To grow, plants need a number of mineral elements (broadly only 16 elements are generally considered essential for most plants) .
These are split into two broad groups: Macroelements and microelements.
Macro elements consist of:
- Hydrogen
- Carbon
- Oxygen
- Nitrogen
- Potassium
- Calcium
- Magnesium
- Phosphorus
- Sulphur
Micro elements otherwise known as trace elements consist of:
- Chlorine
- Boron
- Iron
- Manganese
- Zinc
- Copper
- Molybdenum
About 90% of the fresh weight of a plant is water (H2O). When a plant is dried to remove this water then 90% of what remains consists of compounds of Hydrogen, Carbon and Oxygen. So these three elements make up more than 98% of the weight of a typical plant.
For nutrient stock solutions for tomato growing, I mix up 50 litres at a time of an A solution and a B solution at 100 x concentration. These can then be diluted to make up a nutrient solution using 1 litre of each stock solution ( 1 x A and 1 x B) and 198 litres of water in a 200 litre water butt.
I use two different stock solutions (A and B) and 3 stages of development using the following weight of chemicals.
Stage 1: Germination to seedling stage
Stock A (using 50 litres of water)
- Calcium Nitrate: 2.3kg
Stock B (using 50 litres of water)
- Potassium Nitrate: 1.15kg
- Monopotassium Phosphate: 0.9kg
- Potassium Sulfate: 0.8kg
- Magnesium Sulfate: 1.0kg
- Microelements: 0.15kg
Stage 2: Seedling to first fruit set stage
Stock A (using 50 litres of water)
- Calcium Nitrate: 3.45kg
Stock B (using 50 litres of water)
- Potassium Nitrate: 0.95kg
- Monopotassium Phosphate: 1.25kg
- Potassium Sulfate: 1.95kg
- Magnesium Sulfate: 1.65kg
- Microelements: 0.15kg
Stage 3: First fruit set onwards stage
Stock A (using 50 litres of water)
- Calcium Nitrate: 4.6kg
Stock B (using 50 litres of water)
- Potassium Nitrate: 1.55kg
- Monopotassium Phosphate: 1.45kg
- Potassium Sulfate: 2.6kg
- Magnesium Sulfate: 2.25kg
- Microelements: 0.15k
The microelements were purchased in a tub that has all the essential microelements required in broadly the right mix. This eliminates the need to measure chemicals at small weights (under a gramme).
Hi, What could happen if I use the stage 3 formula in all the growth stages of the plants?
Hi. Thanks for the question. Firstly if you were doing it commercially you would be adding cost for no good reason. Secondly the young seedlings would not necessarily cope with the stronger solution and depending on the plant can sometimes looked “burned” and overgrow if the solution is too strong.
That said I have on occasions cheated a little and just diluted the 3rd stage solution for a small number of plants at stage 2 so the concentration is halved. This is not optimum for commercial operations where yield is important.
Using a hobbyist solution like Formulex for stage 1 would probably be a better approach if you do not want to go to the trouble of making up your own lower strength solution.
Hi,
Thanks for such useful information…
For a 1000 tomato plant, how mush chemical needed for complete session? I trying to make an economic calculation as I am thinking to start a hydroponics system.
Have a nice day.
Nabeel (Iraq)