Gil Landry

Source(s): Gil Landry, PhD., Coordinator – UGA Center for Urban Agriculture, The University of Georgia.

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Grass, like all other plants, requires nutrients for growth. Unfortunately, most soils in Georgia are naturally not rich in all these nutrients. Therefore, apply fertilizers to supply those elements not present in the native soil.

The three macronutrients are: nitrogen (N), phosphorus (P) and potassium (K). Of these, nitrogen is required in largest quantities, potassium second and phosphorus third. Most home lawn fertilizers sold in Georgia contain these three macronutrients in the largest amounts.

Fertilization programs should be based on turfgrass requirements, soil tests, maintenance practices, and desired appearance. For example, the bermudagrasses have a larger nitrogen requirement than most turfgrasses. A soil test is needed to determine the supply of phosphorus and potassium in the soil. When grass clippings are removed, the amount of fertilizer needed may be doubled. Increased irrigation on sandy soils will also increase fertilizer requirements. Finally, a higher quality, dark green lawn will require more nitrogen, as well as more clipping and watering.

Some considerations for determining what fertilizer material to use are ease of handling, price and availability. Since nitrogen is the key nutrient for lawn grasses, it is important to understand the differences in the nitrogen sources. There are three types of nitrogen carriers:

1. synthetic inorganic,
2. organic, and
3. synthetic organic.

Synthetic Inorganic Nitrogen Carriers

Ammonium nitrate and ammonium sulfate are examples of synthetic inorganic nitrogen carriers. Some advantages are:

• rapid initial plant response,
• minimum temperature dependence, and
• lower cost per unit of nitrogen.

Disadvantages are:

• subject to loss by leaching in the nitrate form,
• high foliar burn potential, and
• a rapid surge in growth.

Natural Organic Nitrogen Carriers

This is nitrogen bound in complex organic compounds such as decayed living matter, sewage sludge, manures, and bone meal. Nitrogen released from these compounds is dependent upon microorganisms to break down organic matter. Advantages are:

• low foliar burn potential,
• longer lasting,
• very little leaching and
• more even growth of grass.

Some disadvantages are:

• low analysis, thus requiring a great deal of bulk,
• slow response and

at low temperatures, very little nitrogen is released through microorganisms activity.

Synthetic Organic Nitrogen Carriers

These nitrogen carriers are synthesized in the laboratory and can be divided into two groups:

1. primarily water soluble compounds and
2. primarily water insoluble compounds.

The water soluble compounds, such as urea, resemble the synthetic inorganic carriers in their activity, while the water insoluble compounds, such as urea formaldehyde, resemble the natural organic carriers in their activity.

Most mixed fertilizers contain more than one source of nitrogen. 12-4-8 is one example of a mixed fertilizer containing several different sources of nitrogen.

Guaranteed Analysis: 12-4-8

• Total Nitrogen(N) = 12%
  • 6.50% Ammoniacal Nitrogen
  • 1.00% Nitrate Nitrogen
  • 0.90% Other Water Soluble Nitrogen
  • 3.60% Water Insoluble Nitrogen
• Available Phosphate Acid(P205) = 4%
• Soluble Potash(K20) = 8%
• Total Available Plant Food, Not Less than = 24%

Fertilizer Programs

Applying fertilizer at the right time is as important as knowing what fertilizer to apply. Generally, spring and fall fertilization with a complete fertilizer (contains N, P and K) is recommended for the warm-season grasses. The spring application should be made about the time the grass begins to green-up and grow. The fall application should be made about 6 weeks before the average first frost date. Normally, the first frost date ranges from the latter part of October in the piedmont area to the end of November on the coast.

In the absence of soil test recommendations, the complete fertilizer used can range from 16-4-8 to 10-10-10 and 5-10-15, etc. Most of the warm-season grasses require 3 to 7 pounds of nitrogen per 1000 square feet per year to remain hardy and attractive. This fertilizer is usually applied in 3 to 5 applications during the growing season. A typical example would be 10 pounds of 12-4-8 per 1000 square feet in early spring when green-up begins, 10 more pounds in mid-summer, and 6-8 weeks before the average first frost date. This gives a total of 3.6 pounds of nitrogen.

