ph and EC probes. An inline model is also available to measure the same variables just before the solution is given to your crops. Controlling equipment: Bluelab ph Controller: Continuously measures and automatically adjusts the ph of a given solution to a pre-determined value using an inbuilt peristaltic dosing pump. Bluelab Pro Controller: Continuously measures and automatically adjusts the ph and EC of the reservoir. Also measures the temperature and has the capability to control this if connected to a heating or cooling unit. Solution heaters and chillers can also be used to keep the solution temperature within required limits. Independent monitors are also often used to watch EC, temperature and ph levels, as a back-up to the controller. Ideally, the full control of all environmental factors will be automated, however, this can become very complex and expensive. Controlling the values of EC, ph and temperature is the best first step. Dosing equipment: Bluelab PeriPods: Currently come in a medium or large size with 3 (M3 & L3) or 4 pumps (M4). With the Bluelab Pro Controller, they automatically and accurately adjust nutrient and ph levels in growing reservoirs. Three PeriPod units (maximum 12 pumps) can be connected to allow experienced or experimental growers the ability to dose nutrient components and add other supplements individually. Find these products and many more at bluelab.com How is the ph controlled? We already know the importance of ph and why it is controlled, but how can we control it? The trend shown by most growing systems is that the ph will rise during the growing cycle and on addition of nutrients. This requires the addition of acid to increase the level of Hydrogen ions (H + ) to bring this level down to the optimum value. These control agents are commonly known as ph down adjusters. The commonly used types of acid are nitric acid (HNO 3 ) and phosphoric acid (H 3 PO 4 ), both of which separate into hydrogen ions and either nitrate or phosphates respectively, thus providing extra nutrients to the reservoir. As this addition will increase the concentration of that essential nutrient ion, you must be aware of this and adjust your nutrient mix if needed to compensate for the additional nutrients. The acid ph should be used at a 5-10% strength to have more control over the changes of ph and to avoid nutrients dropping out of solution on contact. Acid at a higher concentration poses a significant safety hazard as it is a highly corrosive agent and will cause damage to skin and equipment (especially the pump hoses). If increasing the ph value, ph up is needed. Potassium hydroxide can be used as it will split into potassium ions (K + ) and hydroxyl ions (OH - ). This of course provides a source of potassium ions, so just as with the use of a ph down agent, this additional amount should be considered when making up a nutrient mix. Note: Even when diluted, these acids should still be treated with extreme care and contact with skin and eyes avoided. Nutrient A ph ECA ECB Nutrient B If you want an accurate and reliable system to take care of your hydroponics set up I highly recommend the Bluelab Pro Controller Connect. It has given me peace of mind knowing that my crop is controlled with this automated system. The back up support from the Bluelab team has been second to none. Nutrient solution out to crop Flow adjusting valve Recirculating pump SCOTT PILCHER - PASSIONFRUIT GROWER Pilcher Farms Produce Ltd, New Zealand Return/recirculated water from crop Reservoir / tank 27 Bluelab Grow Book bluelab.com 28

16 Growth media A requirement for successful plant growth is that the plant and its root system must be supported. This is done by using a growth medium, which is chosen to compliment different methods of crop cultivation and different crops. These can vary from the traditionally used soil to mixes of soil-less media and substrates such as stone wool and solution based hydroponic methods. From these categories we can simplify them into two: soil vs. soil-less and solution based growing. The difference is that in the latter two (defined as hydroponics) the plants are being fed directly as opposed to feeding the soil, which is then broken down into nutrients that the plant can use. All these media types must meet the same criteria to support plant growth and provide: Constant supply of oxygen Supply of water to the roots to keep them hydrated Sufficient drainage to prevent the roots from becoming waterlogged and rotting Sufficient supply of nutrients to be transported by water through the media and to the plants root zone The coarseness and porosity of the medium is what determines the ratio of pores and voids that are occupied by oxygen and water/nutrient ions. Fact File Moisture content The moisture content of the soil is the amount of water present in the soil and thus available to the plant. Measuring this ensures that the plant roots are