What do the three numbers on the fertilizer label stand for?
Most people believe N-P-K to stand for the nitrogen, phophorous, and potassium, but that is somewhat incorrect. These are commonly referred to as the major elements along with calcium, magnesium, and sulphur. They are the major contributing compounds in plant growth.
N: nitrogen, used to stimulate new vegetative growth and overall health.
P2O5: phosphorus oxide, used to stimulate flower development and rooting.
K2O: potassium oxide, used to stimulate stem growth and overall health
N-P-K ratings on the labels of fertilizers are misleading at best. They represent N: nitrogen, P2O5: phosphorus oxide, and K2O: potassium oxide. These molecular compound ratios are not the same as the elemental ppm of the associated primary element, except in the case of N. They are only the guaranteed minimum amount of the molecular compound.
A fertilizer labeled 30-10-10 can have up to a total of 80% N, along with 10% P2O5, and 10% K20 and still be "accurate". It could have any combination of N, P2O5 and K2O adding up to 100%, as long as it has at least the MINIMUM listed of any of the three. You could have 50% nitrogen in 10-30-20. These types of labels are misrepresentative. Anyone using them to establish a controlled nutrient balance is not doing their plants any service.
As a general guidline, the N-P-K numbers can be roughly converted to elemental ppm. N, nitrogen is the only element to convert from the label at the ratio of 1 to 1. P2O5, phosphorus oxide, converts to elemental P, phosphorous at a ratio of 1 to .4. K2O, potassium oxide, converts to elemntal K, potassium at a ratio 1 to .8. This demonstrates the radical difference between an N-P-K of 1-1-1 and an actual elemental ratio of 1-.4-.8.
I have only found Botanicare and Green Air Products Genesis nutrients to give the actual ELEMENTAL ppm after dilution. I used to mix my own solutions from ammonium nitrate, calcium nitrate, magnesium nitrate, potassium nitrate, potassium phosphate and other reagents and know from nutrient analysis of the misleading nature of N-P-K labels.
Definition: N-P-K refers to the ratio of important elements in a fertilizer or soil amendment. N stands for nitrogen, which is responsible for strong stem and foliage growth. P is for phosphorus, which aids in healthy root growth and flower and seed production. K stands for potassium, which is responsible for improving overall health and disease resistance.
NPK, FERTILIZER,GENERAL DESCRIPTION
Fertilizer is a material that is added to the soil to supply one or more elements required for plant growth and productiveness. The major three elements are nitrogen, potassium and phosphorus), the secondary elements are calcium, sulfur, magnesium, and other elements are boron, manganese, iron, zinc, copper and molybdenum. Fertilizers enhance the natural fertility of the soil or replace the chemical elements taken from the soil by harvesting, grazing, leaching or erosion. Organic fertilizers include poperly managed barnyard manure, compost and green manure. Manure contains nitrogen and phosphate content. It is sometimes modified with superphosphate to make it a better balanced fertilizer. Compost, decayed to a relatively stable, amorphous state, is made from plant materials mixed with manure and some soil. Green manure is a herbaceous plant material plowed into the soil that has not undergone decay. Artificial fertilizers are inorganic fertilizers formulated in appropriate concentrations and combinations supply three main nutrients: nitrogen, phosphorus and potassium (N, P and K) for various crops and growing conditions. N (nitrogen) promotes leaf growth and forms proteins and chlorophyll. P (phosphorus) contributes to root, flower and fruit development. K (potassium) contributes to stem and root growth and the synthesis of proteins. The common inorganic fertilizers include ammonia (82% nitrogen), NPK combinations, urea (46% nitrogen), superphosphate, mono and dibasic ammonium phosphates (containing nitrogen and phosphate), calcium ammonium nitrate, potassium chloride (muriate of potash).
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