Potentially health-threatening nitrate levels in the Raccoon River reached a record high of 18.3 milligrams per liter (mg/l) – the ninth record set since 1991.

The Environmental Protection Agency’s maximum contaminant level for nitrate levels in drinking water is 10 mg/l. When nitrate levels in the source water reach 10 mg/l, the nitrate-removal system is activated, costing approximately $3,000 per day to operate.

High nitrate concentrations in untreated water pose a greater health risk to infants under six months of age. Nitrates are converted into nitrites in an infant’s body and react with hemoglobin. This reduces the ability of the blood to carry oxygen and results in Blue Baby Syndrome.

Most people associate nitrates with farm fertilizers; however, nitrates also come from human and animal wastes, decaying plant matter and lawn fertilizers.

Historically, the Raccoon River watershed has been one of the highest nitrate-yielding watersheds in the United States.

“The conditions in the watershed are ideal for high nitrate levels leaching into groundwater,” said Dennis Keeney, emeritus professor of agronomy. “The watershed has high organic matter, intense cropping systems and high concentration of animal-confinement units.”

Each year Iowa corn growers apply more than one billion pounds of nitrogen fertilizer in the form of anhydrous ammonia.

“Having nutrients readily available for plant uptake is essential for crop production,” said John Creswell, field specialist in the cooperative extension field program.

“Management of all nutrient sources, including commercial fertilizer, compost and manure, within the constraints of farm production systems and operational goals is essential for both profitable crop production and environment sustainability,” Creswell said.

Some producers chose to apply anhydrous last fall instead of in the spring.

“But there were disadvantages to fall applications,” said Mike White, field specialist in the cooperative extension field program. “Fall application rates could not be tailored to spring moisture conditions and planting dates. And above-normal moisture and/or soil temperature in the late fall increased the risk of nitrates leaching into groundwater and streams.”

Proper application of anhydrous ammonia is dependent on knowing the soil temperature. “Microbial activity that converts ammonium to nitrate is greatly reduced once soil temperatures drop below 50 degrees [Fahrenheit],” said Don Arendt, former Howard County extension director. “This means there would be less loss.”

Iowa State has created a Web site that gives producers and agricultural fertilizer dealers’ soil temperature history, future projections, and a 6-10-day air temperature and moisture forecast.

Creswell said the site can be used in the fall to track daily soil temperature averages at a four-inch depth for each of the 99 counties in Iowa.

By utilizing the Web site, producers and agricultural chemical dealers will know when soil temperatures are 50 degrees Fahrenheit and below.