Causes Of Bent Grass And Effect Of Soil Compaction On Turf Recovery - Coursework Example

?CAUSES OF BENT GRASS AND EFFECT OF SOIL COMPACTION ON TURF RECOVERY Parklands, college campuses, athletic fields, and farms have an interest in controlling the damage to turfgrasses from foot traffic. The consequences of heavy traffic to grasses, as well as soil are quantified. Measurements and variables are described that influence the height potential of turfgrass, as well as its ability to recover from the damage induced by foot traffic. Analyses were conducted to determine the greatest height attainment by grass transections, and the correlation towards soil conditions; particularly soil compaction. While there is abundant research evidence that soil compaction due to foot traffic impedes grass growth in many ways, in this case there was insufficient correlation between height and compaction to conclude a detriment to turf grasses. INTRODUCTION Even the most cursory of observations within a well-traveled outdoor area reveals the apparent lack of ground cover plants in areas of high foot traffic. Regardless of whether the traffic is human or animal origin. An obvious trail of bare dirt illustrates the way grass and other forms of plants that serve as ground cover are restricted in their growth through trampling. While it is apparent that heavy traffic can kill or impede grasses, a thorough understanding of botany requires the elucidation of the extent to which this is true; how much data can be gathered regarding how much grass is restricted by what amount due to a particular level of human or animal foot traffic? A significant body of research already exists relating to this topic in addition to the data presented herein. Studies of this sort have a great value in terms of the conservation of natural resources. This is especially true pertaining to the unification and maintenance of Parkland in suburban settings. Where groundcover is in danger, adequate resource planning in addition to architectural and design strategy are helpful in terms of the preservation not only a wilderness areas, but of groundcover existing at schools, universities, and other public places. Over time, the consequences of traffic can cause problems in agriculture as well. Vehicles used to till the soil may at the same time diminish that soil's ability to defuse nutrients unless special care is taken. (Reintam et al. 2005) Sports fields and golf courses must also seriously consider and the impact of human foot traffic upon it. On these sorts of fields or fairways severe damage in the form of turf removal can occur, the sort of removal can also be known as a divot. The implications of wear and tear on the turf grass essential for the appearance they wish to cultivate. Harivandi describes the genetic tolerance of turf grasses to withstand foot traffic as wear tolerance. (Harivandi, 2002) vehicular traffic may also be a concern if it is consistent, and localized to a specific, narrow region of groundcover. Wear tolerance reflects the ability of a particular turfgrass to survive pressure that can compress or crush the stems, or leaves of grasses and other types of plants. In essence, the result is two primary challenges posed by foot and vehicular traffic: damage to the plants themselves, as quantified by wear tolerance of the grasses – and soil compaction, which affects the soil itself and its ability to support life and to provide the fertile ground for new growth; under dry conditions. (Brosnan et al. 2005) High traffic areas, if left unattended can be sorely defaced through the additional process of soil displacement. This is a topic of concern upon wet soils especially. Under these conditions increased damage to various forms of turfgrass and higher levels of the root system can be severe. (Harivandi, 2002) Kentucky bluegrass tends to be the most common form of turfgrass used for athletic fields. (Puhalla et al. 1999) Over time, the damage from considerable foot traffic has the potential to become a cumulative. As the soil grows increasingly compact, the viability and fertility of the area in terms of plant renewal, and new growth may be compromised. (Whisler et al. 1965) Bluegrass in particular is largely dependent upon morphology as a determinant of wear tolerance; specifically shoot density, as well as lower water content. Leaf Width and strength are a factor for the popular Kentucky Bluegrass, and are likely to prove important for other varieties as well. (Brosnan et al. 2005) This article will discuss the consequences of foot, animal, and vehicular traffic as it affects the soil conditions, specifically pertaining to the effects of compaction of the soil. Compaction has the potential to influence nutrient uptake, which can control the health of the plant, affecting other metrics such as the aforementioned wear tolerance, as well as the specific densities and general viability of structures including leaves, shoots, and roots. HYPOTHESIS A likely hypothesis in terms of turfgrass tolerance would be the issue of soil compaction. This factor has the potential of influencing all other aspects of plant survivability, and can be directly affected by foot and vehicular traffic. It is reasonable to propose that soil compaction is the most important determinant of growth in turf grass, by influencing recovery from foot-traffic damage. It is proposed that compaction outweighs soil pH, moisture content, and fertilizers. Compact soil has the potential to control these other factors by influencing diffusion through the soil to the root system