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The impacts of soil compaction on irrigation and drainage of golf course Zhang, Wenxiu 2002

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THE IMPACTS OF SOIL COMPACTION ON IRRIGATION AND DRAINAGE OF GOLF COURSE by Wenxiu Zhang B. Sc., The Inner Mongolia Agriculture University, 1984 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF T H E REQUIREMENTS FOR T H E D E G R E E OF MASTER OF APPLIED SCIENCE in T H E FACULTY OF GRADUATE STUDIES Department of Chemical and Biological Engineering (Bio-Resource Engineering Program) We accept this thesis as conforming^ to the^ec^ared standa/a/ T H E UNIVE^SITfY OF BRITISH COLUMBIA September 2002 © W. Zhang, 2002 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Chemical & Biological Engineering The University of British Columbia Vancouver, Canada Date September 9, 2002 Abstract Soil compaction caused by heavy play is a serious problem in golf course as it affects nearly all properties and functions of soil, physical, chemical as well as biological, which in turn cerate irrigation and drainage problems and influence the healthy growth of turfgrass. However, knowledge regarding the interactive effects of play intensity and soil moisture status on irrigation, drainage and turfgrass growth is still lacking. The objectives of this study are to examine the interactive effects of play intensity and soil moisture levels on some important irrigation and drainage parameters and turfgrass growth, and to evaluate the impact of soil compaction on water quality in terms of nitrate concentration. A green house study was carried out under simulated soil compaction on golf course fairway. Three play intensity level treatments and three soil moisture level treatments were tested. The results showed that the state of soil compaction not only is largely influenced by traffic intensity, but also is closely related to soil water content. Hence control of traffic and soil moisture is equally important for minimizing soil compaction. This investigation clearly demonstrated that soil compaction significantly changes the soil hydraulic properties, the infiltration, hydraulic conductivity and drainable porosity, and has adverse effects on irrigation and drainage. Both shoot and root growth declined as a result of soil compaction. It was observed that root biomass of turfgrass was reduced by as much as 47 to 75 percent under soil compaction condition when compared to non-compaction. Soil compaction is very detrimental to root growth. The study revealed that favorable soil water content for turfgrass shoot growth depends on traffic intensity. For heavy play golf course, maintaining adequate low soil moisture is more favorable to turfgrass growth. This study found that N 0 3 " concentration in leachate increased as a result of soil compaction. However, the detected N 0 3 " concentration under soil compaction was still extremely low, well below the drink water requirement. i i Table of Contents Abstract i i List of Figures vi List of Tables viii Acknowledgement x 1 Introduction 1 1.1 Significance of the Golf Course Industry 1 1.2 Problem Statement 2 1.3 Research needs 3 1.4 Scope and Objectives 5 2 Literature review 7 2.1 Sources of soil compaction 7 2.2 Factor affecting soil compaction 8 2.3 Compaction and soil physical properties 10 2.4 Soil compaction and turfgrass growth 13 2.5 Compaction and water quality 14 3 Materials and Methods 16 3.1 Experimental Design 16 3.2 Experimental Setup and Procedure 17 3.2.1 Container 19 3.2.2 Soil profile 19 3.2.3 Turfgrass 21 3.2.4 Soil compaction 21 3.3 Cultural practices 24 3.3.1 Irrigation 24 3.3.2 Fertilization 25 3.3.3 Mowing. 25 3.3.4 Topdressing 25 3.4 Measurements and methods 26 ii i 3.4.1 Soilmoisture 26 3.4.2 Bulk density 27 3.4.3 Void ratio 27 3.4.4 Soil strength 28 3.4.5 Infiltration rate 29 3.4.6 Field Capacity and Drainable Porosity 29 3.4.7 Saturated Hydraulic Conductivity 31 3.4.8 Drainage Water Quality 33 3.4.9 Evapotranspiration of turfgrass 34 3.4.10 Turfgrass Growth 36 3.5 Statistical analysis 36 4 Results and discussions 37 4.1 State of compaction under different traffic intensity 37 4.1.1 Bulk density 37 4.1.2 Void ratio 41 4.1.3 Penetration resistance 42 4.2 Compaction effects on irrigation 45 4.2.1 Infiltration rate 46 4.2.2 Filed capacity 49 4.2.3 Evapotranspiration 50 4.3 Compaction impacts on drainage 57 4.3.1 Hydraulic conductivity 58 4.3.2 Drainable porosity 61 4.3.3 Drainage water quality 64 4.4 Effects of soil Compaction on turfgrass 74 4.4.1 Shoot growth 75 4.4.2 Root growth 78 4.4.3 Turfgrass quality 81 5 Summary and conclusions 83 6 References 87 iv Appendix A Computed reference ET and measured daily ET 96 Appendix B Infiltration rates of different degree of soil compaction treatments 104 Appendix C Irrigation schedule of different treatments (L) 109 Appendix D Drainage water volume (mL) I l l Appendix E Comparison of visual quality of turfgrass under different degree of soil compaction 115 v List of Figures Figure 1 Experimental setup in greenhouse 18 Figure 2 Special container used in experiment 18 Figure 3 Soil profile used in the experiment 20 Figure 4 Balance used in the experiment 27 Figure 5 Penetrometer used in the experiment 28 Figure 6 Diagram for drainable porosity measurement 31 Figure 7 Diagram of the constant-head system for saturated hydraulic conductivity measurement 32 Figure 8 Lachat QuickChem FIA+ Automated Ion Analyzer used for nitrate concentration measurement 33 Figure 9 Changes in soil bulk density due to repetitive application of impact load 39 Figure 10 Influence of soil moisture on bulk density under diiferent level of traffic 40 Figure 11 Changes in penetration resistance with depth due to different level of traffic intensity and soil moisture levels 43 Figure 12 Comparison of PR changes resulted from different moisture levels 44 Figure 13 Changes in infiltration rate with time without turfgrass 46 Figure 14 Comparison of infiltration rate of different soil moisture treatments under turfgrass cultivation 47 Figure 15 Relationship between steady infiltration rate and void ratio under different level of soil compaction 49 Figure 16 Comparison of ET of different level of soil moisture treatments 53 Figure 17 Correlation between crop coefficient and soil moisture under soil compaction and water stress 56 Figure 18 Comparison of hydraulic conductivity of different level of soil moisture treatments 60 Figure 19 Relationship between steady hydraulic conductivity and void ratio under different level of soil compaction 60 Figure 20 Comparison of drainable porosity of different level of soil moisture treatments under soil compaction 63 Figure 21 Relationship between steady drainable porosity and void ratio under different level of soil compaction! 63 vi Figure 22 NO3" concentration in drainage water in relation to soil compaction before May 29 measurements : 68 Figure 23 NO3" concentration in drainage water in relation to soil compaction after May 29 measurements 68 Figure 24 Comparison of N 0 3 - concentration in leachate as influenced by soil moisture before May 29 measurements 69 Figure 25 Comparison of N03- concentration in leachate as influenced by soil moisture after May 29 measurements 69 Figure 26 Cumulative amount of drainage water of different level of traffic treatments with high moisture during measurement period 70 Figure 27 Cumulative amount of nitrate in drainage water from different level of traffic treatments with high moisture during measurement period 70 Figure 28 Cumulative amount of drainage water of different level of traffic treatments with medium moisture during measurement period 71 Figure 29 Cumulative amount of nitrate in drainage water from different level of traffic treatments with high moisture during measurement period 71 Figure 30 Cumulative amount of drainage water of different level of traffic treatments with low moisture during measurement period 72 Figure 31 Cumulative amount of nitrate in drainage water from different level of traffic treatments with high moisture during measurement period 72 Figure 32 Cumulative amount of nitrate in drainage water as affected by different soil moisture level 73 Figure 33 Comparison of clippings yield under different level of soil compaction .76 Figure 34 Comparison of accumulative clippings of the treatments with different levels of soil water content 77 Figure 35 View of root system of Kentucky bluegrass without soil compaction 79 Figure 36 View of the profile of root growth of Kentucky bluegrass under severe soil compaction 79 Figure 37 Effect of different level of soil compaction on root growth of Kentucky bluegrass..: 79 Figure 38 Comparison of root growth of different traffic treatments 81 Figure 39 Comparison of root growth of different soil moisture treatments 82 vii List of Tables Table 1 Experimental design 17 Table 2 Soil particle size analysis 20 Table 3 Summary of applied compaction on soil column 23 Table 4 Effect of traffic intensity and soil moisture levels on bulk density 38 Table 5 Changes in void ratio under different traffic intensities 41 Table 6 Summary of analysis of variables for traffic intensity, soil moisture levels and their interactive effects on some irrigation parameters 45 Table 7 Summary of statistical analysis of steady infiltration rate as influenced by traffic intensity and moisture levels 48 Table 8 Changes in field capacity under different level of traffic intensity 50 Table 9 Weekly averaged ET rates of different soil compaction treatments and estimated ET rates with weather data 52 Table 10 Changes in total Evapotranspiration due to traffic and soil moisture stress over study period 51 Table 11 Crop coefficient under compaction and moisture stress 54 Table 12 Summary of analysis of variables for traffic intensity, soil moisture levels and their interactive effects on some drainage parameters 57 Table 13 Summary of statistical analysis of hydraulic conductivity as influenced by traffic intensity and moisture levels 58 Table 14 Minimal requirements of hydraulic conductivity of topsoil layer or root zone of sports field, as proposed by various country 59 Table 15 Summary of statistical analysis of drainable porosity as influenced by traffic intensity and moisture levels 62 Table 16 Mean nitrate concentration of drainage water after different traffic and soil moisture treatment 65 Table 17 Significance levels of F values for turf growth parameters as influenced by traffic intensity 75 Table 18 Mean quality rating values of all treatments across three replications 82 viii Acknowledgements I wish to express my deep appreciation and my feeling of indebtedness to Dr. S.T. Chieng, my thesis supervisor, for his guidance, constructive criticism and whenever available help throughout the course of this study. I am very grateful to Drs. K. V . Lo and A. Lau, professor and associate of the Department of Chemical and Biological Engineering, University of British Columbia, for their reviewing this work. Thanks are also due to Dr. P.H. Liao and Mr. J. Pehlke for their assistance with the laboratory analyses. Finally, I wish to extend my love and thanks to my wife, Guiping, not only for her understanding and support, but also for her rewarding discussions and thoughtful suggestions when I met various aspects of the problems