Grass buffer strips may be a useful tool to prevent pathogens in manure from washing into surface water, according USDA Agricultural Research Service scientists.

Researchers compared the filtering ability of grass filter strips with bare ground on two soil types – clay loam and sandy loam. They applied fresh manure along the top of sloped ground of those soil types and used overhead sprinklers to simulate rainfall.

No pathogens were found in the runoff water below the vegetated, sandy-loam slope and only 0.6 percent of the pathogens present in the manure were found in the runoff from the vegetated, clay-loam slope.

In contrast, runoff from the bare, clay-loam slope contained nearly all of the pathogens present in the manure. However, 75 percent of the pathogens remained in the bare, sandy-loam slope instead of ending up in the runoff. The reason, say the researchers, is that sand allows water and microbes to sink into the soil more quickly, rather than run off the surface.