Improvement of Salt-affected Soils, Part 2: Interception of Capillarity by Soil Sintering

Abstract

In this paper, a new method is discussed for the soil improvement of salt-affected soils in regions where a sufficient amount of rainfall occurs in summer. The sub-soil is made coarse by soil sintering, and the capillarity from groundwater is cut off. Thus, the rise to the soil surface of salts which are dissolved in the groundwater can be prevented, and even if the groundwater level is high, the evaporation of water from the soil surface can be reduced. Moreover, the salts that accumulate in the topsoil can be washed out by rainfall (leaching) during the summer season. Consequently, this method has the same effect as when the groundwater level is lowered. This paper deals with the determination of the degree of aggregation of the soil particles and the height of water raised by capillarity due to different soil sintering temperatures. The results show that the behaviour caused by sintering was similar for all soils. Sintering creates more and more coarse conditions and black colour. Non-sintered soils were saturated with distilled water and became permanently dispersed. In the soils sintered at more than 800 °C, there was no disaggregation of the soil particles in the water, so it is considered that the sintering temperature should be greater than 800 °C. In the non-sintered soils, the mean diameter of the soil particles was small (0·005–0·013 mm). If these soils were sintered, the soil aggregate size increased sharply. Even at the lowest sintering temperature (600 °C), the mean diameter of the soil aggregate increased to about 4 mm. When the sintering temperature was 1300 °C, the mean diameter of the soil aggregate rose to about 8 mm. The capillary water heights of the non-sintered salt-affected soils were predicted at some metres. With sintering, this water height was less than 0·15 m, even when the sintering temperature was the lowest (600 °C). If the soils were sintered with temperatures higher than 1000 °C, the water height by capillarity was less than 0·09 m. Thus, if about 100 mm thickness of the sub-soil just below the B horizon can be sintered, the capillarity from the groundwater can be intercepted, thus reducing water loss through evaporation and increasing salt removal through leaching during the rainy season.