A Way to Calculate a Fertilizer Formulation, N-P-K, for Maize.

A question that farmers always ask to technicians is how much fertilizers, N-P-K, should they put in their fields for nutriment their maize crops. This question is tricky to answer because there are a lot of uncertainties due to the amount of nutriments the crop can assimilate, the moment and how fertilizers are applied, air temperature during the crop season and, at least, the water availability. The type of soil, its characteristics and the results of a soil analysis, is important but does not define the amount of fertilizers, it just adjusts the final amount. Agriculture research institutions have determined the amount of nutriments that a crop would require through fertilizer field trials at a certain location. From these trials, the amount of available water and air temperature are the major factors that define the amount of nutriments that a maize crop would require in order to achieve the highest yield at a certain location. Location is the principal factor that defines the amount of nutriments that a maize crop is able to assimilate, because its productivity potential is determined by its water availability and temperatures. Maize variety may also adjust the final amount due that varieties have different capacity of nutriment assimilation and therefore yield. For a minimum of 300 mm/year of rain feed, a minimum amount of 40-40-40 N-P-K fertilization formulation would be needed, and grain yield could be around 3.0 t/ha; and for a rain feed of about 700 mm/year, a 220-100-80 fertilization formulation would be required for a maize grain yield of 9.0 t/ha for a warm climate. For a temperate climate the nutriment requirement would be between 40-40-40 and 180-80-60 for 300 and 700 mm of rain feed, respectively. Between these, for a given amount of water availability or rain feed, an interception can be determined. Also agriculture practices like how and when fertilizers are applied or the previous crop could modify the final amount. The amount of fertilizers that a maize crop needs would first depend of the amount of water availability and temperature during the growing season.