Abstract
The removal amount of nitrogen at a percolation spill-over irrigation paddy field has been increasing proportionally to more than a certain T-N concentration of irrigation water concentration. The other side, not more than that certain concentration was affected by water pollutants. That is to say the paddy field has a boundary concentration which is the irrigation water concentration in which neither purification nor contamination appear. The T-N boundary concentration is 1.5mg/L - 2.0mg/L, although, T-P is 0.24mg/L - 0.25mg/L. In this research study, we investigated the boundary concentration of T-N,T-P,NO3-N and COD in a percolation spill-over irrigation paddy field which has an area of 1.7 hectare, and uses Inba lake water for irrigation. Also, we examined a column experiment used to study the field’s soil to reproduce the result at field test. As a result, the field research and column experiment were an approximated concentration of past reports. So, we confirmed reproducibility and credibility.
