Abstract:
The method of rain-leaching for improvement and desalinization of the Bang Pakong soil series by the intensive shallow drainage field was investigated. The changes in salinity, available potassium and nitrogen contents in water and soil of the paddy soils during the year 1982 to the early of 1984 were investigated. The field area under the responsibility of the Band Pakong Soil Conservation Center Amphoe Bang Pakong, Chachoengsao Province was used as the model for the entired experiments. Two main plots, namely, an intensive shallow drainage field and a paddy field were established. The results showed that the quality of surface water was dependent upon the drainage system, the amount of rainfall and the intrusion of sea water. While the underground water was dependent on the fluctuation of tidal regime, hence there would be less salinity and available potassium content in water of the paddy field than those in the intensive shallow drainage field. The reclaimation of the paddy soil revealed that available potassium and nitrogen contents, the salinity, sodium and chloride contents were effectively decreased during the rainy season but all of these parameters were conversely increased during the dry season. In general, during the rice cultivation period, the salinity in the paddy field was lower than the one in the intensive shallow drainage field. At a certain time, there was no significantly difference between the ammonia nitrogen contents in the water and in the soil of both plots, and the utilization of urea showed no effect on the ammonia nitrogen contents in the water and soil. As the consequence, in order to reduce salinity in the salt-affected area, the application of the rain-leaching means coupled with the intensive shallow drainage field was recommended. Prior to the actual rice transplantation, it was essential to fertilize the soil and to fill the paddy field with water as it was carried out in the traditional way.