during this investigation. ix 1 Introduction 1.1 Significance of the Golf Course Industry Today golf has become one of the most booming industries in the North America. National Golf Foundation's 2000 survey showed that as of the December 31 of 1999, United States supplied 16747 courses, and 26.4 million people were playing the game of golf (NGF, 2000a). Golf related consumer spending reached $22.2 billion in 1999 (NGF, 2000b). Canadians are, per capita, the number one golfing nation in the world. There are over 2000 courses and 5.2 million golfers in Canada. Approximately 20 % of all Canadians play golf. This is the highest golf participation rate in the world. Golf has become a strong contributor to the overall economy of Canada (RCGA, 2000). British Columbia, with its strategic geographic position in the Pacific Rim is ideally situated to access the major tourist golfer markets from Asia and the United States. The scenic and diverse BC environment, combined with a moderate climate, provides an unparalleled range of golfing experiences that can be enjoyed year-round. For this reputation, the US Professional Golf Association (PGA) Tour selected BC as one of the limited number of the designated world-class PGA tour golf destinations (International Sports Inc., 1993). Currently there are 297 golf courses in BC, attracting an estimated 450,000 golfers each year from across Canada and around the world, and the number of courses still increases by two or three each year (UMA Engineering Ltd., 1997). The golf industry is a significant player in the economy of British Columbia. In 1990, the golf industry was already recording total revenues of $150 million and a wage bills of over $58 million. The total GDP impact due to all golf activity (including investment, leased activities and spin-off effects) amounted to $216 million (Pacific Analysts Inc. et al., 1992). It is believe that the golf course industry will play a more and more significant role in the BC economy in the future. 1 1.2 Problem Statement As the popularity of golf increase, so do the problems the industry face with. Heavy play is promoting unhealthy growing conditions on the millions of areas of turfgrass in the golf course industry. Direct physical damage of plants through shearing action is only one factor in the equation. More serious long-term pain promoted by the intensity of play, however, is the influence of soil compaction (Isaac, 1993). A number of problems could arise under soil compaction: • causing waterlogging and even leading to the breakdown of drainage systems especially for some old courses where drainage system was not adequately designed; • reducing the quality of the playing surface; • leading to turf diseases duo to water ponding and wet soil condition; • resulting in potential water pollution associated with pesticides and fertilizer runoff and nitrate leaching; • and most importantly, causing loss of profits due to the reduction of playable time. Drainage has certainly become one of the most pronounced problems caused by escalating levels of play. Compaction affects nearly all properties and functions of soil, physical, chemical as well as biological (Hakansson et al. 1988). The most degrade changes caused by soil compaction is the reduction of pore space and the redistribution of pore size among pore size groupings. The reduced soil pores may adversely influence the hydraulic conductivity and hence restrict water movement through the soil leading to waterlogging, even breakdown of drainage systems. The poor drainage situation probably is one of the most painful problems in the eyes of the golf course superintendent, because it exerts an important adverse influence on the profitability of golf course due to the reduction of playable days. Irrigation obviously is another big issue under soil compaction. Probably the most serious concern for golf course management is the drastic reduction in infiltration rate or the capability of the soil to absorb the applied irrigation water. A lowering infiltration rate on compacted soil site may 1) increases the risk of runoff, 2) results in a higher percentage of evaporation losses, 3) lowers the amount of water stored in root zone, 4) reduces available soil water, and 5) decrease the water application efficiency. 2 Interestingly, growers often apply more water to their compacted sites. One of the reasons might be that for the slower shoot growth, turfgrass managers unconscientiously attempt to stimulate shoot growth by applying more water and watering more frequently in their compacted site (Carrow et al., 1992). This practice leads to excessive water that may be more than the turfgrass needs, result in surface runoff and further aggravates drainage problems. Eventually, the overall results of the overwatering, which was also often coupled with overgenerous application of fertilizer was a swift increase in presence of annual meadow-grass, an overall deterioration in the condition of the playing surface. Golf courses use a significant amount of nitrogen fertilizer. The fate of fertilizer is of growing concern because of the potential for groundwater contamination and health risk with high nitrate levels in groundwater (Kenna et al., 2000). In addition to the potential environmental problems associated with nitrate leaching, the economic impact on the golf course management can also be considerable. Leaching loss of nitrate a major avenue of nitrogen loss from turfgrass field. Some researchers suggest that as high as 80% of the fertilizer N was leached as nitrate (Petrovic, 1990). Nitrogen is one of the most expensive cash input for golf courses, and the loss of this nutrient means reduced profitability. 1.3 Research needs Considerable efforts have been made on how to modify soils to eliminate soil compaction on golf course (Waddington, 1992). Aeration, topdressing and topsoil amendment with sand peat mix, which recommended by U S G A , are all very successful examples. However avoidance is always far more preferable than cure. Our understanding on how and why compaction influences this modified soil under turfgrass is a recent development (Carrow et al., 1992). Because very little quantitative data concerning changes of modified turf-soil system due to compaction is available, the compaction factor is largely ignored in the design of irrigation and drainage system especially for the construction of old courses. 3 Research on how irrigation affects turf on soil compaction site is limited, especially for the interaction soil compaction and moisture levels. Watson (1950) studied interacting effects of compaction and soil moisture status and concluded that moisture levels influenced turf quality more than soil compaction. Harper (1953) continued Watson's work and came to similar conclusion. In contract, Agnew et al. (1985) compared well-watered with moisture-stressed Kentucky blue grass under soil compaction and noted that compaction influenced turf quality more than irrigation levels. The conflicted results suggest more research is needed to understand the effects of irrigation practices in conjunction with soil compaction. Soil moisture not only affects the turfgrass ET directly, but also largely influences the degree of compaction of the soil. Knowledge regarding the interactive effects of soil moisture and traffic intensity on ET of turfgrass is still lacking. There are a number of studies on the changes in soil physical properties under soil compaction including bulk density, porosity, penetration resistance as well as hydraulic properties. Among the soil physical properties, hydraulic conductivity and drainable porosity are perhaps the most important parameters that must be determined for designing a drainage system, and the hydraulic properties and associated processes are still the least understood in relation to compaction (Horton et al, 1995). Therefore, studies on the hydraulic properties in compacted soils such as infiltration, drainable porosity and hydraulic conductivity should be extended. Research on the environmental impact of soil compaction is still at a rudimentary level. This is especially true within the area of turfgrass field. Soil compaction is shown to result in changes in soil properties which control the emission of greenhouse gases, the runoff of water and pollutants into surface waters, and the movement of nitrate and pesticides into groundwater (Soane, 1995). While much research has focused on the effects of cultural practices on nitrogen losses through leaching mostly in the conditions of sand based putting green (Johnston, 1999), little research involved in soil compaction to study its impacts on nitrogen leaching under the golf course fairway conditions. Because of the persistent nature of soil compaction on golf course, understanding changes in nitrogen leaching due to soil compaction is very important to the management of fertilizers for both profitable and environmentally sound golf courses. 4 1.4 Scope and Objectives Among the play surfaces in golf course, the fairways most reflect the characteristics of the landscape. This is because not only the characteristics of the soils and underlining land formation, which are reflected in the fairways to produce a variety of growing environment, but also the importance of the turf in terms of the area, which is 15 times more than the putting greens and tee boxes. Also it takes up more than 90% irrigation and drainage area in a course. Therefore, this study emphasizes on the compaction problems on golf course fairways. The overall goal of this study is to contribute to the understanding of the impacts of soil compaction on irrigation and drainage under golf course fairway conditions. Specific objectives of this thesis are: 1) To assess the state of soil compaction under different traffic intensities and soil moisture contents in terms of bulk density, pore space and soil strength. 2) To examine effects of soil compaction on some important irrigation and drainage parameters that are susceptible to soil compaction and to establish their relationship to the degree of soil compaction 3) To investigate the interactive effects of soil compaction and soil moisture content on water requirements of turfgrass 4) To evaluate the impact of soil compaction on drainage water quality in terms of nitrate concentration 5) To examine the reaction of turfgrass to different degree of soil compaction in terms of shoot and root growth as well as visual quality For a particular golf course, the performance of its irrigation and drainage system is the ultimate consequence of soil properties and soil hydrological characteristics in response to the soil compaction. Therefore, by first assessing the degree of soil compaction, and analyzing the soil physical properties and hydrologic characteristics subjected to soil compaction, a rational basis would be provided from which to understand the soil compaction problems faced. Following determination of turfgrass water use, a foundation for better design and management of irrigation system would be 5 formed. By further examining the drainage water quality and turfgrass growth in response to different level of soil compaction, golf course managers would be better informed and reassured about what consequences to anticipate from their compacted turf site. The results of this study would provide valuable information for modeling, design and management of irrigation and drainage systems in golf course. 