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Tomatoes 2008
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For the turfgrass plant to fulfill its missions of controlling erosion, providing environmental benefits and contributing aesthetically and economically to the landscape, it must be furnished with optimum or at least near-optimum growing conditions. As with all plants, it is very sensitive to its environment. Any dramatic changes may severely test the plant’s ability to adapt and survive. Nearly all turfgrass plants are perennial, living more than one or two growing seasons. They require plant nutrients, water, an optimum temperature and air to complete their life cycle. Two groups of turfgrasses are used for lawns throughout the United States (Figure 4.1). One group is the warm-season grasses; these have optimum or ideal growing temperatures which range from 80° to 95°F. The other group is the cool-season grasses; their best growing temperatures range from 60° to 75°F (Tables 4.1 and 4.2). These two groups of grasses react very differently to yearly temperature variations (Figure 4.2). Because of their lower optimum temperature requirements, cool-season grasses have high growth rate periods in spring and fall regardless of whether or not they are grown in the North or South. Warm-season grasses peak in summer when the growth rates of cool-season grasses are reduced. The high stress period for warm-season grassplants is during winter, and the high stress period for cool-season grasses is during summer. A plant naturally reacts to stress by entering a state of dormancy. It is normal for a warm-season grass plant to turn brown in early winter and remain brown or dormant until warm days return in early- to mid-spring. The plant is not dead but has "retreated" to its growing points which are basically the crown, stolons and rhizomes (Figure 4.3). Cool-season grass normally enters dormancy by turning brown during the heat of summer. Water is applied for its cooling effect to keep cool-season grasses from going dormant during the hot summer. Water cools as it evaporates; this process is called "syringing." All turfgrass plants spread vegetatively in one or more of three different ways (Figure 4.3 and Table 4.3). One method is by an above-ground lateral stem called a stolon or runners. Alternatively, a rhizome is a below-ground lateral stem. Both these structures are able to produce nodes, which in turn can produce a new plant. These lateral stems are organs that store carbohydrates for the plant’s survival during periods of dormancy. Once favorable weather returns, the nodes produce new plants. The third type of vegetative reproduction is tillering and is the slowest method of spreading. The new plant is produced at the base of the original plant. These grasses form clumps and are sometimes called bunch grasses. Very few of the 500 species of grass that grow in New Mexico are suitable for turf. Unlike other types of grasses, turfgrasses are not permitted to mature normally and produce seed. Instead, the leaves of turfgrasses, which manufacture the food materials needed for growth, are frequently removed by mowing. Few grasses tolerate the close, frequent mowing required to maintain a turf. Your choice of a turfgrass depends on your geographic location, the amount of water available for irrigation, the amount of shade present, the time and money you are willing to spend for lawn establishment and the kind of use you expect. Warm-Season Turfgrasses Warm season grass lawns are actively growing from mid-April to mid-Ocober. They are termed "warm season" grasses because they grow during warm weather. Most produce stolons and/or rhizomes. Stolons are above ground runners, while rhizomes are under ground runners. Both are stems that help produce plants and help warm season grases fill in areas and recuperate after stress events. Bermudagrass Bermudagrass is the turfgrass most widely used in Southern New Mexico. It is a narrow-leaved, vigorous perennial with its origin being traced to Africa. Bermudagrasses are warm-season grasses that go dormant with cool fall weather and "green-up" when warm spring weather returns. Bermudagrasses are all fairly salt-tolerant, but none have any significant shade tolerance. In Spring, bermudagrasses start growing when soil temperatures reach 60°F and as a group, they are aggressive, spreading both by rhizomes and stolons. The need to edge sidewalks and trim around trees, shrubs, buildings and fences is almost constant. Bermudagrass used as turf: does not grow in medium to dense shade. turns brown after frost in the fall and, with continued low temperatures, does not become green until after the last spring freeze. is more of a nuisance than other turfgrasses in flower beds and gardens because of the runners and rhizomes. is subject to scalping when mowed infrequently. Common This is a fairly wide-bladed bermudagrass. Its biggest advantage is that it can be established from seed. It has a fairly low maintenance requirement and survives on little water and fertilizer. The best cutting height is 1½ inches but can be maintained at slightly lower heights if frequently cut. It does not produce thatch. However, production of unsightly seed heads can be a problem, especially for those with allergies. There is very little Common sod available because it is so easy to start from seed. Common is used for a great number of home lawns, athletic fields and other moderate- to low-maintenance areas. There are more and more "named"seeded varieties of bermuda being introduced and they tend to have a finer texture than common, but not as fine as Tifway. Tifgreen (328) This is one of the smallest-leafed, hybrid bermudagrasses available. Its ideal cutting height ranges from 1/8 to 1/2 inch and requires heavy fertilization and abundant water to perform well. This grass is best suited for use on golf course putting greens and tees across the South. It is propagated by sprigs or sod. Tifgreen II was released as an improved mutant of Tifgreen. Tifway (419) Tifway is a true hybrid. It has a slightly wider leaf blade than Tifgreen, but is not nearly as coarse as Common. The best cutting height for this bermudagrass is 3/8 to 1 inch. Thatch problems may occur if it is overfertilized and overwatered. It can be established using either sprigs or sod and is perhaps the best of the hybrid bermudagrasses for lawn use. Tifway II This is an improved variety of Tifway. Texturf 10 This grass was developed by the Texas Agriculture Experiment Station and is a selection of Common bermudagrass. It has a more horizontal growth habit than Common, thus resulting in a thicker lawn and an ideal mowing height of about 1 inch. Texturf-10 recovers rapidly in the spring, produces few seedheads and is widely used for athletic fields. In humid climates it is highly susceptible to leaf spot diseases. Texturf 10 is established either by sodding or sprigging. Santa Ana bermudagrass was selected by the California Agricultural Experiment Station in 1956 for its desirable turf characteristics and its salt