Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012.
Present address: 1 Central Horticultural Experimental Slation, Plandu, Tala Road, P.O. Rajaulatu, Ranchi, 834010.
An investigation under greenhouse condition was conducted during kharif 1992 and rabi 1992–93 to study the feasibility of three urea enriched greenmanures,. viz. dhoincho (Sesbania aculeata L.), cowpea (Vigna unguiculata L.) and guar (Cyamopsis tetragonolaba L.) as compared to split application of urea nnder rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping sequence. Grain yield, dry matter yield, N uptake, agronomic efficiency, N recovery efficiency, physiological efficiency and relative agronomic effectiveness of rice with 3 per cent urea enriched guar were as good as split application of urea. Residual effect of greenmanures and their enriched counter parts in terms of yield, N uptake and efficiencies of wheat was better than that of urea treated soil during preceeding rice season. Quadratic models can effectively explain the variations in yield and N uptake of rice with N application up to 180 kg N ha−1. Significant and positive correlations exist between soil organic N after rice and yield and N uptake of wheat. Linear models constituted with soil organic N after rice and N uptake and yield of residual wheat can significantly describe the varations.
Enriched greenmanure, rice-wheat system, soil organic N, residual effect
