Significance of disposable presowing irrigation in wheat in increasing water use efficiency and maintaining high yield under winter wheat-summer maize rotation in the North China Plain

Water scarcity in the North China Plain (NCP) is threatening irrigation of predominant winter wheat-summer maize rotation and thus rotation yield. To maximally reduce irrigation input while maintaining relatively high yield is urgently needed and an enduring challenge. Here we present an innovative practice that considers the water use of the entire rotation system, i.e., application of presowing irrigation to reach 85% of the field capacity for wheat (W0) compared with the common practice of applying twice more irrigation with each 750m(3) ha(-1) during the wheat season (W2). After sowing maize, 750m(3) ha(-1) irrigation was applied for both practices. The main hypothesis was that reducing wheat irrigation would lead to lower water content in the soil, which would in turn preserve more rain in the maize season, and that earlier maturity of wheat caused by reduced irrigation would advance earlier maize-sowing to utilize more radiation and thermal inputs resulting in higher maize yield which would compensate for decreased wheat yield. From 2012 to 2016, the 0-200 cm soil water contents, as well the yield and its components, were monitored at key growth stages of wheat and maize. There was consistently lower water content under W0 than under W2 from flowering to maturity of wheat making 4-5 days earlier maturity under the W0 practice, and led to a higher accumulated temperature of maize relative to the W2 practice. The grain yields of wheat, maize and rotation were 6694 to 9218 kg ha(-1), 7284 to 12,843 kg ha(-1), 16,336 to 20,605 kg ha(-1), respectively. The temperature accumulated after silking well explained the interannual variation in maize yield. In contrast to temperature, rainfall during the maize season explained the yield difference between two practices. The maize yield was 6.4% higher under the W0 practice than under the W2 practice, in a year with sufficient rainfall, above 451 mm, and this trend was unpronounced under rare drought stress, below 250 mm of rainfall, leading to a 7.5% lower yield. The average yield of the four rotation rounds under W0 was equal to that under W2. Nevertheless, the W0 practice significantly increased the water use efficiency under rotation by 12.9%. On average, the irrigated amount in each rotation under W0 was significantly reduced by 1126m(3) ha(-1) relative to W2. Therefore, the W0 practice is a simple and promising water management strategy for addressing shortages of water and labor while maintaining relatively high rotation yield in the NCP.