Hydroponics Hydropon ics Made Easy
CHAPTER 7 NUTRIENT MANAGEMENT FOR AUTOPOT AUTOPOT SYSTEM SYS TEM Food for plants is the simple definition of nutrient. But in hydroponics, when we speak of nutrient we are not speaking of just part of the food chain for the plant, it’s the whole thing. Because hydroponic media makes no contribution to the health, welfare or general nurture of the plant other than to give an anchoring point, everything that the plant needs other than light, warmth and location must come in the nutrient solution.
Hydroponic Nutrients Nutrients Are they Safe? The answer is YES. Vegetables grown with hydroponic nutrients are very safe to eat. In fact, it is generally more nutritious than soil grown crops.
Are they Chemicals? Chemicals?
The major components required are Nitrogen Potassium Phosphorous Calcium Magnesium and minor quantities (called trace elements) of Iron, Manganese, Cop per, Boron, Molybdenum and Zinc. All of these are present in the various Autopot hydroponic formulations and in most commercial hydro ponic nutrients. • • • •
Hydroponic nutrients can be more accurately classified as minerals rather than “chemicals” as they are very similar to common table salts. Table salts are extracted from sea water and purified for human consumption.
•
These nutrients are different from common garden fertilisers in at least five important ways 1. they are 100% soluble 2. they come come in a form that is immediately immediately useable useable by the plants 3. they are of a much higher degree degree of purity, being formulated and and manufactured to what is called technical grade 4. they are more expensive than common common garden garden fertilisers fertilisers 5. they generally generally come as a two part mix called called Part A and Part B
Two Part Mix Nutrients The main reason for having two part nutrient mixes is that the nutrients are chemically active when the two parts are mixed in their concentrated form but they are OK to mix in diluted form. The solution will gradually becomes less potent once the reaction that takes place when the two parts come together has occurred. You can also buy three part mixes, but as far as the Autopot System is concerned, this has little practical advantage. advantage.
Normal Garden Garden Plant Food Some normal complete plant foods are labelled as being suited to hydroponic use, but seldom are. They are quite different to hydroponic nutreints and are formulated for use with soil, which already contains substantial amounts of nutrients, rather than the commonly used inert growing media like perlite or rockwool. The most obvious difference between hydroponic plant food and non-hydroponic type is that the hydroponic plant foods usually come in two part packs.
The specific formulation of the two part mixes is greater than the almost 1 litre A/B pack.
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endless number of suppliers of mixes, but as a general rule one part usually consists of the Calcium nitrate end of the total formulation which supplies the required calcium and most of the nitrogen requirements and the other part usually comprises the Potassium, Potassium, Phosphorous and trace element parts of the formula.
A range of Autopot nutrients in both liquid and powder forms. They are specially formulated for use with the Autopot System.
Customising nutrients Some people will always try to get a little more performance out of their cars, skis, profession or their hydroponic system and this can be done. We believe this is better left to the experts, but it is not really all that difficult in principle. By increasing the proportion of calcium nitrate portion in the mix, you make more nitrogen available to the plants. This is good for stimulating vegetative growth and is useful, for instance, during early growth of many vegetables, and good for leafy vegetables such as lettuce, silver beet, spinach, celery and the like. By increasing the level of the second part in the mix you increase the availability of Potash and Phosphates which stimulates good root growth and is useful for developing fruit such as when tomatoes start to flower and develop fruit.
Which Nutrient ? There is a wide variety of branded and plain brand labels which come at a wide variety of prices. No two are quite alike although most will be similar and virtually all are at the worst, quite adequate. The Autopot branded nutrients are specially formulated to suit the Autopot System but there is no problem trying out a variety of nutrients. If you are a beginner in the hydroponic business, business, we suggest suggest to you that you will be wise to stick to the standard Autopot nutrient and the mixing ratios dictated on the label. There are also a lot of special formulas that are very good for a particular crop or which give a slight overall better result. Try a few. Keep notes. Find the nutrient that suits you best. Various forms of powdered nutrient mixes are available from hydro ponic stores. This is the cheapest way to obtain your nutrient but it has the disadvantage of being relatively inconvenient and can cause problems if you do not get both the proportions and the mix exactly right. Very few pre-mixed nutrients will cause problems, but an improperly made up powdered nutrient can cause untold damages.