6 2 Literature review Soil compaction has been identified as one of the leading causes of soil degradation from agricultural field through forestland to recreational turf field. During the last half century, considerable research has been conducted and voluminous literature is available in each of these areas. This chapter attempts to summarize the developments in the soil compaction research. However, the discussion is restricted to the compaction problem of turf-soil system. Considering there is a considerable body of literature concerning this subject, only these works that are directly related to the present study will be treated in depth. 2.1 Sources of soil compaction Soil compaction is defined as the process of pressing soil particles together causing reduction in pore space between them. Major sources of soil compaction on turf site typically originated from raindrop impact, foot traffic and vehicular traffic (Carrow et al., 1992). Raindrop impact may come from either rainfall or irrigation. For turf soils, raindrop impact has little effect on soil compaction, since ground vegetation can considerably absorb the kinetic energy of raindrop. However, impingement of raindrops on a bare soil surface does produce compaction. Increases of 15 percent in soil bulk density in a 1-inch surface layer have been attributed to the effects of raindrop (Cohron, 1971). As a whole, effect of raindrop impact on soil compaction on turf site is minimal except for very special conditions such as extremely heavy rain event and little vegetation on ground. Without a doubt, foot traffic is one of the major sources of soil compaction in golf course. This can be illustrated by Charles Cogan's study (cited by Dr. V . A . Gibeault et. al., 1983). "He found golfers take an average of 26 full steps (52 paces) per green. The average golf shoe has 12 spikes; i.e., 24 spikes per golfer. Therefore, each golfer leaves 624 spike marks on each green. On 18 greens, he leaves 11,232 spike marks. If there are 200 rounds of golf played a day, there are 2,246,400 spike marks left behind. If this goes 7 on for 30 days, you have 67,392,000 spike marks per month." No wonder how significant the foot traffic is. The degree of compaction induced by foot traffic depends on shoe type, the speed of foot traffic and the weight of golfer. A few studies have evaluated the effects of shoe type on turf soil compaction. The general consensus of these studies is that golf shoe spike or any shoe with nobs, studs or protrusions causes greater damage to grass and adversely affects green quality more than flat shoe (Gibeault et al., 1983; Skorulski, 1999; Hamilton et. al., 1997; Rogers et al., 1999). High speed of foot traffic such as running can produce much greater compacting force than walking person. A running athlete could create 1.52 MPa pressure, whilst under static condition, only 0.04 MPa, a 38-fold difference (Carrow etal., 1992). Vehicular traffic, taken in aggregate, unquestionably comprises the primary source of soil compaction in golf course. The popularity of carts among today's golfers cannot be denied. Golf carts and pull carts exert several forces on the turf and soil. A vertical force created by the dynamic load of the wheel, sheer stress created by wheel slippage, and forces from vibration all impact the turf and surface of soils (Skorulski, 1999). Carrow (1997) reported that a typical golf cart might exert 5 psi on the turf surface based on a weighing 900-1100 pound car with one passenger. However, considerably greater pressure may be concentrated on the outer edges of a tire by turning golf car. Burton observed that sharp turn damage by golf car was three times more severe than straight line driving. 2.2 Factor affecting soil compaction The potential for soil compaction can be influenced by a number of factors. The primary factors include following (Beard, 1973): (a) soil texture, structure and particle size distribution, (b) soil water content, (c) severity of pressure applied, (d) frequency at which the force is applied, and (e) amount of vegetation. The compactibility of soils varies with the texture. Fine textured soils such as clays are far more prone to compaction, since their large pores can relatively be eliminated 8 easy. While coarse textured soils such as sand subject to compaction, the bridging between the hard sand particles can help to prevent the elimination of large pores (Carrow et al., 1992). Therefore, the adverse effects of soil compaction of fine textured soils are much greater than coarse textured soils. In terms of soil susceptibility to compaction, three groups can be distinguished (Horn et. al., 1995): (a) Sandy soils with a single-grain structure are only slightly susceptible to soil compaction. (b) Soils derived from silt, such as silty loams, with a low colloid content and a weak structure, are easily compacted by external force. (c) Medium- and fine- textured loam and clay soils are resistant to mechanical pressure at low water contents but they are highly susceptible to severe compaction at high soil moisture contents. The influence of particle size distribution on soil compactibility has been extensively studied. Particle size analysis gives the proportion of different sized particles presented in soil. Well-graded soil contains both coarse and fine-grained particles, and the number of particle contacts and the area of contact for any one particle will be larger than in poorly graded soil. Therefore, the resistance to shear-induced motion will be greater (Harris, 1971). The structure of a soil also plays a role in its potential for compaction. A soil with higher levels of organic matter generally has better structure and resists compaction better than soils with lower organic matter levels. The amount of soil water is a critical factor in soil compaction potential. Water acts as a lubricant between the soil particles and assists in the compacting or sliding together of the soil particles into a dense, imperious state (Beard, 1973). Dry soil is not easily compacted since there is insufficient water to create lubricating effect between particles. As soil water content increases, the potential of soil compaction also increases due to the lubricating role played by risen water content. However, when soil water reach a point where most of pore space in the soil is filled by water, water between the soil particles will carry some of the load of the soil resisting compaction. Therefore, a saturated soil will not be compacted as much as a moderately moisture soil. But the soil structure is 9 more easily destroyed (Beard, 1973). Studies showed that an optimum moisture content exists at which maximum compaction occurs for a given amount of energy applied during the compacting process. Many researchers suggested that compacting at field capacity results in the greatest compaction in terms of soil bulk density (Carrow et al., 1992; Adam and Gibbs, 1994). The intensity and frequency applied by traffic have a major influence on the degree of soil compaction. Smith and Dickson (1990) reviewed previous work, which shoed that topsoil compaction mainly influenced by ground contact pressure. Generally, the greater the intensity of pressure applied by traffic, the greater the degree and depth of soil compaction that occurs (Beard, 1973) The degree of compaction also increases when compacting forces repeated (Madison, 1971). Repeated wheeling causes the consecutive destruction of inter- and intra-aggregate pores, which results in the formation of dense aggregates and increase the degree of compaction. Repeated footprint concentrated in a small area such as the approaches leading onto a fairway at the end of a cart path can become densely compacted. The presence of turfgrass and other tissues on soil surface may influence to some degree the ability of soils to resist compaction (Carrow et al., 1992). Rogers et al. (1988) evaluated the effects of verdure and thatch of turf on impact energy absorption capability of a surface. They found that the duration time and peak deceleration of impact measured on full turf treatment were significantly longer than bared soil, in which turf acted as an impact absorbent in lengthening the impact. The presence of turf and thatch on surface improved shock attenuation under most conditions. Henderson et al. (1988) also reported similar results. Although no data are available on how the amount of vegetation affects soil compaction, it is logical to speculate that the greater amount of vegetation, the less the soil compaction under traffic. 2.3 Compaction and soil physical properties Compaction affects many aspects of soil properties. The soil physical properties that could be seriously affected are those that control the content and transmission of water, 10 air, heat, and nutrient and those that change soil strength (Raney, 1971), including bulk density, soil porosity and pore distribution, soil strength, infiltration and hydraulic conductivity etc. Changes of all these parameters due to soil compaction may create irrigation and drainage problems. The compaction process is basically a simple operation — a change in volume for a given mass of soil. This change is variously designated as a change in bulk density. Generally, when a given soil subject to a set of external constrains, the lower the initial bulk density, the greater the volume changes (Harris, 1971). Bulk density was frequently used to characterize the state of soil compaction, although the bulk density in itself is of little value in assessing soil conditions for plant growth (Arvidsson, 2000) and is difficult to use to predict the behavior of a soil subjected to an applied load (Harris, 1971). Some researchers used a so-called critical bulk density at which root growth is stopped or greatly retarded to assess the sensitivity of plant to soil compaction (Jones, 1983; Mapfumo et al., 1998). However, critical bulk density values vary substantially with soil texture, structure and moisture. A suitable bulk density range for turfgrass growth recommended by U S G A is 1.19 to 1.72 grams per centimeter (USGA, 1993). For turf soils, traffic induced bulk density changes mainly occur in the top layer. Beard (1973) noticed that the majority increased in bulk density due to traffic happened in the top 8 cm of the soil surface. Sills and Carrow (1982) and O'Neil and Carrow (1982) found that the soil bulk densities were influenced by traffic mainly in the upper 3 cm. Associated wit the increased soil bulk density is a decrease in soil porosity. In fact, compaction not only results in the reduction of pore volume, but also alters the distribution of pore system, both with respect to the pore size distribution, the mean pore diameter, the total number of pores and/or their function (Horn et al., 1995). Large pores, which have a dramatic effect on soil transmission properties, are most likely altered during compaction from traffic. Compacting soil aggregates may destroy enough of these large pores to restrict oxygen to transfer to root. Destroying large pores may also change the composition of soil air. Under severe soil compaction, soil atmosphere could become saturated with carbon dioxide and other gases that are toxic to turf root system (Beard, 1973). 