From the apex of her aptly named Rolling Acres Farm in Brookeville, MD, Pam Saul pointed to the gridlike pattern of horse paddocks below. A brown square of wooden fencing encloses each one, allowing for a row of grass between them that Saul said keeps the horses from playing across the fence, making mud tracks along the edge.

Saul noted that the grass sections also act as buffers to absorb manure runoff, with four of them and an open field separating the top paddock from the meandering stream below. But, unlike riparian plantings along streams, grass strips between paddocks aren't a traditional best management practice — or one known to help reduce pollutants to the Chesapeake Bay watershed for livestock operations.

And the extra grass is unlikely to earn the horse farm relief from new requirements that it build a fence alongside the rest of the stream to prevent horses from accessing it.

"Everything that we could do so far that made sense to us, we've done," said Saul, who has run the former cattle farm as a horse boarding facility with her parents and two sisters since the early 1970s.

Now, she said, the Maryland Department of Agriculture "is asking us to do stuff that's so expensive... You name another business that has to comply with nutrient management laws that add no value to their business. We can't pass it on."

It's a tune that much of the agricultural community in the Chesapeake watershed has sung as stricter regulations to improve water quality in the Bay have been enforced on farms in several states. As one of the fastest growing sectors of agriculture in the region and one that fares best close to urban areas, horses are becoming a bigger part of states' nutrient control efforts.

Yet many people distinguish horses from other livestock — they are often considered recreational rather than agricultural animals, and their owners can be as diverse as their breeds. As a result, some in the equestrian community were surprised as regulators in parts of the watershed began to knock on farm doors.

In Maryland, a new set of regulations approved in the fall changes, among other things, when manure can be applied to land and requires sources of nutrients (including animals) to be kept 10 feet away from waterways on farms. In the horse community, the latter has been interpreted as a requirement that by July of next year they fence off all streams to which horses would otherwise have access. And many are still uncertain about how the manure application changes, effective in 2016, will impact their operations. Horses produce 20–50 pounds of solid manure a day, whether in the stables or on the pastures, and the industry is exploring options like composting to make the most of the nutrient.

The new rules apply to operations with eight or more horses, which were already required by the state to have nutrient management plans.

"One of our primary objectives in developing this last set of regulations was to achieve greater consistency in how the land is managed and how people that use and produce manure on their farm are regulated," said Royden N. Powell III, assistant secretary for the Office of Resource Conservation at the Maryland Department of Agriculture.

While the new rules impact several types of livestock and crop farmers, the equestrian community's reception of them has been varied. Some, like Saul, find the fencing requirement irrelevant to their operations, because they say horses don't have a habit of standing in streams the way that cows do. Saul estimated that extending an existing fence to the rest of her stream would cost her $50,000, and, in the past, the state's cost-share program only paid for a quarter of the type of wooden fencing she deemed best for her horses. (The regulations do include a caveat that livestock owners can work with their soil conservation districts to determine whether other conservation measures could abrogate the need for fencing.)

Other horse owners who have the finances to implement conservation plans are moving forward with them, hoping to benefit from a greener image among customers while reducing their impact on the Bay.

'At the front door of agriculture'

Every state in the watershed counts horses as agricultural livestock and, as with cows and chickens, their manure is a nutrient that can become a pollutant in the region's waterways. But each state has a slightly different approach as they work to bring horse operations of all sizes — and the sizable acreage they represent — into the conservation fold.

Horses are ridden, raced, bred and sold, used more today for recreation than for work-related purposes. It is also distinct from the rest of animal agriculture in that, at least in United States, horses aren't food.

As Ann Swinker, a horse specialist at Pennsylvania State University Extension, pointed out, horse people run farms but are not necessarily farmers. Traditionally, horse owners don't raise crops, besides grass on pastures, and they aren't as naturally intertwined with the agricultural agencies that provide assistance with conservation measures.

Yet horse farms are "at the front door of agriculture," Swinker said, positioned close to the residential areas that provide customers to their riding stables or boarding facilities. They are the anchors of that open green space suburbia wants to maintain. But that proximity to the city also means that the farm is more likely than its more rural counterparts to garner nutrient-related complaints, such as when a neighbor's dog rolls in a pasture's freshly applied manure.

In Pennsylvania, farms with one livestock animal have to have a self-regulated manure management plan on file and can be fined if, upon a visit from state regulators — and after an extended compliance period — they do not have one.

