The effect of biochar and manure on soil physicochemical properties under the production of a biofuel crop

Interest in using biochar as a soil amendment to enhance crop productivity is growing, but applying biochar alone or with manure on soil physicochemical properties during biofuel crop cultivation has not yet been fully explored. This study examined the impact of sole pinewood biochar and its co-application with cattle or kraal manure on soil properties under sweet sorghum cultivation. The experimental design was a randomized complete block with six treatments (four replications): control, cow manure (CM), biochar (BC), kraal manure (KM), kraal manure and biochar (KMB), and cow manure and biochar (CMB), each applied at 10 t ha− 1. Soil samples were taken from two fields (Field A (2020/2021) and Field B (2021/2022)) at sweet sorghum harvest. Measured soil properties included NH4+, NO3, P, K, S, Na, pH, OC, CEC, Ca2+, Mg2+, Cu, Fe, Mn, Zn, bulk density (BD), soil porosity (SP), gravimetric water content (GWC), volumetric water content (VWC), and mean weight diameter (MWD). Results in Field A showed significant differences (p < 0.05) for P, K, Ca2+, Mg2+, Cu, Fe, Na, Zn, pH, OC, MWD, and BD, while Field B showed significant differences (p < 0.05) for P, K, S, Ca2+, Mg2+, Na, pH, OC, SP, GWC, VWC, MWD, and BD. In Field A, BC showed the greatest improvement in P, K, Cu, Fe, Zn, pH, OC, MWD and BD, whereas in Field B, BC showed greatest improvement in P, pH, OC, SP, GWC, VWC, MWD and BD. This study confirms biochar’s potential to positively alter soil physicochemical properties under biofuel crop cultivation.