tolerance. Santa Ana performs well in high-pH soils and where irrigation water is relatively high in salt. Floratex is a medium-textured variety of bermudagrass released jointly by the Florida and Texas Agricultural Experiment Stations in 1993. Floratex was developed as a low-maintenance grass that provides acceptable color and density with relatively low inputs of fertilizer, water and pesticides. Zoysiagrass This turfgrass is native to the Orient. It is not as shade-tolerant as St. Augustine, but it is wear-resistant and more cold-tolerant than bermudagrass. Although it has a fairly low growth rate, zoysiagrass spreads by both rhizomes and stolons. Zoysia is slower to spread than bermudagrass and St. Augustine and requires longer to establish a complete cover. However, it requires mowing as often as bermudagrass if a uniform, attractive appearance is desired. If established with sprigs or plugs, it may take two or three seasons to fill in, depending on the sprig rate or plug spacing. Zoysiagrass is used for home lawns and golf courses, especially in the transition zone. There are three different varieties of Zoysiagrass, and these include Emerald, Meyer and Japanese lawngrass. Emerald has a much finer leaf blade than Meyer and forms a dense, dark-green turf that is dense-growing. The leaf blade of Meyer is a little wider than that of Common bermudagrass, and it also forms a dense turf. St. Augustinegrass This turfgrass, native to the West Indies and the Texas Gulf Coast, is widely grown in the warm, humid parts of the United States. Its best attribute is its outstanding shade tolerance. St. Augustinegrass is usually established by sod, but plugs of newer varieties are now available. It spreads quickly by stolons but has low wear tolerance which may make it undesirable for heavily used lawns. St. Augustinegrass varieties have wider leaf blades than most other turfgrasses. It produces a thick thatch over time and is slow to grow back from severe verticutting. It does not take to overseeding. Like bermudagrass, it does go dormant during the winter months when it is cold. It has limited use in our state. It's use is limited to the Southern part of New Mexico. Buffalograss This is the only turfgrass native to the North American great plains from Texas to Canada. It is a warm-season turfgrass that spreads by stolons. Buffalograss has fine leaf blades that are bluish green in color. It does not form as dense a turf as bermudagrass, and if left unmowed, it does not reach more than 4 or 5 inches in height. It can survive extreme drought conditions but may turn brown during dry summer periods and green up again when it rains. It can be used for golf course parks, roughs or other low-maintenance areas. Common bermuda can be a serious "weed" problem in buffalograss. Buffalograss is established from seeds called burrs. The seed is larger than other grass seed and overall production is low, making the price expensive. Buffalograss is the only turfgrass that is dioecious (there are male and female buffalograss plants). The male flower is produced on the end of a stalk, while the female flower is produced at the base of the plant. Buffalograss has no particular insect or disease problems. Its biggest enemy, perhaps, is overwatering and overfertilizing. Buffalograsses will not persist in shade. It performs best on fertile, well-drained, heavy soils in full sunlight. Buffalograss used as a turf: tolerates infrequent mowing, is not aggressive and is easily removed from flower beds and gardens and burrs maybe uncomfortable to bare feet is very drought-tolerant. "Prairie," developed at Texas A&M University, and "609", developed at The University of Nebraska, buffalograss are selections of female plants with a darker green color and more dense growth habit than common buffalograss. Both "Prairie" and "609" buffalograss must be established from sod or sod plugs. Seeded varieties of buffalograss include Common, Texoka, Commanche, Plains and Topgun. Cool-Season Turfgrasses Cool-season perennial grasses are used successfully as lawn grasses in higher altitudes where irrigation is available. Cool-season grasses are also used in combination with established bermudagrass to provide year-round green lawns. Tall Fescue This is a cool-season or northern turfgrass. However, if managed correctly, it is tough enough to tolerate southern summers and be used as a permanent lawn. Tall fescue is from Europe and is one of the most heat- and drought-tolerant northern grasses. It is a bunch grass and spreads by tillers; thus, it requires little edging and will not invade flower or shrub beds. Tall fescue’s greatest advantages are its ability to grow well in fairly dense shade and that it can survive winters in the South without any problem. Plus, it stays green all winter. Tall fescue grows at its highest rate during spring and fall. Watering every 3 or 4 days during summer should be sufficient to keep it from going into summer dormancy. Water helps keep the soil cool. However, additional watering increases the potential for disease. Mowing at 2 inches or higher keeps the growing point cooler. The old standard tall fescue variety is K-31 which is still available. However, many new varieties with finer blades and improved heat and shade tolerance are available, including Olympic, Rebel, Falcon and Houndog. For best results, a blend of three or four different Tall Fescues is recommended. Ryegrasses Perennial ryegrass and annual ryegrass are suited for temporary cool-season turfgrasses. The ryegrasses are fine-leaved bunch grasses that spread by above-ground tillers. They are best adapted to cool, moist environments which are not found in New Mexico. In the United States, the northeastern and northwestern states are well suited to ryegrass. In the transition zone, perennial ryegrass may provide a permanent turfgrass. But in New Mexico, both species serve as cool-season annuals. Ryegrasses are adapted to a wide range of soil conditions, but favor moist, well-drained, fertile soils. The ryegrasses possess little drought tolerance and must be irrigated during dry periods to ensure survival. Shade tolerance of the ryegrasses is good in southern climates where shade conditions reduce the extreme heat during summer. Perennial ryegrass often survives the hot, dry summers of the South in moderately shaded sites. Both species of ryegrass are used for temporary grass cover during the fall and winter months in New Mexico. Their quick establishment from seed (rapid germination and rapid seed growth) makes them ideal for protection against erosion on newly prepared sites in the fall. They are also used to provide temporary green color during winter months when bermudagrass is dormant. The ryegrasses have become very popular for overseeding athletic fields, golf courses and lawns during winter months. The improved turf-type perennial ryegrasses have greater cold tolerance, wear tolerance, disease resistance and persistence than the annual types. New varieties also have better turf characteristics -- finer texture, greater density, darker color and