Uniform application of nutrients throughout the top 6 to 8 inches of the root zone is very important. Unless the entire rooting zone has a consistent pH and adequate nutrients and is sufficiently porous, turfgrass roots will struggle to occupy this zone and may die during periods of stress. Applications to the surface have little effect beyond the top 2 or 3 inches, while turfgrass roots may extend more than 8 inches into the soil. Nutrients and lime that are relatively immobile in the soil are best applied following core aeration.

Trees and shrubs may need to be pruned to reduce shade and improve air movement. Shade and reduced air movement cause the relative humidity and moisture levels to remain high for long periods, promoting conditions favorable for disease. Eventually, either the trees or the turfgrass may need to be removed because it is difficult to maintain a good lawn in the shade.

Improper watering of lawns results in waste of water, added cost, and unhealthy turfgrass. The following watering practices are essential to maintaining an established lawn.

1. Water only when lawns show signs of moisture stress. Indications that the lawn needs water include a dark, bluish-gray color; footprints that remain in the turfgrass for some time after walking through it; and wilted, folded, or curled leaves. Unless the turf is being allowed to go dormant, a delay in watering at first signs of wilt can result in permanent damage to turfgrasses.

2. Adjust any automatic irrigation system to account for rainfall so that the lawn is not overwatered.

3. Water in the early morning to reduce the risk of disease, water loss through evaporation, and uneven water distribution due to wind. Also, the demand for water by industry and municipalities is usually low at this time.

4. Water established lawns to a depth of 6 to 8 inches to encourage deep rooting. Usually, applying 1 inch of water per week will suffice. Cans or a rain gauge can be used to determine how much water is being delivered during a specified period. It requires 640 gallons of water to supply 1 inch of water to 1,000 square feet of lawn.

5. Match watering technique to soil type and site slope. Apply water to clay soils until the point that runoff is about to occur; wait 30 minutes for the water to be absorbed and rewater until the desired depth or amount is achieved. This same technique can be used for slopes and compacted soils. Few lawns established on clay soils can absorb more than 0.5 inches of water per hour. Sandy soils require more frequent watering; 0.5 inches of water every third day is usually sufficient.

Equipment

Generally, rotary mowers are used on landscape turfgrasses. Reel mowers may be used for some turfgrasses when low mowing heights (less than 1 inch) are desirable. The cleanest cut and best-quality mowing are achieved when the mower blades are sharp. Dull mower blades reduce lawn quality by tearing the turfgrass instead of cutting cleanly, creating many ragged leaf ends that quickly wither and bleach and provide easy ports of entry for disease. Using a sharp mower is especially important for turfgrasses that are difficult to mow, such as zoysiagrass and bahiagrass. A properly sharpened and balanced mower blade will also reduce mower vibration, lengthen mower life, and reduce fuel consumption by as much as 22%.

Frequency

To maintain a high-quality lawn, mow often enough that no more than one-third of the leaf height is removed with each mowing. The frequency of mowing is determined by the desired turfgrass height and by the amount of growth. Growth rate depends on temperature, fertility, moisture, sunlight, and the natural growth rate of the turfgrass. In most instances, this may amount to weekly mowing. Suggested mowing heights are presented in Table 1. If the lawn gets too tall during wet periods, wait until the turfgrass is dry and then raise the mowing height to remove no more than one-third of the leaf. Gradually return to the proper height of cut by mowing more frequently (wait one or two days between mowings) but at gradually lower heights until the proper height is achieved.

Most organic fertilizers contain between 3% and 10% nitrogen. However, this nitrogen is usually slow to release, as it is typically tied up in complex organic molecules. The nitrogen is released as soil microbes break down the molecules for food and as the molecules slowly dissolve in water. It is called "slow release" because it may take several weeks or months to become available to the plant. As such, growth response by the turfgrass plants may be gradual over a period of one to two months. When fertilizing with organic fertilizers, expect slower greening in the spring and extended growth in the fall if temperatures remain adequate for growth. Extended dry or cold periods may delay release of nitrogen from organic fertilizers.

To maintain pH in the range of 6.0 to 6.5 (5.5 for centipedegrass) and to prevent nutrient deficiencies, test the soil every two to three years. For established lawns, the recommended sampling depth is 3 inches. Lime may be applied any time during the year; however, winter is often the best time of year to lime because there is less traffic, gentle winter rains minimize runoff, and alternate freezing and thawing cycles help incorporate lime into the soil.

Nitrogen (N) requirements cannot be determined by a soil test. Use Table 5 for determining the amount and timing of N applications. To decrease susceptibility of turf to pests and environmental stress, do not apply high-nitrogen fertilizer to cool-season turfgrasses in the late spring or summer or to warm-season turfgrasses in the fall or winter.

The availability of organic fertilizers is increasing in response to a growing demand. Organic fertilizers, as defined in this publication, come from animal, plant, or mineral sources and contain no chemically formulated additives. They are commonly made of livestock waste, municipal waste, bone meal, dried blood, manures, vegetable meals, feather meal, fish scraps, and crushed minerals. Some products claim to be "organically based" and "natural based," but these contain artificial chemical formulations of either nutrients or pesticides. Careful inspection of the label is the best way to determine the organic status of the product. Table 6 provides more information on organic sources of fertilizers.

Timing

To keep turfgrass healthy enough to withstand weeds, insects, and diseases, it is important to fertilize the plants when environmental conditions are right for their optimum growth. A soil pH in the range of 6.0 to 6.5, adequate moisture and oxygen, and temperatures above 50°F favor microbial activity and enhance nutrient release. Do not fertilize when the turfgrass is not growing and cannot take up the nutrients. Nutrients not used by the turfgrass will be available to weeds, and stimulating shoot growth at the wrong time increases susceptibility to disease. Table 5 suggests basic fertilization schedules for different turfgrasses in North Carolina.

Soils that are subject to heavy traffic are prone to compaction. Compacted soils reduce drainage, increase runoff, and inhibit root growth. Aerifying helps to alleviate compaction.

1. Use a device that removes soil cores, and be sure to aerify after a soaking rain or irrigation to ensure that the soil is penetrated to a depth of 2 to 3 inches.

2. Chop the cores with a mower and, if possible, distribute them by dragging with a chain-link fence.

3. Aerify when the lawn is actively growing so that it can recover from any injury. It is best to core cool-season turfgrasses in the fall. Coring cool-season turf in the spring may promote unnecessary weed growth. Core warm-season turf in late spring or early summer.

4. Some lawn care and landscape companies offer coring service if rental equipment is not available.

Sod-forming turfgrasses such as Kentucky bluegrass, bermudagrass, zoysiagrass, St. Augustinegrass, and centipedegrass tend to build a thatch layer when they are heavily fertilized and watered. When thatch exceeds 0.5 inches, lawns should be dethatched. Thatch can be reduced by using various tools, including hand rakes, verticutters, and dethatchers.

1. Make several light power-rakings instead of trying to remove too much debris at one time.

2. Small accumulations of thatch (less than 0.75 inches) can be removed from warm-season turfgrasses by mowing as low as possible at the time of spring green-up and then raking.

3. To avoid injury to centipedegrass and St. Augustinegrass, use 3-inch blade spacing on a power rake.

4. Some lawn care and landscape companies have specialized equipment and offer power-raking services.