Abstract
The water quality and discharge from a tea field area in Shizuoka were measured daily and the outflow loads of fertilizer components in runoff water estimated. The results are as follows: The amount of nitrogen fertilizer applied was about 1000kg·ha-1·yr-1 in the tea field. The annual of T-N effluent load from the tea field was 531kg·ha-1·yr-1 and it was 49% of the amount nitrogen fertilizer applied. 97% of the T-N load was composed of the NO3-N load. Its outflow load, which consisted of storm water, was 51%. The outflow NO2-N and NH4-N loads were small in the first half of the investigation period. The T-P outflow load from the tea field was 0.18kg·ha-1·yr-1 and the leaching rate was very low, at 0.05%. Most of the phosphate fertilizer was absorbed by the red-yellow soil in the tea field. The average T-P concentration was as low as 0.01 mg·l-1. However, the T-P concentration was very high after heavy rain in June and September of 2000. Storm water had a T-P outflow load concentration of 64%. The K+ outflow load was estimated to be 89kg·ha-1 for the year. The leaching rate was 14%. The percentage was very low because K+ was absorbed by surface soil containing clay minerals. The annual Mg2+ and Ca2+ outflow loads were 292kg·ha-1·yr-1 and 266kg·ha-1·yr-1, respectively. Their leaching rates were 63% and 26%, respectively.
