Experimental Research On The Impact Of Straw Returning For The Use Of Soil And Water In The Costal Area Of Yancheng

With the implementation of coastal development strategy, the industrial water and domestic water requirement of coastal area have been continuously increasing, and the contradiction between supply and demand of water resources has become more acute. More attention has been paid on the scientific and efficient ways of using shallow groundwater and the ways of reducing the water resource bearing pressure.In this paper, we studied the impact of depth of straw returning and buried depth of phreatic water for soil moisture and evaporation in the coastal area of Yancheng through the combination of soil column and field experiments, which would provide theoretical basis for using shallow groundwater more effectively and the main findings of the study were as follows:(1) The Y6 processing had a better effect on increasing the 0.8～1.4 m soil layer moisture than the Y3 processing. Y6,Y3 two processing were in order of Y6<Y3 at 0.1～0.4m soil layer moisture and in order of Y6>Y3 at 0.8～1.4m soil layer moisture in different depths of groundwater table.The groundwater and surface evaporation inhibition rate and the soil moisture storage of the Y6 processing were higher than the Y3 processing while the depth of groundwater was more than 1.0m.(2) Returning equivalent quantity of straws in different depths made differences in the 0.6～ 1.4 m soil layer moisture. D4, D2, CK three processing were in order of D4>D2>CK at 0.6～ 1.4m soil layer moisture while the depth of groundwater was between 0.8～1.6m. The D4 processing had more soil moisture storage than the D2 processing while the depth of groundwater was more than 0.7m; the groundwater evaporation inhibition rate of the D4 processing was higher than the D2 processing while the depth of groundwater is more than 1.1m. There was no obvious difference between the two processings at the surface evaporation inhibition rate.(3) Wheat evaporation derecreased while groundwater depth increased. The groundwater recharge got to the maximum while the depth of groundwater was less than 1.9m. The suitable depth of groundwater is 2.2～2.5m when the wheat plants are in emergence, clover, tillering, jointing stage and is 2.0～2.2m when the wheat plants are in heading, flowering, maturity stage in the coastal area of Yancheng.(4) The 0.2m soil layer moisture of rice fields decrecreased while ground water depthincreased; the suitable depth of groundwater is respectively:0.5～0.6m,0.4-0.5m,0.4-0.5m,0.5～0.6m when the rice plants are in tillering, jointing-booting, heading-flowering,yellow maturity stage in the coastal area of Yancheng. The ground water depth increased while the ditch water depth increased; the water-storage processing of ditch saved irrigation water effectively and increased yield by 3.75%; impact of ground water depth for the ratio of groundwater recharge and the evapotranspiration of rice gradually decreased while ground water depth increased, the ratio dropped to 60%～70% while the ground water depth was more than 0.8m.