Each year, farmers managing more than 2.2 million acres of croplands in the Bay watershed pull out plans that guide how they apply animal manure and commercial fertilizer on fields of corn, wheat, hay and other crops.

What they do with those plans, and exactly how much their actions reduce the amount of nutrients entering the environment, is at the center of a long-running controversy.

Most in the agricultural community embrace nutrient management — an effort to optimize fertilizer applications with crop yields — as the cornerstone for on-farm stewardship.

But others are skeptical of its real-world benefits and question whether the plans are fully implemented.

“Nutrient management has always been a lightning rod,” said Mark Dubin of the University of Maryland, who is the agricultural coordinator with the Chesapeake Bay Program. “You can’t go out there and lay eyes on it. There is this inherent distrust of things you can’t see.”

This issue has simmered within the state-federal Bay Program partnership since last fall when a panel of experts recommended increasing the amount of nitrogen and phosphorus reduction credits attributed to certain types of nutrient management actions.

That change would help states achieve Chesapeake Bay pollution reduction goals because nutrient management is a widely used nutrient control practice. Even small adjustments, when applied over many acres, could significantly change the estimates made by computer models used to track Bay cleanup progress.

But, critics argue that the recommendations were poorly documented and could result in nutrient reductions that exist only on paper. “I don’t want to reach our goals by changing the way we count rather than changing actions on the field,” said Tom Simpson, a soil scientist with a long history of work on Bay issues. “I’d rather be doing more things on the field that we can show are improving water quality.”

After sharp criticism, the expert panel in late June revised its earlier recommendations by substantially lowering the reductions associated with some nutrient management actions, as well as the amount of land those actions could apply to.

Christopher Brosch, an agricultural modeling specialist with Virginia Tech who chaired the expert panel, said the changes reflect the reality that nutrient management plans became more rigorous in the last decade as they incorporated new U.S. Department of Agriculture guidance.

“I think there has been a significant increase in the pounds of pollution prevented,” he said.

Brosch guessed that the new expert panel recommendations might increase the reductions attributed to nutrient management by about a fifth.

The new recommendations are open for public comment through July 29. A final Bay Program decision is expected in late summer or early fall.

But Brosch and others acknowledge that the question about how to appropriately credit nutrient management — and ensure that plans are implemented — won’t soon be answered.

Use of commercial fertilizer soars

In the aftermath of World War II, the advent of commercial fertilizer, coupled with improved varieties of crops, especially corn, resulted in vastly increased harvests. Fertilizer use soared.

Over time, research showed that increasing nitrogen applications beyond certain points did not significantly increase crop yields. Land grant universities began recommending application rates to farmers that better matched anticipated production.

Reduced fertilizer applications could also reduce runoff. Over time, nutrient management became the cornerstone of agricultural nutrient reduction efforts in the Chesapeake watershed and was touted as a win-win solution for farmers and the environment — farmers saved money; streams got less runoff.

But the reality is more complex. Farms that rely on purchased commercial fertilizers can save money. But those with stockpiles of animal manure face a different situation. Animal operations often have more manure than their crops need. For those operations, following application rates in nutrient management plans can increase costs if they have to pay to haul excess manure elsewhere.

That situation became more difficult in many areas when nutrient management plans began putting more emphasis on phosphorus. Unlike commercial fertilizers, which can match the amounts of nitrogen and phosphorus to a crop’s needs, manure typically can not. Animal waste, especially poultry litter, tends to have a higher ratio of phosphorus to nitrogen than a crop needs. If a farmer applies only enough manure to meet a crop’s phosphorus needs, he typically has to buy additional commercial nitrogen— and is left with a pile of excess manure.

“Until there’s a way to recoup that, why would any business go into a negative cash stream operation just to be doing the right thing?” asked Frank Coale, of the University of Maryland, and a former chair of the Bay Program’s Agriculture Workgroup. “They can’t do that and stay in business.”

That problem became apparent over the years as the Bay Program tried to balance the amount of agricultural nutrients, both purchased and in manure, with the available amount of cropland.

Inevitably, if farmers were following nutrient application recommendations, it resulted in huge manure surpluses. For years, that problem was resolved simply by removing excess manure from the balance sheets. Officials even developed a term for it: “poofing.”

When a new computer model of the Bay watershed was put into use in 2010 for the Chesapeake Bay Total Maximum Daily Load, it required accounting for all of the nutrients in the watershed. Manure could no longer be “poofed” away. When, in the model, that manure was applied to the land, the nutrient reduction estimates associated with nutrient management were greatly reduced.

States objected to the change. Nutrient management was one of the most widely used best management practices. Further, they noted that uneven data quality greatly distorted the model’s estimated application rates for some counties.

