Water use-yield relationship of maize as influenced by biochar and inorganic fertilizer applications in a tropical sandy clay loam soil

Empirical relationship between maize yield and evapotranspiration as influenced by biochar and inorganic fertilizer has been scarcely investigated. Therefore, the study's objectives are to; (i) determine the yield response factor (K-y) of maize under drip irrigation with/without biochar and inorganic fertilizer application; (ii) deter-mine if soil hydrophysical and chemical properties affect the response of maize to water stress under biochar and inorganic fertilizer applications, and (iii) determine the possible mechanism by which biochar improves yield and water use efficiency of maize under deficit irrigation. Field experiments were carried out using a factorial design. Two rates of biochar application (0 and 20 t/ha), two levels of fertilizer (0 and 300 kg/ha) were adopted under three water management strategies (100 % of Full Irrigation Treatment; FIT, 80 % FIT, and 60 % FIT) using drip irrigation. The crop evapotranspiration was determined using the soil water budget method while the grain yields were measured at harvest. Soil samples were collected at harvest and analyzed for chemical and physical properties. The relationship between maize yield, soil properties and Ky were determined using correlation analysis. Results from the study showed that the sensitivity of maize crops to water stress was greater than one 1 but reduced in soil treated with biochar compared to those without biochar. Ky under the unamended plot was 1.64 and reduced to 1.52 when applied with biochar. Ky was 1.45 in soil amended with only inorganic fertilizer and reduced to 1.27 when co-applied with biochar. Biochar decreased water depletion by maize, with the highest reduction in soil water depletion occurring in treatments that received the least water. A significant (P < 0.05) correlation between Ky and the soil properties showed that the soil chemical (Nitrogen, Phosphorus and Po-tassium) properties are primarily responsible for the reduced sensitivity of maize yield to water stress.