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| Wear and Traffic Stress |
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| There are four general types of traffic problems. |
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| Soil compaction is the pressing together of soil particles, resulting in a more dense soil mass with less pore space. |
| Wear is the injury to a turfgrass from pressure, scuffing, or tearing directly on the turfgrass tissue. |
| Rutting or soil displacement is the displacement of soil particles due to pressure, which results in a rut or depression. |
| Divots are pieces of turf removed by the action of a golf club, polo mallet or other such object striking the sod. |
| With sandy soils or soils below field capacity in moisture content, wear is the dominant injury. |
| Soil compaction often becomes a major traffic problem on soils high in silt and clay and when heavy loads are applied. |
| Rutting occurs primarily when excessive loads are applied to a soil above field capacity in moisture content. |
| With a thatchy turf, divoting could be a problem. |
| Soil compaction |
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| Sources of soil compaction |
| In general, foot and vehicular traffic cause considerably more compaction on turfgrass sites than water drop impact. |
| Water droplet impact |
| Water droplet impact from either rainfall or irrigation is thought to have little or no effect on soil compaction of established turfgrass sites. |
| However, during the establishment period, rain droplets caused a 15% increase in bulk density of the surface 2.5 cm of soil on an unvegetated soil compared to vegetative soil (Cohron, 1971). |
| The degree to which water droplets cause soil compaction is a function of clay mineralogy. |
| Soils containing expanding-lattice clay fractions when hydrated will expand, then shrink and have considerable surface cracking during the drying phase. |
| Subsequently, the cracks or voids can be filled by surface soil reducing porosity and increasing bulk density (Cohron, 1971). |
| Rain intensity and drop size can affect the magnitude of soil compaction due to kinetic energy differences. |
| Cohron, (1971) reported that drizzle-type rain, with a precipitation rate of 7 X 10-5 mm s-1, had a kinetic energy level of 2.2 Jm-2 h-1. In comparison, a heavy intensity rain with a precipitation rate of 4.2 mm s-1 had 343.3 Jm-2 h-1 of kinetic energy. |
| Except for isolated heavy intensity rainfall events, water droplet impact should have only a minor effect on soil compaction due to the minimal kinetic energy. |
| Foot traffic |
The degree of soil compaction created by foot traffic is influenced by:
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| Van Wijk at all. (1977) reported that a running athlete could exert 1.52 MPa pressure, but under static conditions, only 0.04 MPa, a 38-fold difference. |
| Watson (1961) described an example of a 90-kg person wearing either football shoes or street shoes. The football shoes had a contact surface of 4.45 cm² corresponding to 1 MPa static pressure compared to the street shoes with 109 cm² of contact area and 0.04 MPa static pressure. The 25-fold difference in compacting pressure created by the football shoe could result in a greater degree of soil compaction. |
| While it may be possible to apply wear to a grass without compaction, the reverse is not possible. |
| However, in soil compaction studies, the use of a smooth power roller can minimize wear. |
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Precautions that will reduce wear are
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| Vehicular traffic |
During the forward movement of a drive wheel, there are three primary types of forces exerted on the soil, which include the following (Sloane et al., 1981):
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| All three forces can be manipulated to some degree to minimize compaction. |
| It is commonly thought that it is possible to compensate for larger, heavier vehicles by increasing the tire diameter or width without increasing soil compaction. |
| This is based on the belief that the actual contact pressure (weight/unit area) can be the same between vehicles, thus, no increasing compaction forces. |
| From studies done with agricultural equipment, Blackwell and Sloane (1981) showed that heavy equipment with larger, wider tires did increase the depth of soil compaction compared to light vehicles with narrower tires at the same tire contact pressure. |
| Rapid starting, stopping, and turning which causes wheel slippage can further compact soil to a much greater degree than by increased weight, (load) (Davies et al, 1973). |
| However, when wheel slippage is not occurring, increasing the tractor speed from 0.2 to 5 m s-1 reduced the degree of compaction by as much as 50% on the surface 5 cm of soil. |
| Tire tread design can also influence the soil compaction effect of vehicular traffic. |
