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.