Abstract
We investigated the influence of the percolation pattern on the removal of soluble elements and rice plant under inundation during the cultivation with models of strati-fied layers of cadmium polluted paddy fields. At that models, plow layer and plowsole consisted of cadmium polluted soil but gravel filled subsoil is not polluted. These models had different percolation pattern in the plowsole and subsoil. In the closed system model, every layer had water flow in a closed system while the open system model had water flow in an open system in plosole and subsoil over the groundwater. The following results were obtained. At low groundwater levels, plow sole and subsoil over the groundwater had water flow an open system and hence oxidized layers. On the contrary, at high groundwater level, every layer had water flow in a closed system and hence reduced layers. The electrical conductivity values of water flow in a closed system were larger than those in water flow in an open system. In the same way, concentrations of iron, calcium and manganese in water flow in a closed system became larger than those in water flow in an open system. Plant height, number of stems and dry matter weight of rice plants under the closed system model are larger than those of open system model. But no significant difference is recognizedwhile considering leaf age and heading. The total weight of grains and filled grain ratio of rice plants under closed system treatment were better than those in open system. The root elongation depth of plants under both the models were about 60 cm. Cadmium concentration in the brown rice of plants grown under open system models are about ten times higher than that of plants grown under closed system. The above results made it clear that under inundation conditions during the cultivation period, the removal of the soluble elements, concentration of cadmium in brownrice, growth and yield of rice plant were affected by the percolation patterns.