| Lugged or knobby type tire designs, with the same tire diameter and width, will have considerably less contact surface area, thus greater compacting pressure then smooth tires. |
The smoothed "turf type" tire design, widely used on much of the turfgrass equipment, is an excellent example of how to minimize this type of compaction. |
| Turf maintenance equipment with "turf type," pneumatic tires generally apply 0.03 to 0.05 MPa static pressure (Van Wijk et al., 1977). |
| Distribution of soil compaction |
| Soil compaction can occur in different zones within the soil. |
In turf grasses, the most common soil compaction situations would be:
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| Each of these circumstances would result in different effects on air, water, and root movement, as well as presenting unique management or correctional problems. |
| Beard (1973) noted that a majority of compaction in turfgrass situations occurred in the top 8 cm of soil surface, mostly in the upper 3 cm. |
| Sills and Carrow (1982) and O' Neil and Carrow (1982) found that the soil bulk densities were influenced mainly in the upper 3 cm. |
| This type of compaction is the easiest to correct because cultivation equipment can penetrate this surface zone. |
| A thicker compacted layer at the surface can result from heavier traffic, such as tractors with lugged tires. Vanden Berg et al. (1957) determine the vertical stress on a soil from a rear tractor tire exerting an average pressure of 0.37 MPa. |
| Near the surface, pressures were 0.35 MPa, that even at the 35 cm depth pressures of 0.07 MPa were detected. |
| Sometimes a compacted zone can occur below the surface. For example, in housing developments the original topsoil may be stripped, construction equipment run on the subsurface, and then 8 to 20 cm of topsoil is applied on a top of the compacted subsoil. |
| It is also the most difficult soil compaction to correct. |
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| Compaction may be continuous or discontinuous over an area. |
| On turfgrass recreational sites, traffic tends to be random over an area from maintenance equipment and humans. |
| However, concentrated sites of traffic are not uncommon, such as a center area of a football field, in front of a soccer goal, in foot paths, and on golf course tees. |
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| Effects of compaction on soil properties |
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| Bulk density |
| As pressure is applied to a soil, soil aggregates are deformed and individual particles are reoriented. |
| Total pore space declines, especially the larger pores that are important for gas and water movement and as channels for root penetration. |
| The soil becomes more dense and the pore-size distribution is altered with fewer macropores but more micropores. |
| Compaction influences the air-water relationship by increasing moisture retention. |
| Soil strength |
| As soil particles are pressed together during compaction, cohesive forces are enhanced, particularly as a soil dries. |
| Soil strength increases upon compaction. |
| This property is measured by civil engineers on a dry soil by a test called the modulus of rupture. |
| While the modulus of rupture is only measured on a dry soil, a property that is more directly related to root growth is penetration resistance, which can be determined at any soil moisture content and is measured by a penetrameter. |
| A hard, compacted soil with high cohesive forces plus large pores results in high penetration resistance and mechanical impedence for root growth. |
| Soil aeration |
| Oxygen is consumed in the soil by plant roots and microorganisms, while CO2 is produced from respiration by living organisms. |
| Without adequate gas exchange between the soil and aerial atmospheres, soil O2 becomes limiting to plant growth and CO2 increases. |
| When a soil drains after wetting, sufficient air-filled pores are necessary for gas exchange. |
| Many of these pores are interaggregate (between the aggregates) pores in a well-aggregated soil. |
Destroying interaggregate pores by compaction results in
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| Since 02 diffuses through air 105 times faster than through water, it should not be surprising that reduced aeration is a major problem under compaction. |
| The air-filled pores are also important for water infiltration, percolation, and root penetration. |
| Moisture relations |
| Since water-filled porosity increases with compaction, total moisture content is often higher for compacted soil at a particular matrix potential. |
| In a loamy sand soil with poor inherent moisture-holding capacity, this could be beneficial, but with a fine-textured soil, the result is excessive moisture. |
| The water retained often is not readily available the plants, especially at more negative potentials. |
| Infiltration and percolation |