Proper fertilization of centipedegrass is very important to its survival. Most people tend to over-fertilize centipede. One pound of nitrogen per 1000 square feet per year is ample nitrogen on most centipede lawns. On sandy soils in high rainfall areas, 2 pounds per 1000 square feet per year may be needed. Apply 5 pounds of 12-4-8 per 1000 square feet in early spring. If a second application is needed, apply 5 pounds of 12-4-8 per 1000 square feet in early August. Never apply lime to a centipede lawn unless soil tests show that the pH is extremely low. If the grass shows signs of iron chlorosis, which is observed by the yellowing of leaves, apply ferrous sulfate at the rate of one tablespoon per 3 gallons of water to each 1000 square feet of grass.

The cool-season grasses, such as tall fescue and Kentucky bluegrass, normally should receive the majority of their fertilizer requirements in the fall. An example of cool-season grass fertilization would be 10-15 pounds of 16-4-8 per 1000 square feet in early September and April. Additional nitrogen or complete fertilizer may be applied in November if desired.

Fertilizer Application

Listed below are some key points to remember when applying fertilizer.

• Don’t apply fertilizer when the grass leaves are wet. This can increase the potential of leaf burn.
• Use a mechanical spreader to distribute the fertilizer. Don’t apply it by hand. Use the two direction application procedure as described for seeding.
• If possible, water all fertilizer applications thoroughly.

Soil Acidity

Another important factor in plant growth is the soil acidity level. This is measured in terms of a pH scale which is graduated from 0 to 14 with 7 being neutral. Any number below 7.0 is considered acid with 5.0 being more acid than 6.0. Any number above 7.0 is considered basic with 9.0 being more basic than 8.0. Most turfgrasses, with the exception of centipedegrass and carpet grass, grow best at a pH of 6.0-6.5. Centipedegrass and carpet grass grow best at a pH of 4.5- 5.5. A pH either too low to too high will reduce the availability of plant nutrients. Therefore, it is very important that a proper pH be maintained.

Lime

If the soil becomes too acid, correct this by applying lime. Use a good agriculture grade of limestone. In most cases, a dolomitic source of limestone should be used. Base all lime applications on soil test results.

More detailed information concerning fertilization can be obtained in the Fertilization for Lawns, Bulletin No. 710.

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Resource(s): Lawns in Georgia

Center Publication Number: 136

Source(s): Gil Landry, PhD., Coordinator – UGA Center for Urban Agriculture, The University of Georgia.

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Proper mowing of turgrasses is essential in order to produce an attractive, healthy lawn.

Proper mowing will have tremendous effect on the appearance of a lawn. Height of cut, frequency of cut and type of mower used are all important factors to consider when mowing a lawn. For the best appearance, a grass should be kept at its best height for growth.

Reel mowers are best suited for the hybrid bermudas and zoysiagrass. The other grasses can satisfactorily be cut with a rotary mower. Dull mower blades tear leaves instead of cutting them, thus producing a poor appearance and increasing the possibility of disease problems.

As a general rule, a grass should be mowed often enough so that you never remove more than 1/4-1/3 of the plant material. Example: If a bluegrass lawn is cut at a height of 2 inches, the grass should be cut when it reaches 3 inches. Removal of too much plant material can shock the grass.

The most damaging mowing practice is a sudden reduction in mowing height. This upsets the balance between the grass leaves and roots. It also gives a scalped appearance and usually injures the grass. If the grass becomes too tall between mowings, gradually reduce the cutting height until the recommended height is reached.

During stress periods, such as summer heat, it is a good idea to raise the height of cut slightly. This is especially helpful to the cool-season grasses because it reduces the stress on the grass. After the stress is gone, lower the height of cut gradually. Grasses in shaded areas should be cut higher than normally suggested for better growth. Raising the mowing height of warm-season grasses as fall approaches will help the grass survive the winter months.

If lawns are properly fertilized and mowed, grass clippings will not promote thatch accumulation. In fact returning the clippings to the soil will recycle plant nutrients and reduce fertilizer requirements. However, on high level maintenance lawns, such as hybrid bermuda and zoysiagrass lawns, clipping removal is advised, otherwise thatch will accumulate. This “thatch layer” (Figure 10) is an accumulation of dead plant material at the soil surface. It prevents penetration of water into the soil, harbors insects and disease organisms and leads to a shallow root grass which is heat, cold and drought susceptible. Many people like a dense soft mat of turf on their lawns, but this is usually a sign of excessive thatch and generally leads to problems.

