There's no doubt that earthworms benefit agriculture by theirtunneling. But a recent study has shown that their burrows might alsobe funneling liquid manure--and possibly other contaminants--tounderground drainage pipes. These, in turn, flush contaminated wateronward, bypassing normal filtering and cleansing by soil.
Agricultural Research Service soil scientist Martin J. Shipitalo, atthe ARS North Appalachian Experimental Watershed Laboratory inCoshocton, Ohio, and Frank Gibbs, with USDA's Natural ResourcesConservation Service in Findlay, Ohio, did the study in no-till fieldswith liquid manure applied.
They found that water moved through wormholes twice as fast when theholes were within two feet of drainage pipes. The pipes providedoutlets that helped the water flow along, instead of slowly percolatingthrough small openings between soil particles.
The study suggests that the most practical solution is for farmersto install shutoff valves so they can turn off drainage during liquidmanure application and for a short time afterwards. Some Ohio farmersalready do this, with cost-sharing from the Ohio Department of NaturalResources. Another solution would be to install catch basins at theedges of fields to capture water draining from pipes and hold it forreuse. Both would help downstream water quality.
Worms--especially nightcrawlers--are especially attracted to no-tillfields in areas that require drainage. They like the combination ofno-till, drainage pipes, and the liquid manure farmers often apply tofields.
The worms eat the leftover parts of crops left on the surface byno-till, which skips plowing before planting, and they see the manureas food, too. The drainage pipes aerate the soil nicely, loosening itup for easy digging, especially the soil used to cover the drainagepipes. Plus, the crop residue offers them shelter, and with no-tillthere's no fear of a plow breaking up their tunnels.
ARS is the U.S. Department of Agriculture's chief scientific research agency.
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