Research On The Effect Of Groundwater Depth On Crop Water Ecological Adaptability In Huaibei Plain

The effect of shallow groundwater depth on crop water ecological adaptability in Huaibei Plain was researched in this paper.In this paper,the lysimeter experimental data and meteorological data of Wudaogou Hydrological Experimental Station from 2011 to 2015 were used,including surface runoff,phreatic evaporation,infiltration recharge,precipitation,water surface evaporation,relative humidity,average wind speed,etc.Winter wheat and summer soybean in Huaibei Plain were chosen as the research objects.Two typical soils of Shajiang black soil and Yellow fluvo-aquic soil in Huaibei Plain were applied to study the limit depth of groundwater utilization for summer soybean.Six buried depths of 0.2m,0.4m,0.6m,0.8m,1.0m and 1.5m were selected.The water balance equation,Jensen’s model,the calculation method of crop water demand recommended by the United Nations Food Organization(FAO)and the equation of farmland water balance were applied.The changes of effective precipitation,water sensitive index,water demand,irrigation water consumption and coupling degree of water demand and precipitation in winter wheat and summer soybean under different groundwater depth and different growth stages in the Huaibei Plain were revealed.According to the water ecological adaptability index model,the water ecological adaptability law of winter wheat and summer soybean in different groundwater depths was revealed.The relationship between coupling degree of precipitation and irrigation water consumption and water ecological adaptability was identified.The main research results are as follows:(1)In Shajiang black soil,the effective precipitation during the whole growth period of winter wheat reached the maximum at 1.0m buried depth,which was 1.08～7.90 times that of other buried depths.The effective precipitation during the whole growth period of summer soybean reached the maximum at 1.0m buried depth,which was 1.23～3.85 times that of other buried depths.In Yellow fluvo-aquic soil,the effective precipitation during the whole growth period of winter wheat reached the maximum at 1.0m buried depth,which was1.26～7.75 times that of other buried depths.The effective precipitation during the whole growth period of summer soybean reached the maximum at 1.0m buried depth,which was2.44～5.99 times that of other buried depths.(2)From the perspective of different growth stages,the maximum water demand of winter wheat appeared in the period of returning to green-jointing and heading-maturity.The total water demand of winter wheat in two periods was 243.37 mm,accounting for 65.53% of the total growth water demand.Therefore,to ensure the water demand of winter wheat from returning to green to maturity plays an important role in increasing production and income of winter wheat.The water demand of summer soybean reached the peak at flowering and pod stage,which was 141.39 mm,accounting for 38.17% of the total growth water demand.Therefore,to meet the water demand of summer soybean in flowering and pod stage is the key factor affecting the high and stable yield of soybean.(3)In Shajiang black soil and Yellow fluvo-aquic soil,the irrigation water consumption of winter wheat and summer soybean in the whole growth period was the least at 1.0m buried depth.It can be concluded that the control of groundwater depth of about 1.0m in the two soil types can reduce the amount of artificial supplementary irrigation.(4)In Shajiang black soil and Yellow fluvo-aquic soil,the coupling degree of precipitation of winter wheat and summer soybean in the whole growth period reached the maximum at1.0m burial depth.The coupling degree of precipitation of winter wheat and summer soybean at different groundwater depths and different growth stages was less than 1.The research results showed that the effective precipitation cannot meet water demand for crop growth.In addition,reasonable supplementary irrigation should be carried out according to the water shortage of winter wheat and summer soybean at each growth stage.(5)The water ecological adaptability index of winter wheat and summer soybean was directly affected by the precipitation coupling degree and irrigation water consumption.The precipitation coupling degree of summer soybean during the whole growth period was the largest and the irrigation water consumption was the smallest at 1.0 m buried depth.Therefore,the water ecological adaptability index of summer soybean at 1.0 m buried depth was higher than that in other buried depths.In Shajiang black soil,the maximum water ecological adaptability index of winter wheat was 0.441 at 1.0 m buried depth,which was 1.12～8.48 times that of other buried depths.The maximum water ecological adaptability index of summer soybean was 0.525 at 1.0m buried depth,which was 1.25～4.20 times that of other buried depths.In Yellow fluvo-aquic soil,the maximum water ecological adaptability index of winter wheat was 0.202 at 1.0m buried depth,which was 1.18～7.48 times that of other buried depths.The maximum water ecological adaptability index of summer soybean was 0.229 at 1.0 m buried depth,which was 2.46～6.03 times that of other buried depths.In conclusion,winter wheat and summer soybean had the strongest water ecological adaptability at 1.0m buried depth.