The changes of soil organic carbon (SOC) content in paddy soils (sandy loam) were assessed from data of the 59 years fertilization plots in which the continuous rice cropping experiment started in 1954. The treatments were no fertilization(no fert.), NPK fertilization (N, NPK), NPK plus rice straw compost (NPK+C), and NPK plus rice straw compost, silicate fertilizer and lime (NPK+CLS). After 41 years, SOC content in NPK+C and NPK+CLS treatment in surface soils (0∼15 cm) reached at the highest, followed by maintaining a plateau level for 8 years. After 51 years, they showed a tendency to decrease. Peak concentrations of soil organic carbon were 20.1 g kg -1 in NPK+CLS, 19.1 g kg -1 in NPK+C, 13.3 g kg -1 in NPK, 11.9 g kg -1 in N, and 11.6 g kg -1 in control. Dissolved organic carbon(DOC) contents in surface soil solution were about 2.3 times higher in NPK+C than that in NPK+CLS. Therefore, SOC in subsurface soil(15∼30 cm) was greater in NPK+C than the other treatments. These results indicate that continuous application of rice straw compost and silicate fertilizer affected significantly on the level of SOC in surface soils, subsurface soils, and soil solutions. Thus, the combined applications of NPK fertilizers with organic compost and silicate as a soil amendment are recommended as the best fertilization practice for soil carbon accumulation, environment conservation, and enhancement of soil fertility status in the continuous rice cropping system.

This study was conducted at the organic farming fields which garlics were planted. The treatments were as follows; water of 3,850 L ha-1 (Control), plots applied 1 time, 2 times and 3 times with sea water of 3,850 L ha-1. In 3 times sea water treatment plot, the level of EC, Exch. Na and Cl were 1.1, 2.1, and 3.3 times higher than control plot, respectively. Due to seawater application, the contents of inorganic elements such as T-N, Ca, Mg, Na, Fe, Mn, and Zn in garlic were generally lower than Control, but not significant.