1 litre A/B pack.
5-litre A/B pack .
10-litre A/B pack.
2-kg & 1 kg packs.
Mixing Powdered Nutrient The best procedure is to mix up stock solutions so that you have a sup ply that t hat will last a while. It is a good idea to get hold of two clean 10 litre tanks. One for your part A and the other for the part B. Read the manufacturer’s instructions carefully and follow their directions. Normally they will recommend something like the following; Weigh out two kilos of part A and two kilos of part B and put each portion in a separate labelled 10 litre container. A translucent container is 2
10-kg A/B packs.
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probably best so that you can visually check that the solution has dissolved. Add about 3-5 litres of very hot water to the container and shake it all about until all the powder has dissolved. Top up with warm water. Do this to both containers. Keep the two part separate until you are ready to mix a working solution and then mix in the ratio of 5ml of each of part A and part B to each litre of working solution. It is a good idea to add dyes to their stock solutions, such as a small sachet of blue food dye in part A and a sachet of yellow in part B. If you always use the same amounts, you have a visual check on the balance of the working solution which should be light green if blue and yellow were the primary dye colours.
Mixing your own formula nutrients Unless you are a trained horticultural scientist or have relevant working knowledge in the field, we strongly suggest that you avoid mixing your own. The best you could possible get would be a slightly better result and the more likely result would be a disaster on the scale of a t otal kill of your plant stock. Keep to the commercial mixes, make sure you use as recommended and you will play safe.
Nutrient concentration concentration can be measured with this hand held TDS (total dissolved solids) meter. This is a use ful instrument to own.
Nutrient Boosters There are various products or procedures that are interesting to try and which may offer advantages and are not likely to cause damage. The following are a few that users have reported give them good results: •
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Earth Juice, a name given to worm castings. You can either buy these or make your own by extracting the liquid from worm castings and pulverising. This is claimed by a number of its devotees to be very good stuff. You mix small amounts into your working solution. Possibly you would start with about a teaspoon full to the litre of working solution. It does seem to improve the performance of the plants. Vital. A manufactured liquid that is generally used as a foliar spray. Many users have said it works wonders when used sparingly, say 1ml to 1 l itre of water.
Other Mixes •
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•
Bioponic solution. Another manufactured proprietary line that is mixed in the ratio of 10ml in 10 litres of working solution. It seems to work well and to improve both yield and the longevity of the plant. Super Thrive. Also reputed to produce good results when added at the rate of a few drops per litre of working solution. Various Foliar Sprays. Most are generally quite good, but if your system is working well, and properly maintained, the added results compared to the extra cost and trouble might be a matter of debate, but if you feel like trying foliar sprays, do so. If you you use as directed you are not likely to do any harm and might help.
Usually it is the way that nutrient is managed rather than specific for 3
Superthrive is a popular popular plant tonic for hydroponic growing. All that is needed is a few drops of the concentrates in a litre of nutrient solution.
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formulation of the nutrient that dictates the best results and environmental factors are very important i mportant in nutrient management. management. Meticulous nutrient management will not produce a premium result if light is lacking. l acking. A large shade tree overhanging a greenhouse would be an example of this.
Conductivity Conversion Chart Ms/cm
CF
X 10
Ppm
X 70
Nutrient troubleshooting in your Autopot System
0.5
5
350
1.0
10
700
Once you have become accustomed to how your Autopot System operates and the results you can expect, the following advanced technique suggestions could be of interest and benefit to you. We wish to stress that you will get good results using the standard nutrient and that all attempts to get a better than normal result also carry the risk that you might get worse than normal by varying from the standard procedure.
