A measure that limits the nutrient content of lawn fertilizer and restricts when it may be applied by homeowners was signed into law by Maryland Gov. Martin O'Malley on May 19 to help the state meet its Bay cleanup obligations.

The law would prohibit homeowners from using fertilizer after Nov. 15 or before March 1. Further, that fertilizer can contain no phosphorus unless it is for specific uses, such as establishing a lawn or repairing turf. It also restricts the amount, and type of nitrogen that can be used in fertilizer, and requires that at least 20 percent of nitrogen be slow-release.

Proponents say it is one of the toughest measures regulating the use of lawn fertilizer in the country, and estimate that it would reduce the amount of phosphorus reaching the Bay from Maryland by about 3 percent a year. Nitrogen reductions have not been estimated.

The law was championed by the Chesapeake Bay Commission, which worked with various groups to reach agreement on the measure. "We found that all of the stakeholders were concerned about the health of the Bay and with a little prodding they all agreed to do a little bit more to improve water quality in the Bay," said Del. Jim Hubbard, a Democrat from Prince Georges county who is chairman of the commission's Maryland delegation.

The commission is an advisory panel that represents the legislatures of Maryland, Virginia and Pennsylvania.

Chris Wible, director of environmental stewardship for Scotts Miracle-Gro, said the law set "some of the nation's most comprehensive, and protective standards for lawn fertilizer content and use" and pledged to help educate homeowners about proper use.

The law also stipulates that no fertilizer can be labeled for use as a de-icer. Labels must also contain a statement warning users not to apply it near water, storm drains and drainage ditches, or if heavy rain is expected.

Professional fertilizer applicators must be certified by the Maryland Department of Agriculture and be trained by an MDA-approved certification program. They have slightly more leeway, and are able to make applications Nov. 16 to Dec. 1 if they use only water-soluble nitrogen and apply it at a reduced rate. Commercial applicators may also continue to apply organic fertilizer that contains phosphorus, although the amount of phosphorus is limited starting in 2013.

Homeowners who violate the law could be subject to a $1,000 fine.

The bill also prohibits the local regulation of fertilizer.

Pennsylvania lawmakers are expected to introduce similar legislation soon. The Virginia General Assembly this year approved legislation restricting phosphorus content in fertilizers.