sufficiently hydrated and not becoming waterlogged. This is particularly important as the physical properties of different growth media retain water differently and can cause issues if not monitored. Measuring the moisture content of your growing medium will help you to decide how frequently your crop requires irrigating. Hydroponics: The term hydroponics originates from the Greek words hydro meaning water and ponos meaning labour or toil, giving a meaning of working water. It is now used to define growing systems that operate without the use of soil. This bypasses the use and cultivation of the soil ecosystem as the nutrients are made directly available for absorption by the plant by passing a nutrient rich solution through the root zone. This method is proven to significantly improve crop yields compared to traditional in-soil growing as the plants don t have to exert as much energy growing complex root systems to seek out and extract nutrients and can use this energy to grow larger instead. However, both methods of growing have their challenges and complications. Hydroponics can be a highly controlled growing system, where the grower can establish and maintain the plants optimum growing conditions so that it always has exactly what it needs to grow. Furthermore, as hydroponic systems aren t reliant on arable land, they are able to be grown in closer proximity to distribution centers, which reduces the food miles and means that the crop can be a lot riper and nutrient rich when harvested. Water is becoming one of the most valuable resources on the planet and both agriculture and horticulture are primary users of this. Hydroponic systems typically use around 80-90% less water than soil-based agriculture, which is extremely important as 70% of the world s fresh water is used in agriculture, mainly for irrigation.(lagues, Barbosa et al., 2015). In hydroponics systems we are providing the plant with optimum levels of nutrients in the water we are supplying to them. Because of this, it is preferable that the growth medium used is inert. Inert means that it will not decompose and release any nutrients that could disrupt the carefully calculated nutrient ratios as this could be detrimental to the plants health. Some media require treatment prior to use to ensure their natural properties (ph or contaminants present) will not affect the ph or electrical conductivity of the growing environment. 29 Bluelab Grow Book bluelab.com 30

17 Coconut coir: The fibrous casing of the coconut. Pros Renewable and sustainable source Inexpensive Excellent porosity Cons May contain a high level of salt, so may need to be thoroughly treated and buffered prior to use Known to sequester and release different nutrients so may require special coir nutrient mixes Does decompose at a very slow rate. This is not seen to be a significant issue Clay pebbles: Made by expanding clay with heat. Pros Excellent drainage Structure can be modified through crushing to improve water retention Chemically inert medium Reusable and durable Cons Requires more irrigation Floats if not holding sufficient water Requires soaking and rinsing prior to use to remove dust particles clogging equipment Due to relatively large gaps between pebbles this medium isn t ideal for starting seeds as they can fall through these gaps. Perlite: Naturally occurring medium made from volcanic rock. Pros Highly porous Requires minimal treatment before use Neutral ph Reusable (if treated before the next use) Inert medium Cons Due to light weight, perlite isn t often used as the sole medium Poor water retention (also seen as a positive characteristic of having good drainage) Stone wool: Inorganic growth media from steam treated molten rock or slag. Pros Inert medium Good water retention Good aeration of the roots Comes in different shapes and sizes Cons High (initial) natural ph, due to containing basalt, so requires prior treatment Can risk becoming saturated and damaging roots Is a skin and lung irritant These growth media are used by themselves or in combination with other soil-less growth media. Using a combination can make an ideal medium for a certain crop by combining the properties of different media. 31 Bluelab Grow Book bluelab.com 32

