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To avoid contamination of nearby waterways, no-tillers should not apply liquid manure to their fields when a tile line is flowing, according to a USDA researcher.
Martin Shipitalo also cautions no-tillers to limit applications of liquid manure to 10,000 to 15,000 gallons per acre, injected at a depth of no more than 8 inches. “And be ready to make a dam if there is flow from a tile,” he warns.
Shipitalo’s recommendations are based on his studies of runoff at the North Appalachian research farm near Coshocton, Ohio, as well as previous studies. His work confirms that no-tilling generally decreases surface runoff of water and contaminants.
However, he warns that the combination of earthworm burrows and drainage tiles increase the risk of pollution to waterways from no-tilled fields.
Liquid manure and other contaminants infiltrate the worm channels and travel to the tiles, from there moving to adjacent waterways, he says.
He points to earlier research showing a strong correlation between the application of liquid manure, either by injection or drag line, the number of worm holes in an area, the number of tile lines and the number of fish kills in nearby waterways.
In 4 years, Cooperative Extension Service staffers in Ohio counted 98 fish kills near the research farm tied to the runoff of manure through the tile lines, he says.
“No-tilling is much better (than conventional tillage) for earthworms. We have populations of 1 million to 2 million per acre with no-till,” he adds.