Fertilizing Your Lawn

Feed Your Lawn Right

The right amount of nutrients at the right time can improve a poor lawn and maintain a healthy lawn better than most other actions. But one thing is never true, and that is “If one pound is good, two pounds is twice as good”. Over-fertilization causes problems for the lawn and the environment. Here are tips for feeding your lawn while protecting our bays and groundwater from contamination.

When to fertilize your lawn

Timing matters when deciding when to fertilize your lawn. 

55°F

Grass only absorbs fertilizer when it is actively growing (above 55˚F).

Allow grass to come out of winter dormancy before applying fertilizer.

Only use lawn fertilizers between April 1 and December 1.—Why? It’s actually NY State law.

NYS Nutrient Runoff Law

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Don’t waste time and money on summer fertilizers!

Heat stress and drought slow grass growth and fertilizer can burn your lawn in the heat.

Fertilization Schedule for Long Island

Mid-April to May

  • No more than 1 lb. slow-release nitrogen (N) per 1,000 sq. ft. (32’ x 32’).
  • Leave clippings on lawn to recycle nutrients and organic matter.

September – Best time for feeding

  • No more than 1 lb. slow-release nitrogen (N) per 1,000 sq. ft. (32’ x 32’).
  • Leave clippings on lawn to recycle nutrients and organic matter.

How to fertilize your lawn

  • Feed your lawn slowly. Use controlled-release fertilizers to get more bang for your buck.
  • Sweep granules off hard surfaces and back into the lawn. Don’t let them wash away with the rain (or you’ll pollute the bays and Long Island  Sound).
  • Leave clippings on the lawn. This returns nitrogen and other nutrients to the soil.  
  • By law, New Yorkers must use zero-phosphorus fertilizers. Phosphorus is already high, too much can stunt plant growth, and the excess runs off, causing algae blooms in fresh and salt water. More information is available below.
sign indicating that the water is not safe due to harmful algal blooms

The Science of Fertilization

Lawn grasses need a variety of nutrients, water and sunlight to grow. There are primary, secondary, and micronutrients, defined by how much your lawn needs.

What's in fertilizer?

Major plant nutrients are nitrogen (N), phosphorus (P) and potassium (K). The letters are elemental symbols and are usually shortened to N-P-K, represented by the percent-by-weight of each element. For example, an N-P-K of 16-4-8 means: 16% nitrogen, 4% phosphorus and 8% potassium by weight. Therefore, in a 100-pound bag of fertilizer there would be 16 lbs of nitrate, 4 lbs of phosphate and 8 lbs of potassium. 

Test your soil before you fertilize
Fertilizer nutrient analysis of 100lbs Joe's lawn fertilizer. 16-4-8, 16lbs of nitrogen, 4lbs of phosphorus, 8lbs of potassium. 72lbs minor nutrients and carriers.

N

nitrogen

Nitrogen is needed for growth. However, it is the leading cause of poor water quality in Long Island’s fresh, salt and ground waters.

P

phosphorus

It is illegal to use phosphorus on Long Island lawns. Phosphorus-free fertilizers (for example, 16-0-8 NPK) are easy to find.

K

potassium

Potassium is naturally found in our groundwater. It is added to fertilizer because it helps build strong roots.

How do I know what my lawn needs?

Cornell Soil Health Laboratory can analyze your soil nutrients to optimize conditions for growing healthy grass and saving money. 

Major plant nutrients

Major plant nutrients are nitrogen (N), phosphorus (P) and potassium (K). The letters are elemental symbols and usually shortened to N-P-K, represented by the percent-by-weight of each element. Testing your soil will tell you how much of each nutrient you need.

For example, an N-P-K of 16-4-8 means:  16% nitrogen, 4% phosphorus and 8% potassium by weight. Therefore, in a 100-pound bag of fertilizer there would be 16 lbs of nitrate, 4 lbs of phosphate, and 8 lbs of potassium.

Testing your soil will tell you how much of each nutrient you need.

Most fertilizers are complete, with all 3 primary nutrients. Some fertilizers may have only 1 or 2 of these nutrients, giving them a formula that looks like 16-0-8 or 36-0-0. These fertilizers will supplement nutrients and help you avoid pollution when soil analysis says a nutrient is plentiful.

Secondary plant nutrients

Secondary nutrients include Calcium, Magnesium and Sulfur; Micronutrients include Iron, Manganese, Zinc, Boron, Chlorine, Copper, Molybdenum and Nickel.

Choose slow-release fertilizer over fast-release fertilizer

Long Island’s soils are very sandy, resulting in rapid percolation of rainwater into the ground, which brings surface nutrients and chemicals down into groundwater. Nitrogen is the leading cause of poor water quality in Long Island’s fresh, salt and ground waters. 

Slow, or “controlled-release" nitrogen fertilizers break down slowly, releasing small amounts of nutrients, which is good for steady plant growth and deep roots.

Long Island Nitrogen Action Plan (pdf)