Noting increased concerns over sediment and phosphorus runoff from agricultural lands, researchers at Iowa State University and the National Soil Tilth Laboratory in Ames, Iowa, conducted trials using buffer strips with different levels of grazing. They used three blocks of five, 1-acre paddocks grazed by beef cows over the course of three years. Management in the paddocks ranged from ungrazed control to rotational stocking with different levels of grazing impact. At four times during the growing season, they conducted rainfall simulations and collected runoff from the paddocks for analysis.
ISU animal scientist Jim Russell, PhD, says results showed that losses of sediment, total P and total soluble P generally were higher from grazed paddocks than ungrazed paddocks. However, losses from paddocks with two of the grazing management treatments did not differ from ungrazed pad-docks. One of these was a rotational stocking system, leaving forage height at 4 inches. The other was a system in which they harvested hay during the summer and grazed during the winter. The re-sults indicate that buffer strips, managed to maintain adequate plant cover, could reduce sediment and phosphorus losses in pastures.