of turf grasses. RISK ASSESSMENT The known risk factors on a study such as this would include the normal hazards of extended periods in the woodlands. While most studies of use in landscaping would involve stable lawns and fields without significant risk; extensive studies may involve investigation of forest biomes, possibly as a control factor. In this case, the known risks would include: 1.) Potential exposure; 2.) Falling branches; 3.) Becoming Lost; 4.) Thorns/nettles. But for the purpose of landscaping needs; the low frequency of these potential dangers are deemed unlikely to pose a risk to the investigator. Experiments with soil compaction and grass are deemed safe to study. METHOD As a test of this hypothesis, a section of turfgrass was cordoned off and transected to derive samples for height measurement. The five tallest blades of grass were measured, and the degree of soil compaction was quantified. This provided data allowing the comparison between the greatest height that could be attained in a high-traffic area. Five blades of grass were measured from each transection and then averaged together. The correlations between average height and soil compaction were analyzed. The distance between quadrants was 3 meters. The data was collected by the tallest 5 plants, light intensity, soil compaction and soil pH from every quadrant. These data was calculated as the mean value by statistical method. Two meter tapes were used for field work. Electronic pH meters were used without barium sulphate. Photometers were used to record conditions of sun and shade. The line transection was conducted with care that the plants suffered no unnecessary damage. RESULTS Ten measurements of average plant height were gathered and averaged from the transections, ranging from 10.6 to 29 millimeters. Spearman’s rank correlation was used to quantify the ten ranks of height with the corresponding levels of soil compaction. While the lowest value of soil compaction did correspond to the five tallest plants, other low-height grasses were also within the loosest area of soil. The loosest soil had the 29 mm height, as well as a measurement of 14.4, within the same category. The rs value from the Spearman’s rankings coefficient was -0.78, which is below the threshold at which the Null hypothesis can be rejected. As a consequence, no definitive correlation can be inferred between grass height and soil compaction with this sampling. DISCUSSION Issues with Soil Compaction Compact soil can restrict the ability of new plant shoots to effectively penetrate the soil. This creates stress on the soil, and thus the plants within it. Stress tolerance, wear tolerance, as well as the ability of the soil and anything within it to recover from damage decrease with increasing levels of compaction. (Shearman, 1988) This is one physical factor that will limit the viability of groundcover, and ultimately lead to the death of turfgrass and similar plants. Compaction also contributes to Bulk Density in soils. As density increases, pore space in the soil diminishes in size. (Harivandi, 2002) Harivandi also describes water retention issues affecting grass growth as a consequence of compaction. More compact soil as a result of foot traffic renders soil better able to hold moisture. Moisture infiltration is impeded as Earth grows increasingly compact. On the one hand, this does hold in more water that could be of use to growing grass within the soil. Yet the drawback of increased compaction is that it also restricts the soil from taking in new water. This contributes to water runoff when the terrain is sloped, and standing water from rain is more likely to evaporate before adequate infiltration can occur to the benefit of turfgrass. Evaporation is likely to be increasingly severe on compact soil during the summer months. When the interior of the soil has less humidity, temperature can increase to a greater degree which leads to drier soil. This can rapidly progress to a runaway cycle of evaporation and dessication. When rain does occur, compact soil as a result of foot traffic contributes to standing water puddles which themselves contributes to disease. But this water retention - to a point - is useful to certain warm-season grasses, such as bermudagrass which respond to high temperatures in order to begin active photosynthesis after winter dormancy. (Harivandi, 2002) Along with the inhibition of water diffusion through compact soil; there are also issues concerning oxygen, and the rate at which it can permeate the soil, particularly the root zone. Compact soil inhibits root growth, and it may be stopped entirely if the ground is sufficiently dense. Where root growth does still occur, within the root zone of grasses, oxygen is necessary for respiration and proper maturation. In the absence of an adequate respiratory exchange nutrient uptake by the root system is impeded, as well as the growth of aerophilic microbes that coexist among the root system and would normally be contributing to nutrient availability. The issue of oxygen deficit is another risk-factor for malnourishment in turfgrass growing in highly compacted soil. (Harivandi, 2002), (Whisler et al. 1965) Another nutrient problem that occurs in agriculture contributes to a similar process. Excess nitrogen from fertilizer can contribute to anaerobic conditions within compacted soil, this can enhance plant nutrient loss. (Reintam et al. 2005) other warning signs can be found within the plants themselves if the observer has the wherewithal to perform chemical investigations of the plant matter. An