Researchers at Iowa State University have completed the first year of a three-year study on the effect cattle grazing can have on water quality.

"The team working on this project is concerned about the impact of grazing on streams and water quality, but we're also interested in helping farmers find ways to continue to graze their streamside pastures," says Richard Schultz, a forestry professor and one of the principal investigators. "Present buffer programs require the removal of livestock from buffered areas. We feel other alternatives exist that will allow grazing to continue, but under more controlled conditions."

The research project is a joint effort between the agroecology and animal management issue teams of the Leopold Center and the Iowa Cattlemen's Association. It's funded by a $550,000 grant from the Iowa Department of Natural Resources and a $64,719 grant from the Iowa State Water Resources Research Institute (ISWRRI) as part of an effort to find ways to reduce non-point source pollution. The Leopold Center is contributing $35,000 each year toward the project.

Research is being done in private pastures and at the ISU Rhodes Research Farm. Pasture size varies from 30 to 120 acres. Three broad grazing techniques are being studied - continuous grazing where animals are left on one pasture for most of the season, rotational grazing where animals are moved between three or four pastures during the season, and intensive rotational grazing where livestock spend just two to four days in a paddock before being moved to another.

The research consists of several parts. Surface runoff is being measured under simulated rainfall conditions and from real storms to determine the amount of erosion and phosphorus movement from the different grazing strategies.

At the Rhodes farm, the sediment trapping ability of installed buffers is being monitored. And a detailed accounting of phosphorus inputs to the livestock and the pastures is being compared to the movement of phosphorus from the pastures in runoff.

The project also involves measuring stream bank erosion. Steel pins are installed in stream banks and measured periodically to see how much of the pin is exposed from the soil. "We believe the major source of sediment and phosphorus from grazed riparian pastures comes from stream bank erosion," Schultz says.

Schultz says it's too early to draw many conclusions. But preliminary data show the rainfall infiltration rate, and thus sediment and phosphorus flow, are highly affected by soil moisture content and the slope of the land. Grazing strategy also seems to be linked to surface runoff and phosphorus movement.

This story was written by Susan Thompson, a communications specialist with the Iowa State University College of Agriculture. The project was featured in her weekly "Agriculture in Action" column.