Quote:
Originally Posted by crazy banana
I also think that it is not only important to have the right N-P-K percentage.
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Why? The most important selection criterion is adequacy and the second is cost. In containers, excesses of N, P and K are eventually leached away therefore the exact ratio is only important insofar as excesses are a waste of money. In the ground, of N, P, K, only excess P is likely to be retained for a long time. I suspect that I have an excess of P from decades of using Miracle-Gro 15-30-15. I'm uncertain of the effects of chronic P overdose on plants. Otherwise, applying additional P in any form would probably just be a waste of money. Maybe, I should have my soil tested.
Quote:
Originally Posted by crazy banana
If it only would be that easy....
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Calculating the elemental ratios or percentages, from the weights or percentages of ingredients, is easy. Calculating the weights or percentages of ingredients, from the elemental ratios or percentages, is much more difficult, but software makes it easier. I covered this here:
FYI, How Professionals Select Fertilizer Ingredients
Incidentally, better free LP software surely exists, but I don't have time to find it.