As the 2019 growing season nears its end, and Iowa farmers and landowners start looking toward 2020, they must consider a variety of factors such as weather, soil health, commodity prices and input costs as they strive to manage their operations to make a profit.
It’s a delicate balance. If something goes wrong with any of these factors, a profit can turn into a significant loss. Some things, such as weather and prices, are out of farmers’ control.
But farmers do have a direct influence over other aspects. Soil health, for instance, can be improved over time with cover crops, which can also help to conserve soil and prevent nitrate from polluting waterways. Many farmers are striving to reduce soil loss and reduce agriculture’s impact on water quality on their farms and in their watersheds. Knowing the facts about potential human and environmental health effects of high nitrate levels can help farmers make an informed decision.
Nitrogen levels in Iowa
Nitrate is a common water-soluble form of nitrogen. Nitrate readily moves through the soil profile and enters subsurface drainage tiles and shallow groundwater. The loss of nitrate and other nutrients, like phosphorus, must be checked to reduce Iowa’s contribution to the low-oxygen dead zone in the Gulf of Mexico, which in 2019 was the eighth largest ever recorded.
But high nitrate levels also pose a significant risk to human and environmental health here in Iowa. Excess nitrate can enter municipal water supplies, where it must either be removed with costly equipment or mixed with uncontaminated water to dilute the nitrate levels so they meet the federal limit of no more than 10 milligrams of nitrate per liter.
Excess nitrate may also contaminate many private untested wells in Iowa, which nearly 300,000 Iowans rely on for their drinking water. While public water systems are required by law to monitor the quality of their water, private wells are outside the scope of the Safe Water Drinking Act. The responsibility to monitor these private water sources falls on the owners. If not tested annually, water from these private wells could be an insidious source of nitrate contamination.
Economic costs, health effects
In 2018, researchers with the Center for Agricultural and Rural Development (CARD) at Iowa State University published a report that cites the economic costs and health effects of nitrate in drinking water.
The report, “Economic Benefits of Nitrogen Reduction in Iowa,” notes that “49 public water suppliers serving over 10% of the state’s citizens treat water for nitrates either by blending or using nitrate removal equipment.”
The vast majority of violations in all periods are for very small systems, often lacking the budget to invest in costly nitrate treatment technologies. As such, nitrate often remains a systemic problem for these utilities.
While the lawsuit brought by the Des Moines Water Works against 10 northern Iowa drainage districts over high nitrate levels in the Raccoon River focused attention on nitrate flowing into central Iowa, it is obvious that water supplies across the state are affected. In the case of smaller water utilities, it is the townspeople — often in small towns with limited resources — who must shoulder the burden, physical and financial, of high nitrate levels.
Health risks in drinking water
What are the health effects of nitrate in drinking water? The link between high nitrate levels and the risk of blue baby syndrome, which can lead to infant death, is well-documented. Preventing these deaths is what led lawmakers in 1962 to set the federal limit for nitrate in drinking water at 10 milligrams per liter.
Other studies have linked a range of health concerns to elevated nitrate levels. While experts agree more research is needed, some compelling reports have emerged in the past few years:
- In 2016, the Iowa Environmental Council reviewed dozens of peer-reviewed health studies and found a link between high nitrate levels and birth defects, cancers and thyroid problems.
- The 2018 CARD report notes that several studies have documented an association between exposure to elevated nitrate in drinking water and a range of health concerns, including reproductive difficulties, birth defects, childhood obesity, bladder and gastric cancer, and thyroid problems.
Cover crops as a response
One proven way farmers can help reduce nitrate levels in Iowa’s surface and groundwater is by adding cover crops to their crop rotation. Not only can cover crops boost soil health, control weeds and save farmers money on input costs, they add living roots to the soil in the off-season for corn and soybeans, and can soak up nitrate that might otherwise end up in waterways.
A long-term study from 2002 to 2016 by plant physiologist Tom Kaspar and others at the USDA National Lab for Agriculture and the Environment found a cereal rye cover crop reduced nitrate in drainage tiles by up to 57%.
A 2007 report by Sustainable Agriculture Research & Education found that a barley cover crop removed an average of 64% of soil nitrogen from eight sites across North America that had received an average of 107 pounds of nitrogen per acre.
Groups like Practical Farmers of Iowa are helping farmers get started with cover crops through farmer-led field days, networking opportunities and on-farm research to learn from and connect with other farmers already using cover crops. PFI also offers cover crop cost-share programs for farmers through partnerships with Unilever and PepsiCo. Funds from these programs can be combined with other cover crop incentive programs, including the Environmental Quality Incentives Program.
Other ways to reduce N loss
Beyond cover crops, farmers can help reduce nitrate pollution with a variety of other practices. Extending the crop rotation, converting some land to pasture, installing saturated buffers and wetlands, recycling drainage water, enrolling land in the Conservation Reserve Program, and sidedressing nitrogen are among many options available. In its publication “10 Ways to Reduce Nitrogen Loads from Drained Cropland in the Midwest,” University of Illinois Extension lists these and other management practices that can help reduce nitrogen levels in our waters.
At MB Water, a company doing water quality sampling, testing and consulting as part of the Iowa Water Quality Initiative, we’ve learned a lot about water quality over the years in helping landowners and others monitor levels of nutrients and other substances and ingredients in water supplies.
One goal in working with farmers and others is to make applying farm chemicals and fertilizer as economically efficient as possible. MB Water also provides a way to assess nitrate levels and assist in reducing nutrient levels in water supplies. Learn more at mbwater.pro.
McAndrew is a water quality specialist with MB Water, a private firm at Coralville, Iowa, doing water quality sampling, testing and consulting.