Budgeting of Primary Nutrients in Soil under Rice-cowpea Cropping Sequences in Alfisols

A field experiment was undertaken at University of Agricultural Sciences, GKVK, Bengaluru, Karnataka, India to study the primary nutrients budgeting in rice-cowpea cropping system in an alfisols. Hybrid rice was tested under aerobic condition during Kharif 2015-16 and 2016-17 with 16 treatments replicated thrice in randomized block design. Notably maximum grain (62.98 q ha-1) and straw (85.26 q ha-1) yield of rice was registered in treatment, which received 100% STCR dose through WSF at 8 DI. Rice has exhibited a notably higher total uptake of N, P, and K in the treatment with 100% STCR dose through WSF at 8 DI (220.68, 44.97, and 137.41 kg N, P, and K ha-1, respectively). In fertigation with 100% RDF through WSF at 8 DI, a significantly greater seed yield (12.94 q ha-1) and haulm yield (26.17 q ha-1) of cowpea were observed. At 4 DI, 100% RDF through WSF showed a closely higher total uptake of N, P, and K by cowpea (68.94, 14.67, and 61.39 kg N, P, and K ha-1, respectively). The maximum net positive balance (148.42 kg N ha-1) was noticed in 100% RDF applied through WSF at 8 DI and minimum net positive balance 53.86 kg N ha-1 was recorded in 100% RDF-CF. During 2016-17, after the completion of second year residual crop cowpea, the maximum net positive balance (148.42 kg N ha-1) was noticed in 100% RDF applied through WSF at 8 DI and minimum net positive balance 53.86 kg N ha-1 was recorded in 100% RDF-CF. The maximum net positive balance (38.27 kg P2O5ha-1) was recorded in 100% STCR dose -WSF 8 DI and minimum net negative balance (15.70 kg P2O5 ha-1) was recorded in 100% RDF-CF. The maximum net positive balance of potassium (98.27 kg K2O ha-1) was recorded in 100% RDF-WSF 4 DI and minimum net positive balance (24.61 kg K2O ha-1) was recorded in 100% RDF-CF 8 DI treatment.