Experimental Study On Soil Water And Nitrogen Transport Under Drip Irrigation In Aeolian Sandy Soil

In order to explore the movement rule of water and nitrogen under the condition of wind-sand soil drip irrigation and provide theoretical guidance for the planting and irrigation of crops,through indoor soil column simulation test,the influence of droplet flow rate,irrigation volume,redistribution and fertilizer concentration on water and nitrogen migration and its distribution characteristics of single point source drip irrigation was studied in this paper.The main conclusions are as follows:(1)The initial infiltration rate of single point source dropper is relatively fast.Its rate of growth slows rapidly over time,but it fluctuates.The growth rate of wetting body area was relatively stable,and the growth rate in the early stage was slightly faster than that in the late stage.The shape of the wet body is two parts,the upper part is similar to the table shape,the lower part is similar to a quarter oval.The vertical maximum infiltration distance is slightly larger than the horizontal maximum infiltration distance.(2)Generally,the larger the droplet flow rate is,the higher the horizontal and vertical infiltration velocity is,but the horizontal and vertical migration velocity fluctuates greatly in the process of infiltration.When the dropper flow is small,the shape of the wetting body is relatively flat,while when the dropper flow is large,the shape of the wetting body is relatively narrow and straight.When the flow rate of the dropper increases,the width and height of the bottom of the circular table increase,and the long axis of the ellipse also increases.The horizontal and vertical distance of the wetting front increases with the increase of the irrigation amount.When the irrigation amount reaches 24mm,the area growth rate of the wetting body becomes slow and its shape is mainly controlled by the irrigation amount,basically independent of the drop head flow.(3)The moisture content of soil and its variation range were decreased with the increase of distance from drop head.With the increase of irrigation and drip flow,the water content in soil also increases.However,when the irrigation amount is too large or the flow is too large,leakage is easy to occur,which is not conducive to the retention of water in soil.After redistribution,the area of moist soil increased,And the increment of vertical migration distance of wetting front is larger than that of horizontal direction.The moisture content in moist soil decreases and is more evenly distributed,The larger the droplet flow,the greater the increment of wetting front migration distance and the more significant the water movement downward.(4)Under the condition of drip irrigation,the transport rule of NO3-N is mainly shown as follows:Increasing the droplet flow is conducive to the accumulation of NO3-N in the surface layer,which is manifested as the increase of NO3-N concentration and the upward movement of accumulation area,and the decrease of NO3-N concentration and concentration in the deep layer.With the increase of irrigation amount,the overall concentration of NO3-N also increases.When the drip flow or irrigation amount is too large,leaching infiltration will occur,which is not conducive to the accumulation of NO3-N in soil.After redistribution,the overall concentration of NO3-N decreases and is more evenly distributed.When the flow rate is too large or too small,it will lead to a large loss of NO3-N.(5)Generally,the higher the concentration of fertilizer,the higher the overall concentration of soil NO3-N.which is manifested as the peak concentration of upper nitrate nitrogen increases and the area of deep nitrate accumulation area increases.When the concentration of fertilizer is 300mg/L,the soil cannot absorb nitrate nitrogen further,and a large amount of NO3-N leaks from the upper layer to the deeper layer and accumulates here.