农田耗水构成、规律及影响因素分析

Analysis of field water consumption, its pattern, impact and driving factors

  • 摘要: 农业用水占总用水量的70%左右, 对农田耗水规律和过程的研究对发展区域节水农业有着非常重要的作用。本文通过回顾中国科学院栾城农业生态系统试验站建站以来在农田水分循环和节水方面的研究进展,对长期定位试验下不同灌溉水量的耗水规律、农田耗水过程及影响农田耗水的因素进行了分析。通过利用水量平衡法和大型蒸渗仪测定等方法确定蒸散量, 用小型蒸发器测定土壤蒸发。长期定位试验的结果表明: 在该区域冬小麦-夏玉米一年两作的种植方式下, 这两种作物耗水量相似, 随着灌溉量的增加, 农田耗水有增加的趋势; 冬小麦的农田耗水量在283~493 mm 之间, 灌溉水量较小处理的变异系数较大。利用大型称重式蒸渗仪和自制的微型蒸发器(MLS)测定的冬小麦和夏玉米季的棵间蒸发均占蒸散量的1/3。因此, 在此基础上可以利用秸秆覆盖减少土壤蒸发且效果非常明显, 20 年的试验表明秸秆覆盖每年可以减少土壤蒸发40~50 mm, 冬小麦秸秆覆盖夏玉米田可以抑制棵间蒸发的58.0%, 夏玉米秸秆覆盖冬小麦田可以抑制蒸发40.4%。长期耕作的定位试验表明: 不同耕作方式下的土壤蒸发也存在明显的差异, 免耕加秸秆覆盖处理的蒸发最小, 而深耕的最大。同时, 不同灌溉制度、种植方式和冠层结构均会对农田耗水产生影响。这些研究结果为以后的节水理论和技术发展提供了依据。

     

    Abstract: Agricultural water use accounts for about 70% of total water consumption in the North China Plain (NCP). So, the researches on field water consumption and its pattern, impact and driving factors critical for developing agricultural water-saving practices and also learning water transfer mechanisms in soil-plant-atmosphere continum (SPAC) are very important. This paper reviewed the proceedings in field water cycle and water-saving research in the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences since its establishment. Long-term site-specific experiments on irrigation schemes since 1985, straw mulching schemes since 1986, tillage schemes since 2002, large weighing lysimeter data streams since 1995, and other agro-experiments have been conducted at the station. Water balance methods and large weighting lysimeter data were used to estimate evapotranspiration (ET) in the station. Soil evaporation (E) was measured using the micro-lysimeter method. The results showed that water consumption during winter wheat and summer maize cropping periods was similar, averaging 430 mm per cropping season. The trend in water consumption increased with increasing irrigation of winter wheat, which had increased on the average from 283 to 493 mm. The coefficient of variation in ET was negatively correlated with irrigation, and was mainly driven by precipitation difference. The ratio of E to ET for winter wheat and summer maize was 1/3, and also similar for the tow crops. This implied that limiting E was a critical water-saving factor in the region. Field experiments at Luancheng station in recent 20 years showed that straw mulching significantly reduced E, to somewhere in the neighborhood of 40~50 mm. Wheat and maize straw mulching reduced E by 58.0% and 40.4% in summer maize and winter wheat fields, respectively. Despite the fact that differences in E existed for different field tillage practices,zero-tillage, as compared with traditional tillage, significantly reduced E. The irrigation, tillage and planning schemes as well as canopy characteristics affected crop water consumption and agricultural water-saving in the region. The above findings laid the basis for theoretical and technical developments of agricultural water-saving practices in NCP.

     

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