Effects of Biochar and Anaerobic Digester Effluent on Soil Quality and Crop Growth in Karnataka, India

Abstract

The application of biochar and anaerobic digester effluent together has the potential to improve soil quality while simultaneously addressing critical environmental challenges. A field experiment was conducted in Karnataka, India to assess the effects of these amendments on soil properties and radish (Raphanus sativus L.) growth over a 15-month period between January 2011 and March 2012. Biochar was applied at the rate of 30 Mg ha−1 and incorporated in the surface 0–10 cm layer to the biochar plots (BC) and biochar + effluent plots (BC + EF). Anaerobic digester effluent was added at a rate of 56.25 m3 ha−1 to effluent plots (EF) and the BC + EF treatment. In the first growing season, yields were 90, 1,291, and 1,374 % greater than the control (Ct) in the BC, EF, and BC + EF plots, respectively. One year after application, soil bulk density (ρ b) decreased by 7.3 % and total porosity (f t) increased by 9.3 % with biochar application (BC) compared to the Ct. These effects were less apparent in BC + EF. The impact of amendments on soil moisture storage was not significant. Application of biochar increased soil pH from 7.21 (Ct) to 7.57 (BC) and 7.50 (BC + EF). In the second year, two new treatments were introduced—conventional fertilizer (C + F) and conventional fertilizer plus biochar (BC + F). BC + F and C + F did not differ significantly in crop yields. Overall, while there were some positive responses to both biochar and effluent addition seen in soil chemical properties and crop growth, respectively, there was limited evidence of nutrient retention by biochar in the second year.