better mowing qualities. At least 50 improved ryegrass varieties have been developed over the past 20 years. Most improvements have been in perennial ryegrass, although intermediate crosses have been made with annual ryegrass. Improvements in turf quality have been in the following areas: Density, texture and color (Pennfine, Manhattan and Derby). Mowing quality (Palmer, Manhattan II, Delray and Loretta). Heat tolerance (Derby, Birdie, Palmer, Citation and Dasher). Cold tolerance (Elton, Goalie, NK-200 and Norlea). Disease resistance (Manhattan II, Palmer, Prelude and Delray). Insect resistance (Repell). Drought tolerance (Palmer and Prelude). Kentucky Bluegrass Kentucky Bluegrass can be established from either seed or sod. Sometimes Roughstalked Bluegrass, a finely textured, bright green perennial grass is mixed in shady lawn mixtures for its tolerance of shade, and damp soils along with creeping red fescue. Kentucky Bluegrass produces rhizomes but no stolons. These rhizomes help produce a thick dense turf. Leaf blades have a tip that is shaped like the front of a canoe. Leaves have a prominent midrib and fine obscure veins. Because Kentucky Bluegrass produces only rhizomes and no stolons, less thatch is produced than bermudagrass. Certain varieties of Kentucky Bluegrass are fairly shade tolerant, such as 'Glade' and 'Nugget'. Kentucky Bluegrass is sometimes sold as seed with other grasses. These may include fine fescue (for shade tolerance) and perennial ryegrass (used as a nurse or companion grass). Do not purchase seed of a Kentucky Bluegrass mixture which has 10% or more ryegrass seed in the mixture. Kentucky Bluegrasses are best planted in the fall in high desert locations or spring in mountain areas. Kentucky Bluegrass will not perform well in low desert areas, and should not be used in fall overseeding of bermudagrass lawns. Turf Establishment Three basic methods are available for establishing a turf — seed, sod or sprigs (stolons). Regardless of the method chosen, preparation of the seedbed, sodbed or sprigbed is the same. Use a soil test to determine desirable seedbed fertilizer analyses and application rates. Production of a fine, firm soil surface is necessary for successful turf establishment. Preparing the Soil The first step in preparing a new turf area is to remove all debris, such as stones, tree stumps and construction debris. In many instances, the character of the soil must be altered considerable. A sandy loam soil high in organic matter is considered most satisfactory for turf. If the original surface soil is a heavy clay, it may be impractical to alter the nature of the soil, but organic matter can be added. This organic matter can be composted manure, well-decomposed sawdust (hardwood) or similar material. Organic matter must be thoroughly mixed in the top 4 to 6 inches of the seedbed. This mixing can be done by repeated cultivation operations such as rototilling. Also, the area should be graded properly to provide surface drainage. Seeding The least expensive way to establish turf is by seed. The best germination temperature for cool-season turfgrasses is from 60° to 85° F. This means the best time to seed cool-season turfgrasses is in late summer to early fall. The second best time is in mid- to late-spring, but it’s better to seed in early fall as the soils are cooling down. New roots of cool-season grasses do not grow well in warm soil. Warm-season turfgrasses are just the opposite of the cool-season turfgrasses in their reaction to temperature. The best temperature range for germination of warm-season grasses is from 70° to 95° F. Therefore, early summer is the best time to seed bermudagrass and other warm-season turfgrasses. Not all turfgrasses produce seed, and if they do, they may not produce enough to be profitable or the seed may not "come true." This means that the plant produced from the seed will not necessarily look or act like the plant that produced the seed. These turfgrasses, such as Tifgreen Bermudagrass and ‘609’ Buffalograss, must be established by sprigs or by sod. Seed quality can be evaluated by reading the seed test information that is required on every seed container. The seed test date should be current. Germination and purity should be as high as possible with a low weed and inert matter content. Buying certified seed insures that the variety you want is indeed the variety you are buying (Figures 4.4 and 4.5). Although hand sowing can be satisfactory, the use of a small seed distributor is recommended. The seed should be divided into two equal parts, one broadcast as you walk back and forth in a given direction, the second sown as you walk back and forth at right angles to the first seeding. This method gives better distribution of seed. Sod Any turfgrass that spreads by a rhizome or a stolon can be grown and harvested as sod. Sodding is the most expensive way to establish turf. The best time to sod is when the turfgrass is actively growing. This means that the sod will root or knit down as quickly as possible. As with seed, certified sod is available and is the only real way to be sure the buyer is getting the stated variety. A problem associated with using sod is the potential effect of differences between soil in the sod field and soil at the new site. If the sod is grown on soil containing a higher amount of clay and silt than the soil at the new site, a problem could develop. The sod may contain a very thin layer of soil that is physically very different from the underlying soil. This difference between the two soils can interfere with water drainage. Lawns should be sprigged in the spring and early summer, though they may be plugged at any time during the growing season when adequate moisture is available. Sprigging is used primarily for establishing hybrid bermudagrasses. The proper distance between sod blocks or sprigs depends on the rate of growth and on how soon a cover is desired. St. Augustinegrass plugs 2 to 4 inches in diameter planted on 2-foot centers should cover within three months if adequately watered and fertilized. Bermudagrass sprigged at 3 to 5 bushels per 1,000 square feet should cover within two months; zoysia may require an entire growing season. After sprigging bermudagrass and zoysia, the sprigs may be covered with a thin layer of topsoil or mulch. Press the sod blocks or sprigs firmly into the soil, and roll the soil to give a smooth surface for mowing. When sodding a lawn, lay the sod blocks or rolls like bricks on a smooth surface that has been firmed. The surface should be free of footprints, stones, depressions and mounds. After the sod is laid, roll or tamp lightly and keep it moist until it is well rooted. Do not overwater! Topdressing with a sandy loam topsoil that is free of weeds, stones and other debris will help smooth the lawn. Sprigs Some turfgrasses that spread by stolons may be harvested and used to establish new turf. Sprigging costs more than seeding but less than sodding. Sprigs are sold by the bushel. A bushel of sprigs is equal to 1 square yard of shredded sod. Overseeding In the South, overseeding