Optimum operational conditions of surface suction leaching method for effective removal of partially accumulated salts from salt-damaged soil

Abstract

Salt accumulation in fields appears partially in a very thin surface layer of the soil at an early stage of its occurrence. At this stage, removing the salts is only efficient in the parts where salt has accumulated. The surface suction leaching method (SSLM) removes the partially accumulated salts in this stage. SSLM equipment consists of three parts: water supply, drainage, and insert parts. The insert part is a disc-shaped container with a stainless guide that is inserted into the soil and connected to the water supply part for leaching and the drainage part for collecting water from the soil water. Through the insert part, the SSLM collects soil salts by alternately supplying leaching water and sucking soil water until a predetermined salt removal rate is achieved. In this study, we conducted 12 cases of numerical experiments that varied the water supply and suction times. We clarified the relationships between the water supply and suction times and their optimum combination that minimizes the amount of leaching water required to achieve the objective salt removal rate and reached the following conclusions: 1) shortening the water supply time and lengthening the suction time effectively reduce the amount of leaching water; 2) excessive suction time increased the amount of required leaching water; 3) the optimum combination of the water supply and suction times under the experimental conditions was 15 seconds for the water supply and 600 seconds for the water suction; 4) we must determine an optimal suction time that is suitable for the water supply times in the SSLM.