11 Soil strength is usually expressed as a parameter of a resistance which must be overcome to cause physical deformation of a body of soil (Chanceller, 1971). Many such parameters have been formulated and used. One of the most frequently used parameters is penetration resistance, which can be quickly measured with a penetrometer. Penetration resistance is a soil mechanical property that can be directly related to root growth. A hard, compacted soil with high cohesive forces plus few large pores has high penetration resistance and results in mechanical impedance for root growth (Carrow et al., 1992). A survey conducted by van Wijk (1980) showed that the more intensively a part of sports turf field is played, the greater the soil strength of top layer is. In a study of mechanical impedance effects on shoot and root growth, Cook et al. (1996) classed 1.4 MPa as a moderate impedance and 2.3 MPa as severe impedance. The most significant changes caused by compaction might be the reduction of soil water infiltrability and conductivity. Since compaction affects large ores, root channels and worm or insect channels, which are of great importance to water infiltrability, infiltration rate into compacted soil may, therefore, severely reduced. For example, Canaway (1978) reported that on a sandy loam the infiltration rate after tow month's traffic were reduced to 2.6 rnrn/hr as compared with 46 mm/hr on an adjacent untrafficked area. Similar result was also reported by Lodge and Baker (2000). Marked reduction in infiltration rate may cause serious irrigation ad drainage problem, lead to increase surface runoff and erosion and/ or water shortage in the root zone. Golf course soil requires hydraulic conductivity for more demanding than other soil uses. On the other hand, hydraulic conductivity is very sensitive to traffic since compaction mainly decreases large pores, which govern the hydraulic conductivity. Even a moderate change in bulk density could decrease the saturated hydraulic conductivity dramatically (Arvidsson, 2000). Drainable porosity is one of the most important parameters used in the design of drainage system. By definition, drainable porosity is the volume of water that can be drained from a unit area of soil when the water table falls a unit distance (Bouwer, 1979). It is equated with the specific yield since it represents the volume of water drained by gravity per unit volume of soil. Drainable porosity has not been included in the soil compaction study in the past, partly because steady state flow is assumed in most of the 12 design of drainage system. As drainable porosity is also closely related large soil pores, it is reasonably assume that drainable porosity would decrease with the increase of soil compaction. 2.4 Soil compaction and turfgrass growth Soil compaction does not directly reduce the plant activity (Trouse, 1971). Instead, it influences soil properties such as soil pore space, pore continuity and its distribution, aeration, penetration resistance permeability and soil water status, which in turn affect plant growth (Mapfumo et al. 1998). Shoot growth and visual quality of turfgrass have been widely reported to be affected by soil compaction. Valoras et al. (1966) reported that compaction greatly reduced the top growth (clippings) as compared to no compaction. But they found that the major effect is during the first half of their seven-week experiment. There was no significant effect over the last half. In the study by O'Neil and Carrow, total clipping yields were reduced by 38 and 53% for their moderate and heavy compaction treatment compared with those of uncompacted treatment. More recently, Ervin et al. (2001) reported that traffic consistently reduced clipping dry weights across all three years of their experiment. However, compaction is not always detrimental to turfgrass, and bluegrass often appears most vigorous during chilly fall weather in paths and tracks where soil has been somewhat compacted (Madison, 1971). Adequate soil compaction such as rolling cultural practice is often helpful to turfgrass shoot growth. A number of researchers have reported declines in visual quality with soil compaction. Carrow (1980) simulated three intensities of compaction on soil plots with three types of turfgrass. Increased levels of compaction were found to cause a significant decrease in turfgrass quality. O'Neil and Carrow (1982) observed that compaction reduced visual quality ratings to below a minimum acceptable quality with three weeks in their test. In a investigation of Agnew et al. (1985), it was noticed that both clipping yields and visual quality decreased eight days after application of compaction. These results indicated that shoot growth appears very sensitive to compaction. 13 There is a number of literature concerning the effects of soil compaction on turfgrass root growth. The reaction of root growth to compaction is primarily reacts of reduced aeration, high soil strength, and altered soil water relations (Carrow et al., 1992). Major responses of root growth to soil compaction include changes in root distribution, reduced root growth rate and root deterioration (Hannaford and Baker, 2000). O'Neil and Carrow (1983) reported that as soil compaction increase, a higher percentage of roots presented in the top 0 to 5 cm zone and lower percentage in the 10 to 25 cm zone were found. Total weights decreased by 20% at the end of their test. Agnew et al. (1985) reported similar results with more increased roots in the 0 to 5 cm zone and decreases root in 15 to 20 cm zone. Total root increased by 14% compared to uncompacted turf. However, root growth may decline in the whole root zone if overwhelming mechanical resistance is very high due to severe compaction. Since soil compaction reduces turfgrass growth, it is no wonder that compaction may also influence the evapotranspiration of turfgrass. Morgan et al. (1966) reported that the ET of common bermudagrass was less when soil was compacted as compared to no compaction soil. Similar results also have been found for perennial ryegrass (Sills et al. 1983; O'Neil et al. 1983) and Kentucky bluegrass (O'Neil et al. 1982; Agnew et al. 1985). Sills et al. (1983) reported a 28% reduction in ET of perennial ryegrass in compacted soil. O'Neil (1983) reported 21 to 49% decreases in ET of perennial ryegrass with compacted soil. A 21% decrease in ET of Kentucky bluegrass was observed by Agnew et al. (1985). But none of these studies examined how ET varies with degree of soil compaction under different soil moisture content. 2.5 Compact ion and water quality Until recently, most of the research on soil compaction has been confined to studies of effects of compaction on soil properties and plant growth. Limited attention has been paid to environmental impacts. However, some evidence already shown that soil compaction adversely influence, either directly or indirectly, the quality of many 14 important aspects of environment (Soane and van Ouwerkerk, 1995), particularly the quality of natural waters. In golf course, water quality is often linked to the use of pesticides and fertilizers on the course and the potential for those chemicals to enter into groundwater and surface water. Groundwater and surface water quality is affected primarily by two mechanisms: runoff and leaching. Runoff describes the movement of water across the turf and soil surface. It can be strongly influenced by compaction owing to the significant reduction in infiltration rate. Although no data are available to demonstrate that how much the soil compaction contribute to surface water quality deterioration, a few reports already linked the soil compaction to water quality problem (Soane and van Ouwerkerk, 1995; Lipiec and Stepniewski, 1995; Horn et al 1995). Soil compaction increases runoff and erosion resulting in more sediment and agrochemicals moving into streams, lakes and drainage ditches and increases the potential for lowering surface water quality. In golf course, agrochemicals affecting groundwater water quality through leaching is more concerned than through runoff, especially for the nitrogen fertilizers. Leaching is the downward movement of fertilizer or pesticides through the soil profile and potentially into the groundwater. Many studies showed that compaction decrease nutrient uptake in many plant species due to its effects on root and shoot growth (Carrow et al. 1992; Lipiec and Stepniewski, 1995). On the other hand, lager amount of fertilizers and pesticides more likely is used on compacted soil in golf course to maintain aesthetic quality and growth rate so as to compensate the stress from compaction. Consequently the excessive agrochemicals increases the possibility to end up into groundwater. Severe compaction could result in the death of most turfgrass and may increase the leaching potential. Hull et al. (2001) studied the nitrate leaching potential following sudden death of turfgrass and found that annual leaching rates from killed turf were three times greater than those of healthy turf. After one year following the turf death, about 10 percent of total nitrogen presented within the turf-soil ecosystem leached below the root zone and likely enter into groundwater. Since there are no published data available in turf literature to show how the different degree of soil compaction affects the water quality, research is obviously needed to quantitatively examine the effects of soil compaction on water quality. 15 3 Materials and Methods This experiment was conducted in the greenhouse, University of British Columbia from September 10, 2000 to July 15, 2001. The environment of the greenhouse was not controlled except for rainfall. 3.1 Experimental Design The potential for soil compaction on golf course fairway is influenced by (a) soil texture, (b) soil structure, (c) soil particle distribution, (d) soil water content, (e) playing intensity, and (f) amount of vegetation (Beard, 1973). Of these factors, the playing intensity and soil moisture are probably the most influential factors to soil compaction problems. It was against this background that the play intensity and soil water content were selected as major experimental factors in this experiment. Three traffic intensity levels and three soil moisture levels were designed. The three traffic intensity levels designed are as follows: 1) heavy traffic corresponding to an intense use of golf courses (80,000 rounds played per year), 2) medium traffic corresponding to an average use of golf courses (40,000 rounds played per year), 3) light traffic corresponding to limited use of golf courses (20,000 rounds played per year). The three soil moisture levels designated are: 1) high soil moisture where moisture maintains above 80% of field capacity, 2) medium soil moisture where moisture maintains above 60% of field capacity, 3) low soil moisture where moisture maintains above 40% of field capacity. A 3 x 3 factorial, randomized complete block design was employed in the experiment. Namely, nine treatments that consist of three traffic levels and three soil moisture levels were used. In addition, a control treatment where there was no compaction was also employed for comparison. The soil water level of control treatment was designed with 60% of field capacity. Thus a total of 10 treatments were employed in 16 this experiment. Each treatment replicated three times. Details of the treatments are given in table 1. Table 1 Experimental design Treatments Compaction Level Play Intensity (rounds/year) Soil Moisture Level Content (% FC) H H Heavy 80,000 High 80 H M Heavy 80,000 Medium 60 H L Heavy 80,000 Low- 40 M H Medium 40,000 High 80 M M Medium 40,000 Medium 60 M L Medium 40,000 Low 40 L H Light 20,000 High 80 L M Light 20,000 Medium 60 L L Light 20,000 Low 40 C Control 0 Medium 60 3.2 Experimental Setup and Procedure The experimental equipment mainly consists of a set of 30 special containers. Soil column was set up in each container. Kentucky bluegrass was sodden in the containers. A fairway sand topdressing program was applied to simulate the actual practice in golf course. Compaction was created by simulated fairway traffic during the peak golfing period (from June to August). Figure 1 showed the whole experimental setup in greenhouse. Details are described as follows. 