Abstract
"Law on promoting proper management and use of livestock excreta" was implemented in November 2004 prohibiting the disposal of animal wastes using unlined storage ponds. To examine the influence of the enforcement of this law, a two-year study of water quality and hydrology was conducted on a drainage canal of an area with intensive livestock production. During the irrigation period, the amount of runoff water was 337 mm, the T-P concentration decreased from 3.0 to 1.7 mg · l-1, and the T-P load decreased from 3.2 to 1.9 kg · d-1. During the nonirrigation period, the amount of runoff water was 548 mm, the NH4-N concentration decreased from 1.9 to 1.1 mg · l-1, the T-P concentration decreased from 2.9 to 1.8 mg · l-1, the NH4-N load decreased from 6.3 to 1.9 kg · d-1, and the T-P load decreased from 13.1 to 2.6 kg · d-1. In addition, the number of days that irregular T-N, NH4-N and T-P concentrations were observed decreased. These results suggest that the amount of effluent containing the NH4-N and T-P from animal wastes decreased.