| Even a thin layer of compacted soil at the surface can greatly reduce water infiltration. |
| Infiltration is highest through larger pores, soil cracks, root channels, and worm or insect channels. |
| Without such means of entry, infiltration occurs through the smaller pores at a much slower rate. |
| A compacted zone at any location in the soil will reduce water percolation and can result in a perched water table if water application rainfall exceeds hydraulic conductivity. |
| Soil temperature |
| A wet, compacted soil retains more moisture than if not compacted. |
| In order for compacted soil to warm up in early spring, the soil matrix plus any retained water must be heated. |
| Thus, compacted soils are slower to warm up in spring. |
| Once a compacted soil is heated up, it will retain heat longer due to a greater thermal mass resulting in higher average soil temperatures in the summer. |
| Factors influencing soil compaction |
| The type of compacting force on a soil has a major influence in the degree of compaction. |
| Primary compacting forces in turfgrass situations are water droplet impact, foot traffic, and vehicular traffic. |
| Other factors that influence compactibility of the soil are soil texture, soil structure, moisture content, particle-size distribution, and plant factors. |
| Soil texture, soil structure and moisture content |
| The degree of soil compaction created by traffic is a function of both soil texture and soil moisture content. |
| Gradually, as a soil moisture content increases a corresponding linear or exponential reduction in porosity occurs until moisture content approaches saturation. |
| Many sports turf areas unfortunately are used extensively in seasons of intense rainfall. |
| Traffic at this point will have a maximum affect on soil compaction adding greatly to the difficulty of maintaining sports turf sites. |
| Boufford and Carrow (1980) observed the effects of intense, short-term traffic on tall fescue turf when the soil was at different moisture contents. |
| Traffic at field capacity (-0.012 MPa matrix potential) resulted in the greatest increase in bulk density. |
| At saturation (0 MPa), bulk density was not affected but the moisture release curve showed a shift from larger to smaller pores. |
| This resulted in destroying the soil structure under saturated conditions even though no compaction occurred. |
| While course-textured soils (sand) may compact, the bridging between the hard sand particles prevents the elimination of most of the larger pores. |
| Thus, adverse effects of compaction on soil physical properties are less evident on sands then fine-textured soils. |
| Taylor and Blake (1981) observed that as the sand content increased from 69 to 93%, the bulk density of the surface 5.3 cm of the mixtures decreased from 1.62 to 1.47 Mg m-3. |
| In addition, the infiltration rate, correspondingly increased from 0.2 to 4.4 cm h-1. |
| Both responses indicate that the increasing sand content reduced the degree of compaction noted under actual golf course conditions. |
| Once sufficient sand is present for the bridging between sand particles to occur, then sand starts to create larger pores and a relatively rigid matrix resistant to compaction is formed. |
| Particle size distribution |
| Of the major factors influencing the severity of soil compaction, much research has centered on understanding the effects of particle-size distribution on soil compactability. |
| After 9 years under field conditions with traffic, Waddington et al (1974) found that a coarse sand with a very uniform particle-size distribution and infiltration of 7.5 cm h-1 compared to 1.3 cm h-1 for a wide particle-size distribution of a silt loam soil. |
| With a wide range of particle size, the space between particles and interaggregate pores are filled with smaller particles. |
| This results in a high initial bulk density and under pressure the soil becomes a dense, compacted mass with few large pores. |
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| Plant factors |
| The presence of plant tissues, living or dead may influence to some degree the ability of soils to resist compaction. |
| High proportions of turfgrass shoots, roots and thatch can absorb and dissipates compacting forces. |
| Van Wijk et al. (1977) observed that the presence of turfgrass increases soil strength, as measured from a cone penetrometer, from 0.2 to 1.0 MPa over unvegetated soil. |
| Tomas and Guérin (1981) found that a turfgrass cover reduce the degree of compaction from a studded roller over no cover. |
| Their data suggested that tall fescue prevented compaction most, Kentucky bluegrass and perennial ryegrass intermediate, and fine fescue and Timothy least. |
| Effects of soil compaction on turf grasses |
| Madison (1971) noted that "compaction is the foremost turf problem" on recreational turfgrass by causing an overall decline in growth, vigor, quality, and persistence. |