bermudagrass lawns for winter color is a common practice. The turfgrass used for this purpose is perennial ryegrass or annual ryegrass. Perennial ryegrass is generally the superior choice. The rate for perennial ryegrass is 4 to 5 pounds per 1,000 square feet, and the rate for Poa trivialis is 1 to 2 pounds per 1,000 square feet. The most important issue associated with overseeding occurs in spring. Ideally, as the weather begins to warm and bermudagrass begins to "green-up," overseeded grasses should begin to die out. As overseeded grasses die, bermudagrass plants take their place. This is how it should work, but many times the weather does not get hot soon enough for the overseeding to die out quickly. The presence of overseeding may act to suppress the return of the bermudagrass from dormancy, and the overseeded grasses may become weeds. Mowing Perhaps the single most important cultural practice associated with lawn maintenance is mowing. When considering the possible effects of mowing on the turfgrass plant, remember that turfgrass is designed by nature to grow and mature at a height far in excess of the selected mowing height. The plant is forced to live at a much lower height. This must be done for the plant to fit the intended use. Mowing, in a sense, is not natural because it upsets the plants’ natural growth patterns. To develop a good mowing program, one must know something about how the turfgrass plant functions. The first, or at least the most apparent effect of mowing, is the reduction of the plant’s leaf surface area. The leaf system manufactures and supplies the plant with carbohydrates. Carbohydrates to the plant are analogous to the food we eat. During the active growing months (spring and fall for cool-season grasses and summer and early fall for warm-season grasses), carbohydrate production is high, and the plant is able to store food reserves. During periods of stress or dormancy, the plant must draw on these reserves to survive. Mowing at heights lower than optimum during periods favorable for carbohydrate storage for the specific turfgrass species may seriously impair the plant’s ability to develop adequate food reserves for stress or dormancy periods. The resulting death of the plant may falsely be attributed to heat or cold injury, when in fact the food reserves were not high enough to carry it through the period. When part of the plant’s leaves are removed by mowing, its first priority becomes the re-establishment or replacement of its former leaf surface area. This flush of leaf growth requires carbohydrates and may reduce the supply of carbohydrates available to the root system for a short period. In the "pecking order" of the plant, the leaf system has priority over roots, rhizomes or stolons for carbohydrates. This demand for carbohydrates by the leaves after cutting may in fact result in a temporary reduction of root growth. The larger the amount or percentage of leaf tissue removed, the longer the root growth may be reduced. Just as the amount of leaf surface removed has an effect on root growth, so does cutting height. There is a direct relationship between cutting height and total volume of the root system. The turfgrass plant, just like all other plants, develops a balance between its top parts and its root system. A certain size of root system is needed to support a certain volume of top growth and vice versa. If either the top parts or the root system is reduced, the plant reacts by reducing the other. When turfgrass plants are mowed, their top parts are reduced. The plant no longer needs the same size of root system, so for the plant to achieve balance, its root system is reduced. The more its top growth is reduced (i.e., the lower the cutting height), the shallower the root system becomes (Figure 4.6). A shallow root system may seriously impair the plant’s ability to withstand stress, especially drought stress. Another important function of the leaf system is insulation. The growing points or crowns of most turfgrass plants are at or near the soil surface and are very high in the chemical activities that control growth processes. These areas of the plant are temperature sensitive. The upper optimum temperature range for cool-season turfgrasses is from about 60° to 75° F and for warm-season turfgrasses from about 80° to 95° F. When the temperature of the growing point goes above these ranges, the growth process begins to slow down. If the temperature of the growing point gets too high for a long enough period, especially with cool-season grass, the plant goes into summer dormancy. The leaf surface insulates the growing point from high temperatures. As the leaf surface area is reduced, the amount of insulation available for the growing point is reduced. The lower the cutting height is from the optimum assigned to a particular variety, the more susceptible the plant is to high temperature injury. This is important when maintaining cool-season grasses. Most turf areas, whether golf putting greens or home lawns, are subject to some degree of wear. The leaf surface area of a turfgrass protects the growing point of the plant from the direct mechanical injury associated with traffic. As the leaf surface is reduced, the overall wearability of the turf is reduced. Turfs cut at low heights are subject to high heat damage and may gradually thin out. Mowing practices may also affect the occurrence of disease. Many times an increase in disease problems is observed with turf maintained below its optimum cutting height. This may be associated with the weaker type of turf plant that results from extremely low cutting heights. Just as proper cutting height is important, so is the frequency at which the turf is cut (Table 4.4). Ideally, the frequency between mowing should be as long as possible to allow the plant to recover from the first cutting. Leaf growth rate and the intended use of the turf will, to a large degree, dictate mowing frequency. A single mowing should not remove more than one-third of the leaf surface; therefore, the application of nitrogen at high rates may force an increase in mowing frequency. This is especially true when high nitrogen rates are applied in a soluble form. For example, a golf course must be cut at fairly frequent intervals to provide a suitably dense putting surface. If, because of high growth rates, the frequency of mowing on other parts of the course becomes too frequent, the owner should consider adjusting both nitrogen rate and source. Slow-release nitrogen materials do not produce the lush, fast growth associated with soluble sources and thus should result in a longer period between mowings. Mowing Equipment Selection of mowing equipment is dependent on a number of factors. Intended use of the area is at the top of the list. For example, a reel mower does a better job than a rotary mower at relatively low mowing heights. The cutting height used for a particular area can even affect the number of blades on a reel (Table 4.5). A rotary mower may do a much better job than a reel mower on lawns that have been assigned higher