Assessment of water and solute transport characteristics during salt accumulation and leaching, and establishment of proper soil management for sustainable agricultural production in arid and semi-arid regions.

本研究的目的是阐明干旱区盐积累和淋溶过程中溶质的运动，并建立适当的土壤管理，防止过度灌溉导致土壤退化。本研究在恒定高地下水位条件下，利用大柱测量了盐积累过程中蒸发过程中的水流量和溶质输运。通过测定含盐量、含水量与土壤反照率的关系，发现土壤表面反照率随盐分积累量的增加而增加。通过对盐积累引起的盐结壳的数字分析，研究了结晶土的水平分布。讨论了砾石覆盖对土壤蒸发的影响，重点讨论了砾石覆盖对土壤表面上下水汽转移的影响。探讨了浸出水质对盐渍土水力特性的影响，并评价了盐渍土的团聚体稳定性。讨论了土壤中阳离子在积累和淋滤过程中的迁移和迁移。开发了WASH-1D软件，用于模拟土壤中水流、溶质和热量运动的一维数值模拟，以模拟降雨引起的蒸发和淋滤引起的盐积累。提出了一种流体控制的稳态蒸发法，用于测定低基质压力水头值下的非饱和水力导电性。讨论了一种测定土壤导热系数的简便方法，以及含水量、溶质浓度和温度对沙丘砂导热系数的影响。在高粱栽培过程中，观察了连续灌溉与间歇灌溉土壤水分电导率的差异。对海水入侵导致地下水盐渍化的沙田土壤水盐动态进行了测量和模拟。确定了砂敷对防止土壤盐碱化的作用。少

Objective of this study was to clarify solute movement following salt accumulation and leaching in arid areas and to establish proper soil management to prevent soil degradation from over-irrigation. In this study, measurement of water flow and solute transport during evaporation was carried out during salt accumulation process under constant high ground water level using large column. After measuring the relationships among salt content, water content and soil albedo, it was found that the albedo of soil surface increased with increasing mass of accumulated salt. The horizontal distribution of rystallizied soils was investigated using digital analysis of salt crust caused by salt accumulation. Effects of gravel mulch on evaporation with emphasis on resistance to water vapor transfer above and below the soil surface were discussed. Effects of leaching water quality on hydraulic properties of saline soils were also discussed and the aggregate stability of sodic soils was evaluated. Move … More ment of cations under accumulation and leaching processes in soils was discussed. WASH-1D software for one-dimensional numerical simulation of water flow, solute and heat movement in soils was developed in order to simulate salt accumulation with evaporation and leaching due to rainfall. A flux-controlled steady-state evaporation method was proposed for determining unsaturated hydraulic conductivity at low matric pressure head values. A simple method of measuring soil thermal conductivity as well as the influences of water content, solute concentration, and temperature on thermal conductivity of dune sand were discussed. Differences in electrical conductivity of the soil water between continual and intermittent irrigation were observed during grain sorghum cultivation. Dynamics of soil water and salt in sand-dressed upland field with salinized ground water due to sea water intrusion was measured and simulated. It was established that sand dressing was useful to prevent soil salinization. Less