Supplemental irrigation strategy for improving grain filling, economic return, and production in winter wheat under the ridge and furrow rainwater harvesting system

The plastic-covered ridge and furrow rainwater harvesting (RFRH) system has been used widely to enhance crop productivity in the semiarid regions of China. We conducted a field study during 2015-2017 where the RFRH method was combined with deficit irrigation to decrease the irrigation water usage and improve the crop water productivity (CWP) and irrigation water productivity (IWP). Under the RFRH system, the amount of irrigation was reduced by half compared with that under traditional flat planting (TF) with border irrigation due to the effects of precipitation harvesting. Half of the deficit irrigation was supplied before wintering and the remaining half at the jointing stage. The following eight treatments were tested: RFRH system with 75 mm deficit irrigation (R-75 ), 37 mm irrigation (R-37), 18 mm irrigation (R-18 ), and 0 mm irrigation (R-0); TF cultivation with 150 mm irrigation (F-150 ), 75 mm irrigation (F-75), 37 mm irrigation (F-37), and 0 mm irrigation (F-0). The results showed that the irrigation volume doubled under conventional border irrigation but the soil water storage was greater under RFRH with deficit irrigation. The R-75 treatment resulted in significantly greater soil water storage, reduced evapotranspiration (44.2%), and a higher grain yield (14.6%), thereby increasing CWP (64.8%), ICWP (irrigation crop water productivity) (44.2%), and IWP (57.0%) compared with F-150. R-75 improved the biomass per plant, leaf area index, and net income for farmers (by 17.5%) compared with F-150. Thus, we recommend R-75 for decreasing the irrigation water usage and increasing the effective consumption of precipitation in semiarid regions.