环渤海低平原农田多水源高效利用机理和技术研究

淡水资源严重匮乏是影响环渤海低平原粮食生产可持续发展的重要限制因素。本文针对该区粮食生产中水分利用效率低、提升潜力巨大,同时该区浅层微咸水资源和降水资源较丰富的现状,以中国科学院南皮生态农业试验站最近3年试验研究结果为基础,综述了在挖掘咸水利用潜力、提高雨水和灌溉水利用效率方面研究工作进展。针对冬小麦夏玉米一年两作种植,研究结果显示品种间产量和水分利用效率(WUE)差异显著,最高和最低品种差异达20%左右,通过选用节水高产品种可显著提升产量和WUE;冬小麦通过拔节期灌溉关键水,在促进地上部生物量积累同时,显著促进地下根系生长,使冬小麦充分利用土壤储水,实现限水灌溉下稳产高效;夏玉米通过缩小行距增大株距的缩行匀播,可提升夏玉米苗期单株作物根系所占土壤体积空间,增加水分养分对作物的有效性,提高夏玉米成苗率和苗期所截获辐射量,比常规种植产量提高10%左右;冬小麦在拔节期利用含盐量不大于4 g×L~(-1)的浅层微咸水替代淡水灌溉,产量与淡水灌溉相同;浅层微咸水替代淡水灌溉并配套土壤有机质提升技术和利用夏季降水淋盐,可实现微咸水灌溉下周年土壤盐分平衡。通过上述措施实施,实现以咸补淡、以淡调盐、多水源互补高效利用,在不影响作物产量条件下可节约深层淡水资源,促进区域灌溉农业可持续发展。

Efficient utilization of various water sources in farmlands in the low plain nearby Bohai Sea

Freshwater shortage is a growing crisis in food production in the plain nearby the Bohai Sea. It is therefore important to efficiently utilize available water resources in the region, including fresh groundwater, brackish groundwater and precipitation during grain production season. This paper summarized the work of a 3-year field experiment at Nanpi Eco-Agricultural Experimental Station, Chinese Academy of Sciences on utilization of saline water in replace of fresh groundwater irrigation of winter wheat, deficit irrigation to reduce water use, high-performance cultivars, and the optimized planting and cultivation technologies in wheat-maize double cropping system. The results showed that jointing stage was critical for irrigation under a single irrigation application in winter wheat. Irrigation at jointing stage improved the growth of both aboveground and belowground parts of winter wheat. The enhanced root growth increased soil water utilization during late growth stages and also reduced the negative effects of water stress on yield under limited irrigation of winter wheat. The study also showed that the use of saline water with salt concentration less than 4 gL^-1 in place of freshwater irrigation at jointing stage of winter wheat did not affect yield, and prevented deep freshwater depletion. To mitigate the negative effects of soil salt in the top 20 cm soil profile after winter wheat harvest on successive crops (summer maize), about 70 mm of irrigation at sowing stage of maize was needed to support maize germination and seedling establishment. The results suggested that the return of the straw of both crops to the soil enhanced soil organic content. While the increased proportion of stable soil aggregates benefited the stability of soil structure, leaching of salt after saline irrigation improved during summer rainy season. The selection of better cultivars of winter wheat and summer maize had the potential to improve yield and water use efficiency by up to 20%. For summer maize, reducing inter-row spacing and increasing intra-row spacing improved the proportion of seedling establishment and interception ratio of solar radiation by crop canopy at seedling stage. This improved maize yield by about 10% compared with traditional planting. The combined results of the measures reduced freshwater use in irrigation, and significantly improved water use efficiency and grain yield of crops. The study showed that it was possible to maintain grain yield and to conserve fresh groundwater resources at the same time in the study area.