mowing heights because of the particular turfgrass variety. In most turfgrass situations, clippings are not removed. Removal may be required when they interfere with the intended use of the turf (for example, a golf course putting green) or if they are too heavy and smother the turf. Generally, the shorter the clippings, the more deeply they fall into the turf and the more rapidly they decompose. Double cutting (running the mower over the same area twice) or using a mulching mower helps to shorten long clippings. Contrary to popular belief, clippings do not contribute to thatch. There is absolutely no need to pick up or remove grass clippings if a reasonable mowing program is followed. Mulching type mowers seem to be the mowers of the future because they produce the smallest clippings. Mowing practices are extremely important in any turfgrass management program. Proper cutting height, proper mowing frequency and the development of a reasonable growth rate have a profound effect on the health and vigor of any turfgrass system. Irrigation Watering is also one of the most basic practices in the maintenance of the home lawn but is the one most often done incorrectly. One only has to experience a summer drought to appreciate the need for periodic watering. Many landscape plants, including the turfgrasses, may not survive a dry summer without the judicious application of water. Deep watering encourages the development of an extensive root system. A well-developed root system can use the nutrients and water in the soil more efficiently than shallow root systems. Light, frequent sprinklings produce shallow, weak root systems, which encourage weed invasion. Shallow rooting does not allow efficient utilization of plant food or moisture in the soil. Lawns should also be watered during excessively dry periods in winter to prevent desiccation. On sloping sites or on slowly permeable soils, water intermittently for short periods to reduce runoff. Plants vary in their expression of drought stress. Leaves of some plants begin to droop, whereas other plants, such as the turfgrasses, dry up and the leaves roll and turn a dull purplish color. This process is termed dry wilt. Just as the lack of water has a detrimental effect on plants, so does too much water. A plant’s root system must take in oxygen and give off carbon dioxide to live. When water is applied too frequently, soil becomes saturated, and the movement of oxygen into the soil and carbon dioxide out of the soil stops. This results in a condition known as wet wilt, and if not corrected, the plant may soon die. There is variation in the relative need for water between the turfgrasses. Consideration of the differences when choosing a turf may significantly reduce irrigation needs during summer (Table 4.6). New Turf Lightly water newly-seeded or sprigged areas at frequent intervals. Keep the seed or sprigs moist, not saturated, during this initial growth period. This may well mean that it is necessary to water as many as four or five times during hot, windy days. The first 10 days to 2 weeks are especially critical. If young plants are allowed to dry out, they may die. After about 2 weeks, root system development should be well under way. Watering frequency should be slowly reduced for about 1 month after seeding or sprigging. Then treat as an established turf. Water newly sodded areas much like established turf except more frequently. After the sod is applied, soak it with enough water to ensure that the soil under the sod is wetted to a depth of 2 or 3 inches. Each time the sod begins to dry out, soak it again. Roots develop fairly rapidly, and within 2 weeks or so it should be treated like an established turf. Established Turf When to water? Ideally, water any turf just before it begins to wilt. Most grasses take on a dull purplish cast and the leaf blades begin to roll or fold. Grass under drought stress also shows evidence of tracks after someone walks across the lawn. These are the first signs of wilt. With some careful observation and experience, it is easy to determine how many days a lawn or parts of a lawn can go between waterings. Early morning is the best time to water. Wind is usually calm and the temperature is low, so less water is lost to evaporation. The worst time to water is late evening because the grass stays wet all night, making it more susceptible to disease, and evaporation rates are at their lowest. How much to water? When a turf needs to be watered, apply enough so that the soil is wetted to a depth of 4 to 6 inches. The type of soil has a great deal to do with how much water is needed to wet soil to the desired depth. In Figure 4.7, note the depth of wetting resulting from the application of 1 inch of water. According to this, it should take about 1/2 inch of water to achieve the desired wetting depth if the soil is high in sand and about 3/4 inch of water if the soil is a loam. For soils high in clay, an inch of water is usually necessary to wet the soil to the desired depth. It takes more than 600 gallons for each 1 inch of water over 1,000 square feet of lawn. If water application rates are too light or too frequent, the turf may become weak and shallow-rooted, which, in turn, could make it more susceptible to stress injury (Figure 4.8). Factors to Consider Soil type Water penetrates a sandy soil much faster than a clay soil. So turf grown on a sandy soil requires more frequent watering than turf grown on a soil high in clay. Because water moves fairly slowly into a clay soil, it should be applied as slowly as possible. Slope Lawns with a high degree of slope present a particular problem. It is easy for water to run down the slope without penetrating the soil. Apply water at very slow rates from sprinklers near the top of the slope. Sprinklers on the slope or near the bottom of the slope may prove ineffective. Fertilizer The faster the turf grows, the more water it requires. Slow release fertilizers that contain materials like sulfur-coated urea or ureaformaldehyde as nitrogen sources do not produce high growth rates. Avoid heavy applications of fertilizers high in soluble nitrogen. Management factors Use of an aerifier or coring device helps to increase water movement into the soil. A surfactant or wetting agent may also help water movement into high clay soils. Water quality There are a variety of sources for irrigation water. Treated city water may have the highest quality, but it may be the most expensive. Rivers, ponds and wells usually supply less expensive water, but water quality problems with these sources are possible. Many materials damage plants by polluting water supplies. Surface water supplies are especially susceptible to pollution. Not only can chemicals such as pesticides be a problem but also fine soil particles like silt and clay. Dirty irrigation water can slowly seal the soil surface and cause serious drainage problems. Another cause of poor water quality may be the presence of high levels of soluble salts. Water testing by a competent lab is a very good practice, especially if there is any reason