Scalping or lowering the lawn mower cutting height and mowing the lawn in several directions just prior to spring “green-up” will help prevent thatch accumulation. The removal of this dead plant material will also encourage early spring growth. Centipede and St. Augustinegrass are spread by above ground runners or stolons, thus they should not be scalped as low as the other grasses or they may not recover. For more information on thatch refer to Cooperative Extension Service Leaflet No. 394, Thatch Control in Turf.

 

Mowing Height for Lawn Grasses in Georgia
Grass	Cutting Height (inches)
Tall Fescue	2-3
Bluegrass	2-3
Common Bermudagrass	1-2
Hybrid Bermudagrass	0.5-1.5
Zoysia	0.5-1.5
Centipedegrass	1-1.5
Carpetgrass	1-2
St. Augustine	2-3
Ryegrass	1-2

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Resource(s): Lawns in Georgia

Center Publication Number: 132

Source(s): Gil Landry, PhD., Coordinator – The Center for Urban Agriculture, The University of Georgia.

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Fall is overseeding time. To keep your lawn vibrant and green year-round may take more than one grass. And you can have just that by overseeding your warm-season grass with a cool-season variety.

For successful overseeding, you need to:

• Choose the proper seed.
• Properly prepare for and time the overseeding.
• Carefully maintain the overseeded grass.
• And attentively manage the spring transition back to the warm-season grass.

You also need to maintain a healthy warm-season turf all year. It’s particularly important to keep the soil fertile, relieve soil compaction and prevent excessive thatch.

The proper seed is the grass with the characteristics best suited to your particular needs. Annual ryegrass has fast been replaced by perennial ryegrasses because of their improved quality, stress and pest tolerance and manageability. Use seed treated with fungicides, too, such as Apron or Koban. This is particularly true for early fall, since seedling blight diseases can be a problem at this time.

Overseeding rates in lawns range between 5 and 10 pounds per 1,000 square feet. Use high-quality, “Certified” (blue tag) seed that’s free of annual bluegrass (Poa annua) to maintain weed- free turf. The 10-pound rate provides a fast stand for fall use. The 5-pound rate provides a thinner stand that doesn’t provide much coverage until spring.

The right seeding rate depends on how you want it to look and how much traffic the turf will bear. Higher-traffic areas need higher seeding rates. However, higher seeding rates may also mean a more difficult spring transition.

Proper timing results in a gradual transition from the warm-season turf to the cool-season turf and back again. Some common indicators for timing include:

• Soil temperatures at a 4-inch depth approaching 75 degrees Fahrenheit.
• Night temperatures consistently in the 50s.
• Average midday temperature below 70, or two to four weeks before the average annual first killing frost.

The best way to make the actual overseeding successful is to get good soil-to-seed contact. Seedbed preparation generally consists of close mowing or scalping, with some light vertical mowing, and sweeping or vacuuming up the loose plant debris.

Generally, the more the turf is opened, the better the establishment rate, but the more competitive the cool-season turf will be in the spring. Seeds that germinate in thatch or above the soil are more likely to dry out and die.

After dragging the seed into the soil, irrigate three to five times per day until the seedlings are well established. But the total water applied during a day would seldom exceed 0.5 inches. Irrigate without causing puddling on the soil surface, for free water encourages disease. After the seeds germinate, gradually cut back on the frequency and increase the time of watering until you can establish a normal irrigation program.

Begin mowing when the seedlings are 30 percent higher than you want. Use a mower with sharp blades and mow when the grass is dry to reduce seedling injury.

Wait to fertilize until after the seedlings emerge. That’s usually three weeks after seeding. Earlier fertilizing may encourage warm-season turf competition. Generally, 1 pound of N per 1,000 sq. ft. per month is adequate.

Most turf managers are recognizing the value of a year-round turf management program to a smooth spring transition. Proper fertilization, irrigation, mowing, thatch control, cultivation and pest management all year affect the transition.

A good transition also requires knowing and making use of normal climatic conditions. Most warm-season turf grasses resume growth when soil and night temperatures approach 60 degrees.