increased anaerobic environment due to soil compaction stress will alter the pH levels in the plant tissues. Research indicates that pH levels will grow increasingly basic in high stress conditions, (Leigh, 2001) and this is highly likely when the soil is sufficiently compact. Thus, the most scientific analytical tool to detect compaction stress in suspected cases would be the analysis of cellular fluid pH in the plant cells themselves. (Reintam et al. 2005) These processes are worthy of study in the interest of the preservation of greenery and defense of natural resources. In terms of recovery potential, Bermuda grasses and seashore paspalum exhibit the ability for an almost total recovery, whereas Dichondra and Bentgrass are the most vulnerable to foot traffic with only a partial ability to recover. (Harivandi, 2002), (Trenholm, 2000), (Shearman, 1988) Researchers have identified a number of warning signs to alert project planners and culturalists of the severity of soil compaction: Shallow root development among turfgrasses with thicker and shorter development among roots. This may promote the growth of undesirable, compact-soil adapted weed plants, such as crabgrasses or clover - whose presence suggests soil conditions less conducive to traditional turfgrasses. Shoot growth is impeded, and new grasses may lack a green color in favor of yellowing; as a result of insufficient nitrogen. General size decreases can occur amongst several vegetative structures, (rhizomes, leaves, and stolons) the grass will experience a general thinning in distribution with high levels of compaction. (Harivandi, 2002) Compaction-risk also increases - as stated above - in wet soils that experience traffic, but fields with a high level of clay content increase soil vulnerability; both from compaction, and soil erosion. (Pratt & Olivia, 1996), (Reintam et al. 2005) The soil will be less porous, root and shoot length will be affected by the greater resistance to penetration within the topsoil, as bulk density increases. Partly due to the risk of soil displacement, water content becomes essential in any discussion on the risk factors of soil compaction, water content must be considered, as well as the likelihood of changes in water content due to the best available projections of seasonal weather during the planning of turf maintenance or agricultural development. (Reintam et al. 2005) Increasing soil density as discussed above inhibits nutrient uptake. A central factor in this limitation relates to restrictive conditions that inhibit the growth of plant roots, in addition to the aforementioned problems with the reduction of pore size in the soil. This mechanical resistance inhibits new plants from becoming established, and results in weaker and less tolerant grasses as a result of shallow rooting systems. If these plants are more vulnerable to environmental stresses, disturbance from foot traffic, and soil disruption as a result of inclement weather. The decline of turfgrass on a body of land then promotes further erosion of topsoil, and bare ground with no form of cushioning whatsoever would be even more prone to soil compaction as a result of further foot and vehicle traffic. While groundskeepers and farmers attempt to use supplemental fertilizer to address the weakness and bare spots on turf, studies indicate that even in the case of abundant nutrients and water, growth was still impeded. Mechanical resistance from compacted soil matters more than plant hormones or nitrogen supplements in terms of the development of a stable and efficient root system. (Reintam et al. 2005) Compaction Recommendations Obvious footpaths encourage further traffic. When possible, sidewalks should be constructed where traffic is intended. If a cement or gravel path is impractical, high traffic areas should be seeded with high-tolerance turf species with high recovery rates. (Pratt & Olivia, 1996) Mowing height, as mentioned earlier improves wear tolerance. Golf courses with large green areas should rotate cup placement to prevent sustained, consistent traffic over a limited stretch of turf. Vehicle traffic, if unavoidable should use pneumatic tires. (Harivandi, 2002) Particular varieties must be chosen in advance by building and project organizers in order to select for varieties that will exhibit considerable tolerance to foot or vehicle traffic, as well as the ability to recover from these injuries. Research indicates that factors which influence wear tolerance include reduced total cell wall content in leaves, the degree of leaf moisture, shoot density and the presence of potassium in the shoot tissues. A high level of potassium corresponds with greater tolerance. Other elements that improve wear tolerance include magnesium and manganese in addition to potassium. And while the content of lignocellulose in leaves has in some studies shown to improve wear tolerance, (Trenholm, 2000) other researchers contend that no single molecular element is definitive in terms of wear tolerance across all plant species. It is a combination of different molecular constituents, including lignin in various balances which contribute to tolerance in complex patterns. In the case of Bermudagrasses, tolerance is aided by increased lignin and decreased cellulose. However, similar mechanics that may influence wear tolerance within species do not necessarily correlate with similar advantages in other grass species. (Brosnan, 2005) Although popular, annual blue grasses as well as rough bluegrass often exhibit low levels of wear tolerance. Sturdier varieties tended