Phosphate Management in Rice-Mustard Cropping Sequence on Acid Soils of Nagland

A field experiment was conducted in 1989–90 and 1991–92 on acidic soils of Nagaland to study the responses of P and farmyard manure (FYM) to rice-mustard crop rotation. Significant response of rice to P was found up to 45 and 30 kg P ha⁻¹ without and with FYM 15 t ha⁻¹, respectively, while in mustard crop the response was up to 20 kg P ha⁻¹ in absence and 10 kg P ha⁻¹ in the plots with residual effect of FYM applied to previous rice crop. The uptake of P, however, progressively increased significantly up to the application of 45 kg P ha⁻¹ in rice and 20 kg P ha⁻¹ in mustard, both in absence and presence of application of FYM. Application of FYM @ 15t ha⁻¹ to rice improved the efficiency of applied P by 12.6 percent in terms of grain yield of rice and 18.4 per cent in case of grain yield of succeeding mustard crop. FYM also enhanced the efficiency of P utilization by rice (18.4%), mustard (29.9%) and rice-mustard cropping sequence (23.4%). The mean P balance in soil of applied P after the crop rotation was low in FYM treated plots indicating enhanced P utilization. The residual available P content of the soil increased with the increase in P supply and FYM had further beneficial effect on it. On an average, 22.2 per cent more net profit was obtained when FYM was applied along with P.