| However, in many instances compaction is not recognized as the cause of turf deterioration since compaction does not directly reduce plant activity. |
| Instead soil compaction acts by affecting other factors influencing growth such as soil aeration, soil strength, plant and soil moisture relationships, or soil temperatures. |
| Compaction is generally considered a hidden stress. |
| Root growth and activity |
| The various physiological or morphological root responses to compaction are primarily a result of reduced aeration, high soil strength, increased ethylene concentrations, altered soil water status, or interactions of these factors. |
| The most conspicuous rooting response to soil compaction is altered root distribution. |
| When determining root growth at 42 and 84 days after compacting a mature perennial ryegrass O'Neil and Carrow (1983) reported a higher percentage of roots occurring in the surface 0 to 5 cm zone and a lower percentage in the 10 to 25 cm zone with increased compaction. |
| The of observation of greater surface rooting under compaction may be due to reduced root growth rate in response to higher mechanical impedances. |
| This would cause roots to accumulate at the surface instead of growing deeper into the profile. |
| Another explanation may be ethylene-promoted adventitious root initiation. |
| Soil ethylene concentrations can be elevated under low soil aeration. |
| At moderate compaction, soil aeration would be the primary influence on root growth, while under heavy compaction both aeration and mechanical impedance are important. |
| With severe compaction, the soil pore sizes are very small and soil aeration is low. Thus, both main root and lateral root growth rates may be restricted by low aeration and high soil strength. |
| Increased root porosity of grasses is well documented under waterlogged situations. |
| It would seem reasonable to assume similar results would occur under compacted conditions, were major effect of compaction is to reduce soil aeration. |
| Immediately after a rainfall or irrigation, compacted soils can exhibit limited aeration for long periods. |
| Shoot growth |
| Whether soil compaction decreases rooting in all root zones or just deep root growth while surface rooting increases, the volume of soil explored by the roots for nutrients and water uptake is markedly reduced. |
| A plant grown on compacted soil will be more susceptible to drought and high-temperature stresses and be less able to recuperate if injured. |
| Shoot growth should respond negatively to this adverse root environment, especially if stresses such as heat, drought, or pest occur. |
| Top growth or yield have been widely reported to be affected by compaction. |
| However, the response highly depends upon soil texture . |
| On sands and loose, friable soils, moderate compaction can increase yield by improving soil moisture conditions. |
| When soils are high in silt or clay, moderate to severe compaction would decrease yield. |
| Another effect of the influences shoot response to compaction is the time of year or and environmental conditions. |
| Cool-season turfgrasses may actually appear greener and be of equal or greater visible quality than a noncompacted turf in the cool periods of the year when moisture and nutrients are not limiting. |
| Regardless of the reason for a shoot growth reduction under compaction, the decline in shoot density, verdure, and clipping yield would produce a sod more prone to wear-the other major traffic stress. |
| A thinner turfgrass stand in conjunction with slow growth would reduce wear tolerance. |
| Nutrient uptake |
| Nutrient uptake and nutrient ratios in many plant species have been reported to be altered by compacted conditions. |
| The reduction in uptake under compaction appears to follow the order K >N > P > Ca > Mg, whileNa uptake may increase. |
| Letey et al.(1964) monitored N, P., K, and Na uptake by 'Newport' Kentucky bluegrass under different soil aeration conditions. |
| At < 6% O2 concentration, N, P., and K uptake declined rapidly, while Na uptake increased threefold. |
| When tall fescue (Sills and Carrow, 1982) in Kentucky bluegrass (Sills and Carrow, 1983) were subjected to different N rates and compaction levels, the percentage of N in the leaf tissues was not affected by compaction. |
| However, compaction caused less N use per unit area of sod (mg of N/100 cm2). |
| In both of these studies, compaction reduced total root growth and deep rooting (15-30 cm depth). |
| However, when high N rates were coupled with compaction, a detrimental synergistic effect on rooting occurred. |
| For example, compaction applied at the lower N rate cause a 13.3% reduction in total rooting but a 45% reduction at the higher N rate on Kentucky bluegrass. |
| These results indicate that additional N applied to an adequately fertilized, but compacted turfgrass stand could cause a marked reduction in rooting. |
| Plant water use and status |
| How does compaction effect water use once the water is in the soil profile? |