In response, the Bay Program’s Agriculture Workgroup in late 2011 created an “expert panel” to review the nutrient management issue.

It was one of many expert panels convened by the Bay Program partnership in recent years to update nutrient reduction “efficiencies” — the term for the amount of nutrient reduction that a given best management practice should be credited with in the Bay Program computer models.

In fall 2013, the panel recommended modifications for basic nutrient management that resulted in few changes. But last fall, when it recommended significant additional nutrient reductions for more advanced forms of nutrient management — such as improved timing of applications and incorporation of manure into the soil — it sparked a huge controversy.

“In our judgment, giving nearly double credit for plans — without verifying that those plans are actually being implemented — undermines the credibility of the Bay model and the confidence of citizens that the single largest source of pollution to the Bay [agriculture] is being addressed,” said the Bay Program’s Citizens Advisory Committee in a letter.

The EPA, the Chesapeake Bay Commission, environmental groups and others weighed in with questions and criticisms. Generally, concerns cited vagueness about the recommended efficiencies, what agricultural land uses these efficiencies would apply to, and which of the several potential actions were required to qualify for the nutrient reduction benefits.

As written, they expressed concern that the changes would credit nutrient management plans with millions of pounds of additional reductions, even though monitored water quality trends in many areas dominated by agriculture showed no significant improvements.

Meeting nutrient goals

Nutrient management is not the most effective agricultural best management practice in terms of nutrient reductions. Bay Program figures indicate it’s responsible for a bit less than 10 percent of the nitrogen reductions attributed to agriculture.

But unlike many practices responsible for larger reductions, such as agricultural land retirement programs, or riparian forest buffers, it does not require that land be taken out of production. As crop prices have increased over the past decade, farmers have increasingly become reluctant to reduce crop acreage.

Therefore, nutrient management becomes an important tool for states to meet their Bay cleanup goals because it can be applied to large swaths of active farmland.

But trying to find the “right” pollution reduction efficiency for nutrient management is tough. The computer models average all row crops into a single category, so the efficiency needs to average out over many acres, and many types of crops. Nutrient management can result in significant reductions for some crops, such as corn, but others, such as soybeans, typically don’t need fertilizer, so there’s no benefit from a nutrient management plan.

Complicating that, scientists say, is that there are often relatively few studies to draw from.

“Nailing these things down is pretty hard, that’s the reality,” said Ken Staver, a scientist with the University of Maryland Wye Research and Education Center, and a member of the expert panel.

Under the June expert panel recommendations, the more advanced forms of nutrient management would be credited with smaller nutrient reduction efficiencies than those recommended by the panel last fall, and be applicable to fewer acres. Overall, states might get about a fifth more nutrient reduction credits — if they can show their programs are consistent with the more advanced practices — but not so much as under last fall’s recommendations.

Jack Meisinger, a researcher with the USDA’s Agricultural Research Service and another panel member, said the criticism improved the final recommendations.

“They gave us a lot of ideas about what wasn’t right, and their suggestions were correct in many cases,” he said. “I feel a lot better with the revised report. The nitrogen pieces are much better defined. And we were able to get a decent amount of literature to bear on estimating the efficiencies.”

Updating reduction efficiencies

But angst over nutrient management is not likely to be over soon. The new recommendations, if approved, will only be in place through 2017. After that, the Bay Program will switch to a new, more detailed, computer model.

A new expert panel has already been created to update nutrient reduction efficiencies for that model.

Some are already pressing for the new panel to re-examine earlier, already approved, recommendations from 2013 for basic nutrient management. Those changes had not greatly altered estimates of the amount of nutrients reaching the Bay, but some questioned the underlying analysis which resulted in significant phosphorus reductions even for nutrient management plans that primarily dealt with nitrogen.

“Most technical people I talk to consider it a pretty obvious flaw that you get a 10 percent phosphorus reduction, but you apply manure based on nitrogen,” said Simpson, who chaired the Bay Program’s former Nutrient Subcommittee, a predecessor of its Agriculture Workgroup.

The new panel will also address the biggest concern about nutrient management — the extent to which plans are actually implemented.

Inspections by the Maryland Department of Agriculture show only about two thirds of nutrient management plans are being followed. Because of its survey, Maryland is the only state that does not take credit for all of the nutrient management acres reported.

A random survey of farmers in the Bay watershed conducted by the USDA Conservation Effects Assessment Project in 2011 found that only 34 percent applied nitrogen on all crops within 21 days of planting. For those using manure — which is more prone to runoff — the figure was 12 percent. Compliance with other nutrient management recommendations was similarly low.

