- Animals: bovine
- Animal Production: grazing - continuous, preventive practices, housing, watering systems
- Education and Training: demonstration, extension, on-farm/ranch research
- Natural Resources/Environment: grass waterways, habitat enhancement, riverbank protection, soil stabilization
- Sustainable Communities: sustainability measures
The effects of cattle grazing on stream stability have been well documented for the western portion of the United States, but are lacking for the east. Stream and riparian damage resulting from grazing can include alterations in watershed hydrology, changes to stream morphology, soil compaction and erosion, destruction of vegetation, and water quality impairments. However, few studies have examined the successes of best management practices (BMPs) for mitigating these effects. The objective of this project was to assess the ability of two common BMPs to reduce streambank erosion along a central Kentucky stream. The project site consisted of two replications of three treatments: 1) an alternate water source and a fenced riparian area to exclude cattle from the stream except at a 3.7 m wide stream ford, 2) an alternate water source with free stream access, and 3) free stream access without an alternate water source (i.e. control). Fifty permanent cross sections were established throughout the project site. Each cross section was surveyed monthly from April 2002 until November 2003. Results from the project indicated that the incorporation of an alternate water source and/or fenced riparian area did not significantly alter stream cross sectional area over the treatment reaches. Rather than exhibiting a global effect, cattle activity resulted in streambank erosion in localized areas. As for the riparian exclosures, changes in cross sectional area varied by location indicating that localized site differences influenced the processes of aggradation and/or erosion. Hence, riparian recovery within the exclosures from pre-treatment grazing practices may require decades, or even intervention (i.e. stream restoration), before a substantial reduction in streambank erosion is noted.
Over a quarter of the land area within the United States is used for grazing activities supporting nearly 100 million cattle and calves (USDA-NASS, 1997; Vesterby and Krupa, 1997). While these cattle are a major component of the U.S. agricultural trade, improperly managed grazing cattle can contribute significant pollutant loads to the nation's waterways. The U.S. Environmental Protection Agency (U.S. EPA) (2000) identified agriculture as the predominant source of nonpoint source pollution (NPS), impairing 48% of the assessed rivers and streams. This value more than doubled the next leading source of NPS, hydrologic modifications. The two leading pollutants for rivers and streams were pathogens and sediment, constituents linked to cattle production (CAST, 2002; U.S. EPA, 2000; Belsky et al., 1999; Clark 1998). Cattle producers often use rivers and streams as the primary water source for their grazing livestock, resulting in increased activity along the water's edge. Streambank erosion occurs when livestock hooves trample banks and excessive grazing reduces riparian vegetation (Belsky et al., 1999).
Controlling or reducing agricultural NPS is an important step towards improving the quality of our nation's streams. A system of best management practices (BMPs) is the most likely means of achieving this goal in an effective and cost-efficient manner. However, developing a successful NPS pollution control program targeting grazing practices can be difficult, especially in the humid region of the United States. The majority of research on the impacts of cattle grazing and the subsequent effect of BMPs to reduce these impacts has occurred in the western portion of the U.S., a region with a markedly different climate than the eastern U.S. (McInnis and McIver, 2001; Belsky et al., 1999; Clark., 1998; Magilligan and McDowell, 1997). While it is important to examine the individual effects of BMPs for reducing NPS associated with grazing activities, an understanding of the water quality benefits derived from multiple BMPs may provide insights that allow for more informed managerial decisions. Minimizing the impacts of grazing on stream health will likely necessitate the incorporation of both structural (i.e. riparian buffers) and cultural (i.e. managed grazing) BMPs (Logan, 1990).
Few studies in the humid region of the United States have examined the impacts of grazing BMPs on water quality (Line et al., 2000; Sheffield et al., 1997; Owens et al., 1989). Only isolated studies examined streambank erosion associated with the use of a grazing BMP, though they yielded promising results. Sheffield et al. (1997) noted a 77% reduction in streambank erosion along a southwest Virginia stream following implementation of an off-stream water source. At a Tennessee stream, Trimble (1994) measured a six-fold increase in gross bank erosion along uncontrolled grazing sites as compared to reaches with exclusion fencing. While these studies provided useful information, they could not fill all the gaps in knowledge. Notably, these studies examined the effectiveness of a single BMP versus multiple controls more commonly implemented on farms, the erosive forces of cattle grazing and stream flow were not separated, and comparisons were not made between fenced and non-fenced treatments. As evident by these gaps in information, a need exists for obtaining additional information with regard to grazing BMPs, especially multiple BMPs, and their effectiveness at reducing streambank erosion. To fill the void, this project sought to determine the ability of an alternate water source with and without exclusion fencing (consisted of a 9.1 m wide riparian zone equipped with a 3.7 m wide stream ford) to reduce streambank erosion along a central Kentucky stream. Results from this project will provide stakeholders with necessary information regarding the effectiveness of these BMPs for reducing streambank erosion in central Kentucky and possibly within the humid region of the United States.
The goal of this project is the provide the agricultural community with a better understanding of the impacts of cattle grazing on stream bank erosion, thus enhancing current cattle production methods on small farms in Kentucky and possibly the eastern United States. Important to note is that this project is a subset of a larger research endeavor into the grazing impacts of cattle and BMPs on the water quality of a Kentucky stream whose objectives are to 1) determine whether the provision of cultural forms of BMPs such as an alternate water source, an alternate shade source, and/or the placement of supplemental feeding areas alter cattle behavior, 2) determine if the above BMPs collectively improve water quality, 3) determine if the inclusion of a fenced riparian zone with the BMP package significantly improves water quality over the BMP package alone, and 4) educate the agricultural community, especially livestock producers, about management systems that minimize the adverse environmental effects of grazing while maintaining production levels. This particular project, in combination with the larger research endeavor of which it is a part, address two main goals of the Sustainable Agriculture Research and Education (SARE) program by providing an assessment and evaluation of animal production practices to strengthen the agricultural competitiveness of Kentucky's cattle producers while seeking to conserve soil, water and stream habitats.