Restoration of carbon and microbial activity in salt-induced soil by application of peanut shell biochar during short-term incubation study.

For the present study, soil samples of four artificially-induced salinity gradients (S0: control, S1: 2.0, S2: 4.0, S3: 6.0 ECiw) was incubated with fine-textured peanut shell biochar at various ratios (B0: control, B1: 2.5%, B2: 5.0%, B3: 10% w/w) for 30 days. At 1, 3, 7, 15, 30 days of incubation, samples were analyzed for soil carbon and selected enzyme activities. Results showed that biochar could increase soil organic carbon on application of highest rate of biochar addition (B3), hence potentially restored the saline soils by less C mineralization, and more sequestration of soil C. However, soil enzyme activities were biochar rate(s), day(s) of incubation and enzyme dependent. The lowest rate of biochar addition (B1) showed highest dehydrogenase (20.5 μg TPF g(-1) soil h(-1)), acid phosphatase (29.1 μg PNP g(-1) soil h(-1)) and alkaline phosphatase (16.1 μg PNP g(-1) soil h(-1)) whereas the higher rate (B2) increased the urease (5.51 μg urea-N g(-1) soil h(-1)) and fluorescein diacetate hydrolyzing activities (3.95 μg fluorescein g(-1) OD soil h(-1)) in soil. All the positive changes persisted at higher levels of salinity (S2, S3) suggesting biochar-amended soil may be potential for better nutrient cycling. Soil enzymes were found to be correlated with soil carbon and with each other while principal component analysis (PCA) extracted the most sensitive parameters as the acid and alkaline phosphatases and urease activities in the present experimental condition. This is the first time report of examining soil microbial environment using peanut shell biochar under a degraded (saline) soil.