Maintaining a mowing height that prevents the overseeding from shading out the warm-season grass is critical to a smooth transition. Lowering the mowing height as the soil warms will stress the cool-season turf and aid in soil warming. When temperatures are high enough, applying soluble nitrogen can encourage warm-season growth and encourage cool-season decline.

The key to successful overseeding is the same as with most other turf management programs: proper year-round management and understanding the growing conditions being dictated by the weather.

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Resource(s): Lawns in Georgia

Source(s): Gil Landry, PhD., Coordinator – UGA Center for Urban Agriculture, The University of Georgia.

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There are three distinct aspects of turfgrass establishment. The first, soil preparation, is probably the most important. The second, planting, may involve seeding, sprigging or sodding. The final step is the care and maintenance for two to four weeks after planting.

The key to successful establishment of a home lawn is proper soil preparation. Without this, most lawns will eventually fail. Soil should be prepared the same whether you are planting by seed, sprigs, stolons, or sod. Outlined below are the steps necessary for proper soil preparation.

 

Take Soil Samples

Base fertilizer and lime applications on the result of soil tests. Contact your county agent for information on how to collect samples.

Clean Planting Site

Remove all the debris from the area to be planted. This includes rocks, bottles, and large roots. Remove all old tree stumps. These will eventually decay and leave depressions in the lawn.

Rough Grading

If extensive grading is being done, remove the topsoil and replace it after the rough grade is set. The rough grading should conform to the final grade after the topsoil is added. A 1-2 percent slope (1-2 foot of the fall per 100 feet) away from all buildings generally gives the best results.

If internal drainage or subirrigation systems are to be installed, this is the best time to do it. Remember, good drainage is a must if a nice lawn is desired.

The subgrade may become compacted during rough grading, especially if the ground is wet. This compacted layer must be broken up by some means. A spring tooth harrow works well on soils compacted lightly, while a small rotavator might be needed for more heavily compacted sites.

Replace Topsoil

Once the subgrade is established, respread the topsoil. Allow for at least 6- 8 inches of depth after the soil has settled. This means placing about 8-10 inches topsoil over the subgrade. Steep slopes or rock outcrops need at least 12 inches of topsoil for proper maintenance. If the existing topsoil is poor, improve it if you cannot purchase new topsoil.

If organic matter is needed, add 1-3 cubic yards per 1000 square feet of lawn area. Materials such as peat moss, shredded pine bark, rotted sawdust (6-8 years) or leaf mold serve well as organic materials. On heavy soils, add 8-10 cubic yards of sand per 1000 square feet of lawn. Mix all of these materials in thoroughly with the native soil to a depth of 6-8 inches.

Add Fertilizer and Lime

Once the topsoil is spread and graded, add fertilizer and lime as indicated by the soil test. Mix the lime thoroughly with the top 3-5 inches of topsoil. The fertilizer should be mixed with the top 1-3 inches of soil or simply applied to the surface. Water the fertilizer lightly prior to planting.

A general recommendation for a starter fertilizer is 20-30 pounds of a commercial grade fertilizer, such as 5-10-15, 6-12-12, 5-10-10, or 7-14-21 per 1000 square feet of lawn. If a soluble source of nitrogen is used, do not apply more than 1 pounds of nitrogen per 1000 square feet. If an insoluble source of nitrogen is used, such as urea-formaldehyde, you can apply 3-5 pounds of nitrogen per 1000 square feet prior to planting.

Final Grading

Final grading and mixing of the fertilizer should be delayed until right before planting time. If this is done too far in advance, some fertilizer may be leached out and the soil may become crusted. On light soils (high sand content), the seedbed should be firmed. This will help prevent drying out of the soil. Once the soil is properly prepared, it is time to plant.

Take care not to destroy the existing trees in the lawn. The cutting of a large percentage of a tree’s roots during soil tillage can severely damage if not kill it. Trees can also be suffocated by deeply covering the roots with soil. If soil is necessary at a tree base, a tree well should be constructed.

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Resource(s): Lawns in Georgia

Center Publication Number: 129

Source(s): Gil Landry, PhD., Coordinator – UGA Center for Urban Agriculture, The University of Georgia.

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There are three distinct aspects of turfgrass establishment. The first, soil preparation, is probably the most important. The second, planting, may involve seeding, sprigging or sodding. The final step is the care and maintenance for two to four weeks after planting.

