Manuring and residue management effects on physical properties of a soil under the rice–wheat system in Punjab, India

Sustainability of the rice–wheat rotation is important to Asia's food security. Intensive cropping with no return of crop residues and other organic materials results in loss of soil organic matter and is not sustainable. We evaluated effect of eight treatments comprised of various combinations of green manure (GM), wheat straw (WS), rice straw (RS), farmyard manure (FYM) and urea alone (control) on physical and hydraulic properties of soil in a rice–wheat experiment (1988–2001) on a loamy sand in Punjab, India. After rice harvest, organic carbon (OC) content in the FYM (0.51%), WS (0.56%) and WS + RS (0.59%) treatments were significantly greater as compared to control (0.42%). With addition of GM to all these treatments; FYM + GM (0.59%), WS + GM (0.60%), WS + RS + GM (0.64%) and GM (0.47%), organic carbon content further increased significantly. Increased OC content of the soil in turn improved its aggregation status, infiltration rate and decreased the bulk density, dispersion ratio and soil strength correspondingly. After wheat harvest mean effects of these organic treatments continued, but their magnitude decreased. The differences in rice yield were not significant among urea, GM and WS applied alone or in combination. However, FYM + GM + urea produced highest yield. There was no residual effect of the long-term application of GM, WS and RS incorporation in wheat yields, but FYM application to rice showed significant residual effects on wheat.