Author(s):

RK Naresh, S Bhaskar, SS Dhaliwal, Arvind Kumar, RK Gupta, Vivek, RS Rathore, Vivak Kumar, Satendra Kumar, Saurabh Tyagi and Nihal Chandra Mahajan

Abstract: Understanding of crop residue mineralization is imperative for crop residue management in crop production. Carbon (C) and Nitrogen (N) mineralization dynamics of rice and wheat residues under surface applied and soil incorporated conditions were evaluated in the review paper. Both rice and wheat residues either incorporated or surface applied immobilized soil mineral N. Incorporated residues increased soil organic carbon and soil aggregate stability significantly by 18% and 55% over control, respectively. This review study indicated that crop residues incorporated into the soil have higher decomposition rate with a quicker mineral N release, more organic matter build up and soil structure improvement than retaining crop residues at the soil surface. Compost amendment also significantly lowered the specific activities of invertase in macro-aggregates and the silt + clay fraction, and this effect was more pronounced than the addition of fertilizer NPK. In contrast, inorganic fertilizer and compost application significantly increased the specific activities of cellobiohydrolase in soil, macro-aggregates and micro-aggregates (but not in the silt + clay fraction), and xylosidase in micro-aggregates. We considered that the increase in organic C in compost-amended soil was therefore probably associated with the accumulation of lignocellulose and sucrose in macro-aggregates, lignocellulose and hemi-cellulose in micro-aggregates and lignin (its derivative) and nonstructural carbohydrates in the silt + clay fraction. Average soil organic carbon (SOC) concentration of the control treatment was 0.54%, which increased to 0.65% in the RDF treatment and 0.82% in the RDF+FYM treatment and increased enzyme activities, which potentially influence soil nutrients dynamics under field condition. Compared to F1 control treatment the RDF+FYM treatment sequestered 0.28 Mg C ha-1 yr-1 whereas the NPK treatment sequestered 0.13 Mg C ha-1 yr-1. As tillage intensity increased there was a redistribution of SOC in the profile, but it occurred only between zero tillage (ZT) and permanent raised beds (PRB) since under conventional tillage (CT), SOC stock decreased even below the plow layer. Increased SOC stock in the surface 50 kg m-2 under ZT and PRB was compensated by greater SOC stocks in the 50-200 and 200-400 kg m-2 interval under residue retained, but SOC stocks under CT were consistently lower in the surface 400 kg m-2. In long term trial, CT lost 0.83 ±0.2 kg of C m-2 while ZT gain 1.98 ±0.3 and PRB gain 0.97 ±0.2 kg of C m-2 in the 1200 kg of soil m-2 profile.

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