WYE MILLS -- Even when farmers voluntarily reduce the amount of fertilizer they use, nutrients still escape from their fields to foul the Chesapeake Bay and its tributaries, University of Maryland researchers have found.
A 12-year study by Russell B. Brinsfield and Kenneth W. Staver at the university's Wye Research and Education Center near here indicates that the conservation practices of most farmers do not go far enough. There are no quick or cheap ways of curtailing farm runoff, a kind of pollution that might be partly responsible for outbreaks this summer of a toxic microorganism.
"There's no silver bullet," said Brinsfield, director of the 1,000-acre research center on the Wye River in Queen Anne's County.
Brinsfield is to present the findings today to the governor's commission studying the outbreaks of Pfiesteria piscicida. The single-celled organism is blamed for killing fish and causing human health problems on the lower Eastern Shore, where parts of three tributaries have been closed to fishing and swimming.
Over-enrichment of water with nitrogen and phosphorus is a major factor in the bay's decline. No connection has been proved, but the nutrients also have been linked with outbreaks of Pfiesteria.
Since 1985, the two agricultural researchers have measured high levels of nitrates seeping into ground water beneath two 20-acre cornfields along the Wye River. One-third or more of the nitrogen fertilizer remains behind when the corn is harvested, and what gets into ground water winds up in the river.
The researchers also have found surprising amounts of phosphorus in the tea-colored storm wa- ter washing off the fields, despite no-till seeding practices thought to prevent its loss.
"Nobody cared until this happened," noted Staver, referring to the Pfiesteria outbreaks, as he showed one of the white fiberglass troughs that capture runoff from a cornfield. Sensors attached to its bottom measure flow and nutrient levels.
The researchers' work suggests that farm conservation practices widely touted by the state are insufficient to reduce the nutrient pollution that is degrading the bay -- and perhaps triggering Pfiesteria outbreaks.
State agriculture officials, scrambling to respond to the fish-lesion outbreaks, acknowledge that. "Our farmers have been willing to do a lot, and they have [done] a lot, but what it appears now is we need to go back and ask them to do more," said Tom Simpson, Chesapeake Bay program coordinator for the Department of Agriculture.
Farmers have helped the bay by reducing fertilizer use through largely voluntary nutrient management planning and by building government-subsidized sheds for storing their animal manure away from nearby streams, Brinsfield and Staver said.
Cover crops urged
The researchers say much more could be accomplished by planting rye, barley or other "cover crops" in winter, when fields usually would lie fallow. The grains would reduce nitrogen losses by up to 75 percent, soaking up the excess left in the soil after harvest and preventing it from seeping into ground water.
"We can get a minimum 40 percent reduction in nitrogen losses from cropland with a long-term strategy of planting cover crops," Brinsfield said yesterday.
For a few years, the state offered farmers up to $30 an acre to plant cover crops, and 25,000 acres were seeded statewide at one time. But the program fell victim to budget cuts, despite a recognized need to plant 170,000 acres of cover crops statewide to meet the bay cleanup goal of reducing nutrients by 40 percent by 2000.
In the wake of the recent Pocomoke River fish kills, Gov. Parris N. Glendening offered $2 million for cover crops and aid to drought-stricken farmers. The money was snapped up in two days, and farmers pledged to plant up to 99,000 acres in grains this fall.
Only about 12 percent of the money will go to cover cornfields in the three lower Shore counties closest to the Pfiesteria outbreaks.
Even if the cover-crop program is better targeted, Brinsfield and Staver said, it will not immediately keep nitrogen from farm fields out of streams. Ground water moves slowly through soil, and what enters streams now might have come from fertilizer applied years ago.
Phosphorus runoff is even more difficult, the researchers said.
Phosphorus binds to soil, and experts had thought that controlling erosion would prevent it from running off fields. As a result, many farmers adopted no-till seeding, which has reduced soil loss dramatically.
But Staver said the researchers' study found that when phosphorus builds up in the surface soil, the nutrient dissolves when rain hits the field and runs off.
Indeed, phosphorus levels were up to 60 percent higher in runoff from no-till fields than in runoff from those that had been plowed.
The Wye soils were so saturated with phosphorus that when the researchers stopped putting it on their cornfield "cold turkey," nutrient levels in runoff dropped only 20 percent in four years.
Phosphorus levels are high on farm fields throughout the Delmarva Peninsula because farmers have been routinely over-applying that nutrient.
Nutrient management plans, which spell out how much fertilizer is needed to grow a crop, deal only with nitrogen.
"Nobody was told that if you use nutrient management planning, the phosphorus problem will continue to get worse," Staver said.
Nutrient migration is largely invisible to farmers, making it hard for them to accept the need to change, the researchers said.
Losing a pound of phosphorus per acre doesn't seem like a lot, but it can raise nutrient levels in a vast stretch of water so much that vital underwater grasses might not thrive.
"A pound of phosphorus is nothing in the back of a pickup truck," said Brinsfield, "but a little bit goes a long way."
Pub Date: 9/24/97