Long Term Fertilizer experiments - status of N, P and K fractions in soil

Abstract

A study was taken up in the existing Long Term Fertilizer Experiment in Tamil Nadu Agricultural University, Coimbatore, conducted since 1972 to know the status and content of various macronutrient fractions and their effect on crop yield, uptake and nutrient availability in the soil. Exchangeable NH4-N and NO3-N were significantly increased by incremental additions of N. Inclusion of FYM along with inorganic fertilizers, had a positive effect on the build up of all the organic N fractions. There was abuild up in total-P content and it was maximum with 150 per cent NPK application. N-alone application drastically reduced the concentration of available P. The Ca-P constituted the dominant inorganic P form. Available K revealed a negative balance due to continuous cropping with a decrease of 22 per cent from the initial level. Lattice-K constituted a dominant fraction of K and water soluble K proved to be the deciding factor in predicting yield variations.