About this time of year, it is common to hear ads on the radio for various lawn care services and products. Often, the recommendation is “Fertilize now for a healthy lawn!”
This is not a good recommendation for most lawns in the Sandhills. Many radio stations broadcast out of the Piedmont, where often lawns are fescue. Fescue is a cool season turfgrass; it’s active growing occurs in the fall and spring, and it is essentially dormant in the summer. Fescue needs to be fertilized in the fall to jump start active growth. By contrast, in the Sandhills most turfgrasses are warm season grasses: centipede, Bermuda, zoysiagrass, and St. Augustine. These warm season grasses are active as weather warms in spring, going dormant in the fall as cooler temperatures arrive. Warm season grasses should be fertilized in the spring — although an important exception is centipede grass, which should be fertilized the first week of June.
So, don’t fertilize — with a fertilizer containing nitrogen — warm season turfgrass in the fall. However, fall is a good time to assess the health of your lawn: is it lush and green; or thin, with bare spots, or lots of weeds? If you aren’t happy with your lawn’s condition, put in motion a plan to get your yard in shape for the next growing season. A critical step is taking a soil sample. Our soils are naturally quite acidic, and even centipede, the most tolerant of acidic soil of all turfgrass, often needs to have the soil pH raised in order to perform optimally. The North Carolina Department of Agriculture provides free soil tests through its lab, except from the end of November until April 1, when it is $4 per sample. Fall is a great time to sample, as you can beat the sample charge and if lime is needed, fall is the best time to apply it. Lime needs between four and six months to modify soil acidity, so a fall application will correct soil pH by the time the grass begins to grow again in the spring.
Not only can the soil report recommendations give you the amount of lime needed to raise the soil pH sufficiently, it can also give you levels of other key plant nutrients. Phosphorus and potassium are two other important plant nutrients that may be present in the soil. Sandhills soils are naturally low in phosphorus, however if fertilizers such as 10-10-10 (or animal manures) are commonly used, phosphorus levels are usually adequate. Once phosphorus is added to the soil, it does not leach readily and is typically present for turfgrass uptake. Low soil pH, however, can bind phosphorus and it can become plant unavailable, even if it’s present. The soil report will show the level of phosphorus in the soil and how much, if any, phosphorus needs to be added. Phosphorus is important for strong root development in turfgrass.
Potassium is another critically important plant nutrient, and often deficient in Sandhills soils. It leaches readily, so unlike phosphorus, potassium (or Potash) must be added regularly – at least annually. Potassium is important for drought tolerance in plants, and it can also improve cold tolerance. Small pores in plant leaves, called stomata, regulate plant transpiration (the release of water vapor) and intake of carbon dioxide. This process is directly driven by the presence of potassium ions, so potassium deficit will strongly impact plant health.
There is one more important reason to focus on improving the health of your turfgrass. Often people call me with weed problems, with the concern that the weeds are “choking out the turfgrass”. There are few plants more competitive than vigorous turf grass. Weed problems are an indication that the turfgrass is not as healthy as it should be, and the weed problem will not go away until the conditions that are weakening the turfgrass are rectified. This usually goes back to soil pH and fertility issues.
As fall sets in, spring may seem a long way away. However, some work now can help your turfgrass be lush and green by next summer.
Paige Burns is assistant horticulture agent at the N.C. Cooperative Extension’s Richmond County Center.