Long Term Effects of Nutrient Management and Cropping Systems on Soil Organic Carbon Stock of Groundnut Based Cropping Systems

Field experiments are being conducted at the research farm of National Research Centre for Groundnut, Junagadh, India since 1998 to assess the long term effects of nutrient management and groundnut based cropping systems on the soil fertility and productivity of groundnut based cropping systems. The ten-year results revealed that soil organic carbon content increased more in the groundnut-legume cropping systems (0.93-1.05 %) compared to groundnut-cereal rotation (0.65-0.70 %). The groundnut+pigeon pea intercropping system increased maximum soil organic carbon content from 0.53 % in 1998 to 0.97 % in 2007. The groundnut+pigeon pea system have accumulated highest organic carbon and added 43 % more over the initial level, as compared to groundnut-groundnut (34 %), groundnut-wheat (5 %), groundnut-wheat-green gram(7 %) and groundnut+pearl millet (32 %). The nutrient management of various cropping systems also affected the soil organic carbon significantly. In groundnut-groundnut, groundnut+pigeon pea and groundnut+pearl millet cropping systems the highest organic carbon content were found with FYM (5 t/ha) + 50 % RDF to groundnut and 50 % RDF to the component crops as compared to 100 % RDF to groundnut and 100 % or 50 % to the component crops. Where as, the groundnut-wheat and groundnut-wheat-green gram sequential cropping systems showed highest soil organic carbon with FYM (5 t/ha) + 50 % RDF to groundnut and FYM (5 t/ha) + 50 % RDF to the subsequent wheat crop. The interaction effects showed that the groundnut-wheat-green gram systems with FYM (5 t/ha) + 50 % RDF to groundnut and FYM (5 t/ha) + 50 % RDF to wheat crop recorded the highest organic carbon accumulation (0.87 %) in the soil over the years.