18 Types of microorganisms commonly present. Soil: For millennia, soil has been the conventional growth medium for crop cultivation with clearly proven success. The composition of soil can vary, but the basic components are air, minerals, water and a small amount of organic matter, all of which can foster a diverse microorganism community. The mineral components of soil are the sand, clay and silt particles contained within it. The different chemical compositions of these components can impact the retention of nutrients in soil and from this, their availability to the plant. This is what is often referred to as the cation exchange capacity (CEC) of the soil and tends to be a way to quantify the fertility of the soil. Clay and organic matter (sometimes called humus) are two common components in soil that have a net negative charge and so can attract and hold positively charged ions, which includes most nutrient ions. This increases their availability to the plant within the soil, as they won t be leached out and will assist the soils natural ph buffering ability. The soils ability to minimise shifts in its ph stabilises the solubility of nutrient ions if the ph is within the solubility range of those ions. However, different soils have different ph values due to their composition and this can impact the solubility of some types of nutrient ions. Plants have adapted to survive in differing conditions without problems, but species unaccustomed to them would struggle and have nutrient deficiencies. An example of this is that blueberries and pine trees grow best at a low ph and don t have nutrient deficiencies. This is the reason for each species having its preferred ph range and because of this it is advisable to measure the ph of your soil before planting to determine what plants will grow optimally. Conversely, if your crops aren t growing well measuring your soil ph may uncover the underlying factor that can then be treated. TOP TIP Don t measure soil ph at the surface of the soil, as most plant roots are lower. The ph at the soil surface may also be affected by accumulated salts which may affect measurements. Measuring close to the root zone and at the same depth will provide a more accurate representation of the growing environment. Just as in hydroponics, it is the soil water that carries the dissolved nutrients to the plant root zone. However, instead of readily available nutrients being directly provided in the irrigation water the nutrients are released from decomposing matter such as compost or converted from unavailable chemical forms through microorganism activity. These microorganisms play an important role in maintaining and improving the fertility of the soil as well as assisting plant growth. An example of this is the process of nitrification where atmospheric N 2 is converted into ammonium ions (NH 4 +) by bacteria, which then is in an available form of this essential nutrient to the plant. Microorganisms are always present in the environment and so will also be present in our growing environment. Microorganism communities will become established in any growth media nutrient solutions, and the root zone and roots of cultivated plants (Vallance et al., 2011). These organisms are very sensitive and any change to their environment such as ph, addition of fertilisers and water levels can impair their performance (Zhao et al., 2016). All in all, taking good care of soil and the organisms that reside in it creates a symbiotic ecosystem that can be relatively self-sufficient and that requires minimal nutrient additives. However, malpractice through industrial farming and the careless use of fertilisers has damaged a lot of arable land by exhausting its natural abundance of essential nutrients and depleted the microorganism community present. The natural soil ecosystem in some areas has been badly damaged, and in order to grow any crop successfully they require the addition of fertilisers for crops to obtain their essential nutrients. In regard to fertilising soils, many decomposable fertilisers derived from the top of the food chain organisms such as animal manure, guano, fish emulsion and even minerals like rock phosphates can contain accumulations of heavy metals. Repeated applications of the fertiliser will cause levels of heavy metals to build up over time. Heavy metals are usually very toxic, and when present can be absorbed by plants and found in their produce. Caution is advised when sourcing these types of fertilisers. Fact File How to measure the ph of your soil Bluelab Soil ph Pen: Handheld device to measure the ph and temperature of your soil. Bluelab Multimedia ph Meter: Handheld device which comes with a multimedia ph probe to measure the ph of solution, soil or any growing media. For other methods of measurement refer to the ph chapter of The Grow Book. Find these products and many more at bluelab.com Microbes can colonise every part of the growing environment, from substrate to nutrient solution. They play important roles in breaking down organic matter to release nutrients, fertilising the soil, recycling nutrients, assisting nutrient uptake and disease prevention (J. Heritage, E. G. V. Evans, & R. A. Killington, 1999). Some microbes can be pathogenic, but completely sterilising your growth environment can do more harm than good. Maintaining a balanced microbial environment is the goal. Bacteria: Decompose organic matter and release nutrients by processing them from unavailable to available forms. Many different varieties of bacteria use the carbon content of the soil as an anchor and food source. Nematodes: Some nematodes (small