Effects of biochar application on the chemical properties of selected soil series in South-Western Nigeria

The present study aimed to investigate the effects of biochar application on the chemical properties of the Iwo and Egbeda soil series. The soil samples used for this study were collected from Teaching and Research Farm, OAU, Ile-Ife. The soil belongs to an Ultisol. Four agro wastes (maize cob, maize husk, maize straw and cocoa pod) were pyrolysed at 400° C, and a 8 week incubation experiment was carried out with biochars applied at the rates of 0, 5, and 10 ton.ha-1. The soil chemical properties analysed include soil pH, organic carbon, total nitrogen, available phosphorus, and exchangeable cations. The assay of the biochars showed the pH values above neutral and contained appreciable amounts of carbon, phosphorus and potassium. The FTIR results of the biochars showed the presence of phenol, carboxylic groups and NH functional groups in most of the biochars, indicating the capacity of the biochars, to enhance the nutrient holding capacity of the soil. Addition of maize cob, maize husk, maize straw and cocoa pod biochars had significant effects on soil pH. Organic carbon levels improved with biochars application rising to 16.38 g.kg-1 at 5 ton.ha-1, with cocoa pod biochar application compared to the control. The effects of biochars on available phosphorus was modest in all the treated pots. However, the impact of biochars on total nitrogen was minimal across treatments, and no significant changes in electrical conductivity or exchangeable cations were observed except in Ca and K. Conclusively, the ameliorating effect of biochars on chemical properties of Iwo and Egbeda soil series was consistent with their chemical composition.