Estimation of flow sheet and load unit to farm soils of nitrogen excreted by animals on the basis of the national statistical data

1) Nitrogen flow of animal waste in Japan was estimated on the basis of national statistical data on the production of animal waste compost and on the compost application in crop production. 2) The following flow was estimated for nitrogen of 743 * 10 E 3 t excreted by all domestic animals in 1998. N volatilized as ammonia was 196 * 10 E 3, N in compost utilized for crop production other than forage was 111 * 10 E 3, N in compost utilized for forage crop production was 34 * 10 E 3, N in compost utilized for other usages than agriculture was 101 * 10 E 3, N in burned animal waste was 9 * 10 E 3 and N input in soils of animal farms as slurry, discarded waste and percolated N during composting was 307 * 10 E 3 t. 3) N input in soils of animal farms as slurry, discarded waste and percolated N during composting and for production of forage crops was estimated to be 55% in dairy cattle, 51% in beef cattle, 29% in hogs and 54% in poultry of N excreted from the respective animals. N mineralized from N input in soils of animal farms was calculated, and N load by animal production was defined as mineral N not absorbed by forage crops in animal farms. 4) The sums of N load by crop production (reported in the previous paper) and N load by animal production in the municipalities were shown to be a good indicator of nitrate pollution of shallow groundwater, because they showed good correlations (significant at p < O . O1) with nitrate + nitrite-N levels in shallow wells in municipalities in Ibaraki Prefecture and Nagano Prefecture. 5) The sums of N load by crop and animal productions of all the prefectures were calculated using 2000 agricultural census data. Some prefectures had much higher N load for animal production than that for crop production and showed high potential risk of nitrate pollution of groundwater due to agricultural production.