The green grasses sprouting in some fields in late autumn may not look like anything special to the casual observer.

To a growing number of Bay advocates, though, those fall cover crops look like the most effective line of defense between nutrients leaking from farm soils and the nutrient-drenched Chesapeake.

Cover crops are planted to improve soil production and reduce sediment and nutrient losses with no intention of harvest for sale, unlike crops such as winter wheat, which requires fertilizer applications to produce a harvestable commodity.

“By far,” said Ken Staver, “they are the closest thing we have to a silver bullet, at least for agriculture.”

Staver and his colleague, Russ Brinsfield, both researchers at the University of Maryland’s Wye Research and Education Center, have compiled stacks of reports showing that planting rye, barley or wheat soon after other crops are harvested can soak up huge amounts of excess nitrogen.

Left alone, that nitrogen would leach into the shallow groundwater and eventually make its way toward local streams and, ultimately, the Bay.

If cover crops offer a “silver bullet,” it is one that has gone largely unfired. A decade-and-a-half after the researchers began reporting their findings, Bay Program figures show that only about 100,000 acres of cover crops, out of an estimated potential 2.8 million acres, are planted each year in the Bay watershed.

Nonetheless, cover crops appear to offer one of the best opportunities for meeting the region’s nitrogen reduction goal, said Ann Swanson, executive director of the Chesapeake Bay Commission. “They are inexpensive, they capture an enormous amount of nitrogen, and there is a huge amount of land available to apply the practice,” she said.

An analysis being completed by the commission, a bipartisan panel representing state legislatures, shows that widespread use of cover crops could achieve about a quarter of the 100 million pounds of annual nitrogen reductions called for by the state-federal Bay Program last year.

For comparison, that’s about two-thirds of the nitrogen that can be removed by upgrading all wastewater treatment plants with “limit of technology” nutrient controls.

Tributary strategies, river-specific cleanup plans written by the states to achieve the Bay Program’s 2010 nutrient reduction goals, seem to acknowledge that potential. Collectively, they call for 2.1 million acres of cover crops by 2010—a 21-fold increase.

And cover crops are hardly alone. The tributary strategies call for a 17-fold increase in the amount of streamside forest buffers over what’s been planted since 1985 as well as a 12-fold increase in the amount of created wetlands and a 31-fold increase in the amount of grass buffer strips. And more.

“We’re calling for implementing a whole lot of things way more than we ever thought about implementing in the past,” said Tom Simpson, chair of the Bay Program’s Nutrient Subcommittee and a soil scientist with the University of Maryland’s College of Agriculture and Natural Resources.

Whether that happens remains to be seen. The tributary strategies don’t say how those levels of implementation would be achieved, or paid for.

Indeed, tributary strategies for the Eastern Shore in the 1990s, written to achieve earlier nutrient goals, also called for large amounts of cover crops but “for many years, we didn’t have any,” Staver noted.

Implementation surged after the Pfiesteria outbreak of 1997 resulted in a spike in state funding, but as that revenue dwindled so did cover crop acreage.

There are huge hurdles for reaching such aggressive implementation goals. While initially cheaper than many other nutrient control practices, cover crops are an ongoing expense for state agencies, and can be a pain for farmers to implement.

“You have to have an annual slug of money to support them,” noted Kelly Shenk, of the EPA’s Bay Program Office, who is helping to coordinate tributary strategy development. “Is that sustainable over the long haul? Even if you have the funding to pay farmers to put in cover crops, will they do it?”

The fact is, no one at this point knows whether the amount of cover crops called for in tributary strategies can be put on the ground and paid for. Of course, that could be said of many of the actions outlined in the strategies.

Cover crops, though, serve as a case study of a nutrient control technique that shows huge promise and the hurdles in implementing it.

Two decades ago, Staver and Brinsfield were looking for signs of herbicides seeping into the groundwater under Eastern Shore research plots because of worries that the chemicals might contaminate drinking water.

What they saw wasn’t toxins, but fertilizer. Nitrates—a form of nitrogen—exceeded the EPA’s drinking water threshold of 10 parts per million.

It was something of a surprise because they were following university-recommendations for fertilizer applications on the fields. More monitoring revealed that the find was no fluke. “For what we were doing, it was pretty clear that the average groundwater concentrations were going to be above 10 ppm,” Staver said.
That was something of a surprise, too. At the time, most considered nitrogen as a surface runoff issue that could be dealt with through such things as conservation tillage and grass filter strips.