17 Figure 1 Experimental setup in greenhouse Upper container for loading soil Figure 2 Special container used in experiment, (a) Stacked water pails; (b) Drainage holes on the bottom of upper water pail 18 3.2.1 Container The special container constitutes two stacked plastic water containers (see figure 2 (a)). The container is 29 cm in diameter and 39 cm high. The upper container was used for setting up soil column. 29 holes in a diameter of 3A" were drilled radially on the bottom of the container for drainage. To achieve effective drainage, the holes distributed uniformly on the bottom of the container as showed in figure 2 (b). The lower container was used to collect drainage water. 3.2.2 Soil profile To simulate the modified soil conditions most commonly found on fairway, a typical two-layer soil system was adopted in the experiment. The upper layer was a 5 cm sandy thatch that was created with sod and topdressing sand. The topdressing program used a normal rate of yearly total of 3A" of sand which recommended by U S G A (Gilhuly, 1999). Under the sandy thatch layer, native loamy sand was used. The soil profile was illustrated figure 3. Soil was collected from near farmland. As required by the regulations of the U B C Plant Science Greenhouse, the soil was pasteurized in the Botanical Garden Nursery using thermal pasteurizer before use. A 10 x 10 mm steel mesh screen was used screening off particles > 10.0 mm in diameter. This removed any larger twigs and rocks from the pasteurized soil to be used in the experiment. A particle size analysis was carried out by sieving to determine the distribution of the soil separates on a mass basis. The size groupings of the soil separates use the U.S.D.A. classification system. Tests were performed on the previously screened soil in which particle sizes less than 10.0 mm in diameter. Each sample was air-dried. A nest of stacked precision wire mesh sieves was used in the tests. Three soil samples were used in the test. The samples were sieved for 25 minutes manually. Table 2 presented the results of the sieving tests. The soil was classified as loamy sand. The organic matter of the soil is 1.2%. 19 Soil was set up in upper water pails. The bottom of each upper container was covered with two pieces of fiberglass screen mesh that overlapped with a 45° angle to prevent soil lost from the top. On the top of the mesh, a 35-cm loamy sand soil was loaded. The loaded soil was irrigated timely and let it settled down for 8 weeks so that it could be close to the intact soil as much as possible. Then sod was placed on the top of the soil column and let it settle down another 12 weeks. Finally, sand topdressing program was applied to simulate the modified soil conditions commonly found on golf course fairway. Table 2 Soil particle size analysis Openings* (mm) Class Collection (%) 2.00 Gravel 3.1 1.00 Coarse Sand 7.15 0.25 Medium Sand 47.31 0.104 Fine Sand 26.96 0.053 Very Fine Sand 4.18 Sieving pan Silt and Clay 11.97 Total 100 This sequence of sieve sizes represents the stacked order in the nest of sieves used in the particle size analysis. 5 cm 34 cm Nylon mess Figure 3 Soil profile used in the experiment 2 0 3.2.3 Turfgrass The primary cool-season turfgrass species for fairway use was Kentucky bluegrass that generally provides an acceptable playing surface. So this experiment used mature fairway sod Kentucky bluegrass that directly obtained from commercial supplies. Sod was used because seeding grass under one year age does not reach a reasonably stable shoot density to resist compaction stress. After the soil column settled down for 8 weeks, turfgrass was established in each container using mature fairway sod Kentucky bluegrass. Sod was paid closely knit together in such a manner that no open joints wider than 5 mm were visible and no pieces were stretched or overlapped. The turfgrass was watered timely and uniformly, and replacing was done as deemed necessary to obtain adequate establishment and uniformity of the turf before treatments. 3.2.4 Soil compaction How to create compaction to simulate conditions on golf course fairway is a vital part of process of this experiment. The build up of compaction on golf course fairway is directly influenced by the overall amount and concentration of play in the confined area. W. Graham Argyle and Associates et al. (1991) reported that rounds played per course were 43182 in "the Lower Mainland" in 1990. However, annual figures of 70,000 to 90,000 rounds per year are not uncommon. Thus the experiment calculated intense, average and light use courses as equivalent of 80,000, 40,000 and 20,000 rounds of golf per year respectively, which also typifies the number of rounds played on many American courses. To estimate the trafficked area on golf course fairway, a simple calculation was made. Generally fairway width of 18-hole courses varies from 90' (narrow), 120' (average) tol50' (wide) plus the width of the intermediate rough (Daniel et. al. 1980). However, traffic usually distributes on the main fairway. Hence the fairway width in the calculation used average width of 120 feet. 21 In B. C , the play days normally is approximately 200 days per year. Take an average use course (40,000 rounds and 200 play days per year) as an example, the seasonal daily play rounds averages 200. In other words there are 200 golfers who play on the course a day. Normally, for a typical 18-hole golf course in B C , following conditions are applicable: 1) the average length of one walking step is 3 feet; 2) the effective area of a footprint is 32 sq. in. (0.222 ft2); 3) the rear tire of a typical golf car and mower have 8.5-inches (0.708 ft.) width; 4) the cutting width of mower is 3 feet; 5) the turfgrass mowing frequency is three times a week in peak play period; For a typical 18-hole golf course in North America, following assumption can be made: A. One out of five golfers use golf car; B. traffic distributes uniformly over the main fairway area. Thus, the daily trafficked area per foot long fairway can be calculated as follows: Golf car: 20% x 200 players x (0.708ft.width x 2tires) = 56.64 ft2 Foot: 80% x 200 players x (0.222 ft2/step)/3 = 11.84 ft2 Mower: (120feet fairway/3 feet cutting width) x (0.708x2 tire width)/(3/7) = 24.3 ft2 Total trafficked area = 56.64 + 11.84 + 24.3 = 92.75 ft2 /day Therefore, for average use courses the traffic passes on fairway per week would be: 92.75 ft2/day x 7days/120 ft2 = 5.4 passes Similarly, for intense and limited use courses the traffic passes estimated would be 9.4 and 3 per week respectively. Values of 9, 6 and 3 passes per week for heavy, mediate and light use golf course are used respectively. Table 3 summarized the traffic applied on soil column, which correspond to different use intensity of golf course fairway. The principal compaction sources on fairway are foot trampling and golf-cart traffic. It has been estimated that a person with street shoe exerts 0.04MPa of static pressure. 22 Turf maintenance equipment with "turf type" pneumatic tires generally applies 0.03 to 0.05MPa static pressure (Carrow et al., 1992). These evidences suggest that the difference of pressure applied by foot and powered golf maintenance equipment is not too big. For simplicity, we simulate foot, maintenance equipment and golf-cart traffic with same compacting force. Table 3 Summary of applied compaction on soil column Corresponding Compaction Play Intensity Levels Intensity Frequency Input Energy (Rounds) (Passes/time) (times/week) (Joules/week) 80000 Heavy 3 3 1022 40000 Medium 2 3 511 20000 Light 1 3 256 0 Control 0 0 0 Cavagna et al. (1964) reported that a man weighing 66 kg expend 27.6 J/m in walking at a most economical speed of 4 km/hr. The length of one step usually is 0.3038 m (3 feet). Street shoes contain approximately 206 cm 2 (32 sq. in) of effective surface area (Beard, 1973). As a result, this 66-kg man would spend 0.1225J/cm2 energy per unit area per step. In terms of energy expenditure per unit area, dropping a 15.89 kg (35pound) weight from 55 cm high is equivalent to a 66-kg weight person in walking, which is also 0.1225J/cm2. Therefore, in this study the soil compaction was created by dropping a 15.89-kg weight on the turf surface. The procedure are as follows: After allowed the soil and sod turfgrass to settle down for 12 weeks, compaction was applied three times a week. A circular hardwood plug was cut to fit inside the cylinder. Compaction was done by dropping a 15.89-kg weight from a height of 55 cm onto the hardwood. The impact velocity was 3.28 m/s. 3, 2 and 1 passes were applied for heavy, medium and light traffic levels respectively three times a week. In Lower Fraser Valley of British Columbia, the average annual rainfall is more than 1200 mm in most of its areas. Some courses may cancel a few matches after heavy rain. But in many cases, play is initiated when the soil moisture beneath the sand dressed layer 23 is at or near saturation. Since it is difficult to determine how often the golf games were played under the circumstance in which soil is at or near saturation, in this experiment compaction was done on a fixed time regardless of the soil moisture conditions. In other words compaction was applied mostly on unsaturated soil. But sometimes the soil was compacted at or near saturation. The soil compaction was created in the first 8 weeks. In order to maintain the created compaction levels, light compaction was then used up to the end of test, in which the same weight was dropped from a height of 30 cm one pass every two weeks. The light compaction applied 46.5 J energy. It is equal to the compacting energy used by other researchers for purpose of keeping compaction (O'Neil et. al. 1982; Agnew et. al., 1985) 3.3 Cultural practices 3.3.1 Irrigation Irrigation was scheduled based on the designated soil water content of each treatment. Namely, water was applied once the soil moistures drop to the designated limitations of 80%, 60% and 40% of field capacity for high, medium and low moisture treatments respectively. The amount of water per irrigation was determined with following equation: IR E Where: IR is gross irrigation requirement (L) WfC is container weight at field capacity (kg) Wj is container weight when moisture drop to allowable limitations (kg) L R is leaching requirement, estimated with 10% of net irrigation requirement E a is irrigation efficiency, use 95%) as it is common used value for estimating the field irrigation efficiency. 