Vegetative Treatment System Evaluation for Two Large Confined Animal Feeding Operations

Vegetative Treatment Systems (VTSs) are a possible alternative method to containment basins for management of manure and runoff from feedlots. There has been some research on VTSs, but none has been conducted on large confined animal feeding operations (CAFOs) In eastern South Dakota and western Minnesota. This study was conducted to evaluate the performance of two VTSs associated with large CAFO feedlots. The performance was determined by the water and nutrient mass balances of the vegetated treatment area (VTA). The balances were calculated using VTA Inflow, VTA outflow, evapotranspiration (ET), precipitation, and nutrient concentrations of the Inflow water, the harvested vegetation, and the soil of the VTA. There were three years of data for the Stevens County, Minnesota VTS and two years for the Minnehaha County, South Dakota VTS. There were no VTA outflow events during any of the five site-years, even though In 2010 and 2011 the Minnehaha County VTS experienced storms that were only 14 mm less than a 25-year, 24-hour storm event. In 2010 at both sites, the precipitation exceeded the 30-year mean precipitation for the same period of the year. At the Minnehaha County VTS, the 2010 precipitation was 703 mm and exceeded the 30-year mean by 182 mm. At the Stevens County VTS, the 2010 onsite precipitation, during the monitoring season, was 589 mm and exceed the 30-year mean by 42 mm. The maximum possible ET was approximated with the short-crop reference ET (ETo), 751 to 826 mm, exceeded the VTA inflow plus precipitation, 474 to 935 mm, for two of the three years at the Stevens County site. The ETo did not exceed precipitation plus VTA Inflow at the Minnehaha County site. The ETo was 838 and 784 mm in .2010 and 2011, respectively. The VTA inflow plus precipitation were 1257 and 817 mm in 2010 and 2011 at, the Minnehaha County site, respectively. At the Stevens County VTS, the total Kjeldahl nitrogen and nitrate do not appear to be accumulating in the soil, but there was elevated phosphorus content. All of this data indicates that VTSs designed for large CAFOs can adequately manage both water and nutrients from feedlot runoff. The information learned from this study is useful in evaluating VTS performance, calibrating VTS models, and provides insight into necessary further research