Most fertilizers suitable for feeding are compatible at their dilute concentration.
However, certain chemicals will react at higher concentrations (usually greater than 20x the feed strength) to form insoluble precipitates. These precipitates can tie up the intended nutrients and clog your irrigation equipment. In general, calcium nitrate must not be concentrated with magnesium, phosphorus, or sulfur containing materials. This is the primary reason why calcium is always excluded in any standard fertilizer formulation. For any crops in polybags or pots planting, calcium is always been overlooked. Calcium content in leafy crops formulation set is about 9.9% as CaO. It doesn’t mean when you are dealing with leafy crops, calcium is NOT important to the crops.
It’s the hydro-store, and the nutrient companies, job to hype their products and stick pretty pictures on their bottles, so you are willing to spend the premium dollars on their products. This is NOT a premium fertilizer, but a DIY balance diet, good enough to promote growth for the seedlings which are housed in the polybags, where their roots are confined to deficiency if proper nutrition is NOT provided. The single element fertilizers come in powder form. Commercially, it is packed into 12.5-kg packing each into 2 separate bags, A and B … the reason, calcium is the trouble maker will react with other elements in high concentration.
With each 12.5-kg bag, you have to dilute it into 50-liter barrel, namely A and B.
This balance diet is derived from the origin 15-15-6-4 formulation which is meant for younger plants. Each elements have to sacrifice a bit to allow room for CaO to be added.
As a thumb of rule, always start at lower dosage to your plant prior to mass application.
Foliar : 2.5ml ( A and B each, equally) / liter of water
Soil drench : 4ml ( A and B each, equally) / liter of water
Frequency : 1 ~2 times / week