The NAEW is the only site in the humid U.S. conducting long-term, watershed research on the environmental impacts of various pasture management systems. During the past 20+ years, pasture systems studied include: non-rotational, unimproved pastures; rotationally grazed pastures with different annual rates of N fertilizer; and rotationally grazed grass-legume pastures. Conclusions include: soil-loss from pastures which are not overstocked, either unimproved or improved, will be within soil loss tolerance limits, and soil losses can be reduced further by fencing streams away from livestock and using a limited rotation of a herd in winter contrasted with constant occupancy in a small pasture: NO₃-N concentrations in surface runoff from pasture will usually be well below EPA's MCL of 10 ppm -- the exceptions will most likely occur within a few days following fertilizer application; high NO₃-N concentrations in groundwater can result from high annual rates of fertilizer application (150+ lbs N per acre), and the NO₃-N concentrations in groundwater under grass-legume pasture probably will be below the EPA standard.