Effect of drip irrigation on wheat evapotranspiration, soil evaporation and transpiration in Northwest China

Abstract

Drip irrigation (DI) has been widely used for corn, potato, and soybean, among other crops, and its water-saving effect has been confirmed by numerous studies. However, how DI affects soil evaporation (E), crop transpiration (T) and total evapotranspiration (ET) of wheat in arid regions and how much it can reduce E, T and ET under sufficient irrigation remain uncertain.Our study aimed to reveal the effect of DI on wheat ET by using contrast tests. ET and soil E were continuously measured in a wheat field with two treatments during 2017–2018 in Northwest China by Bowen ratio energy balance (BREB) instruments and micro-lysimeters simultaneously. The two treatments were DI and border irrigation (BI), and the irrigation scheduling for DI and BI was based on the local irrigation scheduling in arid Northwest China. Numerous soil E data were missing for rain and irrigation. We used the classical Shuttleworth-Wallace model to estimate E/ET. By combining the model with the measured ET, we obtained the ET, E and T every day.The results indicated that the total wheat ET, E and T under DI were 340, 50 and 290 mm in 2017 and 520, 99 and 421 mm in 2018, respectively. The ET, E and T under BI were 362, 57 and 305 mm in 2017 and 542, 99 and 443 mm in 2018, respectively. Compared to BI, DI reduced ET, E and T by 22, 3.5 and 18.5 mm on average, respectively. The ET under DI was decreased by 4 %–6 % during 2017–2018. The reduction in ET under DI was primarily caused by the reduction in crop T. These changes were due to DI significantly lowering the leaf area index by 24 % and shortening the crop growth duration by one week.Our study revealed the effect of DI on wheat ET and provided new insight for understanding the effects of DI on field hydrological and crop growth processes.