1.5
15
1050
2.0
20
1400
2.5
25
1750
3.0
30
2100
3.5
35
2450
4.0
40
2800
4.5
45
3150
5.0
50
3500
SUGGESTION #1. During the very hot period of summer, the plants will use an amazing amount of water. The plants grow faster and consequently need more food. This is carried to them in the nutrient solution automatically. But one of the reasons for the plants increased use of water is that the plant cools itself by evaporating water from its leaves in a process not dissimilar to the use of an evaporative cooler in your home. The water that is evaporated also carries nutrient so in the more extreme extreme conditions you can get an over supply of of this nutrient to the plant. This causes no harm, but it can tend t end to increase the salination level and uses more nutrient than necessary so you can lower your operating costs for that period by decreasing the concentration of nutrient in the water by as much as 30%. SUGGESTION #2. You will never cause damage to a plant by reducing the concentration concentration of nutrient but it is possible to do so by increasing it. If in doubt, try a decrease first. If you are increasing, do so a little at a time and keep a good watch on the plants. Sometimes a small increase can be beneficial and a large increase fatal. Experience is a great teacher and you will learn to increase concentrations by a little at a time until the deep green colour and a healthy looking gloss on leaves tells you that you have the balance just right. SUGGESTION #3. If your plants start to show signs of distress or damage, damage, do not immediately assume assume that the nutrient is the problem. It seldom is. Usually it will be an environmental factor such as temperature, humidity, disease, light and so on. First check that the nutrient solution is getting to the plant. Sometimes because the plants love the nutrient, they cannot wait to get it and send their roots right back into the valve and cause it to fail to allow water through. Pull the roots clear and you are back in business again. Here’s another situation that happens from time to time. You fail to notice that the tank is running dry and then suddenly see that the plants are wilting and quickly top up again. No problem you say. The plants
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Ms/cm (Milli-siemen) CF (Conductivity factor) Ppm (Parts per million)
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spring back into life and look good. A week or two later the plants once again show signs of distress but you cannot find the problem this time. Fact is that it was the damage done when the plant dried out, but by this time you have forgotten about that or assumed that because the plant came good again there was no damage done. Lots of books will suggest to you that a bit of wilt and some yellowing is a sign of nutrient deficiency or toxicity. So you add “corrective” nutrient and the problem gets worse. Your reaction to the diagnosis was correct. It was the diagnosis that was wrong. If the plant starts dying from the roots upwards, it will take a day or two to become apparent in the leaf and is then too late. The nutrient solution in the tank remains constant unless you yourself make some adjustment adjustment to its composition. This is different to most standard recirculating hydroponic systems where the balance of t he nutrient is altered from the moment it is first used and requires daily monitoring and balancing. Any time that your system dries out, the first thing is to fill it up again and then try pruning the lower (often unproductive) foliage. If only part of the root system has been damaged, it will recover but not if it has more on top than the reduced root system can feed. SUGGESTION #4. The 2 part A/B nutrient mix can be varied. Part A carries all the phosphate and potash ingredients and trace elements and part B carries the calcium and nitrogen end of the mix. If you want more vegetative (leaf) growth you increase the amount of nitrogen, and for flower and fruit growth you need more potash and phosphate. So during the plant growth stage before bloom, increasing the part B by 10 to 15% will produce more growth. Then about four weeks before you expect blooming, decrease the part B and build up the part A by 10 to 15%. Do not regard this as a fixed rule. Try it and see how it works for you and for the plants you are growing.
