The effect of irrigation amount and evapotranspiration on regional-scale winter wheat yield and water use efficiency

Abstract

【Objective】 Limiting extraction of groundwater for irrigation is a strategy proposed to alleviate the imbalance between water shortage and crop demands and sustain wheat production in northern China. Understanding the responses of yield (Y) and water use efficiency (WUE) of wheat to irrigation amount (I), evapotranspiration (ET) and spatiotemporal heterogeneities of other factors is essential to minimizing yield loss due to the implementation of the strategy. This paper addresses this based on modelling. 【Method】 Using the SWAP-WOFOST model, we simulated wheat-water interactions continuously for 20 years under the current irrigation schedule, ten limited irrigation scenarios and rain-fed management. We compared seven-textured soils and three precipitations levels, from which we calculated the relationships between Y and I, ET and I, WUE and I, Y and ET, WUE and ET. 【Result】 For the three precipitation levels and the seven textured soils, compared with the current irrigation schedule, decreasing I by 1 mm reduced Y, ET and WUE by 5.40-19.26 kg/hm2, 0.51-0.90 mm and 1.46×10-3-3.78×10-3 kg/m3, respectively. In areas where the current Y and WUE are low and the whole soil profile is sandy or the topsoil is sandy and the subsoil is loamy, decreasing I did not result in decreases in Y and WUE as significantly as in other areas. When I was lower than current value, Y and ET are linearly correlated. In wet and normal years, the relationship between WUE and ET was quadratic, while in dry years, WUE increased with ET. 【Conclusion】 At regional scale, it is difficult to maintain both high yield and high WUE when the irrigation amount is reduced. The implementation of the limited irrigation can prioritize the areas where the soils are sandy and the yield and WUE of wheat are currently low. There is also a potential to increase WUE by reducing ET in wet and normal years.

Keywords

• limited irrigation
• yield
• water use efficiency
• swap-wofost model
• soil texture
• precipitation level