Agronomic responses of cowpea and soil quality bioindicators after biochars application

Abstract

Biochar can favor the production of agricultural crops and soil quality, but its characteristics depend on the residue used and its effects may vary according to the cultivated species. The aim of this study was to evaluate the effect of applying biochar from different animal residues on the agronomic characteristics of cowpea and on soil quality bioindicators. Three types of biochar (bovine, swine and poultry) were applied, combined (BBF: Bovine Biochar + Fertilizer; SBF: Swine Biochar + Fertilizer; and PBF: Poultry Biochar + Fertilizer) or not with fertilizer (BB: Bovine Biochar; SB: Swine Biochar; and PB: Poultry Biochar), and two control treatments with addition of calcium and magnesium oxide (CT) and calcium and magnesium oxide + fertilizer (CTF), totaling eight treatments. There was an increase in stem diameter, number of pods per plant, number of grains per pod and stem dry mass when biochar was added, regardless of the combination with fertilizer. There was no difference between treatments for soil basal respiration and β-glucosidase enzyme activity, while organic carbon (TOC), total nitrogen (TN), microbial carbon and soil labile carbon were higher in treatments with the presence of biochar. Among the treatments with only biochar application, the BBF treatment contributed to obtaining a higher TOC content, while BAF increased the NT content in the soil. Additionally, the application of biochar contributed to the reduction of soil metabolic quotient values. Thus, it can be concluded that biochar associated with conventional fertilization can improve soil quality, and consequently the productivity of cowpea.