Water Quality

It's a long-held belief of pasture management: Give cattle access to streams and they will stir up a nasty brew of fecal matter, biological contamination, sediment and nutrient loadings. The solution to watering cattle has been to pump it upland to troughs located away from the streams and creeks.

Jim Russell, professor of animal science at Iowa State University, is working to develop practices that allow cattle to drink from a stream, but also encourages them not to lounge in it. They have come upon these ideas by watching the cattle.

From those observations they have evidence showing that a well-designed pasture-management plan may allow cattle access to streams and creeks with minimal damage to water quality. What's more, these management practices are competitive with the cost of exclusion fencing and water pumps.

In 30-acre pastures on farms in south-central Iowa, Russell's team has found that cattle really don't hang in the water as much as expected.

"The [percent of time] they are in the water is lower than people might think," Russell said. During the summer, with full access to the stream, the cattle Russell's team watched spent about 2% of the time in the water. Even during the hottest of summer months, they averaged 4% of their time standing in the stream. At night, the cattle tended to stay out of the water. Cattle in these pastures spent no more than 14% of their time within 110 feet of the stream.

When the cattle were confined to riparian areas -- in this study, 110-foot strips on both sides of the stream -- they spent no more than 0.2% of their time in the water. But they can create nutrient, erosion and runoff threats to the water if they are allowed to stay there long enough to create bare spots and allow manure to accumulate.

By limiting the grazing along the streams -- Russell called it "flash grazing" -- the damage is greatly reduced. Flash grazing means the paddock is never grazed more than four days and the grass is grazed no lower than 4 inches in height.

The proximity of the cattle to the stream bank does not seem to create a significant erosion problem, as long as access is managed. Stream-bank erosion, Russell argued, is due more to the velocity of moving water than to grazing.

To test the idea, Russell designed a stabilized crossing structure that allows cattle limited access to streams.

These are crossings stabilized with a fiber mat and polyethylene webbing, covered with stones. The crossings are limited in size, about 16 feet wide, with electric fencing along the sides. Beyond the limits of the fencing are grassed buffer strips to control precipitation runoff. Fenced lanes, a couple of hundred feet long, lead up and away from the crossing.

With the crossings, Russell found cattle spent little time (less than 1%) actually standing in the water. "The animals don't loaf in the water," he said. "They drink and move on. The stabilized crossing seemed to be effective when used with the riparian buffer."

Russell has tested stream water flowing into and out of an area of managed pastures on 13 cooperating farms in southern Iowa. He finds little difference in water quality. This does not mean the water is uncontaminated, only that those cattle don't appear to add significant new contamination under managed grazing programs. Russell does believe that upstream contamination, when no cattle are present, may come from wildlife, companion animals (horses, dogs), humans and their septic systems.

Russell's research is funded by the USDA-CSREES and the Leopold Center for Sustainable Agriculture. Also working with Russell were Mat Haan, former research associate, and Doug Bear and Kirk Schwarte, graduate students at Iowa State University.

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