Hydroponic growing
Growing media.
In standard agriculture the soil is the normal growing media. But even in that situation there is an enormous variation. With hydroponics I have a list of 18 choices, but I am presenting a list of the 5 most common choices, of which I use 4.
Creating seedlings.
I have been struggling to find the best seed sprouting solution. Below is my next plan.
The problem is I was looking for a way to sprout the seed in its ultimate hydroponics growing place. But that only worked about 20 to 30% of the time. So, I have to go to plan B.
I have never used the coco coir, which is made from coconut skin. The problem is I was looking for a way to sprout the seed in its ultimate hydroponics growing place. But that only worked about 20 to 30% of the time. I more or less settled on vermiculite with some perlite on the top, to give the some stability. But the disintegration of the vermiculate created a mess in the tubes. In my last attempt I put 2 seeds in each of 24 net pots. The result was 8 net pots have plants now. But there were 3 issues against me. Firstly it was winter, secondly often not all seeds sprout, thirdly my filling and emptying sequence was erratic, perhaps drowning some of the net pots. I have decided to do the following:
- I am rebuilding my equipment, testing each pump for vermiculite blockages. Also installing larger filling valves with new tubes. These are clear PVC tubes and I will paint them with plastic affinity paint. Unfortunately those valves draw more current than the old ones, which also means making changes to my control system.
- I am going to put 6 or 8 seeds into a damp piece of paper towel and all that goes into a plastic zip lock bag. Then those bags will lay in the day light on a heat mat.
- Those seeds that sprouted and have some leaves visible will be transplanted into a net pot. This pot has a three layers. At the bottom clay pebbles, then vermiculite, and last perlite. If the fill level is a bit low, I can add a few more clay pebbles on the top.
- The task of the clay pebbles is three fold:
- To stop vermiculite bits falling into the tube.
- To stop as much sunlight from entering the tubes, in order to control algae.
- To create ample airspace for the roots. This is assisted by the rapid draining via the pebbles.
Once I have the above plan working I can once more carry out the original experiment. First I can fine tune the timing between ebb and flood. And secondly I can find out if increasing the strength of the calcium nitrate in the nutrient solution, during the early stages, will promote good stem bulk and strong root growth.
Nutrient solution.
After endless hours of researching about nutrient concentrations, I came to the conclusion that this was that traditional question, “how long is a piece of string”. Mind, it is highly dependent on the plant variety and the climatic conditions.
Basically the plant needs 15 to 17 components. They are ranging over metals and acid groups. The total group is spread into three sub groups — major, minor, trace.
The concentrations between those groups drops by a factor of around 10 then 1000 between each consecutive group. Having studied chemistry, has been of considerable assistance.
The concentrations in the nutrient solution is given in parts per million (ppm). But the requirement is for the actual element or acid group. This then has to be translated to the compound to be weighed out and added. You can never create a mix to equal an arbitrary elemental ppm requirement. For example if you want 200ppm potassium and you use potassium nitrate to achieve that, you are not only adding potassium, but also nitrate acid group, which is also on the requirements list. I have a substantial spreadsheet that does all those calculations for me. But you can never match a given set of numbers, but you might come close. That is where my spreadsheet comes in.
Plants require both selective metal ions and acid group ions. I will list then below:
- Major metals.
- Potassium (K), at a concentration of 200ppm.
- Major acid groups.
- Nitrate (NO3), at 800 to 900 ppm.
- Phosphate (PO4) at 150 ppm.
- Minor metals.
- Calcium (Ca) at 80 ppm.
- Magnesium (Mg) at 30ppm.
- Minor acid group.
- Sulphate (SO4) at 90 ppm.
- Trace metals.
- Iron (Fe) at 1 ppm.
- Manganese (Mn) at 0.5 ppm.
- Zinc (Zn) at 0.3 ppm.
- Copper (Cu) at 0.08 ppm.
- Trace acid groups.
- Borate (BO3). but this one is expressed as Boron (B) at 0.2 ppm.
