Effects of Animal Waste Regulations on Drainage Water Quality: An Example of Adaptation Strategies for Sustainable Agriculture

In Japan, the "Law on promoting proper management and use of livestock excreta" (animal waste regulations) was implemented nationwide in November 2004; this law prohibited the disposal of animal wastes in earthen storage ponds. To examine the effects of this law, a 2-year daily analysis of water quality and hydrology of a drainage canal of an agricultural area with intensive livestock production in the Lake Kasumigaura Basin, Japan, was conducted from November 2003 to October 2005. The water quality indices were total nitrogen, nitrate nitrogen, ammonium nitrogen, total phosphorus, and chemical oxygen demand. Considering daily precipitations during the irrigation and non-irrigation periods, both the concentrations of pollutants and effluent loads were compared between the prelaw and postlaw periods. The results suggested that the amount of effluent loads from animal wastes to drainage decreased after the enforcement of this law and that animal waste regulations were among the most effective local adaptation strategies for reducing effluent loads from agricultural areas.