Research On Relationship Between Groundwater Depth And Water Sensitivity Index Of Typical Dry Crops In Huaibei Plain

This study is around the shallow groundwater depth influence on crop water utilization in Huaibei plain.Main research object are two typical dry crops,winter wheat and summer soybean,in Huaibei plain.Long sequence continuous experimental data(1986-2012)of the lysimeter in Wudaogou Hydrology and Water Resources Experimental Station and two kinds soil Shajiang black soil and Yellow fluvo-acquatic soil were taken in this research under 0.2,0.4,0.6,0.8,1.0,1.5m six control depths,the differences in winter wheat and summer soybean growth characteristics under different buried depths were analyzed.Two kinds of water production function were used to calculate water sensitivity coefficient by Blank model and index by Jensen model under different groundwater depths.Winter wheat simulated yield was obtained through calculation and compared it with the actual yield,so as to optimize the better water production function model in Huaibei plain.The trend of water sensitivity index of winter wheat and summer soybean in different growth stages and different groundwater depths were analyzed.The suitable groundwater depth threshold interval of winter wheat and summer soybean was determined,and the relationship between crop water sensitivity indexes and groundwater depths was clarified.(1)The relationship between groundwater depth and crop characteristic value and yield.Winter wheat and summer soybean were selected as research objects.Based on the average plant height,ear length,grain number per ear,thousand kernel weight,full-pod number,wilting-pod numbers grain weight per plant and yield data under different groundwater depths of winter wheat from 2008 to 2012 and summer soybean from 2006 to 2009 in Wudaogou hydrological experimental station.It was found that when the groundwater depth was 1.0m,the average plant height,thousand kernel weight and yield of winter wheat reached the maximum value.As groundwater depth increase,all the characteristic values showed different decrease and the range is 1.6?16.1%.When groundwater depth was 0.8 m,only full-pod number and yield of summer soybean reached the maximum value.As the groundwater depth increase,only full-pod number and yield values showed different decrease and the range is 29.8?30.7%.(2)The relationship between crop yield and water production function.Based on the winter wheat submersible evaporation experiment in Wudaogou hydrological experimental station from 2008 to 2012,the water sensitivity coefficient and index of winter wheat were solved base on Blank model and Jensen model,and the winter wheat yield from 2004 to 2008 was simulated.The results showed that the yield simulated by the Blank model was basically bigger than the actual yield,with an increase range of 5%-20%.Jensen model's simulated production and actual production showed no obvious deviation trend,and the variation range was between 1%and 9%.In comparison,Jensen model showed a better simulation effect than Blank model.Therefore,Jason model is the water production model which is more suitable to be used for crop in Huaibei plain.(3)Research of the relationship between crop water sensitivity index and groundwater depth.Based on the yield and phreatic water evaporation statistics of winter wheat(2008?2012)and summer soybean(2006?2009)from Wudaogou hydrological experimental station,Jensen model was used to calculate the water sensitivity index of winter wheat and summer soybean with different soil,different growth stages and different groundwater depth.The results showed that:the water sensitivity index of winter wheat showed a trend of increasing first and then decreasing during the whole growing period.It reached the maximum in heading-maturation stage and it was 1.85 times higher compared to the turning green-jointing stage.Water sensitivity index of summer soybean showed a trend of decreasing first and then increasing during the whole growing period and it reached the maximum in the flower and pod-bulging pod stage,and the other growth stages were only 48.6%to 53.5%of the flower and pod-bulging pod stage.The water sensitivity indexes of winter wheat and summer soybean increased first and then decreased under different groundwater depths.The water sensitivity index of winter wheat was the highest at 1.0m groundwater depth,which was 1.16-2.45 times of the minimum value in the same growth stage.The water sensitivity index of summer soybean was highest at 0.8-1.0m groundwater depth,which increased by 15%-17.5%compared with the minimum value.Through the regression curve of water sensitivity index under different groundwater depths,it was found that the suitable groundwater depth range of winter wheat in Shajiang black soil and Yellow fluvo-acquatic soil was 0.8-1.2m.The suitable groundwater depth range of summer soybean was 0.8-1.0m in Shajiang black soil and below 1.0m in Yellow fluvo-acquatic soil.Compared with other groundwater depths,winter wheat and summer soybean can reduce artificial irrigation,times of drainage and increase crop yield.