But as Staver stepped up his monitoring, he discovered that more than twice as much rainfall left his fields through groundwater than surface runoff. Further, nitrogen concentrations in groundwater were two to three times higher than in surface runoff. The bottom line: Between six and 10 times as much nitrogen left through groundwater than surface runoff.

“It was pretty clear to us that even if we did a great job managing surface runoff, we were still missing a big slice of the pie in terms of nitrogen losses,” Staver said.

Those losses were mainly taking place in the fall, his monitoring showed. Growing crops greedily absorb nitrogen during the spring and summer, and nitrate levels in the soil bottom out in late summer. But then they begin to rise—even if no more nitrogen is applied.

The reason, according to Staver and Brinsfield, is that microbes continue to release nitrate in carbon-rich agricultural topsoils as they consume organic matter. Because summer annual crops have stopped growing by that time, little of that nitrate gets taken up.

The implication is that even with careful fertilizer use, huge amounts of nitrogen end up in the root zone—the top six inches or so of soil—at the end of the year. Left alone, that nitrogen will seep into the groundwater as precipitation increases during the fall.

The solution the team hit upon was to plant a new crop, such as rye, wheat or barely, after summer crops of corn or soybeans were harvested, to soak up the nitrogen, sort of like a living sponge.

Starting in 1988, and for years after, test plots at the Wye Research Center were planted with rye after harvest each fall. “We just kept on doing the same old boring thing year after year, and lo and behold, the numbers kept going down,” Staver said. After six to eight years, nitrogen levels in groundwater under the fields fell from 15 ppm, to 3 or 4 ppm.

“This is just about as clean as you can keep it and still be using those fields for the production of goods and services for society at large,” Brinsfield said. “The only other thing you could do is plant it in trees and have your corn produced somewhere else.”

Most other nutrient reduction techniques can’t boast the same level of effectiveness. Nutrient management—the most widely promoted practice in the Bay watershed—seeks to minimize pollution by optimizing fertilizer or manure applications to crop needs.

Brinsfield called nutrient management a “logical first step” because it helps to reduce nitrogen in runoff. But because most of the nitrogen leaving in the fall appears unrelated to fertilizer applications, nutrient management alone would not solve the problem.

Further, one of the region’s major crops —soybeans—doesn’t need nitrogen fertilizer. It “fixes” the nitrogen it needs from the atmosphere. After harvest, soils under a soybean crop can contain as much nitrate as they do after a corn crop.

Other heavily promoted practices, such as streamside forest buffers, can help. But in some areas, groundwater bypasses the buffers.

In fact, many of the nutrient reduction techniques promoted over the past decade have proved to be less effective than once thought. In a re-evaluation of those practices, the Bay Program last year reduced its assumptions about the effectiveness of many.

That evaluation increased the nutrient control rating for only one agricultural practice—early-planted cover crops.

There are good reasons why cover crops are not sprouting everywhere in the fall. They pose many challenges for farmers.

For maximum benefit, grasses must be planted in time to grow—and soak up nitrogen—before cold weather stops their growth. In this region, that generally means cover crops must be planted by Oct. 1.

But other crops often are not ready for harvest by that date. And the nutrient reduction benefits of cover crops diminish sharply as time passes. By Nov. 1, the benefit is minimal.

The problem gets tougher in places like western Maryland or Pennsylvania, where the climate is cooler, and the growing season shorter than on the Eastern Shore fields where Staver and Brinsfield did their work.

“It’s almost impossible in western Maryland to plant by Oct. 1 because you have to plant your corn later, and you harvest it later as a result,” said Louise Lawrence, of the Maryland Department of Agriculture. Soybeans, which are usually harvested later, are even more problematic.

Some cover crops, such as rye, can also be difficult for a farmer to kill in the spring, especially if wet weather delays a farmer’s getting into the field. In that case, last fall’s cover crop ends up competing with this spring’s commodity crop for nutrients and water.

Planting cover crops also creates some worries that new diseases or pests may be introduced to the fields.

But the biggest impediment is cost. Cover crops mean more work and added expenses to farmers who get little quantified benefit. That means they get planted only if there is an incentive.

If all 2.1 million acres of cover crops in the tributary strategies were planted and subsidized at $30 an acre—considered the going rate—it would cost $63 million dollars a year.

