西瓜/棉花间作作物需水量计算模型及水分竞争机制

The advantages of intercropping systems are to fully utilize multiple resources and improve crop yield per unit area. On the face of the scarcity of water resources, study on the calculation model of crop evapotranspiration and water competition mechanism between crops has an important significance for promoting the development of intercropping planting techniques and efficient utilization of water resources. Taking the watermelon/cotton intercropping system as a research object, the following main contents will be conducted in this study through the combination method of field experiment with theoretical analysis: (1) establishing the calculation model of crop water requirement in watermelon/cotton intercropping system by analyzing the relationship between crop coefficient and its influence factors, and determining the allocation ratios among watermelon transpiration, cotton transpiration and soil evaporation, as well as the calculation model of the allocation ratios; (2) analyzing the spatial distribution characteristics of root system, and expounding the water competition mechanism in the symbiotic period and the absorption-utilization mechanism of crop to nutrients affected by water competition; (3) determining the irrigation index for efficient use of water in the watermelon/cotton intercropping system. This research will have an important guiding significance for establishing the water and nutrient management system, improving the utilization efficiency of water resources, and guaranteeing crop yields under intercropping planting patterns.

间作种植具有充分利用多种资源、提高单位面积作物产量的优点。面对水土资源日益紧缺的现状，开展间作作物需水量计算模型及水分竞争机制研究，对于促进间作种植技术的发展及水资源的高效利用具有重要的意义。本项目以西瓜/棉花间作群体为研究对象，采用田间试验与理论分析相结合的研究方法，主要研究内容包括：（1）通过分析间作作物系数与影响因子之间的关系，构建西瓜/棉花间作作物需水量计算模型，确定间作西瓜蒸腾、棉花蒸腾及棵间蒸发的分配比例，建立间作西瓜蒸腾、棉花蒸腾及棵间蒸发分摊模型。（2）分析间作作物根系空间分布特征，阐明共生期作物对水分的竞争机制，研究作物对水分的竞争导致作物对养分的吸收利用机理。（3）制定西瓜/棉花间作种植结构下水分高效利用灌水指标。研究成果对于制定间作种植模式下的水肥管理制度、提高间作群体水资源利用效率、保障间作种植的产量优势均具有重要的指导意义。

本项目建立了充分供水条件下西瓜/棉花间作作物需水量计算模型，确定了间作西瓜蒸腾、棉花蒸腾及棵间蒸发的分配比例，构建了间作西瓜蒸腾、棉花蒸腾及棵间蒸发分摊模型。全生育期蒸发量占蒸发蒸腾量的31.41%，蒸腾量占蒸发蒸腾量的68.59%，其中西瓜蒸腾量占间作群体蒸腾量的60.61%，棉花蒸腾量占间作群体蒸腾量的39.39%。. 瓜棉间作各水分处理共生期内耗水强度均表现为前期小，中期大，后期小的规律，全生育期间作充分供水处理耗水量最大，其次为西瓜膨大期70%田持处理，西瓜开花期60%田持处理耗水量最小。各水分处理间作作物产量表现为，西瓜膨大期70%田持处理能同时提高间作西瓜和棉花籽棉产量，西瓜开花期60%田持处理虽然有利于棉花籽棉产量的提高，但西瓜产量明显下降。各水分处理间作总产出值、水分生产效率及土地利用效率方面，西瓜膨大期70%田持处理均表现最高。表明，瓜棉间作种植系统在科学合理的水分调控技术下是相互促进的体系。. 水分亏缺处理（西瓜膨大期70%田持）在共生期结束时间作根系生长发育在0~40cm土层中西瓜根系较棉花生长旺盛，处于竞争有利地位，40~60cm土层中棉花根系下扎量较大，根系处于竞争优势地位；水平方向上，间作系统中西瓜、棉花在距西瓜主根区10cm处存在明显的根系竞争关系，该处棉花表现出明显的竞争趋势，但竞争优势仍小于该处间作西瓜的优势。瓜棉间作处理对水分的竞争与利用使养分在土壤中的运移转化发生了变化，其中，瓜棉间作处理较单作相比土壤碱解氮含量最低，速效磷含量最高，速效钾含量介于单作西瓜和单作棉花中间。