to suspect a problem. No two irrigation systems are exactly alike because both equipment and designs vary. The ideal system has individually controlled zones so that the running time can be set in response to the soil type and topography of the area it covers. Many times, both lawns and ornamentals are in the same zone. This can result in overwatering many ornamental plants. Fertility Program Develop a lawn fertlilzation program based on turfgrass requirements, soil tests, other maintenance practices and your desired results. A reasonable fertility program is another basic part of any lawn maintenance program. Lawns that are underfertilized have thin turf with poor color, while lawns that are overfertilized, especially with high levels of a soluble nitrogen fertilizer, may have thatch problems and be prone to more insect and disease damage. Any fertilization should be based on a soil test. Your maintenance program also has a significant effect on your lawn’s fertilizer needs. If you remove grass clippings instead of returning them to the soil, the amount of fertilizer required may be doubled. Table 4.7 indicates the nutrients contained in clippings from a fertilized lawn. If rainfall or irrigation is heavy on a sandy soil, fertilization must be increased to replace nutrients lost through leaching. Required Nutrients All plants require some 15 or 16 different nutrients for best growth (Table 4.8). In most cases, the soil is a vast reservoir of these plant nutrients; however, it varies in the amount of nutrients it contains and in its ability to supply those nutrients to plants. When a plant requires more of a nutrient than the soil can supply or requires a nutrient not present in a given soil, then fertilizer must be used. Only a soil test determines the soil’s current plant nutrient status. Of all the nutrients required by the turfgrass plant, nitrogen (N), phosphorus (P) and potassium (K) are usually not available in the soil in high enough quantities for good turf growth and must be periodically added as fertilizer. Other elements, such as iron, play important roles in the nutrition of plants. When nitrogen, phosphorus and potassium are balanced properly, other elements necessary for plant growth are usually present in sufficient amounts to produce good turf. If soils are highly acidic or alkaline, other nutrients such as iron or magnesium may be required in some instances. Nitrogen (N) The turfgrass plant requires more nitrogen than any of the other plant nutrients. It’s common for nitrogen levels in the plant to be as much as 4 or 5 percent. Nitrogen is a part of chlorophyll and has a great deal to do with nearly all growth and developmental processes in the plant. As the amount of nitrogen supplied to the plant is increased, the rate of shoot or leaf growth increases. This increase is generally at the expense of root growth. Rapid leaf growth uses up all the food material being produced by the plant, and very little is left for the roots and other organs, including stolons or runners. Therefore, it is possible to produce a turf with high leaf growth and good green color but with a restricted root system. This is one reason why reasonable levels of nitrogen are usually desirable. High nitrogen levels produce a plant with thin cell walls and a high water percentage in its tissue. The thickness of a cell wall is important when a fungus or an insect tries to invade the plant. A plant containing a high percentage of water requires more irrigation and is more susceptible to heat and drought stress. The amount of nitrogen supplied to the turf plant has a great deal to do with the amount of food reserve the plant is able to store for periods of unfavorable weather, such as winter dormancy or summer dormancy. The plant manufactures food material (carbohydrates) in leaf tissue. Since leaves have priority over other plant parts for growth and since nitrogen stimulates leaf growth, the oversupply of nitrogen, especially just before normal dormancy, may promote leaf growth to the point of using up all the food material the plant can supply. If this happens, little food material is available for storage, and the plant may not live through the upcoming dormant period. The goal of a good fertility program should be to produce a reasonable amount of top growth but not at the expense of root growth. Phosphorus (P) For years, many textbooks have suggested that phosphorus is necessary for good root growth. This is true, but only in the sense that all plant nutrients are necessary for the optimum growth of all plant parts. Phosphorus has a great deal to do with the process of energy transfer and storage within the plant. The roots are a primary organ for energy storage and are dependent on phosphorus levels in the plant. The formation and germination of the seed is a process that creates a high demand for phosphorus. A high level of energy must be stored in the seed for it to survive until it can germinate, and the rapid growth processes associated with germination require high energy. Under most conditions, the turf plant is not maintained for its seed production, and its need for phosphorus is low. Most turf fertilizers are low in phosphorus except when a turf is to be established from seed, sod or sprigs. In this case, a fertilizer containing higher phosphorus levels is recommended. Phosphorus is an element that moves slowly in the soil. It may take years for phosphorus to move just a few inches. Of course, the speed of movement depends on the amount of clay in the soil. The higher the clay content, the slower it moves. The slow movement of phosphorus in the soil and the relatively high demand for phosphorus in establishing turf makes it highly desirable to incorporate a fertilizer with an N-P-K ratio of 1-1-1 or 1-2-2 in the soil before seeding, sodding or sprigging. Potassium (K) Many plant growth experts consider potassium to be the plant nutrient that has been passed over and not given credit for the role it plays in plant growth. The way potassium functions in the plant has not been well understood, while functions of other nutrients such as nitrogen and phosphorus have been more clearly defined. Potassium seems to be involved in many growth processes, but one of its most important roles has to do with water relations within the plant. Just as high nitrogen levels produce a plant with thin cell walls and high water content, the absence of adequate amounts of potassium has the same effect. As the amount of potassium supplied to the plant is increased in relationship to the nitrogen level, cell walls become thicker and the water content of the plant decreases. This makes the plant less susceptible to the potential invasion of a disease or an insect attack as well as more stress-tolerant. Potassium has a great deal to do with the balance in the plant between leaf and root growth. As the level of potassium supplied to the plant increases in relationship to the nitrogen level, the rate of leaf growth is reduced. With this reduced demand for food material by the leaves, more becomes available for