Effects of biochar feedstock type and rate on soil properties, soybean nodulation and nitrogen fixation

Abstract

Abstract Restricted nutrient availability in the soil directly limits vital processes like biological nitrogen fixation (BNF) in legumes. Biochar is reported to have some positive effects on soil properties and nutrient availability. However, its feedstock type and application rate affect its performance. This study was aimed at evaluating the effects of different biochar application rates (equivalents of 0, 5, 10, and 15 tonnes ha-1) and locally available feedstock types (maize core and groundnut shell), on soil properties, nodulation and nitrogen fixation in a greenhouse experiment using a split-plot randomised design, with three replicates. Biochar improved (p < 0.05), cation exchange capacity (CEC), total zinc (Zn) and potassium (K). At 15 tonnes ha-1, groundnut shell biochar significantly (p < 0.05) increased the amount of N2 fixed by 22% as compared to maize cores biochar. Biochar application rate significantly affected nodule numbers, dry weight and effectiveness (assessed based on nodule colour). Groundnut shell biochar significantly increased (p < 0.05) nodule dry weight when compared to maize core biochar by 21.1% which implied that both rate and type of biochar are important factors in soybean nodulation. Both groundnut shell and maize core biochar amendments positively enhance soil properties and N2 fixation in soybean, and hence are good amendments to be considered for sustained soil health with implications on crop productivity.