Dairy Open Lot and Lagoon-Irrigated Pasture Runoff Quantity and Quality

ABSTRACT RAINFALL runoff quantity and quality were deter-mined for a dairy open lot and a pasture area receiv-ing regular irrigation of dairy lagoon effluent. Over a 30-month period, percent of rainfall becoming runoff was 21 percent for the open lot and 10 percent for the pasture. The lot runoff had lower nutrient concentra-tions compared to data reported for beef feedlots and dairy lots of higher stocking density. Estimated average nitrogen yield from the lot was 234 kg/yr per hectare of lot. The pasture was irrigated with about 1 cm of lagoon effluent every other week during most of the study period. Concentration data from 11 events indicated that runoff N and P concentration were relatively high com-pared to other pasture runoff studies where the only animal waste input was from grazing cattle, but were similar to concentrations reported elsewhere for plots receiving comparable loadings of animal waste. Concen-trations of N, P, TOC and CI were generally 4 to 6 times greater in the lot runoff than in the pasture runoff.