More Corn a Cause for Concern

The increase in U. S. corn acres planted in response to growing demand from the fuel, feed, food and export markets has raised concerns about water quality in watersheds and could lead to more stringent conservation practices.
By Susanne Retka Schill | January 01, 2008
The prospect of vastly expanded corn acres has set off alarms in two of the nation's watersheds where water quality is heavily impacted by agriculture: Mississippi River and Chesapeake Bay. Simply put, more corn means more fertilizer, and in many places tillage practices that could cause soil erosion. Three reports issued in 2007 expressly examined the effects on water resources and reviewed the best management practices and policy choices needed to deal with increased corn acres. One was prepared by the Environmental Working Group, who raised concerns about the prospect of more corn acres and the need to tighten conservation compliance.

Water quality issues that stem from agricultural practices focus on three areas: nitrogen, sediment and phosphorus. Phosphorus is a nutrient that attaches to soil, says Gyles Randall, a soil scientist at the University of Minnesota's Southern Research and Outreach Center in Waseca, Minn. "If you can keep water on the land and the soil on the land, you can keep phosphorus on the land." On hilly land and in fields near streams, tillage practices can make a big difference in preventing soil and nutrient losses, he says. When hay land and meadows, where there is no runoff or sediment loss, are converted into cropland, it's likely that more phosphorus will enter the nation's waterways.

Nitrogen behaves differently in that it leaches into the soil rather than being carried into streams by runoff and erosion, Randall says. "The more corn we grow, the more nitrogen in the system," he says. "Corn and soybean [fields] are both fairly leaky." By leaky, Randall means that excess nitrogen is able to leach into the ground through drainage tiles in farm fields and flow into streams. According to a report by the Chesapeake Bay Commission, "Biofuels and the BayGetting it Right to Benefit Farms, Forests and the Bay," 150 pounds of nitrogen per acre is typically applied to corn in the region. "In addition, corn is a relatively inefficient user of these nutrients, consuming only 50 [percent] to 60 percent of the fertilizer applied," the report says. "Barring conservation management practices, an estimated 20 to 40 pounds of nitrogen per corn acre is released into the groundwater and streams leading to the bay." The report calls for a full suite of conservation practices to reduce that nitrogen loss. It also says, however, that the potential threat could produce a positive outcome. "The influx of corn, and the threat it brings for significant increases in nutrient loadings to the bay, may improve technical assistance and ramp up implementation of best management practices on farms that, until now, had little financial incentive or ability to do so."

Chesapeake Bay was the nation's first watershed to tackle pollution problems starting with the creation of a tri-state governmental commission in 1983. The mid-1980s marked the beginning of conservation compliance measures and incentives to reduce erosion on highly erodible soils. A report by the National Research Council titled "Water Implications of Biofuels Production in the United States," covers a range of issues surrounding water quantity, biorefinery water use and water quality. The report credits the conservation compliance measures of the 1980s for reducing soil erosion levels and decreasing nutrient losses. The report raises the concern that more corn for biofuels will reverse that trend.

With nutrients from the entire U.S. Corn Belt running into the Mississippi River watershed, more corn acres means more nitrogen draining into the Gulf of Mexico, the report states. Researchers have concluded that excess nitrogen in the river system is the major cause of the oxygen starved "dead zone" in the gulf, where many forms of marine life cannot survive. "This year (2007), we have near-record gulf hypoxia at 20,000 square kilometers (7,700 square miles)," says Jerald Schnoor, professor of environmental engineering at the University of Iowa. "We have a national goal to reduce this hypoxia to 5,000 square kilometers (1,900 square miles). We're going in the wrong direction."

Schnoor chaired the committee of scientists who wrote the National Research Council's report. Aside from describing water quality issues surrounding biofuels, the report reviews practices and technologies that can significantly reduce the impact of increased corn acres. Conservation tillage practices have had a positive effect on erosion. The USDA's National Resources Inventory shows a 40 percent reduction in annual cropland erosion from 1982 to 2003. However, the shift to conservation tillage may have reached a plateau, Schnoor says. "We need new incentives, new encouragement to take us further," he adds. One suggestion offered in the National Research Council report is to make ethanol subsidies variable, and in times of high profitability to divert the funds to cellulosic ethanol research and farmers who improve their practices.