That figure could be low: Maryland’s tributary strategies assume that payments would need to reach $40 per acre to entice enough farmers to participate to meet the goals. “There’s a lot of labor and management involved,” Lawrence said. “Some people have told us it is not worth $20 to $25 an acre to go through all the hoops.”

So far, there is no obvious source of funding that would pay for the level of implementation called for in the strategies. Neither Pennsylvania nor Virginia have an earmarked a source of cash at this point.

Maryland plans to set aside 40 percent of a new $2.50-a-month fee being levied on septic system owners (as part of the “flush tax” fee approved for homes hooked to sewer systems) for cover crops. But that would produce less than $5 million a year.

The state tributary strategies call for 600,000 acres of cover crops and at a cost of $40 per acre that would require $24 million.

Further, states have to pay for plantings every year—whether their coffers are overflowing or empty—or huge amounts of nutrients will head toward the Bay. That causes some to question whether cover crops are the right strategy for the Bay.

“What happens if cost-sharing stops in 10 years?” asked Russ Mader, an official with the U.S. Department of Agriculture’s Natural Resource Conservation Service who works with the Bay Program. “Then the benefits you’re getting from cover crops will be lost.”

Although the 2002 federal Farm Bill contained record amounts of money for conservation programs, the USDA remains reluctant to fund such “annual practices,” preferring instead such things as manure storage facilities, streamside buffers and other permanent, or at least long-term, practices.

Many other federal farm conservation programs are intended to promote behavior change, such as nutrient management or conservation tillage. Once farmers learn such practices can save time and money, they are likely to continue doing them whether there are continuing payments or not, Mader said.

In contrast, few farmers are likely to buy seed and invest time planting cover crops unless they are paid. Mader suggested cover crops are best funded during drought years, when poor crop growth results in unusually high amounts of nitrogen left in the soil.

“Granted, if it is all done correctly, they are very effective, and to do permanent practices that have the same effectiveness is not very easy,” he said. “My concern is that with this annual practice, there is no behavior change, and participation is totally dependent on funding.”

Nonetheless, the size of the nutrient reduction goals, and the apparent effectiveness of cover crops, is spurring new efforts to help get them into place.

Even some federal officials have begun taking a second look at cover crops. The door was cracked open a bit this year when the USDA set aside an additional $5 million for farm conservation programs on the Eastern Shore, and specifically said some of the money could go for cover crops.

To many, that is a reasonable investment. Russ Perkinson, of the Virginia Department of Conservation and Recreation, said there is little financial difference between paying for an expensive manure storage facility—which can cost tens of thousands of dollars—and paying for cover crops each year.

“If you annualize the cost of a manure storage facility, it’s probably quite high per acre,” he said. But what may be equally important, he said, is finding ways to make cover crops work with the way farmers operate, rather than being an extra burden.

Staver and a team of other scientists are taking a step in that direction. In a new study, funded by the nonprofit Maryland Center for Agro-Ecology, they hope to quantify some of the benefits that may accrue to farmers from planting cover crops, such as improved soil quality, increased moisture conservation and weed suppression.

They also want to determine which cover crops work best under normal farm practices, and under different conditions. They want to determine whether livestock producers can use cover crops for forage without losing the nutrient control benefits.

The goal is to help make cover crops something that farmers see as beneficial not just to water quality, but to their own operations. “Right now, this is an extra dead cost to the farmer,” Brinsfield said.

There may be solutions to some other problems, as well.

Aerial seeding may provide a way to plant fields before crops are harvested. That poses some problems—the leaves of existing crops can intercept a lot of the falling seeds—but some believe the process can be refined over time.

Others suggest that subsidizing farmers to grow faster maturing soybeans may help to get more cover crops planted in a timely fashion.

Some are eying ways cover crops can help produce income. Maryland, for example, has experimented with a “small grain enhancement” program in which farmers who grow commodity crops, such as winter wheat, agree not to fertilize them until spring, which can reduce yield.

Normally, such crops are fertilized in the fall and winter—when there is a high potential for runoff and leaching—to maximize yield. Such a practice may not produce quite as much nutrient benefit as a true cover crop, according to some estimates, but “every little bit helps,” Lawrence said.

The ultimate question, of course, is whether all those bits—and enough money —will add up to a 21-fold increase in cover crops.

Agriculture remains the largest single source of nitrogen to the Bay. The tributary strategies have seized upon cover crops as their largest single source of nitrogen reduction from farm lands.

So in the end, as go the cover crops, so may go the Bay. “No one would be for this,” Staver noted, “if everything else had worked.”