NPK fertilizer is usually thought of as a chemical fertilizer, but npk applies to any soil amendment that supplies Nitrogen, Phosphorous, and K, Potassium, including organic fertilizers. What is NPK? An npk fertilizer is usually thought of as a chemical fertilizer, but npk applies to any soil amendment that supplies Nitrogen, Phosphorous, and K, Potassium, including organic fertilizers. The numbers are always in the same order, and refer to the percentage of each element in the fertilizer. Plants need nitrogen for leaf growth, phosphorus for root formation, stem growth, and fruiting, and potassium for flowering and plant immunity. An organic npk fertilizer can be slow-releasing or fast-releasing. Many have both quick-releasing “labile” nutrients, and more “recalcitrant” nutrients that break down slowly and supply a steady stream of nutrients over a longer period. Many organic npk fertilizers need soil organisms to break them down and release their nutrients, so they release more quickly when the soil is warm and the soil food web is at its most active. This is also when you get the most rapid plant growth, and your vegetables really need it.