"It's really frightening when somebody knocks on your door and says, 'You have 90 days to do this and 30 days to do that or we'll fine you,'" Swinker said. "Pennsylvania is at the door-knocking point."

Swinker, who has been working for three years on an abstract that compares nutrient management regulations across the U.S. horse industry, said it's safe to say that regulations for horse owners in the East, and certainly those surrounding the Chesapeake Bay, are more stringent than elsewhere in the country, where 25 states still adhere to the 1970s regulations that require plans only for concentrated animal feeding operations with 500 animal units.

In the Chesapeake watershed, horse businesses compete across state lines, but the regulations regarding horse operators are disparate, depending on the number of horses and the proportion of overall agriculture they represent.

In Pennsylvania and Maryland, where horses represent a big piece of the states' agricultural pies, nutrient management at equestrian facilities is coming under increased scrutiny. Other states may follow suit as they ratchet up regulations to meet the region's overarching pollution reduction goals.

The 255,000 head of horses in Pennsylvania make it the state's second largest animal industry. In Maryland, which has more horses per square mile than any state in the nation, horse farms represent a quarter of its agricultural land.

Virginia has approximately 215,000 horses and each horse is estimated to requires two acres of land. Farms in the commonwealth with 150 horses kept in confinement for more than 45 days a year have to have a certified nutrient management plan. Otherwise, the need for a plan is determined at the county level by phosphorous indexing, and best management practices are encouraged.

Delaware has an estimated 13,000 equine animals on about 120,000 acres, excluding racetracks. The state's regulations mirror those in Maryland, as farms with eight animal units are required to have nutrient management plans and store or record the removal of excess manure from the farm, according to Stan Vonasek, president of the Delaware Equine Council.

A voluntary effort

Horses began to fill the barns left behind when many of Maryland's dairy farms were consolidated or closed in the 1970s. Stables, racetracks and boarding facilities seemed to fare better in locations near cities as suburbia continued to expand into the state's rural areas.

Of all the factors that make the horse community different from other agricultural sectors, perhaps the most interesting is its diversity — from just-making-it-by farmers with a few horses to deep-pocketed hobbyists and storied breeding facilities. Even as new regulations are coming down the pike for horse owners, some in the community are trying to encourage voluntary efforts toward conservation — and hoping that those who are financially able will lead by example.

Kevin Plank, CEO of Under Armour, has funded extensive equine-minded renovations and conservation measures at the 530-acre Sagamore Farm north of Baltimore, formerly owned by the Vanderbilt family, which he purchased in 2007.

The facility recently became the seventh horse farm in the state recognized by the Farm Stewardship Certification and Assessment Program for meeting and exceeding state conservation requirements. Jane Thery, who chairs the Maryland Horse Council's Farm Stewardship Committee, said she'd like to have 10 horse farms land the certification by the end of the year.

A committee meeting Feb. 3 drew two dozen equestrians to another farm that's a picture of ecological thoughtfulness, Wyndham Oaks in Brookeville, MD, where Thery boards her own horse.

Thery explained to the group that she'd like to see the horse community "stay ahead of regulations," adopting best practices voluntarily while there is funding available to help implement them.

"We're pushing on an open door, and that's OK," Thery said. "I think we need to get the leaders out there, then the other people will follow."

Groups like the Horse Council, which represents an industry with $5.6 billion in equine-related assets, have been spreading the word to horse owners about new regulations. But perhaps the hardest type of equestrian to reach is the one that represents the majority of horse owners.

"If you did the math, [smaller farms] are probably outnumbering the larger operators," said Michael Calkins, one of five regional equine specialists with MDA charged with engaging the smaller farms in conservation.

He estimated that the specialists each work with about 50 farms per year, but they still aren't sure exactly how many small farms are flying under the radar. And they've been at it for five years, consulting on nutrient management plans and connecting horse owners to grants or pasture experts. Such plans are not yet required for farms with fewer than eight animal units.

Recognizing the magnitude of its horse industry in the 1990s, Maryland began making horse operations eligible for cost-share programs to help pay for best management practices like fencing off streams. (Pennsylvania horse farms only recently became eligible for state cost-share funds.) But cost share still only pays for part of the efforts and, until recently, changes have mostly been voluntary.

"At the end of the day, we consider horse operations part of agriculture," Powell said. "Therefore, we need their help to reach those goals as far as agriculture's role in restoring the Bay."