Fall Fertility Strategies for Virginia’s Homelawns

Loading player for /content/dam/ext_vt_edu/topics/lawn-garden/turfgrass/turfandgardentips/tips/fall-fertilization-2007.mp3...

There are some definite do’s and don’ts when it comes to fertilizing Virginia’s homelawns in the fall, primarily in terms of appropriate timing and fertilizer rates for the many grasses grown in this state. This podcast discusses fertility programs for cool- and warm-season grasses that will promote the health and quality of your turf, as well as protect the environment. 

There are some definite do's and don'ts when it comes to fertilizing Virginia's homelawns in the fall, primarily in terms of appropriate timing for the many grasses that are grown in this state. This podcast discusses fertility programs for cool- and warm-season grasses that will promote the health and quality of your turf, as well as protect the environment. 

Timing is everything. Fall is the OPTIMAL time to aggressively fertilize cool-season turfgrasses (bluegrasses, fescues, and ryegrasses). Cooling (but still warm) temperatures and shorter days are ideal conditions to maximize root growth and food storage in cool-season turfgrasses. The period from Sept. through Nov. is the time of year to deliver  of the annual N fertilization requirement, so don't miss the chance to optimize your turf quality as well as its health. For warm-season grasses (bermudagrass, zoysiagrass, centipedegrass, and St. Augustinegrass), fall is a time to prepare the turf for winter dormancy. Refrain from additional N applications and ensure your soil test indicates appropriate pH, P, and K levels as you "put the turf to bed" for its winter nap. 

Never forget the value of soil testing. Anytime is the right time to soil test, but fall and winter months are ideal periods to modify your soil during a period when plant growth is significantly slowing. If you have not done so within the past 3 years, perform a soil test to bring your lawn up to speed in terms of pH and major nutrient levels. You can use your local VCE office for the materials and assistance with the test, or you can arrange to have a test done through a private lab through a local lawn and garden center. A full discussion on the steps in conducting a test and interpreting the results is available in a Breeze presentation entitled "Soil Testing for the Lawn and Landscape" found through the VTTURF.com website. 

Fertilizer choices. There are lots of things to consider in fertilizer selection. First, what's in the bag? Left to right, the numbers on the fertilizer bag indicate the % of nitrogen, phosphate, and potash on a weight basis. Hence, a 50 lb bag of 10-10-10 contains 5 lbs each of N, phosphate, and potash (and even for liquid fertilizers, the analysis still represents % by weight). Next, look at the fertilizer label for some additional information on precisely what other nutrients are contained in the bag, and perhaps most importantly, what type of release characteristics the N has. If the source contains slow release N, you will see a reference to a certain percentage of WIN (water insoluble nitrogen) on the label. Many synthetic turf fertilizers purchased right off the garden center shelves contain between 20-30% WIN. These predominantly water soluble sources can be safely applied at levels up to 1 lb N/1000 sq ft. according to the grass and the season. Most organic manure-based fertilizers can contain up to 75-85% WIN. These materials can be applied at levels up to 1.5 lbs N/1000 sq ft and will provide very sustained growth and color responses with minimal potential for environmental impact. However, most are very low analysis (only 5-8% N by weight) and very large amounts of product are needed if trying to apply normal N-use levels. Used properly, almost any source of N can promote desirable turf responses with little if any environmental impact-it's the user, not the fertilizer, who creates the problems. Recommended N levels and timing. The Virginia Department of Conservation and Recreation has an excellent tri-fold brochure entitled "Keep Your Lawn Green and the Bay Clean" that details recommended N levels and timing for our major lawn grasses. Essentially, the information reemphasizes the facts that N applications are highly beneficial on cool-season grasses in the fall and only minimal N should be applied in the spring. Warm-season grasses should be aggressively fertilized after complete greening in mid-late spring through mid-summer. Seasonal N totals range from 2-4 lbs N/1000 sq ft depending on the grass species. 

What about other nutrients? Any nutrient that is deficient will limit growth of our turf and landscape plants, so apply them as indicated by soil tests. However, it is very important that we pay attention in particular to phosphorus applications since it is known to be a major contributor to water pollution when mis- and/or over-applied. The days of using a complete fertilizer such as 10-10-10 should be over when we have fertilizers specifically developed for turf use that emphasize N and minimize phosphorus. Standard turf fertilizers will have N labels of 23-30%, 3-5% phosphate, and 5-15% potash. A popular fertilizer analysis for many fall cool-season programs that is on the lawn and garden center shelves is a "Winterizer" formulation of 22-3-14. This is good, but better still, would be to use a N-only fertilizer source (for example urea, 45-0-0) when you have no need for phosphate or potash. For warm-season grasses, research has shown that ample soil potash levels promote winter hardiness. (Note: K is required by cool-season grasses, but research has shown that the most important component of winter performance in these species is an appropriate N fertility program.) However, in the 22-3-14 "Winterizer" formulation just mentioned, there would be excessive N applied to the turf. If your soil test indicates the need for potash, you can purchase potash-only sources such as 0-0-50 and 0-0-60 at most specialty lawn and garden centers. Remember if your turf needs potash, apply it BEFORE the turf goes dormant. Think about "non-target" effects of your fertilizer. What I mean here is to consider where your fertilizer ends up after the application. 

Your turf serves as an excellent filter of chemicals, nutrients, and water, but it is obviously important to apply these resources TO the turf. If your fertilizer ends up on the street, sidewalk, or patio, take an additional few moments to sweep or blow the fertilizer back into the turf canopy. Any granular material sitting on a hardscape is only minutes away from entering our lakes and streams when we have our next rainfall event. I hope this information and the accompanying handout and extension publications make it easier for you to make informed decisions in fall fertilization. 

For further information, please consult your local Virginia Cooperative Extension office. Finally, how are we doing on these podcasts?! Please take a few moments and complete our survey on the podcast webpage so that we know what you think about our efforts and how we can improve them to better serve your needs.