| In this article,on the basis of analyzing and su mmarizing the research results of membrane hole irrigation technology,combined with the current situation of muddy water irrigation and farmland fertilization in the Yellow River Basin in China,using the technology route combining indoor test and theory analysis,throulgh 4carring out the film hole irrigation test research of infiltration of muddy water and fertilizer,the infiltration characteristic,the migration and distribution characteristics of water and nitrogen and the characteristics of water and fertilize,r coupling in wetted body,and the influence of different influencing factors on the infiltration characteristics of muddy water and fertilizer of the single-point source film hole free infiltration of muddy water and fertilizer were analyzed,The main research results are as follows:(1)The infiltration characteristics of the single-point source film hole free infiltration of muddy water and fertilizer in the layered soil were studied.The results show that the sand layer treatment at different locations has obvious effect on reducing infiltration o f the single-point source film hole free infiltration of muddy water and fertilizer The transverse diffusion of water are inerceased of the sand layer treatment at different locations.After the water passes through the interface of soil and sand,the wet front migration distance of the 0-5 cm layer is still in a power function relationship with the infiltration time,while the 5-10 cm layer is linearly related.The relationship betw een the water content in the horizontal direction of diferent sand layers is similar to that of homogeneous sail,and the distribution in the vertial direction is obvious.The relationship of the distance of the frontal migration of NO3--N concentration in the horizontal direction of each treatment is:0-5 cm layer>5-10 cm layer>homogeneous soil.and the relationship of NH4+ content in the vertical direction of each treatment in 0?5 cm soil layer is:5~10 cm layer>homogeneous soil>0~5 cm layer.(2)Under the conditions of the single-point source free infiltration of muddy water film hole irrigation,the Kostiakov infiltration model fitted well with the cumulative infiltration volume per unit area of film hole and infiltration time of muddy water infiltration and the infiltration of muddy water and fertilizer with different fertilizer concentration,soil bulk density and sediment gradation.The wet front migration distance increased with the power function as the infiltration time increases.The empirical model of cumulative infiltration of unit membrane pore area,wet front migration distance and various influencing factors and infiltration duration were established respectively,and it was verified that the model had high fitting precision.(3)Compared with the infiltration of muddy water,in addition to the soil bulk density of 1.40 g/cm3,the infiltration capacity,wetted body volume,wet front migration distance of the infiltration of muddy water and fertilizer were larger.At the end of irrigation,the infiltration increase rate of fertilizer solution with fertilizer concentration of 600,1300 and 2000 mg/L was 12.62%,23.84%and 37.55%,respectively,and the infiltration rate ? was negatively correlated with the infiltration time t.When the soil bulk density increased from 1.30 g/cm3 to 1.35 g/cm3 and 1.40 g/cm3,the infiltration reduction rates were 13.96%and 24.33%,respectively,and the infiltration reduction rate ? was logarithmically negatively correlated with the infiltration time t.When the sediment median size D50 increased from 0.019 mm to 0.056 mm,the infiltration reduction rates were 20.28%,15.03%and 10.36%,respectively,and the infiltration reduction rate C was negatively correlated with the infiltration time t.(4)Under the conditions of the single-point source free infiltration of muddy water film hole irrigation,the water distribution characteristics in the wetted body of the muddy water and fertilizer infiltration of different fertilizer concentration,soil bulk density and sediment gradation was basically the same,and the soil moisture content at the center of the film hole was the highest.Far from the center of the film hole,the lower the soil moisture content,the more the contour distribution was dense.Under the same infiltration time,the fertilizer concentration and the sediment median size D50 were larger,the soil bulk density was smaller,the wetted body volume was larger.And the soil moisture content at the same location in the wet body was greater.(5)The distribution of NO3-N and NH4-N in the soil wetted body of muddy water infiltration and the infiltration of muddy water and fertilizer was different.When not fertilized was applied,the content of Na3-N and NH4-N in the wetted body near the center of film hole was lower than the background value,while the content of NO3-N and NH4-N near the wet front was slightly larger than the background value.At the end of the irrigation,the content of soil NO3--N and NH4+-N of the infiltration of muddy water and fertilizer decreased with the increase of wetting distance.When the fertilizer concentration and the sediment median size D50 were greater,the soil bulk density was smaller,the greater the content of NO3--N and NH4+-N at the same position in the wet body,the content of NO3--N at the same position in the wetted body was larger.And the content of NH4+-N in the wetted body near the center of film hole was smaller,while the content of NH4+-N near the wet front was larger.(6)At the end of irrigation,the content of soil NO3--N,NH4+-N and water content of O?12 cm in the horizontal direction and 0?10.5 cm in the vertical direction of the center of film hole were in accordance with the quadratic function relationship.The moisture content of soil wetted body of the infiltration of muddy water film hole with different fertilizer concentration was higher,and the contents of NO3--N and NH4+-N were also higher.And the content of NO3--N and NH4+-N increased with the increase of water content.The fertilizer concentration was higher,the content of NO3--N,NH4+-N and the water content at the same position of the wet body were higher. |
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