Fertilizer solubility is one of the key elements in making hydroponic nutrient stock solutions. If you know the fertilizer solubility, you can make optimum stock solutions for any size nutrient tank.
Making stock solutions is extremely simple. All you have to do is to calculate the amount of fertilizers required to make a normal 1:1 solution that can be used directly to irrigate plants. Multiply each amount by 100 and add that amount to the same size tank that would have been used for the 1:1 solution. The new solution is a 1:100 stock solution. If each amount of fertilizer has been multiplied by 50, it is a 1:50 solution. For example, if complex fertilizers are used and the recommended rate is 1 kg.1000 L-1 of chemical X and 1 kg.1000 L-1 of calcium nitrate, a 1:100 stock solution would require 100 kg.1000 L-1 of chemical X and 100 kg.1000 L-1 of calcium nitrate. It is important that the size of the tank is not changed.
An important aspect to take into consideration is the fertilizer solubility. The fertilizer solubility value is the saturation point to which each fertilizer can be dissolved before the various components precipitate The fertilizer solubility value is not a fixed value, it varies according to temperature of the water. Increasing the water temperature will increase the fertilizer solubility value. This is important because mixing close to the maximum solubility limit in hot weather, can cause precipitation during the night when water temperature drops.
If you accidentally mixed too much fertilizer and a precipitate forms, just add more water to the tank. It will take some time for the precipitate to dissolve again.
Common fertilizer solvability ratios in 25°C water are:Approximate solubility levels (g.100ml-1) in cold water (25 °C) of some common used fertilizers used in hydroponics.
|Potassium dihydrogen orthophosphate||KH2PO4||330|
|Magnesium nitrate||Mg(NO3)2.4 H2O||4264|