Abstract
As livestock production in Japan becomes more intensive, livestock wastes cause serious environmental problems. To obtain a fundamental data for solving these problems, nitrogen flows in dairy farms are estimated quantitatively. The nitrogen flow system in dairy farms consists of ten parts; chemical fertilizer, self-supplying feed, purchased feed, milk, sold cattle, beddings, wastes and manure (sold, used for their own croplands and unknown). The estimated amounts of nitrogen in cattle wastes are 3,731kg/farm/year at 1985, 4,965kg/farm/year in 1990 in Hokkaido, and 1,947kg/farm/year in 1985, 2,445kg/farm/year in 1990 in the areas except Hokkaido. In Hokkaido, about 203kg/ha/year (1985: 205kg/ha/year, 1990: 201kg/ha/year) nitrogen in cattle wastes were used for their own croplands. In the areas except Hokkaido, about 513kg/ha/year (1985: 501kg/ha/year, 1990: 525kg/ha/year) nitrogen were used for their own croplands. The differences between loadings of nitrogen onto croplands and removed nitrogen by forage crops were about +102kg/ha/year (1985: +103kg/ha/year, 1990: +100kg/ha/year) in Hokkaido, and about +335kg/ha/year (1985: +316kg/ha/year, 1990: +354kg/ha/year) in the areas except Hokkaido.
