Impacts of Intensive Rotational Grazing on Stream Ecology and Water Quality

Impacts of Intensive Rotational Grazing on Stream Ecology and Water Quality

Summary

The goals of this study were to determine whether intensive rotational grazing (IRG) can be used to allow farmers to harvest forage from riparian areas without compromising water quality and riparian habitats and to produce guidelines for environmentally sound management of riparian pastures.

A total of 21 farms were used as study sites during the two years of the study. All sites were located along spring-fed streams with potential for trout production. Trout streams are a source of recreational and tourism income for local communities, but are often heavily impacted by agricultural land use. Streamside vegetation was managed either as a grassy bufferstrip, a continuously grazed pasture, a rotationally grazed pasture or a woody bufferstrips (limited data collected). We collected data in the following areas: forage production and vegetation community, fish community and aquatic habitat, grassland birds, small mammals, amphibians.

Rotational pastures produced much more forage than continuous pastures. The average amount of available forage on offer was 1,856 pounds per acre for ready-to-graze rotational pastures and 781 pounds per acre for continuous pastures. Forage quality did not differ significantly between pasture types. Grassy bufferstrips tended to have significantly different vegetation structure from rotational and continuous pastures, because they were not harvested in any way. Grassy bufferstrips developed tall, dense vegetation dominated by reed canarygrass and a few broadleaf species. Both continuous and rotational pastures had a shorter, more diverse plant communities with native and non-native wildflowers and legumes.

Streambanks with grassy bufferstrips were the most stable. Grassy bufferstrips had the least bare ground (17 percent) on the bank slope, while rotational pastures averaged 24.2 percent and woody buffer strips and continuous pastures had the most bare soil at 29.9 percent for woody buffers and 33 percent for continuous pastures. Instream habitat was as good at rotationally grazed sites as it was at grassy bufferstrips and was better than at either continuous pastures or woody bufferstrips.

For all types of land management, fish community health was poor to fair. This is typical of this region, which has potential for quality trout fisheries, but has suffered from many years of poor land management. The condition of the watershed upstream from the site accounted for about 90 percent of the effects we saw at our study sites. However, when these upstream effects are factored out, grassy bufferstrips had the highest quality cold-water fisheries, rated fair versus poor ratings for rotational, continuous, and woody buffer sites. For aquatic insects, which are a food source for trout and an indicator of water quality, rotationally grazed sites were similar to grassy and woody bufferstrips and all three were better than continuously grazed sites.

Wildlife work was conducted on all sites except woody bufferstrips. We surveyed amphibians, birds, and small mammals and this work is ongoing. Preliminary results suggest that grassy bufferstrips and pastures provide habitat for specific species groups. Amphibians and declining species of grassland birds preferred pasture sites, while small mammals were found primarily in bufferstrips.

Our results suggest that rotational grazing can provide a reasonable compromise between continuous grazing and fencing livestock out of riparian areas. We are working now to educate landowners as well as agency policy makers and field staff on management strategies for riparian areas. Our efforts include field days, public presentations, published papers and articles, and development of a riparian grazing guidelines handbook.

North Central Region SARE 1998 Annual Report.

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