Abstract
As livestock production in Japan becomes more intensive, livestock wastes cause serious environmental problems. To obtain fundamental data for solving these problems, phosphorus(P) and potassium(K) flows in dairy farms were estimated quantitatively.
The nutrient flow system in dairy farms consists of ten parts; chemical fertilizer, self-supplying feed, purchased feed, produced milk, sold cattle, beddings, wastes and manure (sold, used for their own croplands and unknown). The estimated amounts of nutrients in cattle wastes were 469kgP/farm/year and 3,775kgK/farm/year in 1985, 641kgP/farm/year and 5,226kgK/farm/year in 1990 in Hokkaido, and 249kgP/farm/year and 1,596kgK/farm/year in 1985, 315kgP/farm/year and 2,130kgK/farm/year in 1990 in the areas except Hokkaido. In Hokkaido, about 48.5kgP/ha/year (1985: 50.4kgP/ha/year, 1990: 46.5kgP/ha/year) and 195kgK/ha/year (1985: 194kgK/ha/year, 1990: 196kgK/ha/year) were applied for their own croplands as cattle manure and chemical fertilizer. In the areas except Hokkaido, about 86.2kgP/ha/year (1985: 84.6kgP/ha/year, 1990: 87.7kgP/ha/year) and 448kgK/ha/year (1985: 416kgK/ha/year, 1990: 479kgK/ha/year) were applied for their own croplands as cattle manure and chemical fertilizer. The differences between loadings onto croplands and removed by forage crops were about +32.9kgP/ha/year (1985: +35.1kgP/ha/year, 1990: +30.6kgP/ha/year) and +66kgK/ha/year (1985: +69kgK/ha/year, 1990: +62kgK/ha/year) in Hokkaido, and about +56.9kgP/ha/year (1985: +54.9kgP/ha/year, 1990: +58.8kgP/ha/year) and +191kgK/ha/year (1985: +152kgK/ha/year, 1990: +230kgK/ha/year) in the areas except Hokkaido.
