This year's increased corn plantings in the Bay watershed could generate roughly 3 million pounds of additional nitrogen runoff, according to an analysis of recent figures from the U.S. Department of Agriculture and regional scientists.

The figures show that this year's plantings alone could have the potential to largely offset other Bay-related cleanup efforts. The EPA estimates that the recent pace of nitrogen reductions in the Bay watershed has averaged 3.4 million pounds a year.

Some scientists and officials involved with the Bay cleanup have worried that pressure to grow more corn, spurred by rising corn prices pushed largely by increased ethanol demand, could pose problems for restoration efforts because cornfields tend to lose more nitrogen than other crops.

Such concerns are starting to be elevated in policy discussions. A recent biofuels report from the Mid-Atlantic Water Quality Program, a partnership between the USDA and regional agricultural schools, suggested that nitrogen runoff could eventually increase by 8 million to 16 million pounds a year if 500,000 to 1 million additional acres of corn were planted in the region.

The Chesapeake Bay Commission, a legislative advisory panel, will release a report in September outlining potential strategies to mitigate water quality problems from increased corn production and outlining long-term options for other biofuels that could have less impact, or prove to be beneficial, for the region.

Once it reaches the Bay, nitrogen fuels algal growth, which fouls water quality. The region is working to reduce nitrogen runoff to the Bay to 175 million pounds a year to meet cleanup goals. Currently, the Bay Program estimates about 270 million pounds would reach the Bay in an average rainfall year.

The 3 million pound figure is derived from an analysis of USDA's 2007 corn planting figures released in late June. The figures show that about 325,000 additional acres of corn were planted in the six states containing the Bay watershed-New York, Pennsylvania, Maryland, Virginia, West Virginia and Delaware.

The USDA figures do not provide county breakdowns for 2007, but if new acreage followed the distribution pattern of 2006, it would result in about 180,000 to 185,000 additional corn acres within the Bay watershed portion of the states.

Two independent groups, the team that wrote the Mid-Atlantic Water Regional Quality Program's biofuel report and the other a team of Bay Program analysts, developed estimates of the potential impact from added corn acreage on nutrient runoff.

Those analyses are based on research about the amount of nitrogen that escapes fields from various crop lands and assumptions about the types of crops and other lands likely to be converted to corn production. Those calculations assume farmers will follow recommended nutrient applications and practices, but do not include effects of various "best management practices" such as cover crops or stream buffers that could reduce runoff but would also increase costs.

Both teams came up with similar figures for nitrogen loss and crop land conversion. If those estimates hold true for this year's plantings, it would work out to about 3 million pounds of nitrogen from increased corn acreage. Because much of the nitrogen from cornfields enters streams through groundwater, the actual increase would be spread out over several years.

Projections of 500,000 to 1 million increased acres of corn in the region created controversy among some agricultural groups who say it overstates potential crop conversion. A report to be released by the Bay commission will suggest a lower figure of around 300,000 acres.

"The first year change is dramatic, but you can't say that's how it is going to end up in terms of acres, or the relative distribution," cautioned Tom Simpson, of the University of Maryland's College of Agriculture and Natural Resources, and a co-author of the mid-Atlantic program's biofuel report.

But Simpson said the point of such analyses is not predicting the exact level of transition in the next several years, but to highlight a problem that policy makers need to address.

"The exact numbers aren't as critical," he said. "No one argues that if you switch from a corn-soybean, or in our case a corn-wheat-soybean rotation, you are going to lose substantially more nitrogen."

The effects of new corn acreage can be managed to a degree if conservation measures, such as cover crops, are intensively applied to the fields. Long-term research on Maryland's Eastern Shore shows such actions can, on average, limit nitrogen losses to those seen from soybean fields. (See "States urged to boost efforts to curb runoff from cornfields," July-August 2007.)

But soybean fields also leak relatively high amounts of nitrogen. If other areas, such as hay, pasture or idle lands, are converted to cornfields, nitrogen losses would increase even with intensive conservation measures.

This year's USDA numbers suggest that much of the added corn acreage in Maryland and Virginia came from soybeans. Maryland corn acreage increased by 50,000 acres, while soybeans decreased by 40,000. Virginia corn acreage increased by 50,000 acres while soybeans decreased by 20,000 acres.

But in Pennsylvania, many of the corn acres appear to have come from other uses. Pennsylvania, according to USDA figures, was one of only two states where both soybeans and corn acreage increased-corn increasing statewide by 100,000 acres, and soybeans by 10,000 acres. The other state was New York.

The reason may be that Pennsylvania has a more diverse agricultural base than Maryland and Virginia, said Mark Dubin, agricultural technical coordinator with the Mid-Atlantic Regional Water Program, who analyzes farming issues at the Bay Program Office. "There is more opportunity to convert hay land and idle lands into corn and soybean production than there would be in other states," he said.

"In some of the other states, you were limited in the number of acres available, say in hay land, to convert," he said. "You would be forced to convert more soybean land into corn."

He said it is too early to predict how much land will ultimately be switched to corn in coming years for a variety of reasons. Corn acreage has increased as the price per bushel has nearly doubled from a year ago because of increased demand.

But as corn expands onto other croplands nationwide, the price of other commodities such as soybeans and wheat have increased. A major question will be whether rising prices for other commodities will serve to check the increase in corn production, Dubin said.

On the other hand, he said, corn production is centered in the United States and soybeans can readily be imported from other areas such as South America, which could lead to corn gradually displacing soybeans here.

Despite some of its drawbacks, corn also has some benefits, such as boosting rural economies and increasing the value of farmland, something the USDA has already seen across the country.

"There are potential benefits to agriculture for sustainability and increased profitability," Dubin said. "The concern is that we just need to be honest on what the outcomes are."

The paper, "Biofuels and Water Quality," is available on the Mid-Atlantic Regional Water Quality Program's website: www.mawaterquality.org

The report ,"Biofuels and the Bay," will be available in mid-September on the Chesapeake Bay Commission's web site: www.chesbay.va.state.us.