Use of vegetative filter strips to minimize sediment and phosphorus losses from feedlots. Phase 1, Experimental plot studies


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Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University


A rainfall simulator was used to evaluate the effectiveness of vegetative filter strips for the removal of sediment and phosphorus from feedlot runoff. Simulated rainfall was applied to nine experimental field plots with a 5.5-m by 18.3-m bare source area (simulated feedlot) and either a 0, 4.6-m or 9.1-m filter located at the lower end of each plot. Fresh dairy manure was applied and compacted into the bare portions of the plots at rates of 7,500 kg/ha and 15,000 kg/ha. Water samples were collected from the base of each plot and analyzed for sediment and nutrient content. One set of plots was constructed so that flow through the filters was concentrated rather than shallow and uniform.

The 9.1-m and 4.6-m vegetative filter strips with shallow uniform flow removed 91 percent and 81 percent of the incoming suspended solids, and 69 percent and 58 percent of the incoming phosphorus, respectively. Soluble phosphorus in the filter effluent was sometimes greater than the incoming soluble phosphorus load, presumably due to lower removal efficiencies for soluble phosphorus and the release of phosphorus previously trapped in the filters. Vegetative filters with concentrated flow were much less effective than the shallow uniform flow plots, removing 40 percent to 60 percent less sediment and 70 percent to 95 percent less phosphorus than plots characterized by shallow uniform flow.

Observation of existing filter strips on cropland found that in-field filter strips were not likely to be as effective as the experimental field plots because of problems with flow concentration.