24 Irrigation was done manually with a sprinkling water can. Water was applied slowly and uniformly so as to closing the actual irrigation practice as much as possible. 3.3.2 Fertilization There are many types of fertilizer on the market in both liquid and solid forms. However solid, or slow release fertilizer is the most common type of fertilizer that is used on golf course. This experiment used the slow released fertilizer (IBDU) that is commonly used for fertilizer programs in golf courses. The fertilizer was supplied by UBC Totem Field (Seane Trehearne). The N:P:K ratio of the fertilizer is 16-4-16 (Par Ex Greens Grade). * A l l treatments received the same fertilizer application rate at a 1-pound of N per 1000 ft2 every two months. The fertilizer application was done after irrigation in the early morning in order for the moisture to get into the granular fertilizer to increase the effectiveness. 3.3.3 Mowing Turfgrass was mowed manually approximately once a week depending on the growth rate of turfgrass. The height of cut for turfgrass was 2.54 cm (1.0 inches) as recommended by Newton (1992) for the Vancouver Region. The turfgrass was cut using a pair of 10-inch hand-held grass shears, which could produce a clean cut and result in quick recovery for turfgrass. 3.3.4 Topdressing Fairway topdressing on golf course has been an overwhelming success and widely used in North America. A fairway topdressing program recommended by U S G A (Gilhuly, 1999) was employed in this experiment. The program applies topdressing sand with 1/16" rate on a 4-week schedule. The sand sizes from 0.1 to 1 mm, which includes coarse, medium and fine sands. The top dressing sand was obtained from Target, a 25 commercial supplier of golf course sand. The program was carried out throughout the experimental period. 3.4 Measurements and methods Before starting experiment, soil samples were taken for particle analysis and moisture content determination. Dry soil weight in each container was determined by weighing the container before and after loading soil. The dry soil weight data were used for the determination of soil moisture. Field capacity then was measured directly by using the containers. During 8-week compacting period, following data were collected regularly: 1) Soil moisture 2) Bulk density 3) Irrigation water volume 4) Drainage water 5) Clippings After compacting period, leachate samples for all treatments were also collected for NO _3 concentration analysis. At the conclusion of the experiment, soil infiltration rate, saturated hydraulic conductivity, drainable porosity, field capacity and penetration resistance of all treatments were measured. After these measurements were done, top turfgrass was removed. Turfgrass root distribution was observed and all roots then were collected for weight measurement. The detailed measurement methods are described below. 3.4.1 Soil moisture The determination of soil moisture content was accomplished by direct measurements of loss of weight from soil in each container. The soil water content was 26 expressed as the percentage of oven dried soil weight. Containers were weighted using a balance with an accuracy of 1 gram. The weight of containers was checked three times a week. The measurement was carried out throughout the experimental period. The measured soil moisture data were used for irrigation scheduling. 3.4.2 Bulk density Figure 4 Balance used in the experiment In this experiment, the soil column in each container was treated as a large soil core. During compacting period, soil bulk densities of the compaction treatments varied with time. The changing bulk densities were determined based on soil volume changes in each container. The soil volume changes were measured through checking the soil surface level that was relative to the top of the container following each compaction application. The bulk density data were used for characterizing the variation of the state of soil compaction in the compacting period. 3.4.3 Void rat io Void ratio was calculated using soil total porosity. The total porosity before and after compaction treatment was determined indirectly through soil bulk density and soil particle density. The data can help to further understand the state of soil compaction. The total porosity was calculated using following formula (McLaren and Cameron, 1996): n = l - ^ L ( 2 ) p 2 7 Where : n = total porosity Db = soil bulk density (g/cm3) Dp = soil particle density, use 2.65, which is a standard value for most soil (McLaren and Cameron, 1996). The void ratio e was calculated by (McLaren and Cameron, 1996): n 3.4.4 Soil strength Soil strength can be measured in several ways. In this experiment, penetrometer was used. The penetrometer applied is a hand operated auto-recording cone type (manufactured by Agridry Rimik PTY. LTD.) recording the penetration resistance in KPa met by the cone when slowly at a constant rate pushed into soil. Recorded data can be dumped into computer directly from the penetrometer (figure 4). The measurements were carried out in the conclusion of the experiment. Penetration resistance is dependent on soil water content. Therefore, all soil columns were saturated simultaneously. Penetration resistance measurements were conducted a week after soil saturation. Penetration values were recorded at each 1.5 cm depth interval down to 20 cm. ( a) (b) Figure 5 penetrometer used in the experiment, (a) Data collection, (b) Data processing 28 3.4.5 Infiltration rate Soil infiltration characteristics are influenced by a large number of factors. The most important ones that influence the movement of water through the soil surface are in four categories: (1) soil physical properties, (2) the type and intensity of vegetation, (3) irrigation application or rainfall rate, and (4) initial soil water contents (Julander et al. 1983). Based on our available apparatus, the infiltration rate was measured by two different methods. For all compaction treatments, a constant-head method is employed. Measurements were directly conducted with the soil containers. A graduated water level needle was installed in the middle of soil column for water level observation. A 2.54-cm depth (linch) of water on the soil surface was maintained manually by adding small quantities of water to the cylinder. Added water volume was recorded based on designated time interval. Infiltration rate was determined with following equation: / = l -667g, n (4) t A Where: I is infiltration rate (mm/h), Q i n is volume of water supplied within the time interval t (mL), t is the measured time interval (minutes), A is the cross sectional area of the cylinder (cm2). Since water infiltrate into the soil too quick to maintain a constant water head for non-compaction treatment, the infiltration rate was measured by an alternative way. A 1.5 liter of water (about 1 inch water in the container) was added to each container and the time of water disappears from the soil surface was recorded. Likewise, the infiltration rate can be determined by equation (4). 3.4.6 Field Capacity and Drainable Porosity 29 The drainable porosity (f) varies with time and the rate of fall of water table (Bouwer and Jackson, 1974). In this study, we assume the water table falls slowly enough for the changes of pore space to keep up. Thus the technique of estimating f from the equilibrium water contents above two successive water tables is applied, which could give a reasonable estimation of the f value. The large-column method for laboratory use (Taylor, 1960) was employed in this measurement. The apparatus used in the experiment simply is the containers themselves plus water supply apparatus as showed in figure 6. The experiment followed the laboratory procedure described by Taylor (1960) with a few modifications: 1) Fully saturate the soil column by applying water to the basis of the soil column and increasing water level slowly to saturate the soil from bottom for 24 hours (see figure 6 (a)). 2) Quickly cover the soil surface with plastic film to prevent from evapotranspiration (figure 6 (b)) and allow soil to drain freely. 3) Check the drainage volume released from soil column at 4, 8, 12, 24, 36 and 48 hours after starting drainage respectively. 4) Check the container weight when no drainage is observed The drainable porosity can be determined by (Amoozegar et. al. 1999): / = •££. (5) AL Where: f is the drainable porosity, Qd is the total water volume drained after little drainage is observed (mL), A is the cross-sectional area of the soil column (cm ), L is the length of soil column (cm). At the same time, field capacity can also be determined by following equation using the data obtained through above measurements: FC^W*-W< (6) Wd 30 Where: FC is field capacity (%), W w is the wet weight of soil after no drainage is observed (kg), Wd is the dry soil weight in the container. (a) (b) Figure 6 Diagram for drainable porosity measurement 3.4.7 Saturated Hydraul ic Conductivity There are three lab approaches that can be used to measure the saturated hydraulic conductivity in terms of water application method to soil column, including constant head, a falling-head and oscillating head. Generally, the constant head method is preferable for high conductivity soils. For soils with lower conductivity (usually the flow rate is less than 5 ml/h), the falling-head method is more accurate. The oscillating-head method is useful when there is a possibility for structural changes as a result of leaching that accompanies the water flow through the soil column under a constant or falling head procedure (Amoozegar & Wilson, 1999). Based on the availability of the equipment in our lab, this experiment used the constant-head method. Figure 3 showed the apparatus used for the saturated hydraulic conductivity measurement. The measurement follows the lab procedure described by Amoozegar and Wilson (1999): 31 Water Constant water level Drainage collector Figure 7 Diagram of the constant-head system for saturated hydraulic conductivity measurement 1) Before starting measurement, the soil column was saturated first. Water was applied from the basis of soil column and allowed to move up into the soil column from the bottom so as to allowing air escape from the top of soil column. To prevent rapid movement of water resulting in incomplete saturation, the water level was raised slowly to the top of the soil column. The soil was saturated for 24 hours, as this is sand soil and was just saturated 2 days ago. 2) After the soil column was saturated (direct observation of a thin water film on the top of the soil), water was then added to the top cylinder, and the soil column was quickly moved to the place where the hydraulic conductivity is going to be measured. 3) A graduated water level needle was installed in the middle of soil column for water level observation. A 2.54-cm depth (linch) of water on the soil surface was maintained manually by adding small quantities of water to the cylinder. 