The Relations between Difference of Soil Texture and Characteristics of Salt Concentration

Soil physicasl tudies on mechanisms and countermeasures of salt concentration (I)

Abstract

In order to investigate characteristics of salt concentration due to difference of soil texture, four kinds of specimen were prepared cylindrically with respect to the mixing ratio of Kibushi Clay and Toyoura Standard Sand. These specimens were saturated with NaCl solution and placed in a constant temperature and humidity chamber to concentrate salt. At each step of the drying stages, the specimen was divided into four parts of the sample at 50 mm height from the upper surface. Then, the soil solution contained in the divided sample was seperated by a centrifugal dehydrator at the primary wilting point of pF 3. 8. Characteristics of salt concentration were determined in relationship to concentrations and weights of NaCl in both the extracted solution and soil suspension.
The following results were obtained from the study;
1) Concentration of extracted solution was increased in the first upper layer and difference of increasing ratio of concentration was not recognized in all of soil texture conditions. Increased clay contents, decreased the maximum concentration of the extracted solution. Therefore, probability of damage to crops is estimated to be decreased. On the other hand, changes of concentration of extracted solution could not be recognized in the lower layers from the second layer.
2) Concentration of soil suspension was increased in the first upper layer and there was no evidence of these tendencies in the lower layers except homogeneous soil texture with Toyoura Standard Sand. Increasing pattern of concentration of soil suspension in the first upper layer was similar in all soil. conditions. But, since the concentration of the soil suspension was increased with increasing clay content, its tendency will be important in desalinization.
3) Weight of NaCl contained in extracted solution in the first upper layer resulted to increase with the increase of water evaporation ratio. And after reaching the maximum value, it showed to decrease giadually. However they decreased gradully in the lower layers. Weight of NaCl contained in soil suspension showed the exponential increase in the first upper layer and almostly constant in the lower layers. Depending on these results, characteristics of NaCl-transportation were recognized.