to produce higher total cell wall contents, with greater levels of fibers than the more vulnerable varieties. Turfgrass tolerance to foot traffic can in many cases be manipulated by lawn maintenance practices. An important indicator of low tolerance is plant tissue succulence. The lower it becomes, the greater the plant's tolerance to foot traffic. Tolerance can be influenced by mowing height. The higher the plant, and therefore the higher the mowing height the more cushioning the turf grasses possess against a bombardment of feet or vehicles. When grass is cut lower, tolerance is decreased. (Shearman, 1988) The soil can be supplemented with nitrogen to benefit the durability of turfgrass, but only up to a critical point beyond which diminishing returns set in. In general, when most plants are fed high levels of nitrogen in terms of fertilizer, they can grow more succulent. While a certain basal level is needed for the plant's normal function, as stated above high succulence weakens the plant's ability to survive pressure. (Shearman, 1988) Furthermore, attempts to adjust the nitrogen balance in the soil to more favorable levels respective to the species of turf grass can be confounded by compaction. Even slight compaction can decrease available soil nitrates. (Whisler et al. 1965) But the utilization of nitrogen fertilizer is a common strategy in agriculture when there is a high demand for consistent yield. (Reintam et al. 2005) but while the strategy can prove beneficial this is largely true only at lower levels of soil compaction. Introducing additional nitrogen after a point will no longer provide crop benefit, or turfgrass advantage – but may contribute to the development and establishment of pest species. This is largely due to the possibility of environmental damage resulting from excess nitrogen which can alter the balance of gases in freshwater ponds and lakes. (van den Akker & Soane, 2005), (Reintam et al. 2005) Compact soil can contribute to anaerobic conditions, and the microorganisms favoring such a state within the soil that would otherwise support agriculture or turfgrass. Anaerobic metabolism creates the additional risk factor of changes in the soil pH. Crop plants can be impeded when the pH value becomes increasingly basic. (Reintam et al. 2005) Researchers advise a process of constant involvement, and monitoring in regards to wear tolerance adjustment. When a strategy is selected for increasing the durability of turfgrass, the success of the measure should be evaluated as soon as possible. (Brosnan, 2005) Other researchers have performed quantitative analyses on the degree to which trampling effects grass, and to what degree. All turfgrass is negatively impacted by heavy foot traffic, but the response of different species varies. (Pratt & Olivia, 1996) Thus, it might be assumed that the total composition of turfgrass species in a given area is a determinant factor in the ability of the turf to withstand and rebound from traffic/trauma. The Pratt research determines that after 100 passes from human foot traffic, measurable damage occurs in three grass species. Soil displacement under moist conditions enhances this effect. (Pratt & Olivia, 1996) CONCLUSION Factor concerning grass growth, and thus its ability to recover from the trauma of foot and vehicle traffic can include multiple variables of sunlight, nutrient availability, and the specific species or combinations thereof. In this instance, while soil compaction can lead to serious deficiencies affecting a variety of vital issues needed for the health of turfgrass – it was not a critical factor in this experiment. The traffic in the transected region was not severe enough to outweigh issues of chemical composition in the soil, water content, or sunlight factors. REFERENCES Brosnan, J.T. Ebdon, J.S. Dest, W.M. (2005) CHARACTERISTICS IN DIVERSE WEAR TOLERANT GENOTYPES OF KENTUCKY BLUEGRASS. Published in Crop Sci.45:1917–1926 (2005). doi: 10.2135/cropsci2004.0511. Harivandi, A.M. (2002) Turf grass traffic and compaction: problems and solutions. University of California. Division of agriculture and natural resources. Leigh, R. 2001. Potassium homeostasis and membrane support. Journal of Plant nutrition. Soil science. 164, 193 – 198. Pratt, J. Olivia, M. (1996) The Effect of Human Trampling on Three Vegetation Communities in Mount Elgon National Park. Project Elgon. 1996. http://www.see.leeds.ac.uk/misc/elgon/trampling.html. Accessed: 2/14/2012. Puhalla, J., J. Krans, and M. Goatley. 1999. Sports Fields: A manual for design construction and maintenance. Wiley&Sons, Inc. Hoboken NJ. Reintam, E. Kuht, J. Oogus, H. Nugis, E. Trukmann K. (2005) Soil compaction and fertilisation effects on nutrient content and cellular fluid pH of spring barley. (Hordeum vulgare L.) Agronomy Research 3(2), 189-202, 2005. Shearman, R.C. (1988) Improving sports turf wear tolerance. Proc. Of the 58th Ann. Michigan Turf. Conf. Vol. 17: 153-155. Trenholm, L.E. Carrow, R.N. and Duncan. R.R. (2000) Mechanisms of Wear Tolerance in Seashore Paspalum and Bermudagrass. Crop Science, 40:1350-1357, 2000 van den Akker, J.J.H. & Soane, B. (2005) Compaction. In Hill, D., Hatfield, J.L., Powlson, D.S., Rosenzweig, C, Scow, K.M. Singer, M.J. & sparks, D.L. (eds): Encyclopedia of Soils in the Environment). Elsevier Ltd., Volume 3, First edition, pp. 285-293. Whisler, F.D. Engle, C.F. Baughman, N.M. (1965) The Effect of Soil Compaction on Nitrogen Transformations in the Soil. West virginia University agricultural Experiment Station. College of Agriculture and Forestry. Read More