stolon, rhizome and root growth. Potassium is considered to be the most leachable of the plant nutrients and must be supplied at a constant rate. It may even be lost from the plant through its leaves during rain or irrigation. Use of fertilizers with relatively high potassium levels has been hard to "sell" because unlike other nutrients, its application to a turf does not necessarily result in a change that is easy to see or measure. However, research indicates that when potassium is supplied in optimum levels, the turf plant is less susceptible to other factors such as drought, heat, cold and disease. Other Nutrients From time to time, depending on the local soil and its pH level, nutrients such as sulfur, magnesium and iron may be required. A soil test and/or a tissue test identifies nutrient problems. Most minor nutrient problems are the result of soil with too high or too low pH. When a minor nutrient problem is identified by a soil or tissue test, the missing minor nutrient available to the plant should be applied as efficiently as possible. The best way to do this is to use a "chelated" form of that nutrient. The chelation process helps move the nutrient through the soil solution without becoming unavailable. Fertilizers When the environment cannot supply the turfgrass plant with the nutrients it needs to perform its assigned function, the needed nutrients should be supplied as a fertilizer. Turf fertilizers typically contain only nitrogen (N), phosphorus (P) and potassium (K), but other macronutrients and some micronutrients may be included, depending on local soil conditions. Fertilizer packages or bags have three numbers which represent the percentages of N, P and K. On the back of most bags the guaranteed analysis is provided (Table 4.9). As shown in Table 4.9, the fertilizer is 15 percent nitrogen. It is important to note that 7.5 percent, or one-half, of the nitrogen is in soluble form and the other half is one of the slowly-soluble nitrogen forms (Tables 4.9 and 4.10). Soluble nitrogen materials result in a fast increase in growth rates, especially leaf growth rates and a fast green-up (Figure 4.9). However, this rapid increase is fairly short-lived. Slowly-soluble nitrogen materials result in a relatively slow increase in growth rates and color, but their effect lasts longer. Depending on the material and the environment, some may supply nitrogen from 3 to 4 months up to an entire growing season. Fast growth requires higher amounts of water. However, the plant has thinner cell walls which may make it easier for insect or disease invasion. The plants may also be more susceptible to heat and cold damage. Fertilizer is a salt Fertilizing materials are salts, just like table or rock salt. If fertilizers are overapplied, they can cause plant death, known as "fertilizer burn." Water moves from areas of low osmotic pressure to areas of high osmotic pressure. Normally, solutions inside the plant are higher than the soil solution, so water runs into the plant. If a fertilizer is overapplied, water can be pulled out of the plant, thus killing the plant from lack of water. The possibility of fertilizer burn is countered by watering fertilizer into the soil. Any salt effect is thus diluted. The possibility of fertilizer burn is greater on hot days than on cool days because plants use more water on hot days. Fertilizing materials vary in their ability to produce a burn (Table 4.11). The salt index number has no units and is only used to compare materials. For example, if a fertilizer has urea as its nitrogen source, there is only half the chance for fertilizer burn as when ammonium nitrate is used. Note that all the slowly soluble nitrogen materials have a very low salt index, and thus a very low burn potential. If a soil or water test indicates the presence of a potential salt problem, then it makes sense to use low salt index fertilizer materials. Cultivation Cultivation of turfgrass includes aeration, topdressing and vertical mowing. These practices: improve the aeration of the soil and the infiltration of water, promote the growth of the root system and reduce the compaction of the soil surface and the accumulation of thatch. All of these benefits are essential to producing a vigorous, healthy lawn. Aerification Compaction is a physical process that slowly reduces the amount of oxygen contained in soil (Table 4.12). Roots of the turfgrass plant need oxygen and give off carbondioxide as a product of their growth process. Oxygen from the atmosphere moves into the soil through very small pore spaces to the roots, and carbon dioxide escapes through the soil into the atmosphere. As the soil is trafficked, soil particles in the top 1 to 2 inches are compacted into a layer so that less and less oxygen can enter the soil and less and less carbon dioxide can escape. The net result is a thinner and thinner turf, until ultimately the soil can no longer support any turf growth at all. Only a few weeds can grow in these oxygen-deficient, compacted soils where grasses cannot grow. Since compaction is the result of a physical process, it takes another physical process to reduce or prevent its effects. Aerifiers have a number of hollow or open metal tubes called tines which are used to relieve compaction (Figure 4.10). Some aerifiers have solid metal tines. The tines are 3/8 to 1 inch in diameter and penetrate the soil to a depth of 2 or 3 inches, or as deep as 12 inches. As the tine is pulled out of the soil, a soil core is removed and is deposited on the turf surface. The hole left in the turf becomes an avenue for oxygen to penetrate into the soil and for carbon dioxide to escape. Root growth around the hole is greatly increased, and the vigor of all plants around the hole is enhanced. The greater the number of holes poked in the turf, the greater the increase in that turf’s vigor. The frequency at which any turf area may need aerification is solely dependent on the amount of traffic it receives and to some extent the texture of the soil under the turf. Under a normal maintenance program, areas with foot traffic only may never need aerification. When traffic becomes heavy enough to thin the turf, it is time to aerify. Heavy traffic areas may need to be aerified at least two or three times a year during periods of active turf growth. The best time to aerify is when the turfgrass is actively growing. Roots will rapidly fill the holes and the area will recover quickly. If the turf is aerified during its dormant period, the open holes may allow excessive loss of soil moisture. Occasional Lawn Problems Even with good management, problems occasionally arise as a result of thatch accumulation, weeds, insects, diseases or excess shade. Thatch Accumulation The spongy turf that results from accumulated organic residues between the soil and the green leaves is referred to as "thatch" (Figure 4.11). A certain amount of thatch is desirable, as it adds resilience to the turf, reduces compaction of the soil surface, and prevents soil erosion. However, excess thatch reduces water infiltration, creates shallow-rooted