Flushed with success. The facts and the fiction One of the basic tenets of hydroponics is that you will get a build up of salts from your hydroponic solution and that these must be removed by washing them away with water, which is called flushing. One of the most salt sensitive plants is lettuce and in standard hydro ponic systems, flushing every 7 days is considered good practice. We grow lettuce under cover where the containers cannot be flushed by rain and we always grow them from seed to maturity without flushing. No flushing. NEVER ! But that’s not all. The author has several hundred different plants that have been grown undercover and have not been flushed in t he last three years. Yes, three years. And they are all absolutely in the pink. Not just one plant but hundreds. Not just a single variety but a wide variety including orchids, kalanchoes, many different ferns, tuberous begonias, 5
Autopot Nutrient Nutrient Guide Guide For Mixed Cropping. If you have a mixed crop (for example, tomatoes, silver beet and beans), it is better to have a com promised nutrient rate. We recommend to start of with a CF of 30 for the first 4 weeks and bring it down to 25 untill the end o f the crop. If you can, it is always better to group the plants into three categories with each category feeding from a separate tank. A) High level - tomatoes, beans, eggplants, capsicum etc. B) Medium level - such as cucumbers, melons, cabbages, cauliflowers, broccoli C) Low level - lettuces, strawberry, onions
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strawberries and the list goes on. Enough in variety and number to be able to say that with good nutrient management you will not need to flush your Autopot System. In fact, and this is getting somewhat technical, we have a mounting body of evidence to show that the Autopot System, allows roots to avoid uncomfortable zones where the concentration of salts happens to be high. If the idea of not flushing is too much for you to cope with, flush away. But do it to a regular pattern. Flush every two weeks before the salt concentrates build up. Plug the 4mm tubing above the valve and remove the valve. Water from the top with a hose. A really thorough soaking then drain the container. If it happens to be raining outside, take the plants out and leave them in the rain. This chapter on water describes just how much plants love fresh rain water.
Examples – no no flushing
Polypodium – this fern (a salt sensitive plant) has been growing in an Autopot Hanging Basket undercover for 6 years constantly fed with nutrient of CF20 and no flushing. It is still growing healthily, showing no signs of distress.
One of our very serious growers who used a recirculating system for 15 years before switching to an Autopot System 4 years ago has a system that works very well for him. He uses the standard nutrient supply for five days and then supplies fresh water with no nutrient for one day and back on nutrient for another five and and so on. The author uses a different method for vegetables. Perlite is first used for salt sensitive plants like lettuce and strawberries. When these are finished the same perlite is used for more tolerant plants like tomatoes and finally for the most salt tolerant plants such as cabbages and broccoli. After this rotation the boxes are left out in the open for 2 to 3 months or more to allow a natural leaching to take place.
Alternative nutrient management methods These techniques should ideally be confined to professionals or very serious hobbyists. They will necessitate the purchase of CF (Conductivity factor) meter to measure the concentration of the nutrient solution.
Tomato plants in the Autopot System – picture shows the 6 month old crop growing healthily with no sign of salt toxicity.
Adjustment of the CF will have an effect on the plants. If you are not sure about what initial strength to use, start at a CF of between 20 and 24. This is a good standard and will give a good result without flushing. If the plants have a really deep, rich colour, they are probably getting more nutrient than is good for them. This is OK in the short term but cannot be sustained for the life of the plant. The remedial action is to dilute the nutrient solution to a CF of 15 until the plants show signs of early yellowing. Then build up the CF to 25. Avoid the natural reaction of assuming that if a little extra strength of nutrient performs wonders, a lot more will perform miracles. That way you will need the miracle to raise your plants from the dead ! The authors procedure for adjustment adjustment of CF is to start at planting with around 35 to 40 and to maintain that for some 4 weeks or so. Then (as a general guide only) to gradually bring the CF down to around 24 for the 6
Comparing drip to waste system (on the right) verses the Autopot System (on the left). Plants treated identically. Now after 6 months, the Autopot crop is as good as the drip to waste system without flushing.
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hottest months or CF26 to 28 for the r est of the cooler months. Rob’s method Rob is an experienced hydroponic grower who has adopted the Autopot System as a replacement for a conventional system because it is so much easier to operate and control.
His method is to use one tank of nutrient which he maintains at a constant CF24 followed by half a tank of plain water. He maintains this rotation permanently and is very happy with the results.
