Effect of rice straw biochar and irrigation on growth, dry matter yield and radiation-use efficiency of maize grown on an Acrisol in Ghana

In order to determine whether the current low productivity associated with rainfed cultivation on degraded soils in Ghana can be improved by biochar amendment and irrigation, field experiments with maize were conducted over two seasons in 2017 and 2018. Rice straw biochar at rates of 0 t/ha (B₀), 15 t/ha (B₁₅) and 30 t/ha (B₃₀) was combined with irrigation regimes of full irrigation (I₁₀₀), deficit irrigation (I₆₀) and no irrigation (I₀). The I₁₀₀ treatment was irrigated to field capacity every 3–4 days according to time domain reflectometry measurements while the I₆₀ treatment received 60% of the irrigation amount given to I₁₀₀ but with the same irrigation frequency. The I₀ treatment was not irrigated. In both seasons, the B₃₀ treatment recorded the highest total dry matter yield (TDMY), intercepted photosynthetically active radiation (IPAR) and radiation-use efficiency (RUE) and these were significantly (p ≤.05) higher than B₀ except for RUE in 2017. Irrigation regimes did not significantly affect TDMY, IPAR and RUE in 2017 but compared to I₁₀₀, I₀ significantly reduced TDMY, IPAR and RUE in the relatively dryer 2018 season. Measured ratio vegetation indices differentiated biochar treatments earlier in the 2018 season than during 2017 and increase of leaf chlorophyll content indices with biochar rate in both seasons indicated that biochar amendment improved nitrogen uptake. Our study demonstrated that rice straw biochar is capable of increasing TDMY, IPAR and RUE of maize grown on degraded soils in Ghana. The study further showed that TDMY, IPAR and RUE of deficit irrigated maize for two seasons were similar to the counterpart fully irrigated maize and may be a viable water management option for farmers in Ghana to save irrigation water resources.