worm-like animals) be parasitic and feed on algae, plant roots, fungi, bacteria and other nematodes. They assist and accelerate the decomposition of organic matter and release of nutrients by digesting their food source. Fungi: There are many different species of fungi. Some form a mutualistic relationship with plants and attach to their roots to protect them and assist in nutrient uptake. Here they receive carbon (their food source) from the plant and in return transport nutrients to the plant. Some fungi decompose organic matter into acids, carbon dioxide and fungal biomass. Algae: Increase soil fertility by becoming organic matter when they die. Help increase water retention in soil. Carry out photosynthesis and release oxygen underground, thus aerating the soil. Some species of microbes can produce a variety of substances that promote and protect plant growth, including hormones, auxins, gibberellins and antibiotics. Hydroponic systems using soil-less mediums have also been found to contain the same microbes as soil and assist plant growth and control disease (Vallance et al., 2011). Further reading for the curious grower: Comparison of Land, Water, and Energy Requirements of Lettuce Grown Using Hydroponic vs. Conventional Agricultural Methods. The microbiology of soil and of nutrient cycling. 33 Bluelab Grow Book bluelab.com 34

19 The organic question A result of the diversification of growing technologies has been that new terminology has appeared along with it and sometimes the need to use this terminology is driven by certification in the produce market. How to look after your equipment This chapter will provide you with the basics you need to care for and calibrate your equipment. Full manuals that explain this in greater detail are available for each Bluelab product at bluelab.com. We all freely use the word organic, from growers to scientists to consumers, but each definition and explanation for this word is different and this leads to many arguments and confusion. We can be quick to state whether we use organic nutrients or not without first examining the chemical composition of nutrient types to see what can really benefit our plants. This chapter hopes to explain how we view the word organic with regards to the nutrients we can provide our plants with. Organic nutrients are degradable matter that can be broken down and comes from a source that once was living. This includes fish meal, guano, compost, worm teas and many others that are added to the soil, or in some cases a hydroponic system, to provide slow release nutrients. The decomposition of this matter is essential as the initial particles are too large for the plant to absorb and so need to be broken down by microorganisms into a readily available ionic form that plants can recognise and take up. The microorganisms consume the carbon present in the organic matter and then release the essential nutrients for the plant. Using organic nutrients, in the form of decomposable matter, is an indirect method of providing plants with the nutrients they need by fostering a healthy ecosystem with microorganisms. However, as nutrients are released gradually there is no way of controlling whether the plant has optimum levels of each nutrient at all times and so extra care must be taken to check the plant for signs of nutrient deficiency and toxicity. The essential nutrients that the plant requires for healthy growth are always present in the same form. For example, nitrogen can be available to the plant to absorb as ammonium (NH 4- ) and nitrate (NO 3- ) and potassium is always present as K +. This is because plants have evolved highly selective and sophisticated transport mechanisms to recognise nutrients in these forms and only absorb these. The plant will not selectively absorb nutrients based on their origin as it only considers the nutrients form and this doesn t change between an organic to direct application. The plants growth or health will not be affected provided they have sufficient nutrients available. Fact File When should you calibrate your Bluelab device? If it s been a month since the last calibration. The product will notify you when this time has passed as the successful calibration indicator will disappear from the screen. When you get a reading you weren t expecting. When the probe or meter is new. When you ve done more than 30 readings. When the meter is re-set after an error message. When batteries have been replaced. Calibration: To ensure accuracy. All Bluelab ph meters/monitors are calibrated to two points, most often in ph 7.0 and ph 4.0 calibration solutions. Meters that say they only need calibrating to one point (which is normally 7) can be inaccurate and will not hold their calibration, especially if they say they measure the full scale from If the reading you expect is normally higher than ph 7.0, calibrate with ph 7.0 and ph 10.0 solutions. Looking after your ph probe Your ph