Use of biochar as amendment to reclaim saline and sodic soils
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Information is limited about ameliorating effect of biochar on irrigation water induced salt-affected soils, although increasing data have shown that biochar amendment can improve soil fertility and crop production. Therefore, in the present investigation, soil samples varying in EC and SAR levels, were amended with different rates or types of biochar, for the laboratory incubation experiments at 250C for 8 weeks. First experiment was conducted to determine the effect of addition of different rates of rice residue biochar (0, 1, 2, 4% w/w) on soil properties under varying EC [2 (control), 8 and 16 dSm-1] and SAR [2.5 (control), 20, 30] levels whereas, the second experiment was conducted to compare the ability of biochar (added at the rate 2%) derived from maize stover (MB), poultry manure (PB) and rice residues (RB) in ameliorating salt-affected soils. Soil samples were analyzed to determine dissolved organic C, microbial biomass C, mineral N, pH, EC and SAR, available N, P, K, SOC, CEC in experiment 1 or 2. The study showed that addition of rice-residue biochar increased C mineralization both in saline and sodic soils, greater so at higher rates of addition (2-4%). However, compared to unamended soils, biochar addition at the rate 1% did not significantly affect C mineralization and MBC both on day 14 and 56 at various EC and SAR levels. Consistent with the C mineralization, a positive linear relationship was observed between MBC and increasing rate of biochar addition in all the soils. Moreover, DOC concentration increased in the biochar amended saline and sodic soils and followed the order (B4> B2> B1> B0). NO3--N concentrations increased with increase in period of incubation and the biochar rates whereas, NH4+-N concentration was higher upto day 14 in both soils. Further, soils amended with the poultry manure biochar showed greater C mineralization; MBC and DOC than those amended with rice residue or maize stover biochar suggesting greater release of easily decomposable material by the former for microbial activity and growth. Further, higher available N observed in soil amended with poultry manure biochar compared to rice residue and maize stover biochar in the present study could be due to its lower C: N ratio and thus higher N mineralization. Similarly, concentration of available P was found higher in PB than RB and MB amended soils due to its higher ash content (62%). Correspondingly, rice residue biochar with its greater reserve of potassium can serve as good source of available K in both saline and sodic soils. Thus, the positive effects of biochar addition on C mineralization and the improvement in measured soil parameters like MBC, DOC, SOC, CEC and available N, P and K in the study clearly showed the potential of biochar to be used as an organic amendment in ameliorating saline and sodic soils. The study also showed greater ability of poultry manure biochar in improving the soil properties under stressed condition due to its higher decomposibility and release of plant available nutrients.