Charlie’s choice….. (see diagram #1 next page) is to have a tank with a ball valve at the top of his nutrient tank. This allows the tank to refill every time water is drawn off. Charlie starts with a tank of nutrient mixed to CF40. Each time a little nutrient is used, it is replaced with fresh water and just that little more diluted. This goes on until the CF falls to 15 and then nutrient is added to build it back up to 40 and the cycle starts again. Charlie is also very happy with the results he gets. Tom’s trick…. (see diagram #2 next page) is to use a tank that has a float valve at a point about a quarter of the way up the tank with the valve connected to a fresh water supply. He starts the process with a full tank at CF30.
This remains constant until the top three quarters of the tank have been used, supplying nutrient at a constant CF30. Then the float valve comes into use and dilutes the solution each time the level falls until it drops to about CF15. These are just a few of the techniques used by Autopot users and just a few of the many that could be used. One system that we favour is to mix separate working solutions of both part A and part B and keep them in separate tanks. Say 100 litres of part A and part B. The lines from the tanks are joined at a junction near the tanks. The advantages of this are that the mixture is always fresh and you can alter the ratio of part A to part B by simply building the strength of the appropriate tank without waiting for the system to dry out. If you come up with a system of your own that works, please let us know about it. *****
Autopot Recommendatio Recommendation n For Monoculture. We need to emphasise that these recommendations are meant to provide you with a general idea on how to feed your plants with the Autopot System for a single crop type.
Tomatoes - Start with CF 35 ( use 8.5 ml of part A stock solution and 8.5 ml of part B stock solution in one litre of water). - 4 weeks later, drop the concentration down to CF30 (ie 7.5ml A and 7.5 ml B in 1 litre of water). - 4 weeks later drop the concentration further to CF of 28.
Cabbages, cauliflower cauliflower - Start with CF 30 ( use 7.5 ml of part A stock solution and 7.5 ml of part B stock solution in one litre of water). - 4 weeks later, drop the concentration down to CF25 (ie 6.5 ml A and 6.5 ml B in 1 litre of water). - 4 weeks later drop the concentration further to CF of 20.
Lettuces Lettuces - Start with CF 25 ( use 6.5 ml of part A stock solution and 6.5 ml of part B stock solution in one litre of water). - 2 weeks later, drop the concentration down to CF20 (ie 5 ml A and 5 ml B in 1 litre of water). - 1 week later drop the co ncentration further to CF of 15.
Strawberries Strawberries - Start with CF 25 ( use 5 ml of part A stock solution and 5 ml of part B stock solution in one litre of water). - 4 weeks later, drop the concentration down to CF20 (ie 4 ml A and 4 ml B in 1 litre of water). - 2 weeks later drop the concentration further to CF of 15.
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Diagram #1 – 200 litre tank with top up float valve connected to mains water supply. 200-Litre drum
Nutrient Preparation Preparation from Powder Powder Nutrients. Nutrients. The use of a two part powdered nutrient is more economical. The best guide to nutrient preparation without using a measuring meter is to follow the instructions on the label. As a rule fo thumb, a total of 2 g (1g part of part A and 1 g of part of part B) of the powdered nutrient dissolved in 1 litre of water will give an approximate reading of CF 20. Or Or an increase by 50% of the nutrients into a litre of water will give a reading of CF 30 which is recommended for early stages of growth for tomatoes.
Diagram #2 – 200 litre tank with top up float valve plus a safety valve near the bottom.
Tap opened.
200-Litre drum
Stock Solution Solution To avoid continual mixing the use of a stock solution is highly recommended. Stock solutions are normally mixed at 100 times the strength of the working solution. Preparation of stock solution - dissolve 100 g of part A powdered nutrient in 1 litre of hot water - dissolve 100 g of part B powdered nutrient into a separate litre water of hot water.
The application rates
Tap closed.
200-Litre drum
The bottom float valve ensures against the tank drying out completely. completely.
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- 5ml of part A stock solution and 5ml of part B solution into the same litre of water which will give a reading of CF 20. - or 7.5ml of part A stock solution and 7.5 ml of part B stock soltuion into the same litre of water to get a CF reading of 30.
Hydroponics Hydropon ics Made Easy
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