By analyzing the actual condition of water quality in an irrigation ditch in Saitama Prefecture, the effect of water quality on paddy rice characteristics and soil environment was demonstrated. It was recognized that the function of paddy fields controlled paddy rice characteristics and also became an important factor for the preservation of water quality. Especially, based on experiment and field tests to apply sewage with secondary processing for irrigation, it was confirmed that the actual condition of agricultural utilization of water could be determined by quality checks. Additionally, after the influence of sewage irrigation on the soil properties and growth of crops was investigated, the maximum permissible concentration of nitrogen in irrigation water was determined and criteria for cultivation were developed.