Simulated Experiment On Effects Of Soil Mechanical Composition And Soil Bulk Density On Soil Water Characteristic Parameters

Based on the problems of that drought and water shortage existence at the same time in the north partial area of our country, the decrease of the ability of soil infiltration and the low utilization of natural rain resource in agriculture production, we do the research on the mechanism of the process of soil water storage and quest the effect of soil constitution and structure on the process of the loess soil infiltration-storage-evaporation. By the different level of soil bulk density which was completed in artificial way, we research the measurable influence of the proportion of clay particles and the soil bulk density on the soil infiltration, storage and evaporation. Though designing compound experiments, and give the definition of the different contribution of the mechanism component and the soil bulk density. And this theory form our experiment provides some degree theoretic basis for the efficient utilization of the natural rain resource in the drought area and the development of the production of soil expansion. This thesis gives some conclusions as follows:1. Soil mechanical composition has a great effect on soil infiltration capacity, the more clay contained in soil, the weaker infiltration capacity. The stable infiltration rate and 90-min cumulative infiltration have negative power and exponential function relationship with clay particle content.2. Soil mechanical composition has a great effect on soil water-holding capacity. Soil water-holding capacity strengthened with the increase of clay particle content. The saturated water of experimental soils has exponential function relationship with clay content. Field moisture capacity and wilting coefficient have exponential and power function relationship with clay content when soil clay content less than 30.4%. And the rulaitionship transform to logarithmic and exponential function relationship when soil clay content more than 30.4%. Available water increased with the increase of clay content when soil clay content less than 35.8%, and it decreased after the clay content point. 3. The process of soil evaporation can divided into two stages. At the first stage, the absolute evaporation intensity has no significant correlation with soil mechanical composition, and the relative evaporation intensity weakened with the increase of clay content. At the second stage, two types of evaporating intensity both enhanced with the increase of clay content. Avalaible water holding time decreased with the increase of clay content when soil clay content less than 15%, and it increased when soil clay content between 15% and 30%. But after soil clay content more than 30%, it converted to decrease.4. Soil bulk density has a great effect on soil infiltration capacity. Soil infiltration capacity weakened with the increase of its bulk density. The stable infiltration rate of sandy loam, medium loam and clay loam all have negative logarithmic function relationship with their bulk density. 120-min cumulative infiltration of sandy loam has negative power function relationship with its bulk density. For medium loam and clay loam is negative linear relationship.5. Soil bulk density has a great effect on soil water holding capacity. Soil water holding capacity and specific water capacity both weakened with the increase of its bulk density. The saturated water content, field moisture capacity, wilting coefficient, available water, readily available water, slowly available water of experimented soils respectively has negative power, logarithmic, exponential, exponential, exponential, power, logarithmic relationship with soil bulk density.6. Both absolute and relative evaporation intensity enhanced with the increase of bulk density at first evaporating stage and weakened at second stage. Avalaible water holding time increased with the increase of bulk density.7. Experimental soil mechanical composition has more effects than bulk density on the generalized soil water holding process which involving three links of water infiltration, water holding and water evaporation.In general, after the study of this thesis, the author made some success over the following aspects as generalized soil water storage capacity impact mechanism, particularly the action process and principle of the effects that the soil composition structure producing to itself, obtained partial quantitative relationship of the influential action that soil composition structure parameters producing to each links of soil water storage process, further clarified influential action mechanism that soil composition structure producing to soil water storage process, provided a theoretical basis for the efficient use of natural precipitation and the product development direction of soil storage capacity expansion.