Study On Soil Water And Nitrogen Transport Characteristics And Influencing Factors Of Intermittent Infiltration Of Muddy Water And Fertilizer Solution Under Surge Border Irrigation

On the basis of consulting the relevant literature at home and abroad,combined with the actual irrigation and fertilization status of the Yellow River irrigation area in the Yellow River Basin of China,the indoor experiment and theoretical analysis are combined,and the technical route based on the experiment is carried out.Through the intermittent infiltration test of muddy water fertilizer solution,the soil infiltration capacity,water and nitrogen transport and distribution law,water and fertilizer coupling characteristics and the influence of different factors on the intermittent infiltration characteristics of muddy water fertilizer solution were studied,and the numerical simulation of intermittent infiltration of muddy water was carried out.The main research results are as follows:(1)The infiltration characteristics of intermittent infiltration of muddy water and fertilizer solution were studied.The results showed that the infiltration of muddy water and fertilizer solution had obvious infiltration reduction effect compared with that of clear water and fertilizer solution.When the infiltration time was the same,the wetting front migration distance and the average migration speed of wetting front in each cycle of muddy water and fertilizer solution infiltration were smaller than those of clear water and fertilizer solution infiltration.When the wetting front moves at the same position,the cumulative infiltration per unit area of clear water fertilizer infiltration is greater than that of muddy water fertilizer infiltration.At the same depth of soil,the soil water content infiltrated by clear water fertilizer is larger.The contents of NO3--N and NH4+-N in soil decreased with the increase of soil depth,and the decreasing trend of NH4+-N was more obvious.Soil NO3--N and moisture content are evenly distributed in shallow soil.(2)Under the condition of intermittent infiltration of muddy water and fertilizer,the cumulative infiltration amount per unit area and infiltration duration of muddy water infiltration with different fertilizer concentration,muddy water sediment concentration and sediment particle size distribution were in accordance with the simplified Philip model and Kostiakov infiltration model.The relationship between wetting front migration distance and infiltration duration in each cycle was a power function.The empirical models of cumulative infiltration per unit area,wetting front migration distance and infiltration duration in each cycle under the influence of different factors were established.(3)Compared with no fertilization,the infiltration capacity of muddy water intermittent infiltration under fertilization conditions is stronger.At the end of the third cycle of water stop stage,the infiltration rate of muddy water fertilizer intermittent infiltration in different cycles is positively correlated with the concentration of fertilizer solution,and the average infiltration rate is the largest in the second cycle.Compared with the intermittent infiltration of clear water fertilizer solution,the infiltration reduction rate of intermittent infiltration of muddy water fertilizer solution was positively correlated with sediment content and physical clay content,and the average infiltration reduction rate was the largest in the first cycle.(4)Under the condition of intermittent infiltration of muddy water surge irrigation,the water distribution law of different soil depths of muddy water fertilizer infiltration with different fertilizer concentration,muddy water sediment concentration and sediment particle gradation is basically the same,and the soil moisture content decreases with the increase of soil depth.The distribution of soil NO3--N and NH4+-N in the intermittent infiltration of muddy water and fertilizer solution was different from that in the intermittent infiltration of muddy water.At the end of the third cycle of intermittent infiltration,the content of soil NO3--N and NH4+-N decreased with the increase of soil depth.Without fertilization,the contents of NO3--N and NH4+-N in the surface soil were slightly lower than the background value,while those near the wetting front were slightly higher than the background value.The greater the concentration of fertilizer solution,the greater the content of NO3--N and NH4+-N in the same soil depth.The smaller the sediment concentration and physical clay content of muddy water,the greater the content of NO3--N and NH4+-N in the same soil depth.(5)The curves of soil infiltration rate with the reciprocal of wetting front under intermittent infiltration of muddy water and fertilizer with different viscosity indexes basically intersect at one point,which is close to the saturated hydraulic conductivity of soil used in the experiment.The slope of the relationship curve between the infiltration rate of muddy water intermittent infiltration and the inverse value of wetting front increases with the increase of viscosity index,indicating that the average suction value of wetting front decreases with the decrease of viscosity index.Under the condition of muddy water with the same viscosity index,the average suction value of the wetting front decreases with the increase of the number of cycles,and the Green-Ampt infiltration model including the viscosity index is established.