Study on Water Management against Salt Damages in Arid Areas

通过三年的调查，确定了干旱区资源管理的途径和指导思想。干旱地区的水和土地资源管理在很大程度上取决于当地的自然和社会经济条件。通过在干旱地区引入灌溉，可以在一定时期内进行生产性农业。然而，如果不对土地和水资源进行适当和有效的管理，地下水位就会逐渐上升，进而导致地表盐分积累和土地退化，阻碍可持续农业生产。此外，在干旱地区，水资源是主要的生产限制因素，地下水位的过度降低会增加需水量和灌溉用水量。因此，在干旱地区，将地下水位控制在一定范围内，保持地下水位/需水和盐分积累之间的微妙平衡是非常重要的。除地下水位外，研究表明，盐分损失受到农场水平条件的微小差异，如采用适当的耕作方法、灌溉管理和增加有机质的使用，从而改善土壤结构。通过对干旱地区农业生产重要细节参数的调查，以及对地下水位和水分管理的分析，以及农场水平(耕作、有机质施用、等)，确定了盐分积累过程的机理。加州农业在干旱条件下的案例研究表明，通过适当管理水(灌溉和排水)和土地(耕作措施)资源，可以实现盐碱地的恢复和可持续农业生产。

Through the investigation of three years, the approach and guidelines of managing resources in arid areas were identified. The management of water and land resources in arid areas depends largely on natural and socio-economic conditions of the local area. By the introduction of irrigation in arid areas, productive agriculture can be performed for a certain period of time. However, without appropriate and efficient management of land and water resources, the ground water level gradually increases, which in turn leads to the accumulation of salts on the land surface and the degradation of land, hampering the sustainable agricultural production. Furthermore, in arid areas water resource is the major production limiting factor, and excessive lowering of ground water level could increase water requirement and irrigation water needs. Therefore, the control of the ground water level at certain range is very important in arid areas, maintaining the delicate balance between the ground water level/water needs and salt accumulation.In addition to the ground water level, the study made clear that salt damages are subject to minor differences of on-farm level conditions such as the adoption of appropriate plowing method, irrigation management and increased use of organic matter, which improves the soil structure.Through the investigation of detailed parameters important for agricultural production in arid areas, and the analyses of groundwater level and water management as well as cultural practices of on-farm level (plowing, organic matter application, etc) the mechanism of salt accumulation process was identified. Case studies of California agriculture under arid conditions suggest that the rehabilitation of salinized land and sustainable agricultural production can be realized through the appropriate management of water (irrigation and drainage) and land (cultivation practices) resources.