measuring device is an investment in the success of your crop production, but it is a fragile piece of scientific equipment. By keeping a few simple habits, you could extend the lifetime of your probe. The lifetime of the probe is determined and affected by: The number of ph measurements you take. Age of the probe. Due to the nature of the glass bulb, the probes will eventually fail through normal use. Contamination from the type of solution you are measuring. Contamination can come from touching the probe glass with fingers, the presence of oils, proteins or suspended solids that could coat the probe. So, more cleaning and calibration may be required if using organic nutrients that coat the probe. Contamination of the internal solution. This is caused by the solutions being measured or the solution the probe is stored in entering the probe itself. Avoid leaving probes in calibration solutions other than when calibrating and store in KCl storage solutions. Different temperatures of the solutions. A large temperature change, such as putting a cold probe into a hot liquid, can break the glassware. The glassware is designed to stay wet and must be kept this way for optimal performance. Just like your plants, if they dry out, they die. Lifetime of ph Probe can be extended by - Keeping your probe clean by rinsing it after use, with fresh running water and (depending on the amount of use) cleaning the glass bulb with Bluelab ph probe cleaner and a soft toothbrush. More detailed instructions available at bluelab.com. - Regular calibration to ensure accuracy. - Keeping the probe glassware wet and hydrated. Always replace the storage cap that is filled with sufficient KCl solution after use so that the probe tip is submerged. - Do not use RO, deionised or distilled water as this will damage the chemistry of the glass bulb! Other things to bear in mind: The glass bulb of the ph probe is fragile and can break. Don t knock it against anything or apply sideways force on the probe as this will damage the glassware. The lead in the probe can t be lengthened so don t kink or bend it sharply. Don t submerge the BNC fitting in any liquid. When calibrating, or taking a reading, wait for the reading to fully stabilise or you risk compromising the accuracy of the reading. 35 Bluelab Grow Book bluelab.com 36

20 Looking after your conductivity probe: Like your equipment for measuring the ph, your electrical conductivity meter must also be cared for and regularly cleaned to extend its lifetime and ensure maximum accuracy. Note that only the Conductivity Pen is able to be calibrated in 2.77EC solution. How your conductivity meter works: The meter has two electrodes. A small current is sent from one electrode to another and measures the ability of the solution to conduct electricity. This gives us a general measurement of available nutrients present. Tips for use: The temperature of the nutrient solution can affect the accuracy of the reading. Your probe or meter should have been factory calibrated (like all Bluelab conductivity products) and automatically compensate for temperature. However, you should check this with the manufacturer if not using a Bluelab product. Sometimes you ll be taking a cold probe and putting it into a warmer nutrient solution or conductivity standard solution. If this is the case, leave the probe in the solution for five minutes or so before taking the reading. This way the probe will reach the same temperature as the nutrient solution and ensure accuracy as the probe s reading is temperature dependent. You ll need to do this most often in winter. Cleaning: Conductivity (EC/CF) probes require cleaning at least once a month. This removes the build up from nutrient salts, ensuring better accuracy with your readings. Always test the probe in a known solution after cleaning such as Bluelab 2.77EC Conductivity Standard Solution Only ever buy good brands of conductivity standards only use sachets once and throw bottles away three months after opening. Conductivity probes that give low readings consistently need cleaning. The shroud on the conductivity probe must always stay on the probe tip except when cleaning or the readings will be incorrect. Avoid touching the probe face with your fingers the oil from your skin will contaminate the probe. Rinse the probe head in fresh tap water after each use to reduce contaminant build up. Care instructions come with the product please follow them. FAQ s Q A Q A If I m using organic nutrients why is my EC so low? Is my probe broken? Organic nutrients often must be broken down by microbes into ionic forms that the plant can absorb. Until they are broken down into ionic forms, they don t conduct electricity, and so don t contribute to the conductivity reading. Why can t we just use one bottle of nutrients? If all the nutrients are all present together in a concentrated form some will react together and become insoluble and unavailable to the plant. Using two (or more) part mixes reduces the risk of wasting expensive nutrients. 37 Bluelab Grow Book bluelab.com 42

