In this story, Dan Charles with National Public Radio reports on feedback he received following his story on the Iowa-based Des Moines Water Works’ lawsuit to stop farmers from releasing nitrate pollution into nearby rivers – the source of the city’s water. Sarah Carlson, with Practical Farmers of Iowa and Midwest Cover Crop Council, took issue with the report’s statement that nitrates in water come from farmers using too much nitrogen fertilizer. While technically true, it is a half-truth, says Carlson, because when crops are growing on fields in the summer, they are taking up most of the soil’s available nitrate.
“Our problem is, we only grow plants for five months out of the year,” she said. For the other seven months, nitrate forms naturally in the soil, with rainfall and melting snow carrying it downstream to Des Moines and beyond. Using less fertilizer won’t fix this mess, says Carlson. “The way to fix this is, we need to have something growing from October to May.” Farmers could plant cold-weather cover crops right after the corn or soybean harvest, covering the soil over winter. Scientists who study cover crops have shown the practice can reduce nitrate releases by about one-third. Cover crops also protect the soil from erosion. Still, few farmers in the Midwest use cover crops, mainly because it’s still a new idea, and farmers want to be sure it works before they try it.
Check out the full story at http://www.npr.org/blogs/thesalt/2015/02/02/382475870/heres-how-to-end-iowas-great-nitrate-fight