Special commercial hydroponic solutions are available for growing tomatoes, but for large-scale tomato growing, it makes sense to make your own. Nutrient solution recipes for tomatoes vary depending on the life stage of the tomato plant.
Start with good-quality water that is free from contamination of any kind. Allow tap water to sit before use to remove chlorine. The initial salt concentration should be low and the ideal pH is between 5 to 7. In areas with hard water, use rainwater to make your nutrient solution.
Make the micronutrient concentrate. This concentrate will be diluted in the final nutrient solution. Add the following micro nutrients to 450 ml of water: 7.50 g of boric acid, 6.75 g of manganous chloride, 0.37 g of cupric chloride, 0.15 g molybdenum trioxide, and 1.18 g of zinc sulfate. Stir or mix thoroughly after each addition. Store the solution in a labeled dark bottle.
Fill the nutrient tank with water. Measure the water volume in liters. The given recipe is for 10 l of nutrient solution. Determine the number of grams to add to your nutrient tank by dividing the number of liters by 10, then multiplying by the number of grams given for 10 l of solution.
Add 5 g of magnesium sulfate (Epsom salts), 2.7 g of monopotassium phosphate, 2 g of potassium nitrate, 1 g of potassium sulfate, 5 g of calcium nitrate and 0.25 g of chelated iron for every 10 l of water. Mix well.
Mix in 2.5 ml of the micronutrient concentrate for every 10 l of nutrient solution. Stir to mix well.