The dynamic flow charts on Nitrogen and phosphorus loadings in Japan were drawn with respect to man-made N, P transformation, deriving from natural foods and feeds and industrial fixation of ammonia and phosphate. It was done with relative difficulty, by arrangement various statistics materials with the tracer method, the material balance technics and so on.
The significance of this study is to consider the fundamental causes and policies of control against eutrophication, and to give data of input for the prediction of water quality.
It was pointed out from these charts that the eutrophication in Japan had proceed closely linked to the transition of manuring pattern.
It should be noted that the nutrient cycle, ecologically to be closed, is seriously open, because of introducing large amount of offertilyzer and and importing foods and feeds which amount to half of the foods and feeds required in this country. The amount of N and P through chemical industries was 1, 287, 000 tN and 407, 000 tP, and the amount in the foods and feeds was 1, 305, 000 tN and 199, 000 tP, and also coal and petroleum introduced 1, 234, 000 t of Nitrogen.
It was made clear that Nitrogen loss by gasfication and denitrification are counted as potential output of Nitrogen (2, 029, 000 tN).
From these works, It might be concluded that the policy for eutrophication control has to be urgently directed to recycling N and P resources inorganic wastes to fertilize or feeds.