Variation in soil organic carbon as influenced by climate under different cropping systems in India

Soil organic carbon (SOC) content of fifty-three locations spread across various agro-climatic zones of India was analyzed for its relationship with climatic parameters. A highly significant and positive relationship (r=0.60) was found between SOC and rainfall and combined effect of rainfall and temperature controlled its accumulation. In low rainfall zones, SOC content decreased with increasing temperatures, but in high rainfall zones, the reverse was true. A significant negative relationship of SOC content with soil pH was also observed (r=−0.47). Analyses of grouped data revealed that rice-fallow system had the highest mean SOC content (8.7 g kg⁻¹ soil) followed by rice-rice, maize-wheat, rice-pulse, soybean based, rice-wheat and pearl millet based systems. In all the cropping systems, rainfall exerted highly significant effect on SOC. In rice-rice and pearl millet based systems, relative humidity only developed positive relationship with SOC whereas, sunshine hours exhibited negative relation. In rice-fallow system, sunshine hours exhibited negative relation but other meteorological parameters exhibited positive relationships. In soybean-based systems, relative humidity and sunshine developed highly significant relationship (r= 0.97 and 0.96, respectively) with SOC content but in maize-wheat system it was sunshine hours (r=0.98).