Abstract
Many nutrient mitigation best management practices (BMP) are promoted by state and federal agencies to protect water quality from animal agriculture. The measured effectiveness of these is highly variable in the research literature. Here, we establish pre- and post-BMP monitoring to evaluate the effectiveness of fencing out cattle from the riparian zone on water quality, specifically, phosphorus (P) loads and concentrations. We collected water samples year-round both before and after a cattle exclusion was established at a small mixed dairy and beef cattle pasture where cattle have historically grazed with unrestricted access to first and second order streams, and analyzed for soluble reactive and total P. Immediately after fence construction, we observed a significant reduction in total P in the stream but not in soluble reactive P. We also observed the development of new runoff source areas and short-circuiting of the riparian buffer as well as repeated presence of cows in the fenced-out area, all of which may diminish the potential effectiveness of this practice. Because BMPs will perform uniquely given climate and landscape position and how managers maintain them, we suggest the need for more nuanced guidance for future BMP designs to ensure successful outcomes.
Highlights
Toxic algal blooms can impact drinking water supplies and recreation on lakes due to their effects on wildlife and humans (Correll, 1998)
total phosphorus (TP) concentrations after best management practices (BMP) implementation were significantly lower than pre-BMP conditions at the outlet, 0.022–2.06 mg/L before BMP construction and 0.024–1.27 mg/L after (Figure 4B, p-value < 0.001)
We stress that our findings demonstrate stream soluble reactive phosphorus (SRP) is less influenced by the installation of riparian buffer cattle exclusions than is stream TP
Summary
Toxic algal blooms can impact drinking water supplies and recreation on lakes due to their effects on wildlife and humans (Correll, 1998). Harmful algal blooms and associated eutrophication result from high nutrient inputs to freshwater bodies. The P equilibrium in lakes complicates management of Cattle-Exclusion Riparian Buffer Impacts on Phosphorus this nutrient because P sorbs to sediment particles, is incorporated into algal and bacterial biomass, and exists in biologically available ionic forms (Correll, 1998; Chislock et al, 2013). This equilibrium makes managing for sediment-bound and biologically available P important. Agriculture has been identified as a high contributor of P to lakes and the streams that feed them, and is one important area to implement phosphorus reducing management strategies (e.g., Drolc and Zagorc Koncan, 2002; Ulén et al, 2007)
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