Bioamelioration of a sodic soil by silvopastoral systems in northwestern India

In sodic soils, excessive amounts of salts have an adverse effect on soil biological activity and stability of soil organic matter. The study analyzes the role of silvopastoral systems to improve soil organic matter and microbial activity with a view for effective management of soil fertility. The silvopastoral systems for the present study (located at Saraswati Reserved Forest, Kurukshetra; 29degrees4' to 30degrees15' N and 75degrees15' to 77degrees16' E) are characterized by tree species of Acacia nilotica, Dalbergia sissoo and Prosopis juliflora along with grass species of Desmostachya bipinnata and Sporobolus marginatus. Soil microbial biomass carbon was measured using the fumigation extraction technique and nitrogen mineralization rates using aerobic incubation method. The microbial biomass carbon in the soils of D. bipinnata and S. marginatus treatments were low. In silvopastoral systems, microbial biomass carbon increased due to increase in the carbon content in the soil - plant system. A significant relationship was found between microbial biomass carbon and plant biomass carbon (r = 0.83) as well as the flux of carbon in net primary productivity (r = 0.92). Nitrogen mineralization rates were found greater in silvopastoral systems compared to 'grass-only' system. Soil organic matter was linearly related to microbial biomass carbon, soil N and nitrogen mineralization rates (r = 0.95 to 0.98, p < 0.01). On the basis of improvement in soil organic matter, enlarged soil microbial biomass pool and greater soil N availability in the tree + grass systems, agroforestry could be adopted for improving the fertility of highly sodic soil.