| Many of the alterations in soil physical properties adversely influence irrigation programming. |
| Reduced infiltration and percolation would result in longer irrigation cycles, greater runoff, and a higher percentage of exaporation loss. |
| Using common bermudagrass, ET declined under compaction (Morgan et al, 1966). There are at least a dozen additional studies with ET reductions up to 50%. |
| A major influence on compaction on turfgrass is decreased water use. |
| Turf managers often apply more water to their compacted sites. Several reasons for this phenomenon are possible. Low infiltration rates can enhance runoff and evaporation losses; thereby making it difficult to apply larger quantities of water for deep, less-frequent irrigations. Thus, managers may resort to lighter, more frequent applications that enhance evaporative losses by maintaining a moist soil surface. |
| O'Neil and Carrow (1982) observed that additional water does not improve a compacted turf if it is already receiving adequate water as indicated by tensiometer readings. |
| Irrigating too frequently can result in very low oxygen diffusion rate (ODR) levels for extended periods. |
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| Various mechanisms proposed are shown to influence water use on grasses under compacted conditions. The net result is a reduction in water use. |
| Recent research indicates that soil compaction may decrease leaf water potential. |
| Some evidence exists that compaction can influence stomotal density. |
| Carbohydrate reserves |
| Carrow (1980) determined TNC levels in three cool-season grasses subject to various compaction stresses. During the cooler portions of the year, no difference in TNC levels were noted. |
| In Midsummer, however, TNC levels declined 23 to 50% compared to the noncompacted grasses. |
| Under greenhouse conditions (Sills and Carrow, 1983) and in a feild study sampled in September (Sills and Carrow, 1982), TNC levels were similar for both uncompacted and compacted treatments. |
| These studies would suggest that compaction may contribute to reduced TNC levels primarily when in conjunction with summer stresses. |
| Canopy temperatures |
| Since compaction influences water uptake and turf density, it seems reasonable that it may affect canopy temperatures. |
| In a study were canopy temperatures were measured diurnally by infrared thermometry on a Kentucky bluegrass subjected to three levels of compaction, canopy temperatures were greater for the compacted turf. (Agnew, 1984) |
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| The compacted grass consistently exhibited higher canopy temperatures of 0.5° C. (cloudy days) to 3.0° C. (clear days) relative to the uncompacted treatments. |
| Agnew (1984) and Agnew and Carrow (1985) attributed the higher canopy temperatures primarily to reduced ET cooling of the compacted turfgrasses. |
| Another potential cause for higher canopy temperatures could be a less dense turf allowing higher soil temperatures to occur. |
| Environmental stress tolerance |
| A weakened plant with low carbohydrate reserve growing in a medium with poor physical properties would likely be susceptible to environmental stresses. |
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| Even if soil compaction does not enhance the possibility of a particular stress on turf, it would reduce a recuperative ability of the grass once it was injured. |
| Disease incidence |
| Some diseases are more prevalent in moist microenvironments that are common for poorly drained compacted soils. |
| Vargas (1981) indicated several turfgrass diseases were more common under poor drainage, namely Pythium blight, Rhizoctonia brown patch, Fusarium patch, and Typhula blight. |
| Once a disease infestation occurs the severity may be greater and recovery slower under compacted conditions. |
| Community ecology |
| When compaction alters the physical properties of a soil, not all plant species are affected to the same extent. |
| Some plants have a relative competitive edge over other plants. |
| On sports turf sites, goosegrass, knotweed, and annual bluegrass often invade, while adjacent untrafficked areas have few of these weeds. |
| Gore et al. (1979) subjected 16 mixtures composed of five species to traffic and no traffic treatments. With traffic, total cover of all mixtures declined but the relative proportion of ryegrass, timothy, and Kentucky bluegrass increased while red fescue and colonial bentgrass decreased. |
| This illustrates that compaction can influence community ecology and alter the original composition of turfgrass stand. |
| Alleviation of soil compaction effects |
Cultural practices for preventing or alleviating soil compaction can be grouped into four categories
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| Turfgrass selection |
