Study On Soil Air Reduction Infiltration Characteristics Under Different Irrigation Method

Based on the data home and abroad, combined with the National Natural Science Foundation, use the technical route combine indoor and outdoor experiment and theory analysis, this thesis mainly study the effect factors and reduction infiltration characteristics of air pressure entrapped in soil under one dimension infiltration, two dimension infiltration and three dimension infiltration. The mainly research achievement as following:(1) The paper study the effect factors and change rules of air pressure entrapped in soil under normal one dimension infiltration of heavy silt clay, loam and sandy loam, also study the effect of air pressure entrapped in soil on infiltration. The study show that the change process of air pressure entrapped in soil can divided into three stages include early stage, transition stage and stable stage. And put up the change and reduction infiltration characteristics of air pressure entrapped in soil, establish the quadratic function relationship between infiltration coefficient, infiltration index and soil dry bulk density, original water content; The interaction of soil dry bulk density and water layer depth has the most effect on infiltration, and the initial water content has the smallest influence; the air pressure entrapped in soil and the surface water depth has exponential function relationship.(2) The paper study the reduction infiltration effect of air pressure entrapped in soil on infiltration under one dimension constant pressure infiltration. Soil dry bulk density, initial water content, water layer depth and air pressure entrapped in soil have the effect on constant air pressure infiltration. This thesis establish the quadratic function relationship of Kostiakov infiltration index and coefficient with the soil dry bulk density, initial water content, water layer depth and air pressure entrapped in soil. And divided the reduction infiltration effect to two parts, pure force and adhesion force., separately establish the mathematic model of cumulative infiltration volume and infiltration time, wetting depth and infiltration time, wetting depth and infiltration water volume.(3) The paper study the factors that effect the air pressure entrapped in the soil and the reduction infiltration characteristic effect in soil wetting process and infiltration under furrow irrigation and film silt irrigation, and set up the function relationship between air pressure entrapped in the soil and infiltration time; the value of the air pressure entrapped in the soil under two-dimension infiltration is 0-4.8 H2Ocm. The air pressure entrapped in the soil is usually under the water layer. The pressure isoline is dense and is sparse with distance increase from center. The air pressure entrapped in the soil mainly appears in the wetting area. The soil water content in the area with air pressure entrapped in the soil is about 84.15%-89.68% of that in the area without air pressure entrapped in the soil, that is, total water volume decreases 10.32%-15.85%. Air pressure entrapped in the soil makes infiltration volume decrease by 17.00%-20.01%.(4) The paper study the effect of soil water, soil air, soil temperature and crop physiology under irrigation on the film mulch in the wheat and cotton field. Dry-wet alternation with day-night in the surface layer comes into being under irrigation on the film mulch. The small cycle of coagulation(liquefaction)- boiloff(evaporation)- coagulation- boiloff makes soil water in deep layer accumulating to the superstratum and the soil water distribution is like"V". The soil temperature of film hole irrigation is about 4.3℃more than that of furrow irrigation without film and is 3.6℃of furrow-board irrigation. The soil temperature improves the irrigation water using efficiency in the cotton field. The yield increases 8-12%. The film mulch decreases invalid water consumption in the wheat field by 9.2 mm. The growing period shortens 7-14 days.(5) The paper studied the change law of infiltration and soil entrap under film hole source irrigation and subsurface source irrigation. The soil pressure entrapped in the soil in the infiltration is only 0-3 H2Omm and take place in the transition area. The soil pressure entrapped in the soil under the source 5 cm is 1 H2O mm after infiltration 8 min and 1-3 H2O mm after infiltration 10 min, which is not ignored to withstand effect and time lagging effect.(6) The paper set up the amendatory green-ampt model that take into account the effect of the soil pressure entrapped in the soil. Through verifying data of one-dimension vertical infiltration, the good consistency exit between calculating result and experiment result.