Residual Effect of Biochar on the Productive Performance of Irrigated Cowpea in the Agreste Region of Pernambuco
Organic fertilization; Sewage sludge; Agricultural sustainability; Soil chemical attributes
This study evaluated the residual effect of different rates of sewage sludge biochar on soil chemical attributes and yield components of cowpea (Vigna unguiculata (L.) Walp.) grown in a Regolithic Neosol under semi-arid conditions in Brazil. The biochar treatments (Bio 10, Bio 20, and Bio 40) had been incorporated into the soil over two years prior to the experiment, whereas poultry litter (CA 5, CA 10, CA 15) and synthetic fertilizers were applied at planting. Soil chemical analyses showed no significant differences in pH, exchangeable sodium (Na⁺), and total organic carbon (TOC) among treatments. However, available phosphorus (P) and exchangeable potassium (K⁺) differed significantly (p < 0.0001), with the highest concentrations observed in CA 15 and Bio 40 treatments. Regarding yield components, number of grains per pod (NGP), pod yield, and grain yield were significantly influenced by fertilization. Notably, Bio 20 achieved grain and pod yields comparable to those of CA 15, highlighting the residual capacity of biochar to sustain crop productivity even two years after its incorporation. These findings suggest that sewage sludge biochar continues to enhance soil fertility and crop performance over the long term, offering a sustainable and effective alternative to conventional fertilization strategies in conservation-oriented farming systems in semi-arid environments.