Effect of crop residues on yield and nitrogen economy in wheat-rice system in Uttaranchal Mid-hill soils

Soil organic matter contributes to the productivity and physical quality of soils. As application of crop residues influences soil organic carbon content and nitrogen build up, we analyzed results of a field experiment conducted during 1997–2000 to evaluate the fertilizer nitrogen equivalence of crop residues application in wheat (Triticum aestivum L. emend. Fiori Paol.) - rice (Oryza sativa L.) system under both rainfed and irrigated conditions and its effect on crop productivity. Results revealed that the NPK treatment gave highest grain yield of wheat both in rainfed (1.58 t ha⁻¹) and irrigated (2.59 t ha⁻¹) conditions. The increase in wheat yield due to crop residue application of maize fresh, maize compost, kudzu fresh and kudzu compost were 27.9, 50.6, 68.9 and 89.2% with the corresponding value of 17.0, 68.3, 53.8 and 47.8% in rainfed and irrigated conditions, respectively over control plots. The percent yield increase for the residual rice crop in the maize fresh, maize compost, kudzu fresh and kudzu compost was 21.8, 52.8, 28.8, 38.3 and 36.0, 49.9, 49.9 and 52.1% in rainfed and irrigated conditions, respectively. The fertilizer nitrogen equivalence varied significantly with moisture conditions and it ranged from 25.5 to 61.3 and 39.8 to 75.0 kg ha⁻¹ in rainfed and irrigated conditions, respectively. The soil C:N ratio and total N status after the termination of experiment clearly indicated the build up of nitrogen with crop residue addition though rice crop was grown on residual fertility. Kudzu compost, addition @ 10 t ha⁻¹ gives yield comparable with recommended NPK dose both in rainfed and irrigated conditions. This information can provide basis for effective crop residues management and its comparative yield advantage of alternative locally available organic sources over recommended NPK for increasing productivity of wheat-rice system both in rainfed and irrigated mid-hills agriculture.