Mass balance analyses and water quality model development for goading estimates from paddy fields

摘要

Mass balance analysis and water quality model development for paddy field were performed using field experimental data during 2001 - 2002. About half (47 similar to 62%) of the total outflow was lost by surface drainage, with the remainder (490 - 530 mm) occurring by evapotranspiration. Most of nutrient inflow and outflow were mediated by fertilization and plant uptake, respectively. Nutrient outflow by surface drainage runoff was substantial about 15% similar to 29% for T-N and 6% similar to 13% for T-P. However, the responses of yield and drainage outflow to fertilization were not significant in this study. A water quality model applicable to paddy fields was developed and it demonstrates good agreement with observed data. The nutrient concentration of ponded water was high by fertilization at early culture periods, so reducing surface drainage during fertilization period can reduce nutrient loading from paddy fields. Shallow irrigation, raising the weir height in diked rice fields, and minimizing forced surface drainage are suggested to reduce surface drainage outflow.