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

The 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 the slopes made of these 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 below the vegetated, clay-loam slope.

In contrast, runoff from the bare, clay-loam slope contained almost 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 re-searchers, is that sand allows water and microbes to sink into the soil more quickly, rather than run off on the surface.