21 Growers Glossary Acid: A chemical substance that unites with an alkali base to form a salt. An acidic solution has a low ph below 7.0 ph. Phosphoric and nitric acids are commonly used to lower the ph value of nutrient solutions. Aeration: Introducing air to the growing media and/ or nutrient solution to provide adequate oxygen for plant root zones. Agitation: Mixing or aerating nutrients generally in the holding tank by means of a pressurized jet of nutrient or via a stream of air introduced by an air pump. Alkali: A soluble chemical substance which, when mixed with an acid, produces a salt. An alkali has a high ph, being above 7.0 ph. Potassium hydroxide (caustic potash) is the alkali commonly used in hydroponics for raising the ph value of nutrient. Alkalinity: The alkaline concentration of a nutrient solution. Anion: A negatively charged ion (e.g., sulphate; SO 4 2- ). Atmosphere: The quality of the air or climate in a growing area. Ball cock: A float-operated valve allowing automatic replenishment of water levels in holding tanks (also used in toilet cisterns, etc). Batching: Mixing a volume of ready-to-use nutrient solution. Buffer: A solution that maintains the relative concentrations of hydrogen and hydroxyl ions by neutralizing, within limits, added acids or alkalis, thereby producing a ph-stable solution. Calibration: Adjusting meters and controls to known standards. Cation: A positively charged ion (e.g., potassium; K + ). The opposite of anion (see above). CF (conductivity factor): A scale of conductivity often used in Australia and New Zealand. Calculated by EC times 10. Chemical: A substance with constant composition and defined properties. Colorimetric: A method of measuring chemical values. A chemical will turn a certain colour when brought into contact with the chemical of interest. Colorimetric tape can be used to measure the general ph value of a nutrient solution. Conductivity: Measurement of the electrical current of a solution. Pure or distilled water has no electrical conductivity. Added minerals (dissolved salts) create electrical conductivity. Measured by several different systems. See page 16. Contaminant: An impurity or unwanted chemical or substance. Deficiencies: Poor plant health or low productivity caused through the unavailability of an essential mineral element. Deionisation: Removal of all ions in water. Resulting in ph neutral (ph 7) water. Dosing: Adding concentrated nutrient mixes, or ph correctors, to return the nutrient contents of the growing system to the desired values. Dose on time: The length of time dosing is allowed by the controller. Dose off time: The length of standby (dosing stopped) time, allowing materials to mix in the tank before dosing recommences. Humidity: A measure of water vapour in the air. Hydroponics: A growing system that uses soil-less growth mediums and supplies nutrients via a nutrient solution. Inert: Chemically inactive. A substance that does not react or change form is inert. Ion: An atom or molecule that has a positive (cation) or negative (anion) charge due to having lost or gained electrons. Lock-up: If your nutrient solution is too acidic or too alkaline it can cause nutrient lock-up, restricting certain nutrient elements essential for growth from being absorbed by the root structure. Macro-elements: The major elements for plant growth, including nitrogen, calcium, potassium, phosphorus, magnesium, iron and sulphur. See page 6. Microorganisms: Living organisms (such as bacteria,fungi,viruses) that are only visible under a microscope. Also called microbes. Peristaltic pump: A common component of a dosing system. Moves liquid by mechanically squeezing along a flexible tube, pushing liquid through it. ph (potential hydrogen): The measurement of acidity (below 7.0 ph) or alkalinity (above 7.0 ph) of a solution. Determined by the quantity of H + cations (protons) present. See page 10. ppm (parts per million): Not a true measure when measuring the conductivity of a nutrient solution. ppm has many different scales. Bluelab products use 500 (TDS) and 700 scales. Calculate ppm by multiplying EC by the scale required. See page 16. Precipitation: When a chemical reaction occurs and forms a solid material that subsequently falls, as a precipitate, to the bottom of the container. Reservoir: A nutrient or water-holding tank. Soluble: Is able to be dissolved in water. The opposite of this, insoluble, is a substance that cannot be dissolved in water. Stock solution: The liquid nutrient concentrates added to water to create and maintain a nutrient solution. Suspended solids: Solid particles of matter contained within water or nutrient solution. Can be removed by filtration. TDS (total dissolved solids): The total content of inorganic materials dissolved into water. TDS also stands for the 500 ppm scale as a measure of nutrient concentration. Tip burn: Usually caused by too high a conductivity level, resulting in cell death occurring at the leaf tips and margins. 39 Bluelab Grow Book bluelab.com 40

