河北低平原区春玉米一熟替代麦玉两熟制的水生态与粮食安全分析

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

本研究针对河北低平原区水资源日益短缺的现状,于2011—2014年在河北省吴桥县开展田间试验,以小麦?玉米两熟制(WS)为对照,设置零灌溉春玉米一熟制(SMRF)和适水条件下春玉米一熟制(SMSW)2种种植模式,共3个处理,研究该区改传统高耗水的小麦?玉米两熟制为春玉米一熟制的可行性。结果表明:周年耗水量SMSW、SMRF较WS分别降低48.4%和54.2%;冬小麦耗水主要来自灌溉水和土壤储水,试验年间降雨仅能满足冬小麦耗水总量的32.9%,春玉米生育期内耗水主要来自降雨,试验年间SMSW和SMRF生育期内有效降雨总量分别满足春玉米耗水总量的91.9%和94.9%。SMSW和SMRF周年产量平均较WS分别降低24.4%和45.8%。SMSW和SMRF水分利用效率较WS平均分别高24.8%和0.3%。SMSW和SMRF的经济效益较WS平均分别减少5.2%和36.8%。经济水分利用效率SMSW和SMRF较WS平均分别高56.7%和17.5%。当下WS较SMSW仍具有一定的产量和效益优势,但WS对地下水灌溉依赖严重;而SMSW的水分利用效率和经济水分利用效率显著高于WS,未来随着春玉米高产技术体系的成熟,春玉米产量的进一步提高,在我国粮食总产、库存、进口"三增"的"新常态"下,该区改小麦玉米两熟为春玉米一熟具有兼顾水生态和粮食安全的可行性。

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.