turf, encourages insect and disease infestations and makes mowing difficult. Management practices such as thorough and infrequent watering, close and frequent mowing, proper fertilization and occasional cultivation (aeration, vertical mowing and top-dressing) will prevent excess thatch accumulation. If lawns are mowed frequently, grass clippings will not promote thatch accumulation, and it is beneficial to leave them on the lawn. However, if a lawn is mowed so infrequently that the turf is covered with clippings, then the clippings should be removed. Excess tree leaves should also be removed rather than shredded with a mower. Scalping the lawn by close mowing in several directions at the first sign of spring green-up will aid in thatch prevention. Grass clippings and tree leaves collected after scalping can be disposed of through composting and used in flower and shrub beds or gardens. Excess fertilization with nitrogen leads to thatch accumulation. Lawns should be fertilized in early spring and fall when the grass is not growing vigorously. During the summer months, keep fertilization to a minimum and do not exceed 1 pound of nitrogen per 1,000 square feet every 45 days. If thatch accumulation becomes a problem, lawns should be dethatched in early spring by vertical mowing with a special dethatching tool in two or more directions. For bermudagrass or bluegrass lawns, the vertical blades may be spaced only ½ to 1 inch apart, but for St. Augustine or centipedegrass lawns the blades should be 2 to 3 inches apart. After dethatching, rake or sweep the lawn to remove the organic debris brought to the surface. Aeration should follow the vertical mowing operation. Run a hollow spoon aerator over the lawn two to three times when the soil is moist so that the spoons penetrate 3 to 4 inches into the soil. After aeration, fertilize the lawn to encourage recovery of the grass. Such a renovation may never be necessary, or it may be needed every 2 to 3 years, depending on the turfgrass species and your maintenance program, Shade Shade from tree canopies creates several problems for turfgrasses, including reduced light and competition for water and nutrients. The result is usually shallow-rooted turf that is more susceptible to drought stress, winterkill, wear and disease infestations. Of the turfgrasses, St. Augustine and tall fescue are the most shade-tolerant, zoysia and centipede grasses are intermediate in shade tolerance, and bermudagrass and buffalograssare the least shade-tolerant. However, even St. Augustinegrass requires some sunlight to produce an acceptable lawn in shade. Increase the mowing height for turf growing in heavy shade (St. Augustinegrass and tall fescue should be mowed at 3 inches). Also, reduce nitrogen fertilization of turfgrasses in dense shade to prevent succulent growth that is more susceptible to diseases. If tree canopies are dense and structures or low-growing shrubs screen the lawn, it may be necessary to selectively prune tree limbs to increase light penetration. Root pruning or removal of shallow-rooted trees also will improve conditions for turfgrasses in shade. If dense, low growing trees and shrubs are an essential part of your landscape plan, a shade-tolerant ground cover such as Vinca (Vinca major) can be used in place of turfgrasses. Weeds Because of their variation in texture, growth, habit and color, weeds create an unsightly appearance in lawns. Proper management is the best means of controlling weeds. Thorough and infrequent watering, judicious fertilization and proper mowing are important steps to weed control. However, lawns damaged by insects or disease, wear (compaction) or other problems are highly susceptible to weed invasions. Crabgrass, goosegrass, sandbur and dallisgrass are the major grassy weeds which cause problems in lawns during the summer. The first three are annuals that emerge from seed each spring. Dallisgrass is a perennial grass that recovers from rhizomes in the spring, but also produces seed that spread throughout the lawn. With the exception of dallisgrass, these weeds can be controlled with preemergence herbicides applied in early spring. Dallisgrass can be controlled by spot-treating the plants with a contact herbicide. Cool-season weedy grasses, such as rescuegrass, annual bluegrass and ryegrass, can be controlled by preemergence herbicides applied in early fall, or by contact herbicides applied when the permanent turfgrass is dormant. Broadleaved weeds such as dandelion, chickweed, henbit, clover, dock and mustards can be controlled with selective postemergence herbicides. Only materials recommended for St. Augustinegrass should be used on St. Augustine lawns, as the turf might be damaged by some materials that are safe for bermudagrass. Nutgrass creates special problems in lawns because it grows very rapidly and spreads to ornamental beds and gardens. St. Augustine grass effectively competes with nutgrass and crowds it out; however, when the grass is damaged by insects or disease, nutgrass can become a problem. Caution: Follow label recommendations for all herbicides and use them only on the grasses specified on the label. Insects White grubs, larvae of the May or June beetles, also cause extensive damage to lawns. The grubs feed on roots of lawns 1 to 2 inches below the surface. If the infestation is heavy, grubs consume the entire root system and the sod can easily be lifted or rolled up. To check for the presence of grubs, dig 1-square-foot sections of sod at several locations in the lawn and examine the roots and soil to a depth of 4 inches. (After examination, the soil and sod can be put back in place.) Treatment is justified when more than four grubs per square foot are found. Treatment should be made during the last 2 weeks of July and the first 2 weeks of August. Other insects such as ants, ticks, chiggers and earwigs commonly infest lawns but cause little damage to turf. For complete insect control recommendations, contact your county Extension office. Diseases Properly managed lawns may be attacked by diseases, but they recover much faster than poorly managed lawns. Identification of the disease attacking a lawn is essential to successful control. Some turf diseases have characteristic symptoms that can be readily identified by homeowners. Brownpatch is a fungus disease that damages grasses in spring and early fall. Brownpatch is characterized by circular patches of yellow or brown grass that may vary from less than 1 foot to several feet in diameter. The outside of the circle has a "smoke ring" appearance caused by the actively spreading fungus. In this area, the leaves of the grass may be easily pulled from the stem because of the deterioration caused by the fungus. The grass in the center of the circular patch may recover within weeks, giving the diseased area a doughnut-shaped appearance. The fungus is most active when humidity is high and the air temperature is between 75 and 85 degrees; fungus activity stops when the air temperature reaches 90 degrees. Preventative fungicides should be applied in early fall.
02/01/2009 |