Security of water-ecology and food under replacement of winter wheat-summer maize rotation with spring maize mono-cropping in Hebei Lowland Plains

Hebei Lowland Plains, one of the main grain producing areas in China, has an acute water shortage. To ensure sustainable development in the plains, strategies are needed to manage the water shortage and obtain high crop yield in the region. In terms of water-saving and high-yield farming systems for the region, spring maize mono-cropping has shown to be a promising alternative to the traditional winter wheat-summer maize double-cropping system. A comprehensive comparison between the effects of the winter wheat-summer maize rotation and the spring maize mono-cropping on water ecological security and food security in the study area under different yield levels has not yet been tested. Thus, field experiments were conducted at Wuqiao Experiment Station of China Agricultural University in the Hebei Lowland Plains in 2011–2014 to determine the feasibility of replacing traditional high irrigation costs of the winter wheat-summer maize double-cropping rotation system with the spring maize mono-cropping system. The three treatments implemented in the experiment included a winter wheat and summer maize double-cropping rotation (WS), a rain-fed spring maize mono-cropping system (SMRF) and a fully-irrigated spring maize mono-cropping system (SMSW) — in which treatment WS was used as the control (CK). Four main factors were evaluated — actual annual evapotranspiration (ETa), productivity, water use efficiency (WUE), economic benefit and economic water use efficiency (EWUE) — that influenced the performance of the three treatments. Results showed that average annual ETa was highest under WS, followed by SMSW and SMRF. Average annual ETa under SMSW and SMRF decreased by 48.4% and 54.2%, respectively, compared with WS. Under WS cropping system, precipitation accounted for only 32.9% of total water consumption by winter wheat during the three-year experimentation period, while irrigation and soil water were the two main water sources of winter wheat. Adversely, precipitation accounted for 91.9% and 94.9% of total water consumption under SMSW and SMRF systems. Average annual productivity under SMSW and SMRF systems decreased respectively by 24.4% and 45.8%, compared with WS rotation system. In addition, economic benefits were highest under WS, although those under SMSW and WS were very close, with SMSW only 5.2% lower than WS on average. SMRF economic benefits were 36.8% lower than that of WS. However, WUE and EWUE under WS were lower than those under SMSW and SMRF. While WUE increased by 24.8% and 0.3%, EWUE increased by 56.7% and 17.5% respectively under SMSW and SMRF compared with those of WS. Although WS had higher annual grain yield and economic benefits, this was driven primarily by the unsustainable use of intensive irrigation. In comparison to WS, food security under SMSW system reached 75.7% with 46.7% groundwater irrigation. With advancements in spring maize production technology, there was the potential to increase the productivity of spring maize. Compared to the double-cropping system, the spring maize mono-cropping system was a water-saving, high-yielding and efficient alternative cropping system. To balance water resources and food security in the Hebei Lowland Plains, China’s “new normal” conditions with the “Three Increases” (increases in grain production, storage and import) has shifted the ideal cropping system from the winter wheat-summer maize rotation system to a more sustainable spring maize mono-cropping system.