层状土壤水分运动及其对紫花苜蓿生长的影响

发布时间：2018-07-08 13:55

本文选题：层状土壤 + 土壤水分运动　；参考：《西北农林科技大学》2015年硕士论文

【摘要】：为了了解不同类型层状土柱水分运动规律及其对植物生长的影响,利用砂土和砂黄土2种土壤,设置3种不同厚度分层土柱(11.25、22.5、45 cm)和2种匀质对照土柱,测定了土柱自初始饱和条件下的排水过程、蒸发过程及紫花苜蓿生长过程。利用2种匀质土柱排水过程测定的结果对2种土壤水力参数进行优化,利用优化后的参数通过Hydrus-1D模型对排水和蒸发阶段进行模拟分析,获得了不同类型层状土柱的水分运动规律。结果表明:(1)层状土柱持水能力随着分层厚度的减小而增加,当分层厚度减小到一定程度时土柱持水能力不再随着分层厚度的减小而增加,该临界厚度取决于下层粗质土壤对上层细质土的吸力与上层细质土壤进气吸力之间的相对大小。本试验所用2种土壤分层临界厚度大约在5 cm左右;土柱失水主要来自下层较粗质地土壤;(2)蒸发结果显示表层覆盖砂土可明显抑制土柱蒸发。表层为砂土的各土柱累积蒸发量差异不显著,平均为8 mm;而表层为砂黄土的土柱累积蒸发量可达110 mm;(3)匀质土柱中紫花苜蓿根系密度随深度的增加而降低;层状土柱中紫花苜蓿根系主要分布在质地较细的砂黄土中,总根系密度随分层数量的增加而增加;在相同深度的层状砂黄土中,根系密度也随着分层数量的增加而增加。相对于分层厚度和土层深度,土壤有效持水量(AWHC)是影响细根密度(FRD)的最主要因素;(4)相同灌水条件下,土壤水分变化受土壤分层类型和紫花苜蓿根系分布的影响,土壤分层数量越多,紫花苜蓿根系密度越大,土壤水分变化越剧烈,累积蒸散量越大。紫花苜蓿生物量随着土壤分层数量的增加而增加,不同分层类型土柱苜蓿光合速率在不同时期差异不同,取决于根系到达土层的水分含量。
[Abstract]:In order to understand the water movement law of different types of layered soil columns and their effects on plant growth, three kinds of layered soil columns with different thickness (11.25 ~ 22.5 ~ 45 cm) and two kinds of homogeneous control soil columns were set up by using two kinds of soils, sandy soil and sandy loess. The drainage process, evaporation process and alfalfa growth process of soil column since initial saturation were measured. Two kinds of soil hydraulic parameters were optimized by using the results of the drainage process of two homogeneous soil columns, and the drainage and evaporation stages were simulated and analyzed by Hydrus-1D model. The water movement laws of different types of layered soil columns were obtained. The results show that: (1) the water holding capacity of layered soil columns increases with the decrease of delamination thickness, and when the delamination thickness decreases to a certain extent, the water holding capacity of soil columns does not increase with the decrease of delamination thickness. The critical thickness depends on the relative magnitude between the suction force of the lower coarse soil to the upper fine soil and the inlet suction of the upper fine soil. The critical thickness of soil stratification is about 5 cm, and the water loss of soil column mainly comes from coarse soil of lower layer. (2) the evaporation results show that soil column evaporation can be inhibited obviously by surface covered sandy soil. There was no significant difference in accumulative evaporation of each soil column with sandy soil on the surface, with an average of 8 mm, while that of soil column with sandy loess on the surface was 110 mm. (3) the root density of alfalfa decreased with the increase of depth in the homogeneous soil column. In layered soil column, alfalfa root system mainly distributes in fine sand loess, the total root density increases with the increase of stratified number, while in layered sand loess of the same depth, root density also increases with the increase of stratified number. AWHC was the most important factor affecting fine root density (FRD). (4) under the same irrigation condition, soil moisture change was affected by soil stratification type and alfalfa root distribution. The more the number of soil layers, the greater the root density of alfalfa, the more severe the change of soil moisture, and the greater the cumulative evapotranspiration of alfalfa. The biomass of alfalfa increased with the increase of soil stratification, and the photosynthetic rate of alfalfa with different soil layers was different in different periods, depending on the water content of root system to the soil layer.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S152.7;S541.9

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