Effects Of Groundwater Depth On Water Consumption And Growth Of Maize Under Mulched Drip Irrigation

Water resources of China are scarce,of which agricultural water accounts for more than60%of total water resources.Studying the impact of groundwater depth on crop growth and water consumption characteristics is of great significance for China's construction of high-efficiency water-saving agriculture.To this end,the five different groundwater depths of1.0(D1.0),1.5(D1.5),2.0(D2.0),2.5(D2.5)and 3.0 m(D3.0)were set up by the groundwater simulation system in this paper.Meanwhile,the effects of groundwater depth on soil moisture and growth of maize under mulched drip irrigation were analyzed,which based on the soil water content of different soil profiles and maize growth index,yield and its components observed in the pit test in 2016 and 2017.In addition,the water balance equation and meteorological data were used to analyze the water consumption,water use efficiency and crop coefficient under mulched drip irrigation with different groundwater depths.The main research results are as follows:(1)The ordered sample optimal segmentation method in cluster analysis was used to divide time distribution of soil moisture under mulched drip irrigation with different groundwater depths,which is divided into four periods including soil water stationary period,soil water consumption period,soil moisture fluctuation period and soil moisture recovery period.The soil water storage showed a steady downward trend with the advancement of time,and decreased with the increase of groundwater depth,however,the irrigation amount increased significantly.The vertical distribution of soil moisture under mulched drip irrigation with different groundwater depths is determined by the coefficient of variation method.The vertical section is mainly divided into weakly variable layer and relatively stable layer.When the soil depth is greater than 80 cm,the vertical variation of soil moisture in each growth period is consistent.The depth of the soil layer below 80 cm is a relatively stable layer and is not easily affected by irrigation.(2)The irrigation amount of maize with different groundwater depths increased with the increase of groundwater depth,which was opposite to the change of groundwater recharge,water consumption and crop coefficient.In 2016 and 2017,the groundwater recharge under D1.0 is 210.0?456.4 mm and 225.1?483.4 mm,compared with other treatments,the irrigation amount under D1.0 is 102.5?266.5 mm and 161.6?270.5 mm more than other treatments,which showed the water saving effect is remarkable.The water consumption under D1.0 is significantly higher than other treatments,which is higher than 88.29?139.81 and24.01?136.13.The difference is mainly reflected in the jointing stage and the silking stage.The crop coefficient reached a maximum during the jointing-drawing period,which was1.4?2.6 and 1.3?2.2,respectively.(3)Shallow groundwater can promote the growth and yield formation of maize.In general,the growth index and yield of maize increased with the decrease of groundwater depth.Shallow groundwater can shorten the number of days after planting when plant height and stem thickness reached the peak to a certain extent,D1.0 and D1.5 treatments can shorten the number of days after planting when plant height and stem thickness reached the peak by10?20 d.Compared with the yield of D1.0,the yield reductions of other treatments in 2016and 2017 were 1.83%?16.3%and 1.98%?8.29%,respectively.Through the analysis of the yield composition and path analysis of the factors affecting the yield,the groundwater depth mainly increased the leaf area index of maize and the water storage of 0?80 cm,thereby increasing the ear diameter,grain numbers and 100-grain weight of the maize,and finally increased yield of maize.(4)Considering the higher and stable yield of maize and high-efficiency water saving,the suitable groundwater depth for maize planting in this region is 1.5?2.5 m,the maize yield is around 14 759.0 kg/hm~2,which requires about 457.0 mm of water,equivalent to the reference crop evapotranspiration(445.0 mm),the groundwater recharge and irrigation amount are 218.0 mm and 218.0 mm,respectively,the water use efficiency(WUE)can reach3.40 kg/m~3.