RUNOFF AND SEDIMENT LOSSES RESULTING FROM WINTER FEEDING ON PASTURES

Grazing is an important land use in the humid, eastern U.S. When the g rass is dormant, late fall through early spring, the land is mast vuln erable to the pressures of livestock. Runoff and sediment losses from a small pastured watershed (WS) in eastern Ohio have been studied for 20 years. In Period 1, a beef cow herd grazed it rotationally during t he growing season for 12 years and was fed hay in this WS during the d ormant season (high animal density with feeding). During the next 3 ye ars of this study (Period 2) there was summer rotational grazing only. There was no animal occupancy on this WS during the last 5 years (Per iod 3). Annual runoff was more than 10% of precipitation during Period 1 (120 mm) and less than 2% during Periods 2 and 3 (14 and 6 mm, resp ectively). The decrease in annual sediment loss was even greater with the change in management, yielding 2259, 146, and 9 kg/ha for the thre e respective periods. Over 60% of the soil loss during Period 1 occurr ed during the dormant season. In response to weather inputs, there was considerable seasonal and annual variation in runoff and soil loss wi thin management periods. Low amounts of runoff and erosion from three adjacent watersheds with summer-only grazing supported the conclusion that the increased runoff and erosion during Period 1 resulted from th e non-rotational, winter feeding on pastures. When the management was changed, the impacts of the previous treatment were not long lasting, changing within a year.