Effect of Water-Absorbent Agent ‘Viterra’ on the Water Availability of Kamphaeng Saen Soil Series

Abstract

Water – absorbent agent ‘Viterra’ was mixed with Kamphaeng Saen soil series (Typic Haplustalfs) at 4 rates of 0, 1, 3 and 5 g/l of air – dried soil to study its beneficial effect on the water availability of soil. The soil under study was prepared in two prepared in two ways. The original soil and the potting mixture of soil with duck manure, sand and rice hull for vegetable seedling culture. Only Viterra at the rate of 3 g/l and higher had the effect on soil water availability. At saturation, mixing Viterra at the rate of 5 g/l increased the saturation water content (mass basis) by 26.9% in the original soil and 38.1% in the potting soil, Upon wetting, the bulk volume of the soil also expanded. However, the available water capacity was increased by Viterra only in the original soil. This was the result of an increase in pore volume of 10-60 micrometer size. Not only the available water capacity but also the specific water capacity was greatly improved by the addition of Viterra to the original soil. Potting soil, on the other hand, showed no increase in available water capacity since addition of Viterra increased mainly the volume fraction of the large drainage pore size of > 60 micrometer. Therefore, the water-absorbent agent increased the soil water content at saturation and increased the volume, but the effect on the availability of the water depended on the soils. When mixed with soil which had a greater volume of large-size pores, such as potting soil. Viterra seemed to be able to absorb a much greater amount of water and then expanded fully. This led to an increase in the volume fraction of large-size pores in the soil. In a denser soil, on the other hand the volume expansion of Viterra may be less. So the increase in pore volume of the soil was that of the medium- size pores. This was more desirable as the medium–size pores contained water available to plant.