| Carrow and Troll (1981) evaluated five species with regard to compaction tolerance. Based on visual quality and % turf color following compaction for 56 days, the relative tolerance was perennial ryegrass = Kentucky bluegrass > tall fescue > Colonial bentgrass > red fescue. |
| Recent research (Shildrick and Peel, 1983; Meyer, 1983) indicates that several of the newly developed tall fescue cultivars are superior to Kentucky 31. |
| Cultivars of a species can vary with respect to compaction tolerance. |
| Relative compaction tolerances of warm season turf grasses have received little research attention. |
| Traffic control and water management |
| Schmidt et al. (1989) demonstrated that compaction applied in the fall was less detrimental than if applied at or just after spring greenup of 'Midiron' bermudagrass. |
| Concentrated traffic that severely thins or compacts turf soil should be avioded wherever possible. |
| Design techniques can be employed where possible. Foot and vehicular traffic can be guided or controlled through proper selection and placement of trees shrubs, traps, walks, roadways, and contours. |
| They use of ornamental plants, hedges and shrubs is preferred for their agronomic and aesthetic benefits to the site. |
| Any directed paths should have as many possible alternatives as feasible to minimize any compacting forces on any one area. |
| Plan for shortcuts between paths and install barriers or bridging walkways. |
| One of the most common traffic controls on golf courses is the placement of bunkers near greens. |
| Design bunkers to be far enough from the edge of the green to allow for very good patterns of foot traffic, but close enough to prevent cart traffic. |
| Pin placements should be selected to allow for reasonable entrance and exit from the green over a number of areas. |
| One of the greatest challenges over the next 20 years is providing accessibility to older golfers. With the graying of America and the retirement of the baby boomer generation there will be increased pressure for direct access to all areas of the course, especially greens. |
| Providing close access to the back of the green from cart paths may be come standard. |
| Another problem area is the end of cart paths or the entrance to fairways. If these areas are narrow they generally result in high compaction in the turf at the end. |
| If possible, design terminal areas of cart paths as wide as practical to distribute traffic. |
| For sports fields, particularly practice areas, rotate use of specific areas to distribute traffic patterns. |
| Any very narrow areas such as sidelines will become compacted with traffic. There are alternative root zone support materials or surfaces to distribute the compacting load. |
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Soil cultivation & modification Details will be presented in next class. |
| Wear |
| Wear is defined as injury to a turfgrass stand from pressure, tearing, and scuffing directly on the tissues. |
| Wear damage should be determined within a short period of time after the wear treatment has been imposed. |
| If a period of several days expires between the wear treatment data and the time of measuring plant responses, the researcher may be determining the recuperative ability of the grass rather than wear tolerance. |
| Another confounding factor evident in many "wear" studies is the presence of soil compaction due to the techniques used to impose the wear. |
| Attempting to evaluate both wear and compaction tolerance in a single test procedure can result in misleading information. |
| For example, if Kentucky's-31 tall fescue growing on a fine-textured soil was subjected to a studded, offset roller treatment to apply wear plus compaction, it would not perform well, even with its good wear tolerance. |
| The reason is because Kentucky-31 has poor soil compaction tolerance (Carrow, 1980). |
| Wear studies |
| Carrow and Johnson (1989) demonstrated that wear damage on turf from golf cart traffic was immediate and increased with increased traffic, but with substantial wear occurring with only 15 passes in one day over an area. |
| Straight-line driving patterns cause much less injury then semi-circular or sharp-turned patterns. |
| Younger (1961) used a wear machine that could apply scuffing, tearing, and punching types of wear. Bermudagrass, zoysiagrass, and tall fescue are species with good wear tolerance. |
| Moderate wear tolerance was exhibited by Kentucky bluegrass, perennial ryegrass, creeping bentgrass, and red fescue with colonial bentgrass showing poor tolerance. |
| In a series of studies, Shearman and Beard (1975) were able to identify several characteristics that influenced wear tolerance at the interspecific level. |
| Total cell wall content accounted for 78% of the variation in wear tolerance of seven species. |
| Lignocellulose, cellulose and lignin and were less related. |
| They also found that species with high leaf tensile strength and wide leaf width tended to have better wear tolerance but no correlation was observed for verdure, shoot density, percent leaf moisture, percent relative turgidity, or load bearing strength. |
