春玉米不同生育期土壤湿润层深度调控的稳产节水效应

局部根区水分胁迫可以调节作物的产量、品质及水分利用效率。现有研究多通过调控水平方向作物根区土壤水分分布来构建适宜局部根区水分胁迫环境,而水平方向根区土壤水分分布的调控存在局限性。该文以石羊河流域春玉米为研究对象,通过覆膜和控制不同生育期计划湿润层深度来实现根区土壤水分的垂向调控,分析了调控措施对不同深度土层水分、作物生长指标及水分利用效率的影响。结果表明:根区土壤水分垂向调控措施可以有效调控作物根系分布及根区土壤水分的时空变化;调控中选用大的计划湿润层深度可以有效增加深层土壤内的根长密度及其分布比例,减小不同深度土层水分差异;在调控中,水分胁迫多出现于下部土层(50~100 cm),且含水量随时间在胁迫阈值上下波动,存在空间上的局部水分胁迫和时间上的干湿交替,所构建的水分胁迫环境较为理想;该调控措施亦可对灌水量及作物耗水量进行调控,能够调节作物对降雨及深层土壤水的利用,在各生育期使用较大或较小计划湿润均可以增加对非灌溉水的利用,其中,大的计划湿润层深度有利于对深层土壤水的利用;根区土壤水分的垂向调控也会影响干物质在各组织器官间的分配,实现增产增收。以灌溉水利用效率及水分利用效率来评价各调控方案节水效果,最优根区土壤水分垂向调控方案为:地膜覆盖,灌水下限设为65%田间持水量,苗期计划湿润层深度为30 cm,拔节期计划湿润层深度为40 cm,抽雄期至成熟期计划湿润层深度为50 cm。

Water-saving and stable yield effects of regulation on soil wetted depth in different growth stage of spring maize

Abstract: Appropriate partial root zone water stress not only improves the yield and quality of crops, but also increases crop water utilization efficiency, so as to reduce waste of water resources. It is a much-used method to build the suitable environment of root zone water stress by regulating the crop root zone soil water distribution in horizontal direction in the previous studies. The regulation of root zone soil water distribution in horizontal direction had limitations. In order to disabuse the limitations, in this paper, we took spring corn in Shiyang River Basin as the research object. As such, the crop root zone soil water distribution in vertical direction was regulated by the way of controlling planned wetted soil depth in different growth stage under mulching. In the experiment, there were three levels of planned wetted soil depth, 30, 40 and 50 cm in seeding stage; three levels of planned wetted soil depth, 40, 50 and 60 cm in jointing stage; three levels of planned wetted soil depth, 50, 60 and 70 cm in tasseling to mature stage. This study analyzed the effect of the regulation in vertical direction on soil water content in different depths, the distribution of root, plant height, leaf area, biomass, yield and water use efficiency. The results showed that soil water profile could be better regulated by controlling planned wetted soil depth in different growth stage. The higher planned wetted soil depth could increase root length and increase the root length in deep soil significantly. The higher planned wetted soil depth also could increase the distribution of root in the deep soil layer. Soil water stress tended to occur in the deep soil layer (50~100 cm). And the water content changing with time in stress threshold value fluctuated up and down. Soil water stress didn''t occur in the upper soil layer (0~40 cm). The distribution of crop root system could also affect the changes of soil water in time and space. The regulation in vertical direction could regulate the crop consumption of water, and affect the use of rainfall and water in deeper soil depth, adjusted the allocation of drymatter in crops'' organizations, implementing water-saving for crop production. The higher or lower planned wetted soil depth both could increase the use of irrigation water and rainfall or water in deep soil. The lower planned wetted soil depth made more root distribute in the upper soil layer, so as to increase the use of rainfall. The higher planned wetted soil depth made more root distribute in the deep soil layer, so as to increase the use of soil water in the deep soil layer. Appropriate water stress could increase the harvest index, make more dry matter allocate to corn grain. In the study, both the irrigation water use efficiency and water use efficiency were used to evaluate the treatments'' effect on water-saving, which showed that the optimal regulation in vertical direction was 30, 40 and 50 cm of planned wetted soil depth at seeding, jointing, and tasseling to mature stages under mulching, respectively.