New Fertilization Recommendations For Lawns

Cornell Cooperative Extension – Nassau County has revised the recommendations for fertilizing lawn areas. This is due to environmental concerns (particularly the possibility of nitrogen leaching into ground water and other sensitive areas) and also to new legislation. A law has been passed in Suffolk County that prohibits any lawn fertilization between November 1st and April 1st. The actual portion of the law that prohibits this will take effect in 2009. There has also been preliminary consideration of similar legislation in Nassau County.

Because of the legislation and leaching concerns, we now do not recommend the Thanksgiving or late fall application of turf fertilizer. You will have to adjust your thinking now after many years of us recommending lawn fertilization 3 times a year on the holidays (Memorial Day, Labor Day and Thanksgiving). All of the appropriate “Fact Sheets” that are affected by these changes are being updated. If you have any questions on the law or anything else regarding the new recommendations, call our Helpline on Monday thru Thursday from 10 a.m.–12:30 p.m. at 516–228–0426, extension 7.

The New Recommendations

Lawns should be fertilized 2 to possibly 3 times a year depending on grass type and desired results. The optimum times to fertilize a lawn are late May (around Memorial Day) and early September (around Labor Day). Apply one (1) pound of actual nitrogen per thousand square feet per application for a total of two (2) pounds of actual nitrogen per thousand square feet per year. You will sometimes see the recommendation written as 1#N/1000sq.ft./application.

Use a slow or controlled release fertilizer. Early spring applications at full rate are not usually recommended as this can result in excessive shoot growth at the expense of root growth. Over–fertilized spring fed lawns are more stressed going into hot, dry summers because their roots have grown less.

On some occasions spring fertilization is necessary depending on the condition of the lawn after the winter to promote increased turf density. An increase in turf density allows the grass to compete for space before summer weeds emerge. Ideal spring fertilization rates would be one quarter to one half full rate or 1/4 – 1/2 pound of actual nitrogen per 1000 square feet.