Performance of a Double Cropping System under a Continuous Minimum Irrigation Strategy

Conservation of groundwater resources is very important for the grain production in the North China Plain (NCP). Previous studies showed that under minimum irrigation strategy (MI), the popular double-cropping system of wheat (Triticum aestivum L.) and maize (Zea mays L.) in NCP might achieve sustainable groundwater use with a moderate yield penalty. Field experiments were continuously conducted from 2005 to 2012 to evaluate the long-term effects of MI on the crops performance. The experiment compared the yield and crop water use under MI and full water supply conditions (full irrigation, FI). Results showed that yield reduction rate (YRR) under MI for wheat increased substantially and for maize decreased slightly. The diminishing rainfall during the rapid vegetative growing stages of wheat was partly responsible for this result. Soil moisture stored before sowing of wheat contributed around 61% of the seasonal crop water use under MI, and strongly affected the final grain production of this crop. The depleted soil moisture during wheat season was partly replenished during the maize season. Soil drying trend in deep soil layers under MI was not observed. This result indicated that the MI strategy was sustainable. The average annual crop water use over the 7 yr was 625 and 956 mm under MI and FI. With a 18.3% yield penalty, annual crop water use was reduced by 34.6% from FI to MI. Seasonal atmospheric evaporation demand affected the grain production of both crops under MI and FI.