Effects of Irrigation Regimes and Residue Management Practices on Soil Organic Carbon and Physical Properties under Rice-based Cropping System

Soil organic carbon and physical properties have the immense importance in relation to crop growth and productivity. The effect of different residue management practices (rice straw @6 t ha^-1 and mungbean residue @ 2.5 t ha^-1) and irrigation regimes on soil organic carbon and physical properties was studied under rice–based cropping after four years of the start of experiment. There were three irrigation regimes in rice (CF– Continous flooding, 2–D- irrigation applied after 2 days of drainage of ponded water and 4–Dirrigation applied after 4 days of drainage of ponded water) and six residue management practices viz., R₀–Residue removal, R₀+M– only mungbean residue incorporation, RRR– rice residue surface retention, RRR+M– rice residue surface retention + mungbean residue incorporation, RRI– rice residue incorporation and RRI+M– rice + mungbean residue incorporation. The soil organic carbon concentration increased by 22, 18, 16, 14% in RRI+M, RRI, RRR+M and RRR in comparison to R₀ in 0–15 cm soil layer. Soil bulk density of surface layer was lower in RRI+M, RRI, RRR+M and RRR than R₀ plots. However, there was an increase in soil porosity and mean weight diameter of soil aggregates in plots with RRI+M, RRI, RRR+M and RRR residue management practices than R₀ plots in 0–15 cm soil layer. Pooled rice yield was similar under CF and 2–D irrigation regime but significantly higher than 4–D irrigation regime. The impact of residue management practices was evident in both rice and wheat crop with higher yield under in–situ residue management practices in comparison to residue removal. Thus, residue management practices viz. incorporation or retention improved the crop productivity, soil physical properties and soil organic carbon of surface soil layer in the sandy loam soils under rice–based cropping system.