| On the basis of consulting the relevant literature at home and abroad,combining with the National Nature Fund project,and in view of the shortage of water resources,the natural conditions of farmland and the characteristics of the film-hole irrigation in arid areas of China,adopting the technical route of combining experiment,theoretical research and numerical simulation.In this dissertation,the nitrogen transfer and transformation characteristics of film-hole infiltration with fertilizer solution in layered soil,the characteristics of the soil with ?-polyglutamic acid vertical infiltration and its influencing factors,the characteristics of the soil with ?-polyglutamic acid infiltration under the film-hole irrigation and its influencing factors,the effects of ?-polyglutamic acid on spinach growth and soil structure,and the coupling effects of water-nitrogen on Winter Wheat under the film-hole irrigation have been studied.The main research results are as follows,(1)The effects of sand layer position on soil water and nitrogen transport and transformation characteristics of free infiltration under the film-hole irrigation with fertilizer solution in layered soil has been studied.Using HYDRUS-3D model to simulate soil water and nitrogen transport and transformation under the film-hole free infiltration.The cumulative infiltration of the film-hole irrigation was obviously affected by sand layer.The infiltration capacity increased with the increase of the buried depth of sand layer.The wetting front appeared obvious discontinuity at the loam-sand interface.The infiltration capacity of film-hole increased with the increase of the buried depth of the sand layer.The wetting front had an obvious discontinuity at the soil-sand junction.As the buried depth of the sand layer increased,the shape of the wetting front tended to be semi-ellipsoid.At the end of the infiltration,the sand layer caused the urea nitrogen to be mainly distributed in the upper silt loam,and decreased in the direction away from the center of the film-hole gradually.There were three areas,such as high concentration area,high gradient area and low concentration area.During the redistribution phase,the urea nitrogen content showed a decreasing trend due to the hydrolysis reaction;The ammonium nitrogen content in the soil near the center of the film-hole was larger than that at the wetting front,and gradually decreased in the direction away from the center of the film-hole;Ammonium nitrogen was concentrated in the soil layer above the sand layer,and the content at the soil-sand interface increased significantly;The soil nitrate nitrogen content at the same location increased with time increase;The soil nitrate nitrogen content at the horizontal wetting front increased faster than that near the center of the film-hole,and was larger at the soil-sand interface;the front migration distance of the redistributed concentration of soil nitrate nitrogen increased with the increase of the buried depth of the sand layer.(2)The effects of applying y-polyglutamic acid on soil water characteristic parameters,soil infiltration characteristics,and soil water holding capacity were studied.The application of y-polyglutamic acid changed the soil moisture characteristic parameters and improved the soil water holding capacity.The soil infiltration capacity decreased with the increase of y-polyglutamic acid application rate.Used RETC and HYDRUS-1D software to perform inversion calculations to determine the water characteristic curve parameters of the soil with y-polyglutamic acid.(3)The formation characteristics of the surface dense layer of the mixed application of y-polyglutamic acid one-dimensional vertical infiltration with muddy water and the film-hole free infiltration with muddy water were studied.The HYDRUS-3D model was used to carry out a numerical simulation study on the free infiltration of y-polyglutamic acid under the film-hole irrigation.A model for the distribution of free infiltration,cumulative infiltration and soil moisture content of the soil applicated with y-polyglutamic acid under the film-hole irrigation was established.There was a negative correlation between the cumulative infiltration per unit film hole and the transportation distance of the wetting front with the application of y-polyglutamic acid under the film-hole irrigation and the soil bulk density and the application amount of y-polyglutamic acid.Surface application of y-polyglutamic acid in soil would change the profile of moisture distribution in humid soil.A simplified calculation model for the cumulative infiltration of the film-hole irrigation with muddy water with different dosages of y-polyglutamic acid was established.There was a good power function law between the thickness of the falling silt layer and the infiltration time in the process of mixed application of y-polyglutamic acid one-dimensional vertical infiltration and free infiltration of the film-hole irrigation with muddy water.And the falling silt layer Increased with the y-polyglutamic acid application rate increase.(4)The effects of y-polyglutamic acid application rate under the border irrigation and the film-hole irrigation on the emergence rate,physiological growth indicators,yield,plant water content,nutrient absorption and utilization efficiency,soil structure and soil temperature of overwintering spinach were studied.The emergence rate of spinach under the film-hole irrigation was higher than that under the border irrigation,and the application of y-polyglutamic acid was higher than that of no application.The wet weight and dry weight,yield,dry matter accumulation,spinach nitrogen use efficiency and nitrogen use efficiency of spinach with 0.20%y-polyglutamic acid application rate under the film-hole irrigation were the largest.Both the border irrigation and the film-hole irrigation had higher nitrogen content and plant nitrogen uptake in spinach roots,stems and leaves with y-polyglutamic acid,and that of the film-hole irrigation was higher than that of the border irrigation.The content of water-stable aggregates in the soil increases with the increase of y-polyglutamic acid application rate,and that of the film-hole irrigation was higher than that of the border irrigation.The damage rate of soil aggregates decreased with the increase of y-polyglutamic acid application rate,and that of the film-hole irrigation was lower than that of the border irrigation.The fractal dimension decreased with the increase of y-polyglutamic acid dosage,and the average weight diameter and geometric average diameter both increased with the increase of y-polyglutamic acid dosage.Moreover,the fractal dimension of the soil with the y-polyglutamic acid application rate under the film-hole irrigation was smaller than that of the border irrigation;application of y-polyglutamic acid and the film-hole irrigation could reduce the variation range of soil moisture content and temperature.(5)A simulation model of soil water and nitrogen transport and transformation of winter wheat under the film-hole irrigation was established by using HYDRUS-1D.The characteristics of soil water and nitrogen transport and nitrogen transformation of winter wheat under film hole irrigation,the characteristics of water and nitrogen absorption by winter wheat roots were revealed.Under medium and low water conditions,appropriate amount of fertilization could alleviate the low water absorption rate of roots caused by water shortage.Irrigation amount,nitrogen application rate and water-nitrogen coupling effect had significant effects on winter wheat nitrogen absorption efficiency,nitrogen production efficiency,nitrogen use efficiency,nitrogen partial productivity and apparent nitrogen recovery rate. |
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