Making Recommendations for Lawn Fertilizer Applications

Many Connecticut parks, golf courses, and residential landscapes are located near ponds, lakes, rivers and

coastal waters. These surface waters can be degraded by nutrient loss resulting from over-application or

improper application of fertilizers to home lawns and other turfgrass areas.  Groundwater can also be

contaminated from nutrient lost from lawns.  Recent research has provided data that should change the way 

advise clients in fertilizing and managing lawns and other turfgrass areas.

                       Recommendations for Managing Nitrogen ( N ) on Lawns

•  If an unfertilized lawn is considered acceptable, then do not fertilize.

•  If the lawn is considered unacceptable, assess why ( pests, compaction, shade, low fertility, etc. ). If

            fertilization is deemed necessary:

• Do not apply before spring green-up and apply no later than October 15th.  Avoid mid- summer fertilizing.
• Apply one- half to one- third ( or less ) of that recommended on the fertilizer bag label and then monitor lawn response.  Reapply at the reduced rate only when lawn response starts to fall below acceptability.
• Slow- release formulations are preferable to soluble, fast- release formulations.
• Apply a maximum of 2 lbs. N/ 1000 sq ft/ year on an established lawn 10 years old or older. Newly seeded turf, especially on new home sites where the topsoil has been removed, may require more.
• If a soil test indicates phosphorus ( P ) and/ or potassium ( K ) are adequate, then fertilize with only nitrogen      (N). If only blended fertilizers are available, choose the one with the lowest P content.
• If near surface water ( streams, rivers, lakes, estuaries, bays, coastal areas, vernal pools, wetlands, or drainage areas ), leave a buffer strip of at least 25 feet of unfertilized grasses or other vegetation around water bodies.
• Avoid using combination products that include both fertilizer and weed killers. Fertilizers with herbicides should not be applied within 25 feet of surface water.

•  Other management considerations:

• Return clippings and mow as high as possible (  leave at least 3 inches ).  Clippings can supply slow- release nitrogen to the lawn and allow for reduced fertilizer applications.
• Choose grasses, such as fescues, that require less water and nutrient inputs.
• Maintain soil pH levels between 6.0 and 7.0 for Connecticut lawns.
• Consider seeding white clover or other legumes into the lawn to naturally provide nitrogen.
• If supplemental watering is applied, avoid overwatering. Do not exceed a total of 1- 1 ½ inches of water per week, including rainfall amounts.   
• When establishing a new lawn, if organic matter is below 3%, incorporate compost or another organic material into the soil to raise the % of organic matter content to at least 3%, preferably 5%.

   Recommendations for Managing Phosphorus  ( P ) on Lawns

• If an unfertilized lawn is considered acceptable, then do not fertilize.

• Always test the soil to determine phosphorus levels before applying.

• If phosphorus fertilizer is required:

• Avoid using P fertilizers on bare ground or on low- density lawns, unless it is a new seeding.
• Use P- free fertilizer on established lawns, unless soil tests indicate P is too low.
• Avoid applying phosphorus fertilizers when moderate to heavy rain is in the forecast.
• Leave a buffer strip of unfertilized grasses or other vegetation around bodies of water.
• Never apply phosphorus fertilizers to saturated or frozen ground.
• Avoid using products that include both fertilizers and weed killers as the application rates of such products are based on the weed killer rather than the fertilizer.

• Other management considerations:

• Return clippings where practical. On a well- established lawn, this can often supply adequate P for the lawn.
• Maintain a soil pH of 6.0 to 7.0. This will ensure that most of the nutrients necessary for good turfgrass growth will be available to the grass plants. Monitor pH levels to determine if liming is necessary or not.
• Soil test annually for P when applying organic fertilizers derived from composts to ensure that P levels do not become excessive.

The information on this sheet is adapted from :

Guillard, K. 2008. New England Regional Nitrogen and Phosphorus Fertilizer and Associated Management Practice Recommendations for Lawns Based on Water Quality Considerations. University of Connecticut.

This material is based in part upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under agreement  number 2006-51130-03956.

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