Abstract
For estimating the influence of percolation water on effluent nitrogen load, field survey and laboratory experiments were carried out and nitrogen concentration was discussed. In the result of the field survey, the concentration of soil water was different between a upland and a grassland, between shallow depth and deep depth, and seasonally. The result of the laboratory experiment indicated that the activity of microorganisms was more influential to the concentration of soil water in shallow layer than in deep layer. In the result of the other laboratory experiment using the column apparatus, the concentration in shallow layer decreased when the water input interval was short. When the interval was long, the concentrations in all depth increased in the intervals. The concentration of discharge water from the column became a value similar to that of soil water in deep layer.
