Studies on the soil improvement and desalinization by gypsum dressing in Kasaoka bay polder

1.在日本，从1986年起，笠冈湾圩田作为第一个将大规模的海底圩田改为高地的计划，在1977年夏季排干土地后不久，就出现了盐害生长障碍的问题。土地排水后，进行了各种努力，高地的基础工程和农业技术方案的建立，但脱盐和土壤改良的进展最近停滞不前。其原因的研究表明，土壤物理性质随着脱盐的进行而恶化，这种关系不断导致脱盐的停滞。为此，提出了石膏选矿法，并建立了合理的石膏用量计算理论方程.本文跟踪调查了钙离子与吸附钠离子的阳离子交换在建筑领域的进展情况， ...更多信息 1984年年底开始使用石膏敷料。根据考虑空间变异性的阳离子交换反应理论方程计算石膏用量。通过4年的调查研究发现，石膏拌种使土壤处于絮凝状态，使土壤的保水性提高，稠度指数降低，渗透性增加，水蒸气比增加，从而改善了土壤的物理性质。虽然石膏改良土壤的效果因地而异，但说明各地的土壤改良是逐步进行的.从电导率值（EC）来看，1985 ~ 1988年的脱盐工作进展良好，并出现了实现脱盐目标（40 cm处EC <2 mS/cm）的有利时机。已经实现了。深旋耕机施石膏至50 cm土层，其理化性质得到改善。此后，随着环境整治和农业管理的进展，人们确信，土壤物理性质的改善和盐度的降低进展缓慢但稳定。少

1. In Japan, Kasaoka bay polder was a first case that planned to use a large scale sea bottom polder to upland field from the beginning of prelimirary utilization of polder in 1986 and a growth obstacle caused by salt was feeled uneasy from just after land draining in summer, 1977. After land draining, various effort for a foundation works of upland field and a establishment of technical program about farming were carried out, but the progress of desalinization and soil improvement was stagnated recently. The studies about its reason made clear a vicious cycle that soil physical property grew worse with a progress of desalinization and this relation continuously resulted in a stagnation of desalinization. For its countermeasure, we had pro-posed a gypsum dressing and established a rational theoretical equation for calculation of gypsum puantity.2. We had pursuited and investigated a progress situation of cation exchange of adsorped sodium ion by calcium ion on the construction area of … More gypsum dressing at the end of 1984. The quantity of gypsum was calculated in conformity with the theoretical equation of cation exchange reaction considering space variability. From the results of 4 years investigation, it was found that the improvement of soil physical properties like the heightening of water retentivity, the lowering of consistency index, the increase of permeability and the increase of vapor ratio were gained because soil became floculated condition by gypsum dressing. Though the degree of gypsum effect were different from place to place, it was showed that the soil improvement progressed gradually in eve y places.3. Judging from the electrical conductivity values (EC), the progress of desalinization from 1985 to 1988 was satisfactory and it arised a favorable places that the goal of desalinization (EC become less than 2mS/cm at 40cm depth.) was attained. This effect was found to be exhibited the improvement of physical and chemical properties by gypsum dressing until 50cm depth with deep rotary tiller. Hereafter, in attendance with the progress of environmental consolidation and farming management, it was convinced that the improvement of soil physical properties and the lowering of salinity progress slowly but steadily. Less