PPDL Picture of the Week

December 3, 2018

Fall Fertilization of Home Lawns: Is it too late?

John Orick, Purdue Master Gardener State Coordinator, Department of Horticulture and Landscape Architecture‚Äč

A healthy lawn requires supplemental nutrients delivered through fertilizer applications to maintain growth. Applying fertilizer at the appropriate time is critical to promoting a healthy lawn and maximizing the benefits of nutrients. Purdue turf specialists recommend that homeowners and turf managers apply 50-60% of the total annual nitrogen (delivered through lawn fertilizers) to cool-season turfgrasses (such as Kentucky bluegrass, fine fescues, tall fescue, perennial ryegrass, etc.) between late-summer and mid-fall (e.g. Labor Day through Halloween) to promote root growth, production and storage of carbohydrates, recovery from damage, green color, and turf plant density to compete with weeds (see photo). But, how late into the season is too late to fertilize a turf area?

During late-fall, homeowners and turf managers should be sure to apply products containing mostly a soluble nitrogen source to actively growing turf. Therefore, avoid fertilizing turf when the soil is frozen or turf is dormant due to drought or cold temperatures. On November 30, 2018, the soil temperature in a turf area near the Purdue Horticulture Building was 43 degrees F (see photo). The forecast calls for temperature in the 50's (degrees F) for the next couple days but then temperatures in the Lafayette area are forecasted to drop into the 40's and even into the 30's in the next week or so. As air temperatures drop so will soil temperatures. Plant growth slows when the soil temperature drops below 40 degrees F, which means turfgrass plants will likely not be able to effectively utilize nutrients applied through fertilizer applications.

So, is it too late to fertilize turf? When planning a late fall fertilizer application, homeowners and turf managers in our region are encouraged to check for frozen soil, measure soil temperatures (when possible), and look at the weather forecast for temperature trends before making a decision to fertilize turf areas in late-fall. In general, a good rule of thumb is if Halloween has come and gone then put the fertilizer spreader away.

For more information on proper lawn fertilization, seeding, and other lawn care practices, visit www.turf.purdue.edu.

Resources:

Fertilizing Established Cool-season Lawns: Maximizing Turf Health with Environmentally Responsible Programs (AY-22-W), https://www.extension.purdue.edu/extmedia/AY/AY-22-W.pdf

Purdue Turf Fertilizer Calculator https://turf.purdue.edu/fertilizerCalculator/index.html

Facts About Phosphorus and Lawns (AY-334-W) https://www.extension.purdue.edu/extmedia/AY/AY-334-W.pdf




Click image to enlarge

The lawn on the left is unfertilized while the lawn on the right received regular fertilizer applications including in the fall. (Photo by Aaron Patton)

Soil temperature on November 30, 2018 in turf area surrounding the Purdue University Horticulture Building, West Lafayette, IN. (Photo by Aaron Patton)