Effect of organic manures and inorganic phosphorus on soil fertility status (N, P and K) in rice-blackgram cropping sequence

The present study attempts to relate the phosphorus dynamics in relation to nutrient management in rice- blackgram cropping sequence with respect to changes in soil fertility. Results of two years (2017-2019) experimentation revealed that at all growth stages of rice, significantly highest available nitrogen, phosphorus and potassium in soil were recorded with application of RDNK+Dhaincha @ 10t ha-1(M3) and this was on par with RDNK+ Sunhemp @ 10t ha-1(M2), whereas lowest was recorded in RDNK (M0) alone in all four seasons of study. Among the P levels the available nutrient status (N, P and K) were increased with the increasing level of P from 0 (P1) to 120 kg P2O5 (P5) ha-1, irrespective of the nutrients imposed to rice crop. Significantly highest was recorded in P5 (120 kg P2O5 ha-1) and this was on par with P4 (90 kg P2O5 ha-1), whereas the lowest was recorded in treatment P1 that received 0 kg P2O5 ha-1. However, as like preceeding rice crop the similar trend was observed at flowering and harvest in succeeding blackgram.