Field edge rainwater harvesting and inorganic fertilizers for improved sorghum (Sorghum bicolor L.) yields in semi-arid farming regions of Marange, Zimbabwe

Sorghum (Sorghum bicolor L.) is mainly cultivated in marginal areas of Zimbabwe, where soil fertility is poor and rainfall is low, erratic, and poorly distributed, leading to low yields. The study aimed to determine the effect of tied contour (TC) and in-contour infiltration pits (IP) rainwater harvesting (RWH) methods and varying nitrogen fertilizer application rates on the yield of two sorghum varieties, Macia and Sc Sila. A split-split plot experiment was laid out, with the main plot factor being the RWH method, the subplot factor being sorghum variety, the sub-sub plot factor being nitrogen application, and the sub-sub-sub plot factor being the plant distance from the RWH method. The experiment was done at Mt Zonwe's small-scale farming community in the Mutare region from 2016/17 to 2018/19. The results revealed that TC and IP increased the gravimetric water content (gwc) of the soil. The gwc decreased gradually as the distance from the rainwater RWH method increased (0–5 m > 5–10 m > 10–15 m), with the 2016/17 season having the maximum gwc. In all seasons, TC and IP yielded much more sorghum grain than standard contour (SC). Sorghum grain production was significantly greater at all nitrogen application rates and consistently higher at all plant distances from the RWH method in the 2016/17 season with more rainfall. In comparison to TC and IP, the SC had significantly lower grain yield at all nitrogen application rates. At all plant distances from the RWH method, TC and IP had significantly higher grain production than SC in each variety of sorghum.