Springtime Tips for Lawn Fertilization and Irrigation to Improve LI’S Water Quality

“Our foremost recommendation is not using any fertilizer,” said Kyle Rabin, LIRPC program manager. “If homeowners like how their lawn looks, fertilizer is unnecessary.”

Fertilizer is the second-leading source of nitrogen contamination of Long Island waters; residential wastewater is the primary source. The nitrogen in fertilizer finds its way into waterbodies, stimulating the excessive growth of aquatic plants and algae that consume dissolved oxygen and block sunlight. Overwatering lawns compounds the problem because it increases the amount of runoff.

“People think more is better – more fertilizer and more water will create a better result. That notion is incorrect and has serious environmental impacts. Knowing when to fertilize and how to do it properly can protect water quality and result in a healthier lawn,” Rabin said.

Those choosing to apply fertilizer are encouraged to follow these recommendations from LIRPC and LINAP:

• Fertilize lawns and non-agricultural turf between April 2 and Oct. 31. So, no fertilizer application between November 1 and April 1. This recommendation is, in fact, law in Suffolk County. In Nassau County, the prohibited period is Nov. 15 to April 1.
• Use a fertilizer containing at least 50 percent slow-release nitrogen. This type of fertilizer releases the nitrogen slowly over time so the grass can take up the nitrogen as needed. Fertilizer retailers can direct shoppers to slow-release nitrogen products. Some retailers have helpful online resources about products with slow-release nitrogen.
• Only apply lawn fertilizer to grass. Do not apply fertilizer on any impermeable surfaces, such as driveways, sidewalks, frozen ground, parking lots and storm drains, or where there is standing water on turf.
• Keep grass clippings on your lawn. The clippings are a great source of natural, slow-release nitrogen. By leaving the grass clippings on the lawn, you can reduce the amount of fertilizer you apply by 25 to 50 percent, which will protect the water and save you money.
• If irrigating a lawn, only apply up to 1.5 inches of water per week beyond rainfall and do not water between 10 a.m. and 4 p.m. or during rainfall.
• Be careful when applying fertilizer close to the water. Do not apply fertilizer within 20 feet of any surface water, except where there is a continuous 10-foot wide natural vegetative buffer.

“The recommendations include best practices and are designed to help curb the pervasive over-application and misapplication of nitrogen-laden fertilizers, which leach into our groundwater and enter our harbors, bays and other large surface waterbodies,” Rabin said.

The turf-grass fertilizer recommendations can be found here: https://www.dec.ny.gov/docs/water_pdf/linapfertilizer.pdf.

NYSDEC and LIRPC led a workgroup to develop the recommendations. The workgroup included environmental groups, fertilizer manufacturers, landscaping companies, nursery operators, garden supply retailers, golf course superintendents, and representatives from farming and government.  The recommendations are also based on scientific and experiential information from the Cornell Cooperative Extensions of Suffolk County and Nassau County, Suffolk County Department of Economic Development and Planning, Cornell University, and the University of Connecticut.

LINAP is led by the New York State Department of Environmental Conservation (NYSDEC), LIRPC, and Suffolk and Nassau counties, and includes local governments, area scientists, engineers, environmental and non-governmental organizations, and several supporting professionals.