Cool Season Grasses

In Georgia, most cool-season lawns are established by seeding. Always purchase quality seed, that is, one with a high percent germination and purity. This information should be given on the tag. Inexpensive seed often ends up being quite expensive because of low germination and purity. Reputable seed dealers are always willing to help customers select quality seed. See Table 1 below for seeding rates.

The best way to apply seed is with a mechanical seeder that will distribute the seed uniformly. There are four basic types of mechanical seeders available: (a) drill, (b) gravity, (c) broadcaster, and (d) hydroseeder. For small areas, such as home lawns, the gravity flow or broadcaster work best.

When seeding, divide the seed in two equal parts and then seed in two directions at right angles to each other. Fertilizers and pesticides should also be applied in this manner to insure a more uniform distribution. For some small seed, it may be helpful to mix the seed with a carrier such as dry sand to distribute the seed evenly. If this is done, frequently mix to prevent separation of the seed and sand.

Once the seeds are planted, rake lightly into the soil. On small areas a hand rake works fine. This increases the contact of the seed with the soil, thus increasing the chance of the seed surviving. After raking, roll the seed lightly to firm the soil. Then place a mulch over the soil. A mulch serves two purposes: (1) it helps prevent soil erosion and (2) it helps retain moisture necessary for the seed to germinate. If straw is used, find a source that is free of weed seed. One bale of straw (60-80 pounds) will cover approximately 1000 square feet.

The straw can be left on the lawn to decompose if it is not spread too thick. Peat moss or aged sawdust does not make a good mulch for seeded lawns. These materials compete with the seed for water and resist decomposition. Water the lawn as soon as possible after seeding.

Warm-Season Grasses

With the exception of common bermudagrass and centipedegrass, most warm-season grasses in Georgia are established by planting vegetative plant parts. The seeding procedure is the same for warm- and cool-season grasses. Annual Ryegrass is used as an overseeding to produce green color on home lawns in winter. See Table 2 below for vegetative planting rates.

Sprigging is the placing of grass plants, runners, rhizomes, stolons, or small sod pieces (2-4 inch plugs) in small holes or furrows on the soil surface. Stolonizing is the broadcasting of vegetative plant parts on the soil surface and covering by topdressing or slicing.

To plant sprigs, dig furrows every 8-12 inches and place the sprigs at a 1-2 inch depth every 4-6 inches in the furrows. The closer together the sprigs are, the quicker the grass will cover. After placing the sprigs in the furrow, cover part of the sprig with soil and firm. This can be done with a roller or by stepping on the soil around the sprig. Water as soon as possible after planting.

Broadcasting requires more planting material but will produce a quicker cover. Stolons are broadcast by hand or a mechanical spreader over the prepared seedbed. The stolons are then topdressed lightly with 0.15-0.25 inches of soil or sliced into the soil. Machines with vertical blades for slicing the stolons into the soil are available for this purpose. After topdressing or slicing, roll the lawn to firm the soil around the stolons. Apply water immediately.

Sodding is becoming more and more popular. Quality sod that is free of weeds, diseases and insects should be used. Be sure the soil grade is correct before laying the sod. As soon as the sod is in place, roll, mow if necessary and water.

Relatively new methods of planting are hydro planting and hydroseeding. Sprigs or seed are mixed with water in a large tank and then sprayed under high pressure over the area being planted. The advantage of this method is that the equipment does not have to go over the lawn. This helps prevent compaction, especially in wet weather.

Many zoysia lawns in the south are plugged. While more grass tends to survive when plugged, the rate of establishment is much slower than that or sprigging or stolonizing. Zoysia plugs (2 to 4 inch diameter) should be placed on 6-12 inch centers. The closer the plugs, the faster the cover. Most lawns plugged with zoysia take two years to achieve full cover.

Table 1: Seeding Rates for Lawn Grasses in Georgia
Grass	Seeding Rate (lbs/1000 sq.ft.)	When to Plant	Area of Adaptation
Tall Fescue	5-8	September, October (preferably), or early spring	North of fall line
Kentucky Bluegrass	1-2	Same as above	North, mountain area
Annual Ryegrass	5-10	September- November	All*
Common Bermuda	1-2 (hulled)	May-June	All
Common Bermuda	3-5 (unhulled)	Fall	All
Centipede	1/4 -1/2	May-June	Central south
Carpetgrass	1-3	May-June	Central south
* Annual Ryegrass is used as an overseeding to produce green color on home lawns in winter.