- Molybdate (MoO4). Similarly expressed at Mo at 0.04 ppm.
- Chloride (Cl) at 35 ppm. This compound is challenged. Some plants cannot tolerate Chlorine.
Then there are 2 other metals, being Cobalt (Co) and Nickel (Ni), but a lot of nutrient solutions do not include them. There is also mention of Selenium metal, in very low concentrations. But that, once again, is a sensitive topic, because this metal is poisonous to both plants and people. So I left that one out for consideration.
Next we have sodium, which is not stipulated as being needed by plants, but it is brought into the mix by the various compounds we use. This metal can also be detrimental to the plants health, but it is somehow unavoidable. The trick is to keep it as low as possible.
Just an interjection you can buy bags of fertilizer named NPK mix, which brings those three mentioned compounds into the nutrient. But in that form they are not suitable for hydroponics, but are aimed at soil.
My end product is a 10Ltr standard mixture, containing all the bits the plant might need.
I create this mixture from 7 mixtures at increased strength. Those 7 mixtures are labelled; Premix 10Ltr (Pr) — Calcium magnesium 10Ltr (Ca), ammonium nitrate 2 Ltr (An), zinc boron trace 5Ltr (Zb), manganese 5Ltr (Ma), Iron 5ltr (Fe), copper molybdenum 10Ltr (Cm).
When I make my standard mix I take 7500ml water + 1000ml Pr, + 1000ml Ca, + 100ml An, + 100ml Zb, +100ml Ma, + 100ml Fe, + 100ml Cm.
The reason that I keep some of these mixtures separate, is as follows:
Stronger mixes of Calcium and Magnesium will create a precipitate due to there being sulphate in the final mixture. Some of those sulphates are less soluble. Both manganese and Iron are uncooperative and also give precipitates. Molybdenum is added at a very low concentration at 10mg per litre. It would be inaccurate to weigh very small amounts for small batches. So all these solutions are quite stable over several weeks.
To create those 7 mixtures I use 16 ingredients, so I can manipulate them to get close to my target. The traces are made from one only ingredient, Potassium is in 4 ingredients, Ca & Mg from 3, Phosphate from 2, Nitrate from 4, Sulphate from from 3.
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Premix (Pr) has:
30g potassium nitrate
7 g potassium mono phosphate
12 g ammonium mono phosphate
11 g potassium sulphate
3 g ammonium sulphate
8 g potassium chloride.
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Calcium +Magnesium (Ca) has:
51 g Calcium nitrate 5 hydrate
28 g Magnesium nitrate 6 hydrate
6 g Magnesium sulphate 7 hydrate
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Zinc Boron (Zb)
1000 mg Zinc EDTA Chelate
900 mg Sodium Borate 10 hydrate
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Manganese (Ma)
1300 mg Manganese sulphate
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Iron (Fe)
4000 mg Iron EDTA Chelate
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Copper Molybdenum (Cm)
300 mg Copper sulphate 5 hydrate
80 mg Sodium molybdate
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And then finally Ammonium Nitrate.
I am reluctant to talk about this. It is a fertiliser as well as an explosive oxidant. In solid form it has a common name Nitropril. The solid form is used by the mines, but farmers mostly buy the liquid which is a mixture of Urea and Ammonium nitrate. However every purchaser requires a background check, be registered, buy from a licenced dealer and need to account for all their use. Because I am aiming at a specific mix composition, I cannot have unknown mixtures and concentrations. So I made my own in solution. But it is a tricky task and does require a safe environment and some skills.
My family and friends have asked me why are you building this elaborate greenhouse with all that equipment. Would it not be easier and cheaper to stick the seeds into the ground or just some pots?
Yes and Yes. But I have always had the urge to research, develop, design and find out. I had a go at Hydroponics some 30 years ago. But work drew me away from that. I also strongly believe that in order to feed the world efficiently, farming needs to be done in farming factories of sorts. And greenhouse hydroponics is one of those methods. See Westworld on page one.
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