22 References Ayers, R. S. (1976). Water quality for agriculture, 107. Bamsey, M., Graham, T., Thompson, C., Berinstain, A., Scott, A., & Dixon, M. (2012). Ion-Specific Nutrient Management in Closed Systems: The Necessity for Ion-Selective Sensors in Terrestrial and Space- Based Agriculture and Water Management Systems. Sensors (Basel, Switzerland), 12(10), Bicarbonate bad guy in Western soil, water. (1998, June 20). California-Arizona Farm Press. Dustin Meador. (2016, April 12). Effect of irrigation ph: acidity and basicity; on nutrient availability, plant health and yield of 3 plant species grown in hydroponic-nutrient solution and mix-media with fertigation. The Center of Applied Horticultural Research. Hinsinger, P., Plassard, C., Tang, C., & Jaillard, B. (2003). Origins of root-mediated ph changes in the rhizosphere and their responses to environmental constraints: A review. Plant and Soil, 248(1 2), J. Heritage, E. G. V. Evans, & R. A. Killington. (1999). The microbiology of soil and of nutrient cycling. In Microbiology in Action. Cambridge University Press. Lages Barbosa, G., Almeida Gadelha, F. D., Kublik, N., Proctor, A., Reichelm, L., Weissinger, E., Halden, R. U. (2015). Comparison of Land, Water, and Energy Requirements of Lettuce Grown Using Hydroponic vs. Conventional Agricultural Methods. International Journal of Environmental Research and Public Health, 12(6), org/ /ijerph Paul R. Fisher. (2007). Managing the ph of container media. University of Florida. Reid, R., & Hayes, J. (2003). Mechanisms and control of nutrient uptake in plants. International Review of Cytology, 229, S. M. Deshpande, & Aher, K.. (2012). Evaluation of Groundwater Quality and its Suitability for Drinking and Agriculture use in Parts of Vaijapur, District Aurangabad, MS, India. Research Journal of Chemical Sciences, Uchida, R. S. (2000). Essential nutrients for plant growth: Nutrient functions and deficiency symptoms. Plant Nutr Manag Hawaii s Soils, 3, United States Department of Agriculture. (2014, May). Soil Electrical Conductivity. Vallance, Déniel, Floch, Guérin-Dubrana, Blancard, & Rey. (2011). Pathogenic and beneficial microorganisms in soilless cultures. Agronomy for Sustainable Development, 31(1), doi.org/ /agro/ Wang X., Tang C., Mahony S., Baldock J. A., & Butterly C. R. (2014). Factors affecting the measurement of soil ph buffer capacity: approaches to optimize the methods. European Journal of Soil Science, 66(1), Zhao, C., Miao, Y., Yu, C., Zhu, L., Wang, F., Jiang, L., Wan, S. (2016). Soil microbial community composition and respiration along an experimental precipitation gradient in a semiarid steppe. Scientific Reports, 6, srep24317 *Note that The Grow Book is not fully referenced. Writer Profiles Leila Jones is a recent graduate from Massey University in New Zealand with a Bachelors degree in Chemistry and Genetics. She is interested in the science behind growing plants and how to improve current growing systems in order to sustain global growth. Dustin P. Meador, Ph.D. is the Executive Director of the Center for Applied Horticultural Research, a non-profit organization dedicated to finding practical, sustainable solutions for the horticulture industry. He graduated with a doctoral degree in Horticultural Sciences, with a minor in Soil and Water Sciences in 2012, from the University of Florida, College of Agriculture and Life Sciences in Gainesville, FL. His dissertation entitled: Irrigation water quality, treatment efficacy and nutrient management, has provided guidelines for irrigation monitoring, treatment and safety in horticultural operations. We hope you have found our Grow Book to be a valuable tool for your pursuit of the perfect crop. We want to ensure that the Grow Book remains relevant and provides all the information that will support a new or experienced grower. Please contact us with any suggestions, eureka moments or examples of your experiences or learning with your growing system which we can share with other readers so they may learn from you. Simply chat with us at bluelab.com or send us an support@bluelab.com 41 Bluelab Grow Book Bluelab Grow Book 42

23 Learn more Do more Get more Grow your understanding Chat To Us Global brand with offices in three locations: Chat with us at bluelab.com or send us an P P P F North America Netherlands +31 (0) Rest of World facebook.com/getbluelab Copyright 2018, all rights reserved, Bluelab Corporation Limited GROWBOOK_V03_ Post Bluelab Corporation Limited 8 Whiore Avenue Tauriko Business Estate Tauranga 3110 New Zealand Limited Written Guarantee A limited written guarantee is available with each product from the Bluelab Product Range. Proof of purchase required. SEPTEMBER 2018