Soil carbon and nitrogen mineralization dynamics following incorporation and surface application of rice and wheat residues.

Understanding of crop residue mineralization is imperative for crop residue management in crop production. C and N mineralization dynamics of rice and wheat residues under surface applied and soil incorporated conditions were evaluated in an incubation experiment. Both rice and wheat residues were incorporated and surface applied. Soil moisture was maintained at 18% w/w (≈ - 15 kPa) during course of study. Periodic determinations on CO₂-C and N mineralized were performed over a period of 120 days. The highest peaks for CO₂-C occurred during the first week of the incubation period. Significantly higher emission of CO₂-C occurred from rice and wheat incorporation treatments (50%) followed by surface application treatments (19%) as compared to control soil. Variations between rice and wheat residue either incorporated or surface applied were non-significant. Both rice and wheat residues either incorporated or surface applied immobilized soil mineral N. Peak for N immobilization in the incorporated treatments was on day 15 and then started mineralization while surface applied wheat and rice residue decreased soil mineral nitrogen gradually and continuously up to 75th day of incubation. Incorporated residues increased soil organic carbon and soil aggregate stability significantly by 18% and 55% over control respectively. This 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. [ABSTRACT FROM AUTHOR]