Effect of Gypsum Application and Subsoiling on Soil Physico-chemical Property of Saemangeum Reclaimed Tide Land

Abstract

Soils of reclaimed tide lands have high levels of pH, salinity, and exchangeable Na, K, and Mg and low levels of soil organic matter, available phosphate, and exchangeable Ca. Therefore, desalinization and soil quality improvement are needed for crop cultivation. In this study, experiments were conducted in the experimental field of Saemangeum reclaimed tide land to investigate the effects of subsoiling and gypsum application on desalinization and improvement of soil physico-chemical properties. Expreriments were conducted at two soil salinity levels (< 1.0 dS m-1 and 3.1 dS m-1) and experimental plots were composed of subsoiling, gypsum application (4ton/ha), and gypsum (4ton/ha) + subsoiling. Subsoiling was conducted at 1m intervals to 50cm soil depth, and soybean was cultivated. By gypsum application, exchangeable Ca increased significantly and exchangeable Na, K, and Mg decreased. After subsoiling, the average infiltration rate was increased by 150% (1.78 cm hr-1) at the point of cut line, 49% ( 1.06 cm hr-1) at 25 cm on the side of cut line, and 4% (0.74 cm hr-1) at the midpoint between cut lines, compared to that (0.71 cm hr-1) in the control plot. The initial rate of desalinization was faster in subsoiling plot and gypsum + subsoiling plot than control plot. Yields of soybean were increased by subsoiling and gypsum application in the order of gypsum+subsoiling > subsoiling > gysum > control at low soil salinity level. But at high soil salinity level, soy plants were all withered at harvest time. Our results demonstrate that gypsum application and subsoiling were effective in improving soil physico-chemical property and productivity in Saemangeum reclaimed tide land. Changes of soil EC and exchangeable cations in the experimental field with high soil salinity (EC 3.1 dS m-1) as affected by subsoiling and gypsum application.