EFFECTS OF A DAIRY LOAFING LOT-BUFFER STRIP ON STREAM WATER-QUALITY

A leafing or sacrifice lot is an area located outside of the free stal l barn, where a daily herd spends several hours per day. Sacrifice lot s are usually denuded of vegetation and have high concentrations of ma nure and urine that can contribute significant amounts of sediment, nu trients, and pathogens to nearby surface waters. In this study, stream water quality impacted by direct runoff from a sacrifice lot was moni tored for a period of 20 months. Ambient stream water quality was moni tored by grab sampling upstream and downstream of the sacrifice lot. D uring runoff events, stream water quality downstream of the sacrifice lot was monitored with an automatic sampler. Laboratory analyses were conducted for total suspended solids and nutrients (nitrogen and phosp horus compounds). A grass filter strip (GFS) was installed as a buffer downslope of the sacrifice lot 10 months into the study period. The i mpact of the buffer strip on the standardized pollutant concentrations and loads was evaluated using the non-parametric Wilcoxon test. The W ilcoxon test indicated that there was no significant difference (alpha = 0.05) in the standardized yield of sediment and dissolved pollutant s before and after the GFS installation, except for phosphate-phosphor us and Altered total phosphorus concentrations, and sediment-bound tot al phosphorus and total kjeldahl nitrogen loads that decreased signifi cantly. However, load decrease could have been partially caused by the smaller rainfall volumes after the GFS installation as compared to th e existing condition.