New law regulates phosphorus use on lawns

By Dawn Pettinelli - UConn Home & Garden Education Center
Featured Article - posted Wed., Oct. 2, 2013
- Contributed Photo

Anyone who has purchased fertilizer knows that each package comes with a guaranteed analysis or grade consisting of three numbers such as 5-10-5. These numbers stand for the percent, on a dry weight basis, of nitrogen, phosphorus and potassium contained in that particular fertilizer. Fertilizers contain these three elements because they are often needed by plants in larger quantities than most native soils can supply for optimal plant growth. Plants need a number of other elements too, but they are usually supplied either by the soil itself or by additions of limestone and organic matter.

Typically, nitrogen is associated with green, leafy growth, and that is why many lawn fertilizers have analysis like a 24-2-8. Phosphorus is essential for root growth and flowering, and potassium helps regulate water movement as well as increasing the plant’s ability to withstand stresses like disease and winter injury.

When fertilizers, either organic or synthetic, are applied in the correct amounts and at the appropriate times during the growing season, plants will do well and the risk of nutrients entering water bodies will be minimized. Both nitrogen and phosphorus will cause problems when they enter lakes, streams, ponds and other water sources. Because phosphorus especially is severely deficient in native water sources, even the addition of small amounts will stimulate the growth of algae and other water plants and the water body will become eutrophic. As the lush aquatic plant growth dies and decomposes, oxygen levels in the water body become reduced, often resulting in fish kills. The bottom line is that phosphorus contamination results in weedy lakes that are undesirable for swimming, fishing and other recreational activities.

The phosphorus that enters water bodies primarily comes from failing septic systems and fertilizers. Many towns are working with homeowners that reside near water bodies to rectify problems with septic systems.

The Connecticut legislature decided to weigh in on phosphorus in fertilizers and in May 2013 passed legislation regulating the use of phosphorus on established lawns. It went into effect this past January. Golf courses and agricultural land are exempt from this regulation.

Any fertilizer, soil amendment or compost that contains less than 0.67 percent phosphorus is also exempt and can be used. Typically, leaf composts have low amounts of phosphorus in them and could be used to topdress established lawns if necessary.

So, if you are responsible for maintaining a lawn area, what will this law mean for you? For those that are seeding or sodding a new lawn area or overseeding an existing lawn, no changes to your fertilizer regimen are needed. Generally, new plantings of any crop benefit from the addition of some phosphorus to aid in root growth establishment so turfgrass starter fertilizers or complete garden fertilizers can be used at rates recommended on the package or by a soil test report.

Established lawns do not have high phosphorus requirements, and once optimum amounts are established in the soil, just by routinely leaving the grass clippings on the lawn, you will be supplying much of the phosphorus that your lawns need. The new legislation would prohibit the application of lawn fertilizers containing phosphorus on established lawns unless a soil test, done within a two year time frame, shows that phosphorus is deficient and recommends a phosphorus containing fertilizer.  A quick glance at some name brand fertilizer websites showed that many of the larger companies have no-phosphorus fertilizers available, most likely in response to the growing number of states that are passing laws restricting phosphorus fertilizer use.

The biggest challenge is going to be for those wanting to maintain their lawns using natural organic lawn fertilizer products because it is much easier to manufacture chemical fertilizers that do not include phosphorus than it is to remove phosphorus from an organic fertilizer or soil amendment such as alfalfa meal or compost.

The legislation also restricts the application of any phosphorus-containing fertilizers to lawns between Nov. 15 and March 15. The University of Connecticut, however, recommends applying fertilizers, to lawns or any other plants, only between April 15 and Oct. 15, when plants are typically still actively growing.

No fertilizers containing phosphorus can be used on lawn areas that are less than 20 feet away from any body of water. The law also requires retail establishments to segregate lawn fertilizers with and without phosphorus and to provide signage about the potential for phosphorus pollution and will be enforced by the Connecticut Department of Agriculture.

If you have questions on the phosphorus legislation or soil testing, or on other indoor or outdoor gardening topics, call the UConn Home & Garden Education Center, toll-free, at 877-486-6271, visit or contact your local Cooperative Extension center.

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