 

Table 2: Vegetative Planting Rates for Warm Season Grasses
Grass	Planting Rate* (bu/1000 sq. ft.)	When to Plant	Rate of Establishment
Bermudagrass	2-4	May-July	2-3 months
Zoysias	2-4	May-July	1 year
Centipede	2-4	May-June	4-6 months
St. Augustine	2-4	May-June	3-4 months*
* One square yard of sod approximates: 9 sq. ft; about 1 bu. of sprigs; 2000 Bermuda or Zoysia sprigs; 500 St. Augustine or Centipede sprigs; 324, 2-inch plugs; 84, 4-inch plugs.

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Resource(s): Lawns in Georgia

Center Publication Number: 130

Source(s): Gil Landry, PhD., Coordinator – UGA Center for Urban Agriculture, The University of Georgia.

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There are three distinct aspects of turfgrass establishment.

1. The first, soil preparation, is probably the most important.
2. The second, planting, may involve seeding, sprigging or sodding.
3. The final step is the care and maintenance for two to four weeks after planting.

Care after Planting

Water newly-planted turf areas regularly. The waterings should be light and often enough to prevent the surface from drying. This usually means daily waterings for the first 2-3 weeks. As the seedlings develop, or as the sprigs or sod begin to take root and grow, decrease the frequency of watering and increase the amount applied each time.

The grass should be mowed when it reaches 1.5 times its recommended mowing height. Do not mow young grass when it is wet. See the table below – “Mowing Height for Lawn Grasses in Georgia” for more information.

Newly-planted turfgrasses should be fertilized according to soil test recommendations. In the absence of these recommendations, and in order to obtain rapid cover, monthly apply a complete fertilizer (contains N, P and K) at the rate of one to two pounds of nitrogen per 1000 square feet. Proper fertilizer application is also important and is discussed in factsheet “Fertilization of Turgrasses”.

Newly-planted areas are likely to become weed infested. Weeds should be controlled by frequent mowing and proper fertilization and watering. If chemical weed control is necessary, consult the Weed Control in Lawns bulletin.

**** Mowing Height for Lawn Grasses in Georgia ****
Grass	Cutting Height (inches)
Tall Fescue	2-3
Bluegrass	2-3
Common Bermudagrass	1-2
Hybrid Bermudagrass	0.5-1.5
Zoysia	0.5-1.5
Centipedegrass	1-1.5
Carpetgrass	1-2
St. Augustine	2-3
Ryegrass	1-2

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Resource(s): Lawns in Georgia

Center Publication Number: 131

Source(s): Gil Landry, PhD., Coordinator- The Center for Urban Agriculture, The University of Georgia.

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Proper irrigation is the key to maintaining turfgrasses. Although irrigation may be costly, a green and growing turf improves environmental conditions. The main benefits of a healthy turf include water and wind erosion control. An actively growing turf may have a surface temperature that is 20 degrees F cooler than a dormant turf during the summer.

Turf Drought Maintenance Details

Water use, also called evapotranspiration, is the total amount of water needed for turfgrass growth, plus the quantity evaporated from the soil surface. Turfgrass water use rates depend on soil type, grass species and/or cultivar, management level and atmospheric conditions. Atmospheric water loss increases as temperature and solar radiation increase. Water loss also increases with increasing winds up to four mph, and as humidity decreases. In general, most turfgrasses grown in Georgia use about one inch of water per week to maintain normal growth and color.
Sandy or coarse-textured soils absorb water much faster than clay or fine-textured soils. However, sandy soils retain less water and therefore need water more often than clay soils. Since clay soils absorb water slowly, irrigation rates should be slow and extended over a longer period.
Most turfgrasses grown in Georgia need about one inch of water per week during the summer to remain green and growing. (Table 1). Some turfgrasses, like bermudagrass develop a deep root system to obtain the needed water. But other turfgrasses, like Zoysiagrass, have shallow root system and need weekly irrigation to remain green.
Table 1. provides summer water use rates/drought resistance rankings and irrigation frequency for turfgrass species in Georgia. The water use rate and drought resistance ranking is based on the amount of water used through evapotranspiration and the relative rate the turf begins to show drought stress. The days between irrigations are for mid-summer, high evaporative conditions. The differences between grasses reflect differences in daily evapotranspiration, root depth, viability, and quantity, and turfgrass drought resistance. Under non-irrigated conditions, the relative drought tolerance, or ability to survive without water, becomes more important. Generally, turfgrasses with high water use rates tend to have low drought tolerance.