While some question the accuracy of the USDA figures, which are watershedwide, and not by state, the figures highlight the concern about whether recommendations are being fully implemented, especially for manure which is more difficult to manage and is more likely to run off.

Verifying estimates

Starting in 2018, merely reporting the development of nutrient management plans that meet certain criteria will no longer count toward meeting nutrient reduction goals. The Bay Program is requiring that states develop programs to verify that all types of nutrient reduction controls are in place, maintained and functioning, whether they are urban stormwater controls, forest stream buffers — or nutrient management plan implementation.

Verifying that nutrient management plans are being followed for their timing, placement and rate of fertilizers and manure application is daunting, and many believe verification requirements could result in a significant reduction in the amount of acres counted.

“I’m not comfortable with our ability to verify that nutrient management is achieving the level of reductions that we are giving it,” Simpson said. “I am not able to verify it in my own work.”

He spent years trying to develop a farm certification program for a nonprofit organization. While many nutrient control techniques were relatively easy to verify, Simpson said proving that nutrient management recommendations were being followed was elusive.

The closest he could come to determining whether nutrient management plans were being followed was by trying to estimate an entire farm’s nutrient balance — whether the inputs in terms of fertilizers and manure could be balanced with outputs in terms of crops, animal or milk production, or exported manure. Nutrient inputs not balanced by outputs were unnaccounted for, and could potentially leak into the environment.

The new nutrient management expert panel is charged with recommending how to verify nutrient management.

Coale, who is chair of the new panel, said “The only way you can verify something and have it stand up to critical review by a third party is you have to be able to measure things.”

At the same time, Coale said technologies that allow farmers to apply nutrients — especially commercial nutrients — more precisely than ever before offer the potential of greater nutrient reductions. New equipment allows nutrient applications to be tailored to small portions of fields. Instead of just testing soil and manure, many farmers are testing corn stalks to see how much nitrogen is actually being absorbed.

“We’re subdividing our management into smaller and smaller units, and putting smaller and smaller units of nutrients on them,” Coale said. “We’re getting much more precise, on all different scales.”

The challenge will be figuring out how to estimate, and verify, the reductions..

What is Nutrient Management?

The heart of nutrient management is a plan that ideally uses information from soil and manure tests, the type of crop being grown, climate and expected yields to determine the amount of nutrients to apply. Nutrient management plans are built around the “4Rs”:

  • the Right Source
  • at the Right Rate
  • at the Right Time
  • in the Right Place

The plan factors in the type of fertilizer or manure being applied and its nutrient content, then recommends application rates for particular fields, as well as the timing and placement of those applications.

Plans can get much more detailed, especially when they involve the use of animal manure, which typically is both more difficult to precisely apply and more likely escape the field. For example, some plans may provide more specific recommendations about the timing of applications and whether they should be split over time, whether manure should be incorporated into the soil or if applications near streams and other environmentally sensitive areas should be restricted. The type of tillage used on the land may also affect recommendations. In some cases, the plan may recommend the transport of manure away from the farm if the volume generated exceeds crop needs.

Crediting nutrient management

The computer models used to estimate the amount of nutrients entering the Bay use research to calculate the average amount of nitrogen and phosphorus that runs off different types of land, They then apply reductions — called efficiencies — to account for implemented pollution reduction activities.

For basic nutrient management, the existing models use an efficiency of about 6 percent reduction for nitrogen and 9 percent reduction for phosphorus.

Recommendations from an expert panel adopted in fall 2013 established a reduction efficiency of 9.25 percent for nitrogen and 10 percent for phosphorus for most cropland receiving manure, and efficiencies of 5 percent for nitrogen and 8 percent for phosphorus for most crop lands receiving commercial fertilizer.

Those efficiencies are applied to the most basic, but widespread nutrient management plans, which put most of the emphasis on matching the source of nutrients with application rates.

An expert panel also recommended new efficiencies for more advanced, or “Tier II” nutrient management plans, which put more emphasis on splitting nutrient applications into multiple small doses applied at specific times, incorporating manure into the soil, creating application setbacks for manure, and using the Phosphorus Site Index to better direct phosphorus applications.

Initially, the panel recommended efficiencies of 15.75 percent for nitrogen and 20 percent for phosphorus for crops receiving manure. After a review, the panel in June revised those recommended efficiencies downward to 12.79 percent for nitrogen, and 15.94 percent for phosphorus. The panel also reduced the acreages those actions could apply to by about 40 percent.

Nutrient Management Expert Panel webinar

The Chesapeake Bay Program is hosting a webinar from 10 a.m. to noon July 1 to present the revised recommendations from the Nutrient Managment Expert Panel. For more information, visit http://www.chesapeakebay.net/calendar/event/22716/