Biochar as a soil conditioner for common bean plants

Biochar is a carbon-rich material produced during organic waste pyrolysis. In this context, two experiments were performed to evaluate the effect of biochar produced from rice husks and cattle manure on soil fertility and common bean production, as well as to identify the optimal dose of cattle manure biochar to be applied. The first experiment (Experiment I) was conducted according to a completely randomized design (factorial scheme 2 × 2 × 2 + 1) with six replicates: two types of biochar (cattle manure biochar and rice husk biochar), with and without acidity correction [addition of calcium carbonate and magnesium carbonate (PA) in a proportion of 4:1 (Ca:Mg) to raise the soil base saturation to 60%], with or without the addition of 120 mg dm-3 of phosphorus (P) as ammonium phosphate, and a control treatment (without biochar, acidity correction, and P). Based on the results of Experiment I, a second experiment was conducted according to a completely randomized design, with five treatments (doses of biochar from cattle manure) and four replications. Rice husk biochar, as a conditioner of soil chemical properties, had less prominent effects than cattle manure biochar. Cattle manure biochar functioned as a corrective for soil acidity and a source of nutrients (mainly phosphorus). The dose corresponding to 5.46% of the soil volume led to the maximum grain production by common bean plants.