4) Water volume added to soil column was recorded and outflow from the bottom of the soil column was collected and its volume measured. Using Darcy's equation directly, the hydraulic conductivity can be calculated by: 32 (7) Where: K s a t is the saturated hydraulic conductivity (mm/hr), Qd is the water volume of drainage during the time period t (hour), A is the cross-sectional area of the soil column (cm2), L is the length of the soil column (cm), t is the time period for drainage (hour), AH is hydraulic head difference between top and bottom of the soil column (cm). 3 . 4 . 8 Drainage Water Quality The concentration of nitrate was measured using the Lachat QuickChem FIA+ Automated Ion Analyzer manufactured by Zellweger Analytic, Inc. (see figure 8). The measurement was based on Quikchem Method 10-107-06-2-D (Liao, 1997). Figure 8 Lachat QuickChem FIA+ Automated Ion Analyzer used for nitrate measurement concentration Before major soil properties and turfgrass growth parameter being finished, water samples were collected at different time, since different treatment has different irrigation regime. After finishing soil properties and turfgrass growth measurements, all treatments 33 were then irrigated with same schedule and water samples were collected at same time for a further comparison. A l l samples were analyzed in the Bio-Resource Engineering Laboratory, U B C . 3.4.9 Evapotranspiration of turfgrass Turfgrass evapotranspiration can be determined by direct measurement and indirect methods. Direct methods for ET measurement are important for evaluation of ET estimates by more indirect methods. The direct measurement methods can be generally divided into two categories the weighing method usually using lysimeters and tanks and the non-weighing methods. In this experiment, the actual evapotranspiration of turfgrass was measured by weighing the special containers, where the water loss is directly measured by the change of mass. Using the weights of two adjacent measurements, daily can be determined by soil water balance method. With the conditions used in this experiment, the ET can be calculated by following equation: W, -W, . +/, , -D. ETt = — - i d L ( 8 ) At Where: Wj is the previous measured weight of container Wi-i is current measured weight of the container I i-i is the irrigation water volume between the two adjacent measurements D i is the drainage water volume between the two adjacent measurements At is time interval between two adjacent measurements Since direct measurement is often expensive, the indirect calculation methods that compute ET from meteorological data are more commonly used. The calculation methods involve two steps. First, an estimate of reference ET is made using meteorological data. Then, an estimate of actual ET is obtained by multiplying the reference ET with a crop coefficient, which should be experimentally determined (Jensen et. al. 1980). 34 A large number of methods have been developed over the last 50 years by numerous scientists and specialists worldwide to estimate evapotranspiration. However, both ASCE and European studies indicated that the Penman-Monteith approach in both arid and humid climates is relatively accurate and consistent. It provides values that are more consistent with actual water use data worldwide Therefore, the FAO Penman-Monteith method was used for the computation of the reference evapotranspiration, ETo, in this study. The ET from turfgrass surface was determined by crop coefficients that relate to actual evapotranspiration and reference evapotranspiration ETo. The updated FAO Penman-Monteith approach is described by Allen et. al. (1998) as 0.408A(tf„-G) + y-^-u2(es-ea) E T = 1 + 273 ( 9 ) A + / ( l + 0.34w2) Where: ETo = reference evapotranspiration (mm/day) R n= net radiation at the crop surface [MJ/m2day] G = soil heat flux density [MJ/m2day] T = mean daily air temperature at 2 m height [°C] U2 = wind speed at 2 m height [m/s] es = saturation vapor pressure [kPa] ea = actual vapor pressure [kPa] es - ea = saturation pressure deficit [kPa] A = slope vapor pressure curve [kPa/ °C] y = psychrometric constant [kPa/ °C] Based on above equation and the computation procedure developed by Allen et. al. (1998), the E T 0 was calculated by using the meteorological data from the Vancouver Airport Weather Station, where is very close to the experimental site. Therefore, the crop coefficients of the turfgrass under soil compaction and water stress can be experimentally determined by: Kc=^- (10) ET0 35 Where: K c is crop coefficient ETc is measured ET. ETo is computed reference ET 3.4.10 Turfgrass Growth The growth of turfgrass was assessed with top growth, root growth and visual quality of the turfgrass. During the experimental period, clippings were collected following each mowing, oven dried at 65 °C for 24 hours. Dry clippings of each treatment were accumulated, and weighed every four weeks for top growth assessment. In the course of experiment, turfgrass quality was also evaluated every four weeks based on shoot density, color and uniformity of the turfgrass using a 1-9 scale, where 1 = turfgrass dead or completely dormant, 5 = minimally acceptable turf quality, 9 = ideal turf quality. At the end of study, top turfgrass was removed from containers. Soil in each container was gently broken apart, making sure that a minimal amount of root tissue was lost in the process. A 2-mm sieve was used for collecting the root. Root collected from each pot was placed in a water pail filled with water and soaked for 10 minutes to facilitate separation from attached soil. Then the washed root was oven dried at 65 °C for 24 hours and weighted for root growth evaluation. 3 . 5 Statistical analysis Statistical analysis of all recorded parameters was conducted using the NCSS 2000 statistical software package. Analysis of variable (ct=0.05) for these parameters using the Generalized Linear Models procedure for completely randomized design. Data for turfgrass quality were analyzed separately for each evaluation. Means were separated using Fish's LSD Multiple-comparison test. 36 4 Results and discussions 4.1 State of compaction under different traffic intensity The state of compaction of a soil largely determines the physical and related chemical soil conditions that control the content and transmission of water, air, heat, and nutrient, and that control the responses of plant. In a golf course, the state of compaction of a soil influences top growth, root development of turfgrass, and in fact the overall quality of the play surface. The design and management of irrigation and drainage system in golf course must be directed toward minimizing the compaction problems on the basis of prediction of the state of soil compaction at the different level of traffic. This section is intended to describe the change in state of soil compaction under different level of traffic on golf course fairway conditions. Compaction of soil is seldom measured directly. The usual procedure is to determine the changes in a parameter or a set of parameters as a consequence of compaction. A number of the state parameters have been used to characterize the condition or state of soil compaction. Each parameter has its advantages and limitations. In this study, a set of parameters including bulk density, void ratio and penetration resistance were measured and used as indicators of the state of soil compaction, because these parameters are all useful in different ways, and are commonly used in literature in characterizing the state of soil compaction. 4.1.1 Bulk density Soil bulk density provides a measure of how close the soil particles are packed (Freitag, 1971). It probably the most frequently used parameter to define the degree of compaction. Figure 9 shown the changes of soil bulk density by simulated compacting process on golf course fairway. During the compacting period, the soil behaved similarly to different levels of traffic. Generally the soil bulk density increased with the repetitive 37 application load. Under heavy traffic, the first three impacts resulted in 79 to 90 per cent of the volumetric strain obtained with 12 or more impacts as showed in figure 9 (a). At the mediate traffic level, five impacts resulted in the same range of the volumetric strain obtained with 12 or more impacts as showed in figure 9 (b). With light traffic, however, 12 impacts were needed to gain 70 to 90% of its volumetric strain obtained with all 18 impacts as showed in figure 9 (c). Noteworthy is the soil response to traffic under different soil moisture levels. During the compacting period, the bulk densities resulted from heavy and mediate traffic were very close to each other at high moisture level. However, the bulk densities resulted from different level of traffic were significantly different from each other at medium and low moisture levels. This indicated that soil moisture greatly influence the behavior of soil in response to traffic. Table 4 presented the statistical analysis of final bulk density as well as the changes of bulk density in percentage relative to their original values. It can be seen that soil bulk density was greatly reduced as a result of soil compaction. In comparison to their original values, heavy traffic treatments increased bulk densities by 40 to 50%. Mediate traffic treatments increased bulk densities by 38 to 45%. Even the light traffic treatments, the bulk densities increased by 25 to 30%. This result indicated that the soil was severely compacted especially for the heavy traffic treatment. Table 4 Effect of traffic intensity and soil moisture levels on bulk densityf Traffic levels 40 Final BD (g/cm3) 60 80 40 Changes (%) 60 80 Heavy 1.07a 1.08a 1.02a 46.4 50 39.8 Mediate 0.99a 1.04b 1.02ab 38.1 45.1 40.7 Light 0.93b 0.94c 0.94b 30.2 30.1 25.1 Control - 0.76d - - - -f Values followed by same letter within columns are not significantly different from each other at 0.05 probability level; n = 3 for each treatment. 38 1.2 -j 1.1 -C>-J 1.0 -CT 0.9 -G CD 0.8 -0.7 -nfi -60% of F C 1 i i i i i 2 4 6 "i i i i i—i—i—i—i—i 8 10 12 14 16 Impacts 1.2 -j 1.1 -55 1.0 -i 0.9 -Q CO 0.8 -0.7 -n R -40% of F C "i i i i—i—i—:—i—r n i i—r—i—r 2 4 6 8 10 12 14 16 Impacts Figure 9 Changes in soil bulk density due to repetitive application of impact load 39 As most of the previous studies indicated that soil moisture also influence the behavior of turf-soil system under traffic. Statistically, heavy and mediate traffic treatments did not result in significant difference in bulk density (Probability level < 0.05) under high soil moisture level. But the final bulk density resulted from light traffic treatment significantly differed from those of heavy and mediate traffic treatments. At the medium moisture level, bulk densities resulted from different level of traffic were significantly different each other. With the low moisture, mediate traffic did not result in significant differences in bulk density from both heavy and light traffic, although the bulk densities of heavy and light traffic treatments did differ from each other. The results further support the opinion that from the perspective of compaction, control of play intensity and soil moisture are equally important in the management of soil and water on golf course fairway. M Traffic level _3 80% g 60% B 40% Figure 10 Influence of soil moisture on bulk density under diiferent level of traffic. