[Nitrogen balance in dairy farm: research progress].

Large dairy farm with intensive management has high stocking density, but generally does not have enough space and normative feces disposal system, resulting in the discharged nitrogen surpassed the environmental carrying capacity of unit area land. Dairy farm is one of the major emission sources of nitrogen discharges in agriculture, where the nitrogen balance has being aroused attention by the experts abroad. The research on the nitrogen flow and nitrogen balance in dairy farm is the basis of the dairy farm nitrogen cycling and management study, as well as the basis for the construction of environmental laws, regulations and policies.