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.
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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 Bay—Getting 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.
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