Tools for better surface waters
WOOLSTOCK – Arliss Nielsen, who farms in rural Woolstock, hosted his neighborhood farmers on Sept. 10 to talk about the layers of conservation practices on his farm, with a special guest attending – Bill Stowe, chief executive officer of the Des Moines Water Works.
Stowe has long been outspoken about what he says are Iowa farmers’ field practices that are allowing excessive amounts of nitrates into surface waters, particularly the Des Moines and Raccoon rivers, which Des Moines draws upon for its drinking water.
Last March, DMWW filed a lawsuit against drainage districts in the counties of Calhoun, Buena Vista and Sac for releasing nitrates levels that far exceed the federal standard for safe drinking water.
Stowe did not speak to farmers during the water quality field day, but attended the demonstrations said he left with an appreciation for the nitrate management practices that are available to farmers, and for the farmers who are employing them.
“But at the same time it’s disappointing,” Stowe said, “that these practices are scarcely being used.
“I hope that eventually we’ll have more resources to close this gap.”
He said he recognized that farmers have an expense in curbing nitrate escapes from their fields, while DMWW also incurs expenses in removing them.
“We’re all working out of self-interest,” Stowe said. “I get that.
“But something has to bring our two sides together or we’re going to keep pushing and pulling and that won’t do anyone any good.”
What Stowe and the others heard on Sept. 10 was a talk about the effectiveness of cover crops and bioreactors to keep nitrates from escaping into surface waters, controlling the amount of drainage that flows through tile lines and no-till crop management.
Nielsen had dug a trench in a field that he said has been under no-till with cover crops for the past six years.
Pat Chase, a soil scientist with the Natural Resources and Conservation Service, based in Fort Dodge, took a reading of the nitrates that were in Nielsen’s tile line – 20 parts per million, roughly double what the federal government considers safe for potable water.
Bruce Voight, who directed the Boone River Watershed project for NRCS, based in Clarion, said the 20 ppm underscored the importance of Nielsen’s 40-acre bioreactor at the lower end of the tiling system.
But the tile water Chase tested was not flowing out. In fact, it was being held back by a control structure.
Nielsen said he installed a series of structures that he uses to allow excess water to leave the field, but when closed, backs water up through the system, keeping more nutrient-rich water available to plants during times of hot and dry weather.
“I always liked this concept,” Nielsen said. “In fact, years ago, I wanted to stop the tile outlet with a boulder to keep the water in.”
He said he doesn’t think of the device as drainage control, but as nitrate control.
The control structure systems were installed in his 240-acre corn-soybean rotation field for less than a year.
However, he said he expects future data will show a significant drop in nitrate levels at the tile outlet, with the combination of cover crops sequestering nitrogen and the control structure holding nutrients in the field for roots to use.
Another benefit, he said, is less nitrogen will have to be applied each corn-growing year.
“We know cover crops work,” he said, “we just have to be patient enough. And cutting the cost of fertilizer can compensate for the cost of the cover crops.”
Chase explained the mellow soil profile typical of a multi-year no-till system.
He said the soil is loaded with organic matter, which helps hold the soil together and holds more water. There are more earthworms that burrow through the soil, whose channels act as conduits for water and oxygen. They also pull residue below the surface adding to the volume of organic matter.
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