The EWG goes a step further in its recommendations. EWG spokesperson Michelle Perez was the lead author of the report "Trouble Downstream: Upgrading Conservation Compliance." She says while her group works to improve funding for the USDA's voluntary conservation programs, the report recommends expanding conservation requirements. "In exchange for taxpayer support, we make the case that farmers should provide a minimum level of environmental performance," she says. Current laws require those farming highly erodible land to implement conservation measures to qualify for several farm programs. EWG is proposing that the eligibility requirements include qualifying for crop insurance. They also recommend that the minimum standards be expanded from soil conservation measures to include requirements for nutrient management plans and the planting of grassy buffer zones along surface waters that trap sediments and nutrient runoff.

In its fact sheet, "The Unintended Environmental Impacts of the Current Renewable Fuel Standard," the EWG summarizes the concerns environmentalists have with increased corn production for biofuels. The group lists five major unintended environmental impacts: loss and degradation for wildlife habitat, an increase in aquifer depletion, herbicide and insecticide pollution, nutrient pollution and soil erosion. "The majority of corn is not grown under conservation practices," Perez says. "Many farmers still conventionally plow every year. The estimate of how much soil erosion occurs with each gallon of ethanol produced is a major number." EWG calculates that 24 pounds of soil is lost per gallon of ethanol produced. (In its calculations, EWG uses the latest USDA National Resources Inventory figure for average cropland erosion of 4.9 tons per acre for 2003, plus the 2006 national average corn yield of 149 bushels per acre and ethanol production of 2.7 gallons per bushel of corn.) Coupled with nutrient losses amounting to an average of 25 pounds of nitrogen per acre of corn, she says farmers are not optimizing nutrient management practices. "Our national policy is not sending the right signals to farmers. There is no regulatory policy, and the voluntary cost incentives we have are under funded and don't send as strong a signal as they could." EWG reports that 75 percent of farmer requests to participate in voluntary programs go unfunded. "I don't think anyone's against corn farmers or ethanol producers in general," Perez says. "Because of these environmental concerns, we want ethanol done right. We don't want to trade our energy policy and global warming potential gains for local and regional losses in water quality, air quality and wildlife."

Soil scientists are sympathetic to the farmers' position as well. "Sometimes farmers are stuck in the middle," says Andrew Sharpley, a soil scientist who worked in the Chesapeake Bay watershed until moving to the University of Arkansas in Fayetteville. "As we've seen in the past, forces outside the farm drive what farmers do on the farm. The water quality impacts tend to be indirect and after the fact." Sharpley compares agriculture's attempts to improve its environmental impact on water to the experience of municipal water treatment facilities. "Cleaning up the first 30 [percent] or 40 percent is relatively easy," he says. "To clean up the water further gets increasingly more expensive."

There are some positive environmental outcomes on the horizon. High energy costs could prompt farmers to till less and manage fertilizer applications to optimal levels. Precision farming is considered to be a promising technology to help optimize fertilizer use. New foliar nitrogen applicators are equipped with sensors to identify nitrogen-deficient plants and can apply variable rates of nitrogen where needed. While the use of yield monitors in combines has caught on, Randall says the move toward farmers using the equipment to manage variable fertilizer rates on the land is slow to catch on. "Quite often the payback isn't there," he says. "The environment isn't included in that equation for success, if it doesn't pay out in higher yields." Sharpley, who is an expert on phosphorus issues, agrees, "If your livelihood depended upon it, you'd want to be sure to apply enough fertilizer to get good yields."

Times change, however, and farmers may need to heighten their environmental awareness. "Farmers are doing a pretty good job given the information and programs that are available to them," Sharpley says. "When things change, like we've been seeing with oil prices and the drive for biofuels, we see changes." That may mean reacting to the potential for increased amounts of nutrients leaching and flowing into the nation's waterways as grain production becomes more concentrated. "We need to be aware of the consequences and not go headlong into this and afterwards say we have got a problem," he says.

Susanne Retka Schill is an Ethanol Producer Magazine staff writer. Reach her at or (701) 746-8385.