A comparative study of yield, cost-benefit and water use efficiency between monoculture of spring maize and double crops of wheat-maize under rain-fed condition in the North China Plain

In order to build a water-saving planting system and control water over-exploitation in the North China Plain, a field experiment was conducted to compare yield, cost-benefit and water use efficiency between spring maize monoculture and winter wheat-summer maize double cropping system under rain-fed conditions. The field experiment was conducted in 2007 2013 under rain-fed conditions at the Luancheng Agro-Ecosystem Experimental Station (LAS) of the Chinese Academy of Sciences (CAS), which is in the northern region of the North China Plain located at the base of Mount Taihang. Winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation is the most commonly used cropping system in the region. There were two treatments in the experiment, one was the winter wheat and summer maize rotation system (T1) and the other one was the single harvest of spring maize cropping system (T2). The winter wheat was grown from the first 10 days or mid-October to mid-June of the following year. Then summer maize was grown from mid-to-late June to early October, while spring maize was grown from mid-to-late May to the first 10 days of September. The varieties of winter wheat and summer maize used were 'Kenong199' and 'Zhengdan 958', respectively. Also the varieties of spring maize used were 'Nongda 108', 'Xundan 20', 'Zhengdan 958' and 'Xianyu335'. No irrigation was adopted in the experiment over the period from September 2007 to June 2013. The results showed that under rain-fed conditions, wheat yield was relatively stable while summer maize and spring maize yields varied with different climate years. Summer maize yield was especially strongly influenced by soil water content at sowing. Maize did not germinate normally in many seasons due to dry soil and little rain after sowing. Delayed summer maize germination decreased maize yield. Although crop yield under T1 treatment was 34.1% higher than that under T2 treatment, cost-benefit of T1 was 279.97 Yuan·hm^-2 lower than that of T2 due to higher input of winter wheat. The proportions of agricultural materials and machinery investments were higher while labor input accounted for a small proportion of the inputs for the three crops. Fertilizer input accounted for a significant proportion in the agricultural materials. The input-output ratios of winter wheat, summer maize and spring maize were 1.42, 2.66 and 3.42, respectively. Under rain-fed conditions, input-output ratio of winter wheat was the lowest and that of spring maize the highest. Water consumption analysis suggested that soil water was the largest water source of winter wheat, while rainfall was the dominant source of spring and summer maize. In practice, farmers gradually reduced planting area of winter wheat and enlarged that of spring maize. In view of food security, it was needed to adjust the agricultural cropping system to control over-exploitation of groundwater resources and ensure sustainable development of agriculture in the study area.