Influence of Integrated Nutrient and Water Management on Soil Organic Carbon in Rice-Wheat Cropping System

A field experiment on a rice-wheat cropping sequence was carried out to investigate the effect of tillage in rice and the effect of integrated nutrient management (INM), water management and tillage in wheat on status of soil organic carbon (SOC). Although tillage in rice crop had some effect on the SOC content during wheat and second rice season, the effect was not evident at the harvest of both the crops. While the organic carbon content of the soil decreased with reduction in irrigation levels to both rice and wheat during the first year, no clear trend was observed during the second rice season. Amongst the nutrient treatments, organics supplied in conjunction with inorganic-N improved the SOC content. Highest SOC value was recorded under T₄ (25% N substituted by FYM) in both rice and wheat, followed by T₉ (100% N + PK + crop residue) and T₈ (100% organics). Incorporation of rice and wheat residues had a positive effect on build up of soil organic carbon. Organic carbon content of the soil increased from the initial value (0.62%) up to wheat harvest during the first year, following which it declined slightly in all the treatments barring T₄ and T₉. There was no significant difference in status of soil organic carbon after the lapse of 3 cropping season (rice-wheat-rice). However, proper combination of tillage, water and nutrient management prevented further decline in status of SOC. Tillage in wheat crop had no effect on the SOC content.