| The influence of golf cart tire design and golf shoe design on wear of turf was reviewed by Beard (1973). Only minor differences in golf cart tire tread designs on wear injury were observed by Carrow and Johnson (1989). |
| With the same tread configuration, no difference between radial and nonradial tires was found on wear of Tifway bermudagrass . |
| A study by McNitt and Landschoot (2002) was conducted to determine the effect of various types and rates of soil reinforcing materials on soil bulk density, soil water content, surface hardness, and turfgrass density of a high-sand root zone exposed to three levels of simulated traffic (wear). |
| Six soil reinforcing materials were mixed at varying rates with a high-sand root zone. These included DuPont Shredded Carpet, Netlon, Nike Lights, Nike Heavies, Turfgrids, and Sportgrass. |
| Wear level treatments were applied with a Brinkman Traffic Simulator (Cockerham and Brinkman, 1989). |
| Surface hardness and soil bulk density were correlated during the 2-yr test period (r =0.63). The reinforcing treatments that lowered soil bulk density and surface hardness were DuPont Shredded Carpet, Nike Lights, and Nike Heavies. |
| Reinforcing material treatments that increased or did not affect soil bulk density generally resulted in increased surface hardness compared with nonamended controls. These treatments included Netlon and Turfgrids. |
| Surface hardness generally became more pronounced as the level of wear increased for Netlon, Turfgrids, and Sportgrass treatments. |
| The Sportgrass treatment consistently measured lower in soil water content than the control and had a turfgrass density lower than the control on all rating dates in 1996 but did not differ from the control in 1997. |
| Traffic on dormant turf |
Several types of traffic-related injuries have been observed during the winter months on turfgrasses:
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| Rutting and soil displacement |
| Rutting and soil displacement are a result of compression and the physical removal of soil. |
| Both are caused by foot and vehicular traffic on sports turf. |
| The problem of rutting and soil displacement occurs most often on wet, fine-textured soils. |
| Traffic events that occur under periods of high soil moisture content, typically in fall, winter, and early spring, on fine-textured soils can result in considerable rutting and soil displacement. |
| Van Wijk (1980) found that both the turfgrass root system and the magnitude of organic matter amendment of sand have a major role in rutting and soil displacement. |
| They've found that the presence of turfgrass root systems increased penetration resistance (determined with a cone penetrometer) which results in less rutting and soil displacement, especially at a low soil organic matter content (2.3%). |
| Prevention and correction |
| Prevention of rutting and soil displacement is based on the surface soil zone being firm enough to withstand penetration. |
| Determination of soil strengths of the surface 2 to 3 cm of soil with 81 cm2 base, 60 degree cone-type penetrometer. |
| Penetration resistance had to be at least 1.4 MPa. |
| Prevention of rutting and soil displacement is accomplished by developing a firm soil surface. |
| Drying the soil will dramatically increase the penetration resistance of fine textured soils. Therefore, providing for rapid surface and subsurface drainage is important. |
| In many cases, allowing the site to adequately drain after an irrigation or rainfall prior to an athletic event can help reduce rutting and soil displacement. |
| Rolling can removed minor variations in surface contours and provide a smoother surface. |
| The practice of rolling is often used prepare a sports turf site for intensive traffic. |
| In this case, soil is compacted to the point at which rutting and soil disbursement cannot occur. |
| Divots and ball marks |
| Beard (1973) reported that the size of the divot depended on the player, turf species, and cutting height. |
| Rhizomatous turfgrasses are characterized by relatively small divots and a more rapid recuperative potential since regrowth and recovery can occur from rhizomes under the center of the divot as well as from the sides. |
| Bunch-type and certain stoloniferous turfgrass species are characterized by larger divot size with most of the recovery limited to regrowth from the edges of the divot. |
| The comparative divot size of three commonly used cool-season turfgrasses cut at 0.5 in. ranks in the following order: bentgrass annual bluegrass Kentucky bluegrass |
| Ball marks |
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| Other factors may also be involved such as the thatch level and moisture status of the turfgrass and underlying soil. |
| If the ball Mark is not repaired before the next morning the raised portion is removed leaving a small dead area. |