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Irrigation Association of New York

Recommendations for Fertilizer Nitrogen Applications on Residential and Commercial Turfgrass


  • All equipment used to spread fertilizer should be calibrated to a single application rate of a maximum of 0.6 pounds of total nitrogen per 1,000 square feet at least once annually or each time fertilizer products are changed.


Spreaders must be properly calibrated if they are to deliver fertilizers to the turf at correct application rates. If calibration is not done or done incorrectly, the product may be misapplied and either too much or too little of the product will reach the turf.15 Calibration directions are included on spreaders used by professionals and spreaders marketed to individuals should be able to be readily calibrated to a rate of 0.6 pounds of total nitrogen per 1,000 square feet.



  • Irrigation systems should be operational and ready for use prior to any fertilizer application. Systems should be able to provide an application of ¼ inch of water to fertilized areas within 24 hours of application, if no rainfall has occurred.
  • Systems should be equipped with either a rain sensor, moisture sensor or an EPA Water Sense approved smart controller or any combination of these devices.
  • Systems should be in proper working condition, such as having no broken or malfunctioning equipment and work to the capabilities as designed.
  • As consistent with Nassau County Regulations, systems should not run between the hours of 10:00 am and 4:00 pm daily; except where new sod/seed lawns are being grown and/or where an application of pesticides requires immediate watering as directed on the label.
  • Systems should not provide more than 1 ½ inch of supplemental water per week.
  • Systems should not run during rainfall.


Making sure irrigation systems are in proper working order will help reduce overwatering lawns, which can lead to leaching nitrogen into the groundwater. Fertilizer manufacturers and scientists both recommend light watering after fertilizer application.16 Irrigation control technologies can significantly reduce overwatering by applying water only when plants need it. 17 In the Nassau County Ordinance No. 248-A-1987, there is a prohibition against paper writings irrigation between 10:00 am and 4:00 pm.


15 PennState Extension. Calibrating Your Fertilizer Spreader (2018).

16 Suffolk County Department of Economic Development & Planning. Healthy Lawns Clean Water. “For Homeowners: Fertilizer Application Tips.”

17 US EPA. Water Sense. “Water Sense Labelled Irrigation Controllers.” (2017) .

Long Island Nitrogen Action Plan