Status and Depletion of Soil N, P and K Fractions at Harvest of Blackgram Grown on Residual Fertility in a Hybrid Rice - Blackgram Cropping Sequence

摘要

Cropping system involving hybrid rice during Kharif and blackgram during rabi was studied under the influence of high levels of N,P and K fertilizer applied to kharif rice. Blackgram was grown on pure residual fertility. The soil inorganic fractions of N, P and K were studied. After harvest of rice the soil showed highest contents of these fractions in those treatments which received highest levels of these nutrients, respectively. Even after the harvest of rabi blackgram the trend remained same. There was a depletion in N fractions after harvest of blackgram despite the fact that leguminous blackgram fixes atmospheric nitrogen. Among P fractions the depletion at harvest of blackgram followed the order S-P>Ca-P>AI-P>Rs-P>Fe-P indicating that S-P andCa-P are preferred forms of P by blackgram. Exchangeable K was the most depleted fraction among other inorganic K fractions.