Sorghum (Sorghum bicolor L.) grain yield response to contour-based rainwater harvesting and organic fertilizer in rainfed farming systems

Rainfall variability and low soil fertility are negatively affecting sorghum grain yield in smallholder farming systems. This study investigated the effect of contour-based rainwater harvesting (RWH) systems and cattle manure on grain yield of two sorghum varieties Macia and Sc Sila. A factorial experiment was laid out in a split-split plot design and replicated three times. Rainwater harvesting practice (tied contour, infiltration pits, standard contour) were the main plot factor, sorghum variety (Macia, Sc Sila) sub-plot factor, cattle manure application rates (0; 5; 8; 10; 15; 20) t/ha sub-sub plot factor, and distance from rainwater harvesting practice (0-5 m; 5-10 m; 10-15 m) sub-sub-sub plot factor. Grain yield under tied contour (TC) and infiltration pits (IP) rainwater harvesting systems were compared with the control - standard contour (SC). The results showed that TC and IP improved soil moisture content by 1.83% and 1.71% respectively compared to SC. Sorghum grain yield was significantly higher (p < 0.05) under TC and IP at all cattle manure application compared with SC. Grain yield significantly differed (p < 0.05) in the order TC (2.51 t/ha) > IP (2.10 t/ha) > SC (1.49 t/ha) at cattle manure application rate of 20 t/ha. Sorghum variety Macia had the highest grain yield of 2.01 t/ha at cattle manure application of 20 t/ha. In both sorghum varieties, TC and IP had higher sorghum grain yields than SC at all distances from the RWH practice in both seasons (2016/17 and 2017/18). The findings suggest that the use of TC and SC RWH practices, and cattle manure may increase sorghum grain yields in rain-fed smallholder farming systems.