Improper irrigation of lawns results in wasted water, added cost, and unhealthy plants. Water should be applied only when a reasonable portion of the lawn shows signs of moisture stress. A dark bluish-gray color; footprints that remain some time after walking; and wilted, folded, or curled leaves are indications that it is time to water. A delay in watering at the first signs of wilt will generally not result in permanent damage unless the turf is being allowed to go dormant. If irrigation is not available or desirable, then an alternative to irrigating is to allow the turf to go semi-dormant to dormant. Tall fescue, bermudagrass, and zoysiagrass are tolerant of drought if allowed to go dormant.
General watering recommendations include the following:
Take certain precautions if you do not plan to irrigate throughout the summer. Slowly ease a lush, actively growing lawn into dormancy. This can be accomplished by allowing the drought stress symptoms to appear between infrequent irrigation cycles, by mowing high, and by not over-fertilizing with nitrogen. Brown, withered leaves are normal signs of dormancy, so do not be alarmed by them. If the lawn is conditioned for this stress and has a reasonable level of maintenance, it should survive without permanent damage. Most turfgrasses can withstand 3 to 6 weeks (or longer) without rainwater or irrigation and exhibit minimal or no damage, depending on the situation.
In the absence of rain, water dormant lawns with a minimal amount (about 0.25 inch) every three weeks to keep the growing points hydrated. It is difficult to maintain vibrant green color in cool-season grasses during the summer. Irrigation helps maintain color, but may also increase the risk of disease. For this reason, it is particularly important that cool-season grasses not be overwatered.
Use either a rotary (centrifugal) or reel (cylinder) mower. The reel mower is preferred if grasses are cut to less than 1 inch.
A soil test should be made at least every two to three years to determine the amounts of lime, phosphorus, and potassium needed by your established lawn. See page 11 of Carolina Lawns for the method used to obtain a good soil sample. A complete fertilizer with an n-p-k ratio of 4:1:2 or 4:1:3 can be used in lieu of a soil test, but it is a poor substitute.
Determine the amount of fertilizer, ratio of nutrients or fertilizer elements, and time of application based on the grasses being grown. See Carolina Lawns Table 6a, b, or c, depending on your region, to determine the amount of nitrogen fertilizer to apply and the time of application.
Avoid any nitrogen fertilization of cool-season grasses, such as tall fescue, after the February application until September for the central piedmont.
If one additional application of nitrogen is made between these dates to improve the color, the rate should not exceed 0.5 pound of nitrogen per 1,000 square feet. This nitrogen should be applied in the central piedmont no later than April 15 (two weeks earlier in the coastal plain and two weeks later in the mountains). This application will not improve the longevity of tall fescue but will enhance its green color.
The application of high rates or repeated low rates of nitrogen to cool-season grasses in the spring or summer greatly increases the severity of brown patch (Rhizoctonia species), which can kill the grass and should be avoided. If spring or summer nitrogen applications, or both, are applied to tall fescue, fungicide applications may be necessary to reduce disease symptoms.
Avoid fall or winter applications of nitrogen to reduce winter injury.
Lime. Most soils in North Carolina are acidic and often require the application of lime to sweeten the soil. For most turfgrasses, except centipedegrass, soil pH should be between 6.5 and 7.0 for optimum nutrient availability. Centipedegrass requires more acidic soil with a pH close to 5.5. Lime may be put on any time during the year. Winter is usually best, however, because there is less traffic. Gentle winter rains minimize runoff, and alternate freezing and thawing help incorporate lime into the soil.
Fertilizers and lime should be applied uniformly with a centrifugal (rotary) or drop-type spreader. Apply half the fertilizer in one direction and the other half moving at right angles to the first pass to ensure uniform coverage Carolina Lawns (see Figure 3).
Soils that are subject to heavy traffic are prone to compaction. Coring will alleviate this condition. Use a device that removes soil cores. Chop up the cores, and, if possible, distribute them by dragging with a span of chain-link fence or a mat.
Coring should be accomplished when the lawn is actively growing so that it can recover from any injury. Core cool-season grasses in fall or early spring. Core warm-season grasses in late spring or early summer. Some lawn care and landscape companies offer coring service if rental equipment is not available.
Sod-forming grasses, such as Kentucky bluegrass, bermudagrass, zoysiagrass, St. Augustinegrass, and centipedegrass, tend to build up thatch when they are heavily fertilized and watered. When thatch exceeds 0.75 inch, lawns should be power raked and cored.
A light power raking is better than trying to remove too much debris at one time. When not excessive, thatch buildup can be removed from warm-season grasses by cutting as closely as possible at spring green-up and then raking by hand. To avoid seriously injuring the lawn, a 3-inch blade spacing is required to remove thatch from centipedegrass and St. Augustinegrass. Some lawn care and landscape companies have specialized equipment and offer power raking services.