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Fertilizer Fact Sheets

Fact Sheet: Fertilizer Application Timing

KEY POINTS

Careful fertilizer use is important to protect Long Island's water:

  • Pay attention to soil temperatures - grass must be active to benefit from fertilizer.
  • When using slow release fertilizer allow adequate time for grass to absorb the fertilizer before going dormant in the fall.
  • Apply fertilizer only within dates

Overview

Grass can only absorb fertilizer when it is actively growing. Turfgrass plants stop growing - become dormant - when the soil temperature is below 55°F or in the heat of the summer. Cooler soil temperatures also slow the bacterial action that makes some fertilizer nutrients available to the plants. Fertilizer not absorbed by grass leaches into the subsoil and makes its way into groundwater or runs off into surface water, where it acts as a pollutant, contributing to algal blooms and poor water quality.

Spring Application

The University of Connecticut Turfgrass Nutrient Management Bulletin of 2017 (PDF) (1 MB) describes why the timing of nitrogen applications is important to reducing nitrogen losses: Allow turfgrasses to come out of dormancy in the spring before applying fertilizers. Soils should be allowed to warm and dry out before fertilization…Application of nitrogen fertilizers to dormant or semi-dormant turf in the spring, increases the risk of nitrogen loss.

In the spring, soil temperatures on Long island (link leaves DEC website) typically reach 55°F only by April 1. In the absence of measuring soil temperature mid-April is a good start date if fertilizer is found to be necessary.

Summer Application

Fertilizer application is not recommended during the summer when heat and drought stress turfgrass leading to low or no growth and minimal if any need for fertilizer.

Fall Application

The University of Connecticut Turfgrass Nutrient Management Bulletin referenced above also speaks to fall applications: There is evidence to show that fall fertilization constitutes a high risk for nitrate leaching and that this risk increases with later fall applications. This is because lawns become dormant and stop absorbing fertilizer and microbial activity is reduced when soil temperature drops below 55°F in the fall.

On Long Island, soil temperatures (link leaves DEC website) typically do not drop below 55°F until sometime in November4. Plant growth, however, slows down earlier in the fall. Consequently, fall fertilizer applications, especially slow release fertilizers, must be applied early enough for the plants to absorb and utilize it before they go dormant. Suffolk County's Healthy Lawns Clean Water guidance suggests early September for fall fertilizer application.

Application Timing Restrictions

New York and Long Island counties have restrictions on fertilizer application timing designed to make sure the fertilizer is absorbed by the grass and does not end up polluting the environment.

  • New York State - no application between December 1 and April 1
  • Nassau County - no application between November 15 and April 1
  • Suffolk County - no application between November 1 and April 1

Apply Fertilizer Carefully

  • Grass must be actively growing to benefit from fertilizer. In the absence of measuring soil temperature, mid-April is a good start date if fertilizer is found to be necessary.
  • Application in early September should allow adequate time for grass to absorb the fertilizer before going dormant.
  • Apply fertilizer only within dates set by state and local regulations.

Workgroup Survey Responses

A workgroup of stakeholders was convened by the NYS DEC. The group met and was surveyed by DEC about current fertilizer use and ways to improve proper fertilizer use on Long Island. Survey respondents, through their work group responses, agreed that fertilizer application is most effective when attention is paid to plant and soil science (i.e., requirements and soil temperature).

Printable PDF of Fertilizer Application Timing (PDF, 420 KB)

Fact Sheet: Managing Irrigation

KEY POINTS

Careful irrigation is important to protect Long Island's water:

  • Don't overwater. Pay attention to the amount of rain your area has received before watering.
  • If you have an irrigation system in place, ensure it is properly set up to avoid over watering.
  • Nutrient leaching occurs frequently during periods of slow turf growth. During these times, reduced irrigation can help limit leaching.

Overview

Water is necessary for plant growth and properly managed irrigation can help maintain your lawn's health. However, Suffolk County's Healthy Lawns Clean Water website states that watering your lawn in excess of what it needs can harm the environment and the plants themselves.

Water and Your Lawn

Long Island receives an average of 3-5 inches of rainfall (link leaves DEC website) a month during the growing season1 and according to Cornell Cooperative Extension, Long Island lawns (link leaves DEC website) generally only need 1-2 inches of water per week. Consequently, most lawns will need little to no irrigation.

Watering in excess of the soil's infiltration rate can lead to grass diseases, such as root rot, and accelerated weed growth. Irrigation that exceeds uptake by plants and microbes increases the movement of nutrients like nitrogen and other contaminants into groundwater and surface waters.3 A sure sign of overwatering is water pooling on flat lawn surfaces.

If irrigation is desired, the amount and frequency will vary based on grass species, temperature, soil type, humidity, time of year, hours of sun exposure, and other factors.3 Additionally, irrigation methods themselves can influence how turf grows. Cornell Cooperative Extension recommends deep, thorough watering once, or at most twice, per week to encourage extensive root growth for more efficient water and nutrient capture and a healthy lawn.3

Nutrients and Irrigation

Rain water and irrigation move nutrients into the soil and root zone (link leaves DEC website) to make them available for uptake while the plant is growing. During periods of slow turf growth (link leaves DEC website), nutrients are taken up more slowly and leaching to groundwater is more likely. Those times include in the early spring and late fall when soil temperatures are too cool for plant growth and microbial activity, as well as mid-summer when drought causes plants to go dormant. While fertilizing is not recommended during those times, reduced irrigation will also help reduce nutrient leaching.5

How You Can Irrigate to Enhance Your Lawn and Protect the Environment?

  • Ensure the system includes a rain sensor, soil moisture sensor, or evapotranspiration-based controller.
  • To avoid water loss to evapotranspiration, irrigate only between the hours of 6:00 - 10:00 pm or 4:00 - 8:00am.
  • Set the system to deliver about an inch of water one or at most two days per week with adjustments made for weather.
  • Make sure your system is functioning correctly by doing regular maintenance such as checking for leaks.
  • Abide by any municipal restrictions.

Workgroup Survey Responses

A workgroup of stakeholders was convened by the NYS DEC. The group met and was surveyed by DEC about current fertilizer use and ways to improve proper fertilizer use on Long Island. Survey respondents, through their work group responses, agreed that while there were no specific questions pertaining to watering or irrigation management on the surveys, the importance of irrigation at the right time and in the right amount to reduce nitrogen runoff and leaching should be recognized and stressed.

Printable PDF of Managing Irrigation (PDF, 380 KB)


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