Carbon sequestration potential of rice-based cropping systems under different tillage practices

A four-year field experiment was conducted to evaluate the effect of different tillage practices and cropping systems on total organic carbon (TOC), oxidisable C fractions, water stable aggregates (WSA) and associated carbon in an Inceptisol of Eastern Indo Gangetic Plains (EIGP). The study covered nine treatments resulting from combining three rice-based cropping systems [rice-wheat (RW), rice-lentil (RL) and rice-maize (RM)] with three tillage practices [conventional tillage (CT), reduced tillage (RT) and reduced tillage with 30% residue retention (RTR30)]. The data showed that the combined treatment RL-RTR30 registered the highest carbon stock (23.3 Mg ha(-1)) and TOC (13.8 g kg(-1) soil) in soil. Reduced tillage with 30% residue retention maintained the highest macro-aggregate (65.5%) and the lowest micro-aggregate percentage (19.6%) compared to CT. Carbon associated to all aggregate size fractions was highest in RL-RTR30. Carbon stock exhibited a significant (p < 0.01) positive correlation with less labile carbon. Macro-aggregate percentage was positively correlated with C-stock, TOC, organic carbon fractions and aggregate associated organic carbon, whereas micro-aggregate showed an inverse correlation with all the afore-mentioned parameters. We conclude that RL-RTR30 is the best rice production system to promote C sequestration in the soils of eastern Indo-Gangetic plains of India.