The present study was carried out to evaluate nutrient losses that occur during the course of agricultural activity from rice paddy fields of reclaimed tidal flat. For this study, we chose a salt-affected rice paddy field located in the Saemangeum reclaimed tidal area, which is located on the western South Korean coasts. The plot size was 1,000 m 2 (40 m · 25 m) with three replicates. The soil belonged to the Gwanghwal series, i.e., it was of the coarse silty, mixed, mesic type of Typic Haplaquents (saline alluvial soil). The input quantities of nitrogen and phosphorus (as chemical fertilizer) into the experimental rice paddy field were 200 kg N ha -1 and 51 kg P 2 O 5 ha -1 per annum, and the respective input quantities of each due to precipitation were 9.3-12.9 kg N ha -1 and 0.4-0.7 kg P ha -1 per annum. In terms of irrigation water, these input quantities were 4.5-8.2 kg N ha -1 and 0.3-0.9 kg P ha -1 per annum, respectively. Losses of these nutrients due to surface runoff were 22.5-38.1 kg N ha -1 and 0.7-2.2 kg P ha -1 for the year 2003, and 26.8-29.6 kg N ha -1 and 1.6-1.9 kg P ha -1 for the year 2004, respectively. Losses of these nutrients due to subsurface infiltration during the irrigation period were 0.44-0.67 kg N ha -1 and 0.03-0.04 kg P ha -1 for the year 2003, and 0.15-0.16 kg N ha -1 and 0.05-0.06 kg P ha -1 for 2004. When losses of nitrogen and phosphorus were compared to the amount of nutrients supplied by chemical fertilizers, it was found that 11.3-19.1% of nitrogen and 0.5-1.7% of phosphorus were lost via surface runoff, whereas subsurface losses accounted to 0.2-0.8% for nitrogen and only 0.02-0.04% for phosphorus during the 2-year study period.

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The relationships between nitrogen (N) and phosphorus (P) concentrations in surface flooding water and those in the leachate of various soil depths were monitored, and temporal variation of leaching losses of N and P from a paddy plot during rice cultivation was estimated under the conditions of southern Korea. Even flooded conditions nitrification in subsurface soil was identified, but nitrate concentrations in leachate were less than 10 mg/L, the standard drinking water nitrate concentration set by the World Health Organization (WHO). The NO 3 -N and ortho-P concentrations in the leachate were generally higher than those in the surface flooding water. Field data implied that leaching losses would not be accurately estimated under the flooded conditions of the paddy field when using the N and P concentrations of surface flooding water and infiltration depth. The leaching losses of NO 3 -N from paddy fields were high immediately after fertilization. The study results suggested that proper fertilization and irrigation strategies are required to reduce leaching losses of NO 3 -N from paddy fields.

, W×L×D) was performed in a greenhouse to remove salts from saline soil. Initially, the greenhouse soil had high electrical conductivity (EC), about 9 dS/m, and contained mainly Ca 2+, Cl − and SO 4 2− ions. After 2 weeks of EK treatment, the soil EC was reduced to 52% compared with its initial value. The EC reduction was mostly achieved within the first week (47%) due to removal of Na + and Cl − ions, but ions with a high adsorption capacity such as Ca 2+ and SO 4 2− ions were difficult to be removed. During the EK test, the soil temperature increased and it reached around 50 o C at some regions. For in situ application to soils in cultivation, the current should be controlled to limit increases in temperature, especially near the cathodes. In conclusion, the in situ EK technique is feasible for the restoration of saline greenhouse soils in or no cultivation and an appropriate strategy is necessary for more effective remediation.

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