Influence of Streambank Fencing and Cattle Access Sites on Concentrations of Selected Chemicals in Riverbank of Lower Little Bow River Using PRS®-probes
Miller, J.J., E. Bremer and T. Curtis. 2012.
Abstract
Unrestricted grazing of native pastures by cattle that are located adjacent to rivers or streams may cause water pollution by fecal and urine deposition, as well as physical damage to riparian zone such as compaction, pugging, bare soil, and streambank erosion. Streambank fencing is a possible beneficial management practice or BMP to protect rivers and riparian zones from cattle. Riverbanks are the critical interface linking agricultural land use on soils to water quality in the river. We used PRS® (Plant Root Simulator™) probes (anion) to study the influence of streambank fencing and cattle access sites on concentrations of nutrient, metals, and trace elements in soils of the riverbank along the Lower Little Bow River in southern Alberta. A pilot study using 70 probes was conducted in August (two week incubation) of 2012 to determine operating parameters for the main study, and 242 probes were installed in the main study in September (one month incubation). A MIXED model statistical analysis was conducted to determine the main treatment effects of fencing (fenced vs unfenced), cattle access sites (cattle access versus no cattle access or control sites), and the possible two-way interaction. Streambank fencing significantly (P ≤ 0.05) decreased concentrations of available P, Fe, and Mn in riverbank soils compared to unfenced reaches for both the pilot and main study. Concentrations of B were also reduced in the fenced reach for the main study. Cattle access sites significantly affected certain chemicals but the effect was not consistent in the pilot and main study. In the pilot study, concentrations of Mn, Cu, Zn, and Pb were significantly greater for no-cattle access sites compared to cattle access sites, which was the reverse trend of what we expected. Nitrate-N concentrations in the main study were significantly affected by fencing and cattle access interaction. Mean NO3-N concentrations were similar for cattle access and no-access sites for the fenced reach, but values were significantly greater for cattle access than no-cattle access sites for the unfenced reach, and the latter trend was attributed to increased cattle activity, and increased fecal and urine deposition at cattle access sites. These preliminary findings suggest that PRS®-probes may be a useful tool to examine the effects of streambank fencing and cattle activity on available nutrients, metals, and trace elements in riverbank soils.
