Lawn Clipping and Fertilization in Established Lawns

Allowing clippings to remain on lawns is recommended for many reasons: eliminating fuel consumption while hauling clippings, not filling landfills, encouraging microbiological activity to promote healthier grass, and recycling nitrogen back into the lawn.

On new lawns with low organic matter, lawn clipping return provides nitrogen but is not a “tipping” factor in the fertilization equation. Lawn soil organic matter levels peak at 30 to 40 years of age and this organic matter supplies one to two pounds of plant available nitrogen per year.

After the first 30 years of a healthy lawn, it could be detrimental to keep fertilizing at the same high rate. Applying 4 pounds of fertilizer per season on top of that supplied by soil organic matter and recycled clippings means the lawn could be receiving 5 to 6 pounds of N yearly. This promotes a lush turf that requires higher amounts of water, is more subject to disease and is less tolerant of heat and drought.

When lawns reach 30 years of age and if clippings continue to be returned to the lawn, nitrogen application rates should be reduced to 2 pounds (two applications per year). This assumes the lawn is mowed at the recommended height and irrigated reasonably. In most circumstances, these practices produce a lawn of acceptable quality to most people and one that is easier to manage under Colorado’s environmental conditions.

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Updated Friday, April 19, 2013