Long-term effect of pulses and nutrient management on soil carbon sequestration in Indo-Gangetic plains of India

Venkatesh, M. S., Hazra, K. K., Ghosh, P. K., Praharaj, C. S. and Kumar, N. 2013. Long-term effect of pulses and nutrient management on soil carbon sequestration in Indo-Gangetic plains of India. Can. J. Soil Sci. 93: 127-136. As an important component of crop diversification, pulses/legumes are known to improve soil quality through their unique characteristics of biological N-2 fixation, root exudates, leaf litter fall and deep root system. Changes in the soil organic carbon pool due to the inclusion of pulses in an upland maize-based cropping system were evaluated after seven cropping cycles. The results indicate that inclusion of pulses in an upland maize-based cropping system improved the total soil organic carbon content, being greater in surface soil (0-0.2 m) and declining with soil depth. Of the four carbon fractions of total soil organic carbon (C frac(1)-C frac(4)) measured in the upland maize-based system, the most labile C fraction (C frac(1)) was dominant. Distribution of the carbon pool varied with depth and the size of the active carbon pool was larger than that of the passive carbon pool in the surface soil, whereas in the subsurface soil depth, the size of the passive carbon pool was larger than that of the active carbon pool. Maize-wheat-mungbean and pigeonpea-wheat systems resulted in significant increases (P <= 0.05), of 11 and 10%, respectively in total soil organic carbon, and 10 and 15% in soil microbial biomass carbon, respectively, as compared with a conventional maize-wheat system. Application of crop residues along with farmyard manure at 5 Mg ha(-1) and biofertilizers resulted in greater amounts of carbon fractions and higher carbon management index than in the control and the recommended inorganic (NPKSZnB) treatment, particularly in the system where pulses were included. In plots receiving organic amendments, the variable cumulative carbon input had higher correlation with total organic carbon (R-2 = 0.997), active pool (R-2 = 0.934), passive pool (R-2 = 0.916) and soil microbial biomass carbon (R-2 = 0.664). Inclusion of pulses in the maize-based system and the organic nutrient management system sequestered more organic carbon and maintained better soil health in Inceptisols of the Indo-Gangetic plains of India.