Effects Of Suspended Solid In Soil On Soil Structure And Water Flow

The limitation of total amount of water resources,and the unbalanced spatial and temporal distribution of water resources,incorporated with the increased domestic and industrial water usage,lead to the serious shortage of agricultural water in our country.In present,many places in country start to use reclaimed water for agriculture irrigation.Reclaimed water contains a large number of nutrient,salts and trace elements for crop growth,and the advantage of farmland irrigation is obvious.But unreasonable reclaimed water irrigation causes soil and groundwater polluted,which bring the environment and agricultural production under high risk.Therefore,the study on the risk of reclaimed water irrigation on eco-environments urgent.In this research,the effects of suspended solid concentration,irrigation frequency and alternated irrigation with reclaimed water and freshwater on the irrigated soil structure and properties and the soil water flow characteristics were studied for the purpose of reclaimed water irrigation project design.The main research results are as follows:(1)Irrigation water with different suspended solids concentration(0 g L,1.0 g/L,5.0 g/L and 10.0 g/L)have obvious impacts on the soil structure and water movement.When the suspended solids concentration is low in irrigation water(1.0 g/L),the irrigated soil structure and preferential flow characteristics changed not obviously compared to those soil irrigated with the fresh water.When the suspended solids concentration increased(5.0 g/L and 10.0 g/L),the field infiltration rate and soil porosity were reduced,the soil bulk density was increased,and the preferential flow heterogeneity was increased obviously.(2)Under the same total irrigation amount,different irrigation frequency(once a day,once every two days and once every four days)have obviously different effects on the change of irrigated soil structure and water flow.Big ration with low frequency of irrigation made the suspended solid contained in the irrigation water mainly deposited in the upper soil layer.However,due to the greater applied amount on the soil surface which made a higher infiltration water head,the time for the same amount applied water to completely infiltrated in to the soil surface for the experiments with lower irrigation frequency were much less than those with higher irrigation frequency.Furthermore,the preferential flow heterogeneity increased slightly when the irrigation frequency decreased.(3)Under the condition of the same irrigation amount,different irrigation water contained with suspended solid-freshwater alternative irrigation schedule affect the irrigated soil structural and water flow movement obviously differently.Compared to those experiments only irrigated with water contained suspended solid,the experiment irrigated with water contained with suspended solid and freshwater alternatively decreased the depositon of suspend solid contained in the irrigated water on the soil surface and decreased the blotting of soil pores,which increased the soil infiltration rate and soil water flow homogeneity as fewer solid particles were induced into the irrigated soil in this kind of irrigation schedule.