effects of crop residue management and nitrogen fertilizer on soil nitrogen and carbon content and productivity of wheat (triticum aestivum l.) in two cropping systems

the objective of this study was to investigate the effects of addition of pulses in crop sequences, crop residue management, and application of fertilizer n on soil nitrogen content, soil organic carbon, nutrient uptake, and its consequences for wheat yields. the field experiments were carried out from 2009 to 2012 in the sub-humid and sub-tropical zone of northern india. the treatments were (i) crop residue retained (+residue) or (ii) removed (-residue), (iii) 120 kg n ha-1 applied to wheat, (iv) 150 kg n ha-1 to maize, and (v) a control with no nitrogen applied to either wheat or maize. the cropping systems consisted of a rotation of wheat and maize or wheat and green gram. postharvest incorporation of crop residues significantly (p< 0.05) increased the wheat grain and straw yields during 2010-2011 and 2011-2012. on average, crop residues incorporation increased the wheat grain yield by a factor of 1.31 and straw yield by 1.38. the wheat crop also responded strongly to the previous legume (green gram); grain yield increased by a factor of 1.89 and straw yield by 2.05, compared to the control. application of fertilizer n to the preceding maize crop exerted a strong carryover effect on grain (1.18) and straw yield (1.26) wheat. application of n fertilizer to wheat increased grain and straw yields by, respectively, a factor of 1.69 and 1.79 on average. the overall conclusion is that an improved crop residue management, combined with application of fertilizer n or incorporation of legumes greatly improves the n economy of cereal cropping systems and enhances crop productivity in soils with a low n content on the short term.