Soil surface ridging for improved yield with wider spacing of drip laterals in irrigated spring wheat

This study builds on efforts to reduce overall cost with drip irrigated spring wheat in semi-arid Xinjiang Province by widening spacing of drip laterals and adding wheat rows in between. Here we report the effect of ridging the soil surface downward from the drip lateral to the position midway between drip laterals. For the 3 study years, the non-ridged control treatment (60 cm drip line spacing, 4 equidistant rows) yielded on average 7254 kg ha−1 (2021 − 2023, range 6736 − 7693 kg ha−1). Drip lateral at 80 cm spacing (6 rows) on the non-ridged reduced yield on average 5.8 % (significant in 2 years), and at 100 cm (8 rows) 12.4 % (significant every year.) At both spacings, ridging at 15 ° below the horizontal raised yield on average 6.5 % (significant every year); 10 ° slope was intermediate. Yield with 15 ° ridging averaged 7252 kg ha−1 (80 cm spacing, always not significant with respect to the 60 cm control), but with 100 cm spacing only 6728 kg ha−1, being significantly lower by 10.4 % in 2021 and 2022. Yield components clearly show yield reductions on the non-ridged for rows furthest from the drip lateral (R3 and especially R4) with wider lateral spacing, and with non-ridged compared to ridging. Kernel weight was reduced more than grain number m−2, associated with lower harvest index and total biomass, and lower post anthesis leaf area. Eighty and 100 cm spacing lost yield without ridging probably because in R4 they had lower photosynthesis and biomass production, especially post anthesis; with ridging these rows saw and responded to the extra water, but at 100 cm spacing, it was not enough to overcome the loss. Optimizing irrigation strategies and rationally distributing irrigation volumes at different stages under ridging could potentially enhance yields for wider drip lateral spacing.