Table 1. Summer water use rates/drought resistance rankings and irrigation frequency of turfgrasses used in Georgia.
COMMON NAME	WATER USE/DROUGHT RESISTANCE	DAYS BETWEEN IRRIGATIONS
Bermudagrass	1	14 – 21
St. Augustinegrass	2	12 – 18
Centipedegrass	3	8 – 12
Tall Fescue	4	6-8
Zoysiagrass	5	5-7

During moisture stress periods, raising the mowing height and mowing often enough so that no more than one-third of the leaf tissue is removed can increase turf survival. Raising the mowing height helps the grass maintain a deeper root system which helps it find more water. Irrigate at the first sign of moisture stress. When a turfgrass is under moisture stress it becomes dull and bluish green, the leaf blades fold or roll and footprints remain after walking over the area. If dry conditions continue, the grass wilts. Begin irrigation on that portion of the lawn which first exhibits these signs. Irrigate between sundown and sunrise when the wind and temperatures are lower. Apply enough water to soak the soil to a depth of six to eight inches. This is usually equivalent to about one inch of water or 600 gallons per 1000 square feet but will vary with different soils. A sand would require 0.5 inch of water while a clay would need 1.75 inches to wet the soil to an eight-inch depth. Most sprinklers apply about one-fourth inch of water per hour and thus must be on in one spot for up to four hours to apply one inch of water.

Applying the proper amount of water is one maintenance practice often done wrong. Light, frequent irrigations produce shallow, weak root systems. The shallow root system prevents efficient use of plant nutrients and water in the soil.

If water is being applied faster than the soil can absorb it, either move the sprinkler to a new location or turn it off and allow the water to soak into the soil. To determine the depth of water penetration, use a spade or sharp probe to push into the soil two to four hours after irrigation. The probe will move into the soil very easily where it is moist. The probe becomes harder to push when it hits dry soil.

To test your sprinkler output and application uniformity, place several open-top containers of the same size under the sprinkler. After running the sprinkler for an hour, measure the amount of water in each container. The difference between containers provides an estimate of water distribution and application rate.

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Resource(s): Lawns in Georgia

Center Publication Number: 213

Source(s): Gil Landry, PhD., Coordinator – UGA Center for Urban Agriculture, The University of Georgia.

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Renovation of turfgrasses is occasionally necessary in order to produce an attractive, healthy lawn.

Occasionally a lawn will become thin and spotty and, in some cases, large dead areas may appear. These areas are eventually filled in by undesirable plant species (weeds). At this point, the homeowner must decide: (1) if the lawn can be brought back to desired appearance through normal maintenance, (2) if the lawn requires renovation, or (3) if the lawn has to be completely re-established.

First, the cause of the problem must be determined and corrected. Normal decline causes are: (a) improper maintenance practices, (b) use of a grass not adapted to the area, (c) excessive thatch accumulation, (d) severely compacted soil, or (e) disease or insect problems. Your county extension agent can help solve this problem. Once this is resolved, one of the above procedures can be used to improve the lawn. In most cases, renovation is the answer.

Following are the necessary steps in renovation of a home lawn. Lawns with cool-season grasses should be renovated in early fall (August-September), while lawns with warm-season grasses should be renovated in early spring.

Step 1.  Eliminate all undesirable weeds and/or excessive thatch. Weeds can be removed by either chemical or mechanical means, while thatch will require some mechanical means of removal.

Step 2.  Cultivate the soil by aerifying, coring, slicing and/or spiking.

Step 3.  Correct the soil pH and/or salinity (salt accumulation) problem if one exists. If the pH is not suitable for plant growth, it must be changed. Soil test should be taken to determine the pH and fertility level of the soil.

Step 4.  Apply fertilizer as recommended to the area and water. Use a starter fertilizer such as 6-12-12 or 5-10-15 unless soil test shows otherwise. Apply about 20 pounds per 1000 square feet.

