Nitrogen-rich chicken manure inside a composter near Langley, Washington, that has aged long enough to apply. (Dean Fosdick/AP)

Maryland Gov. Larry Hogan (R) has agreed to a firmer deadline for fully implementing regulations that limit the amount of chicken manure farmers can use as fertilizer — ending tense negotiations among his administration, state lawmakers, Eastern Shore farmers and environmentalists worried about pollution in the Chesapeake Bay.

The regulations are now working their way through a final approval process, according to Hogan’s office, and will soon be in place. Over the next seven years, an increasing number of farmers will have to carefully calculate how much manure they spread on their fields — and, in most cases, dramatically reduce its use.

By 2022, all farmers will have to abide by the new rules, although some farms could be granted an extension until 2024 if major problems arise. An advisory committee will oversee the phase-in process and must approve any extensions.

“We have agreement on a solution that represents one of the most important steps forward in environmental policy in the last decade,” said Doug Mayer, a spokesman for Hogan. “We thank all parties for their hard work on this critical issue.”

The manure regulations have been in the works for years. Maryland’s Eastern Shore is home to numerous chicken farms that produce tens of thousands of tons of phosphorus-rich manure each year. Local farmers have long used that manure as inexpensive fertilizer. But phosphorus and nitrogen in the fertilizer can seep into waterways and pollute the Chesapeake Bay, contributing to the formation of oxygen-deprived “dead zones.”

During the tenure of former governor Martin O’Malley (D), state agriculture officials developed a phosphorus-management tool to help farmers calculate how much manure they could safely spread on their fields — and slowly reduce the amount used in the region.

Farmers argued that the tool would force them to instead buy more expensive fertilizer, and chicken producers say it’s unclear how they should dispose of the manure if it is not used on fields.

O’Malley waited until his final days in office to finalize and begin the process of implementing his manure regulations — a move Hogan criticized as “politically motivated.”

On Hogan’s first day in office, he halted final implementation of O’Malley’s regulations, drawing howls of protest from environmental groups.

Last month, Hogan unveiled his own regulations, which differed from O’Malley’s in a few key ways: Farmers whose land is already highly saturated with phosphorus would have to cease using manure as fertilizer right away, but everyone else would have extra time to adjust. How much extra time was not clear.

Sen. Paul G. Pinsky (D-Prince George’s) said Hogan’s proposal had too much flexibility and could result in the regulations never being fully implemented and in the continued flow of loads of phosphorus into the bay. Hogan’s “regulations, we felt, had a permanent off-ramp,” Pinsky said.

Pinsky introduced legislation that would turn O’Malley’s regulations into law — superceding anything Hogan did. That legislation was modified last week by a Senate committee, which stripped out most of the language and focused heavily on setting a deadline for all farmers to comply with manure limits.

With the bill headed to the Senate floor — where it likely would have prompted an emotionally charged debate about pollution in the bay and the challenges facing the farming community — the Hogan administration began discussing options for a compromise.

“We passed our regulations [out of the committee] on Friday,” Pinsky said, “and the meetings started on Monday.”

Pinsky has not yet withdrawn his bill. But he asked the Maryland Senate on Wednesday to delay discussing it until the compromise with the Hogan administration is finalized.

The Maryland Clean Agriculture Coalition and the Chesapeake Bay Foundation praised the compromise in a joint statement Wednesday evening, calling it “a major accomplishment.” But they warned that their vigilance will continue.

“Organizations working to protect the Chesapeake Bay and Eastern Shore waterways will strive to ensure that Governor Hogan’s regulations do what we hope they will and that they don’t get weakened or delayed in the months or years to come,” the statement said. “We will also be watching over the next seven years to ensure this long-overdue tool gets implemented as it is supposed to do.”