Responses of rainfed wheat productivity to varying ridge-furrow size and ratio in semiarid eastern African Plateau.

Spatial structural variations in ridge-furrow unit size and its ratio can result in the drastic fluctuation of soil hydrothermal status, and thereby affect water use and yield formation in dryland crops. Previous studies were little focused on the responses of dryland wheat productivity to the structural changes in ridge-furrow plastic mulching (RFM) system and its mechanism in semiarid eastern African Plateau (EAP). A two-year field experiment was conducted in Juja, a semiarid area in Kenya from 2015 to 2016. There were seven treatments of ridge-furrow width and ratios in randomized block design as follows: (1) 40 cm ridge width and 20 cm furrow width (R 4 F 2 , the same below), (2) R 3 F 2 , (3) R 2 F 2 , (4) R 3 F 4 , (5) R 2 F 4 , (6) R 3 F 6 and (7) R 2 F 6 , and conventional flat planting without mulching as control (CK). The results showed that R 4 F 2 , R 3 F 2 , R 2 F 2 , R 3 F 4 and R 2 F 4 treatments significantly improved soil water storage and temperature across two growing seasons compared with CK (P < 0.05). Among all the treatments, R 3 F 2 and R 2 F 2 obviously achieved the highest plant height, leaf area, aboveground biomass (AgB), grain yield and water use efficiency (WUE) (P < 0.05). Also, R 2 F 2 had the highest economic benefits in all treatments. The optimal ridge-furrow ratio appeared to be 1.32–1.38, 1.28–1.31, 1.39–1.49, 1.37–1.45 and 1.46–1.56 for wheat yield, AgB, WUE Y , WUE B and harvest index (HI), respectively. In addition, wheat yield, AgB, WUE and HI tended to decrease linearly with the increased ridge-furrow unit size. In conclusion, ridge-furrow ratio of 1–1.5 (R 2 F 2 to R 3 F 2) in combination with the minimum ridge-furrow unit size proved to be the optimum RFM system for the best dryland wheat productivity in accordance to regional soil and climate characteristics in semiarid EAP and other similar areas of the world. • RFM system significantly increased wheat productivity and WUE in semiarid EAP. • The optimal ridge-furrow ratio was 1.32–1.38 and 1.39–1.49 for yield and WUE. • Wheat yield and WUE decreased linearly with the increasing ridge-furrow unit size. • Ridge-furrow ratio of 1–1.5 combined with a minimum ridge-furrow unit was the optimum RFM system for wheat productivity. [ABSTRACT FROM AUTHOR]