Step 5.  If the lawn is overseeded drag, rake or brush the seed down to contact the soil. If the area is planted with vegetative material, place the sprigs in a furrow and lightly topdress.

Step 6.  Whether the lawn is reseeded or planted with vegetative stock, water as soon as possible after planting. Do not allow the newly planted material to become dry. At 3 to 4 weeks after planting, apply 2 to 3 pounds of ammonium nitrate per 1000 square feet to enhance the growth of the new grass. Continue normal mowing practices once the grass reaches 1.5 times its normal mowing height. For more information refer to Cooperative Extension Service Leaflet 263, Renovation of Home Lawns.

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Resource(s): Lawns in Georgia

Center Publication Number: 135

Source(s): Gil Landry, PhD., Coordinator- The Center for Urban Agriculture, The University of Georgia.

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Thatch is defined as an accumulation of dead and living plant material (stems, roots, and shoots) that develops between the soil surface and the green leaves of a turf. Thatch development is a natural process that occurs during normal growth of turfgrasses. Although some thatch is desirable, thatch becomes undesirable when it exceeds a depth of 1/2 inch.

Examine thatch depth by using a knife, spade, or soil probe to remove a small section of turf (soil included). If the thatch layer is thicker than 1/2 inch, dethatching is needed. Remember that thatch buildup is gradual and occurs over a period of years. Therefore, it’s logical that a thatch removal program should also be gradual.

The following cultural practices are effective methods of thatch removal:

1. Topdressing once or twice a year with a 1/4 inch layer of topsoil is the most effective method of thatch reduction. This practice increases the thatch decomposition rate. Heavier applications of topsoil may cause layering, which restricts water, air and fertilizer movement in the soil. However, a top-dressing is also the least practical cultural practice because of the cost of specialized equipment, top-soil and labor. Topdressing can also be a source of weed seed.
2. Vertical mowing is the most common method of thatch removal. This specialized mower has evenly spaced blades that revolve perpendicularly to the turf and slice into the thatch to mechanically remove it. It is very important to use proper blade spacing when vertically mowing different turfgrasses. Use a blade spacing of 1 to 2 inches for bermudagrass and zoysiagrass, 2 to 3 inches for centipedegrass, and 3 inches for St. Augustinegrass. Bermudagrass may be mowed down to the soil level in several directions without killing the lawn because of underground rhizomes. Centipedegrass and St. Augustinegrass should only be vertical mowed in one direction to avoid removing too much plant material and reducing the rate of recovery. If a thatch layer exceeds 1/2 inch depth, the turf area should be carefully vertically mowed and allowed to recover between mowings. Vertical mowing is best done in the spring after greenup where the grass is growing rapidly and when the weather is not so hot that turf water needs are high. Another good time to vertical mow is in early spring just before greenup occurs.
3. Power raking uses the same mechanical principles as vertical mowing. Flexible, spring steel wires revolve at high speed vertically through the turf and loosens the debris for removal. Power raking can be useful for loosening debris, but it is not as effective as vertical mowing.
4. Scalping is a poor substitute for vertical mowing, but its use, especially in early spring may delay the need for vertical mowing where build up is minimal. Scalping is a procedure in which the turf is mowed at a much lower height than normal. Scalping heights will vary with turfgrass species. Turfgrasses with rhizomes, like bermudagrass and zoysiagrass, may be scalped down to near the soil surface. Centipedegrass and St. Augustinegrass spread by above-ground runners called stolons. Removing these stolons would kill the turf. Zoysiagrass is not as sensitive to scalping as centipede and St. Augustine, but it is more sensitive than bermuda. Scalping below the crown or green growing points of zoysia will cause excessive damage.
5. Core aeration benefits thatch decomposition primarily through the indirect effects that stimulate bacterial activity. Core aeration also relieves soil compaction and increases air and water movement into the soil. This is best accomplished by a power aerator that has hollow tines or spoons, so it removes a soil core 2 to 3 inches deep and 1/2 to 3/4 of an inch in diameter. Core aeration should be done during periods of active plant growth and when the soil is moist enough to allow deep penetration. Applying a fertilizer as recommended by soil analysis after a cultural practice will increase the rate of turf recovery.

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Resource(s):

Lawns in Georgia

Center Publication Number: 139