Effect of Long Term Fertilizer and FYM Application on Soil Fertility of a Vertisol under Soybean-wheat Cropping System

The present studies were conducted under All India Coordinated Research Project on Long Term Fertilizer Experiment, which was commenced since, 1972. To assess the effect of 48 years (1972-73 to 2019-20) continuous application of inorganic fertilizers with or without organic manure i.e. FYM on soil fertility status of Vertisols under soybean-wheat cropping system. The results of the present study showed that the application of recommended dose of N, P and K (20:80:20 kg ha-1 to soybean and 120:80:40 kg ha-1 to wheat) with organic manure @ 5 t FYM ha-1 improved the status of available N, P and S but decline in available K. Further, the integrated use of fertilizers with organic manure enhanced the soil organic carbon contents (9.5 g kg-1) from its initial value (5.7 g ka-1). Conjoint use of FYM with 100% NPK substantially improved contribution towards sustaining the soil fertility. A declining trend (228 to 335 kg ha-1) from its initial value (370.0 kg ha-1) of available K status was also observed as a result of continuous application of fertilizer and manure; this indicates considerable mining of available K from the soil. However, the decline of K was of lower magnitude with 100% NPK + FYM and 150% NPK treatments indicating the need to raise the dose of K fertilizer application to meet the demand of crops. Further, soil available nutrients to be adversely affected due to the imbalanced use of nutrients viz., 100% NP or 100% N alone treatments. Thus, the balance use of fertilizers continuously either alone or in combination with organic manure is necessary for sustaining soil fertility and crop productivity.