Winter wheat growth and water use under different drip irrigation regimes in the North China PlainWinter wheat growth and water use under different drip irrigation regimes in the North China Plain

A 3-year field experiment was conducted to evaluate the applicability of drip irrigation, winter wheat growth and water use under different drip irrigation regimes in the North China Plain (NCP) during 2014-2017. Five irrigation regimes with the soil matric potential (SMP) thresholds at 20 cm depth immediately under the emitters were - 10, - 20, - 30, - 40 and - 50 kPa. The results showed that scheduling drip irrigation with SMP thresholds at 20 cm depth obviously affected the soil moisture status in the root zone, and the lower the SMP threshold was, the lower the average soil moisture content was. Soil moisture consumption of winter wheat occurred mainly in 0-60 cm soil layer in anthesis stage, and reached a depth of 80 cm in grain filling stage, and there was no deep percolation but groundwater recharge in 130 cm layer. SMP thresholds had significant effects on grain yield and water use efficiency (WUE), and there was a tendency for the two indicators to reach their highest values when the SMP threshold was around - 40 kPa in the normal years. Both yield and WUE decreased with the decrease of SMP in the dry year. Winter wheat evapotranspiration and irrigation amount decreased by 0.12% and 0.92%, respectively, and the irrigation water use efficiency increased by 1.22% with each unit of SMP decrease. Compared with the average grain yield, irrigation amount and WUE under local surface irrigation management, drip irrigation with the SMP threshold of - 40 kPa resulted in a yield increase of 4.3%, water savings of 46.6%, and WUE increase of 10.5%. The yield increase wasn't significant to attract farmers to adopt drip irrigation technology, but the water saving was obvious. So, in the NCP, if the investment of drip irrigation system was likely to be government subsidized, it was recommended to drip irrigate winter wheat with the SMP threshold of - 40 kPa at 20 cm depth immediately under the emitters.