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level Generally the maximum bulk density occur when soil water content is at filed capacity for a given amount of energy applied during compaction process (Harris, 1971; Carrow and Petrovic 1992; Adams and Gibbs, 1994;Whalley et al, 1995). In this study, it was found that traffic at the medium moisture level (60% of FC) resulted in a little higher bulk density than at both high and low moisture level (80% and 60% of FC) regardless of 40 traffic intensity levels (see figure 10). This result does not agree with previous conclusion. The reason probably is that both high and low soil moisture treatments have a greater amount of roots than the medium soil moisture treatments (see section 4.4.3), which might help to resist soil compaction. 4.1.2 Void ratio Although the state of compaction can be completely specified by giving bulk density, the viod ratio (VR) that can related to bulk density has more meaning as related to soil behavior. Table 5 gives the values of viod ratio before and after treatment. It can be seen that traffic intensity had significant effects on void ratio. Heavy traffic reduced viod ratio by 41.7 to 45.8%. Mediate traffic decreased viod ratio by 37.8 to 41.6%. Light traffic decreased viod ratio by 29.1 to 32.1 %. The viod ratio was more sensitive to traffic than total porosity because it gives directly the change of pore volume as a proportion of the constent volume of solids. Table 5 Changes in void ratio under different traffic intensities Treatment Initial Void Ratio Final Changes(%) H H 2.733 1.593 41.7 H M 2.693 1.461 45.8 H L 2.629 1.479 43.8 M H 2.657 1.598 39.9 M M 2.689 1.544 42.6 M L 2.717 1.690 37.8 L H 2.588 1.834 29.1 L M 2.663 1.809 32.1 L L 2.707 1.845 31.8 At same soil moisture level, viod ratio generally increased with decreased traffic intensity. But the differences in viod ratio between heavy and midiate traffic treatemtns at 41 high soil moisture level was not significant. The largest void ratio was 1.85 that was recorded by the light traffic treatment with low soil moisture. The lowest viod ratio was 1.46 that conresponded to heavy traffic treatment at medium moisture. 4.1.3 Penetration resistance The strength of soil varies in a systematic manner with changes in its moisture content and density, but it can also be responsive to changes in the soil fabric. Although these dependencies are complex, they can provide a basis for determining changes in the state of compaction of the soil. Penetration resistance has long been used to measure the soil strength, since the penetration test can be conducted very quickly, and a number of readings can be easily obtained at various points within the area of interest. In this study, penetration data were collected from 14 different depth of soil column with an increment of 1.5 cm. Figure 11 shown the distribution of penetration resistance of all treatments. The highest penetration resistance was observed at the depth of 4.5 cm for all treatments. This result basically agrees with previous reports (O'Neil et al. 1981, Sills et al. 1983 and Agnew et al., 1985). The lowest penetration resistance was found at the depth of 1.5 cm, partly because most of the applied topdressing sand accumulated on the surface of the soil. In relation to the traffic levels, (1) the values of PR follow the same pattern of heavy traffic > mediate traffic > light traffic regardless of soil moisture levels; (2) significant differences in PR existed among different level of traffic intensity. However, the differences in PR resulted from different level of traffic at high moisture level were much smaller than that at medium and low moisture levels. This could be explained by the fact that soil at high water content is much easier to compact than at low soil water content. High penetration resistance would be expected to hinder root development as it would represent increased mechanic impedance to root penetration. The root growth associated with penetration resistance resulting form different level of soil compaction will be discussed in section 4.4.3. 42 2000 80% of FC 1500 { P 4? 4> <_? $ Depth (mm) Figure 11 Changes in penetrat ion resistance w i t h depth due to di f ferent level o f t raf f ic intensity and soil moisture levels. 43 Figure 12 Comparison of PR changes resulted from different moisture levels 44 When compared the effects of different soil moisture treatments, it is interesting to see that under the same traffic intensity the PR of high moisture treatment was always lower than that of medium and low moisture treatments as showed in figure 12. The possible reason is that traffic with high soil moisture resulted in a relatively high holding water capacity, which in turn contributed to the lower penetration resistance. 4.2 Compact ion effects on irrigation Irrigation is most critical of the turf management practices in golf course and the one that is most difficult to manage because of the highly complex character and almost infinite variability of soil and weather. For a well-designed and operated irrigation system, the determination of soil and plant parameters is essential and a challenge. These parameters include the infiltration rate of soil, the evapotranspiration (ET). This section will discuss how soil compaction affect these important irrigation parameters. Table 6 summarized the results of A N O V A that represents the effects of traffic intensity, soil moisture levels as well as their interaction on these important irrigation parameters. As table 6 indicated, traffic intensity (T) had highly significant effects on infiltration rate and field capacity. But it did not significantly affect the ET. Soil moisture levels (M) had highly significant effects on infiltration rate and ET. But it had no effect on field capacity. The T x M interaction only had significant effect on infiltration rate. It did not significantly affect both field capacity and ET. Table 6 Summary of analysis of variables for traffic intensity, soil moisture levels and their interactive effects on some irrigation parameters Variables Traffic intensity (T) Moisture levels (M) T x D Infiltration rate 0.0001*** 0.0000*** 0.0006*** Field capacity *** NS NS ET 0.4141NS 0.0000*** 0.3369NS Significance at the 0.05 probability level Significance at the 0.01 probability level 45 *** Significance at the 0.001 probability level NS Non- significance at the 0.05 probability level 4.2.1 Infiltration rate Infiltration process is of great importance, since its rate not only determines the runoff over soil surface during rainstorms or irrigation, but also affects the entire profits of the golf course due to longer surface ponding where the infiltration rate is limited. Knowledge of infiltration rate as it relates to soil compaction is needed for efficient soil and water management in golf course. The soil used in this study is very permeable. Before establishing turf the steady infiltration rate of the soil is 104 mm/hr as shown in figure 13. After grown turf, the steady infiltration rate increased to 1036 mm/hr (see table 7), which was ten times greater than before growing turfgrass. The huge increase in infiltration rate can be explained by the massive root growth after establishing turfgrass (see section 4.4.3), since greater amount of roots can greatly increase the path from where water pass through the soil column. This result implies that turfgrass can greatly improve soil infiltrability. 1800 i 1600.H O.1400 J £ 1000 J 200 1 0 50' 100 150 Time.(rriri,). Figure 13 Changes in infiltration rate with time without turfgrass 46 30.0 i c f 3 8 0 % l 6 0 % S 4 0 % 25.0 A b 20.0 A c E 15.0 A io.o A 5.04 a a 0.0 H M L Traffic level Figure 14 Comparison of infiltration rate of different soil moisture treatments under turfgrass cultivation. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level The mean final infiltration rate values of various treatments were presented in table 7. The data indicated that infiltration rate is very sensitive to soil compaction, since soil compaction mainly alters the large soil pores, which is decisive to the infiltration rate. According to the results, under same soil moisture level the infiltration rate generally decreased with increased traffic intensity except for the heavy traffic treatment at medium soil moisture level. But statistically there was no significant difference between heavy and mediate traffic treatments at high moisture level, probably due to the fact that soil at high moisture content is easy to be compacted. Figure 14 compared the final infiltration rates at different soil moisture levels. It can be seen that soil moisture also strongly affected the infiltration rate. At high soil moisture, the final infiltration rate ranged from 0.1 to 3.5 mm/hr. Even the light traffic treatment reduced the infiltration rate to such a degree that soil was almost impermeable. At medium soil moisture level, the heavy traffic treatment did result in a low infiltration rate than that of mediate traffic treatment. But the light traffic treatment gave a mixed signal. 47 There appear to be no consistency. At low soil moisture level, significant differences existed among different level of traffic. Table 7 Summary of statistical analysis of steady infiltration rate as influenced by traffic intensity and moisture levels (mm/hr) f Traffic intensity Moisture (% of F Q 40 60 80 Heavy TJte 19.6a OJa Mediate 15.4b 10.7b 0.3a Light 26.3c 20.3a 3.5b Control - 1036.3NC | Values followed by same letter within columns are not significantly different from each other at 0.05 probability level; n = 3 for each treatment; N C means not compared Establishing an empirical relationship between infiltration rate and the degree of soil compaction to predict infiltration rate under soil compaction is useful for design and management of irrigation and drainage system in golf course. To achieve this goal, regression analyses between steady infiltration rate and soil bulk density, total porosity as well as void ratio were carried out. It was found that the observed steady infiltration rate under different degree of soil compaction was strongly related to void ratio as showed in figure 15. The associated regression equation is: I = 2183e 3-11109e 2+ 18708e- 10420 (11) Where I is steady infiltration rate under soil compaction (mm/hr) e is void ratio The regression has a R of 0.96. From the figure 15, it is obvious that the observed infiltration rates were well predicted by the regression. The regression equation can be used to similar conditions to predict infiltration rate under soil compaction. 48 y = 2183)?- 11109X2 + -18708X- 10420 0 1 2 3 Void : rat io Figure 15 Relationship between steady infiltration rate and void ratio under different level of soil compaction 4.2.2 Filed capacity Field capacity (FC) represents the capacity of soil water storage. It determines how much water should be applied per irrigation. Table 8 presented the mean values of FC before and after compaction. The result shown that field capacity was generally reduced as a result of soil compaction. Heavy traffic treatments reduced the FC by 7 to 15 percent. Mediate traffic treatments decrease the FC by 8 to 13 percent. The light traffic treatments reduce the FC by 3 to 8 percent. However, it was noticed that the changes in field capacity were not as high as bulk density and infiltration rate. This is because soil compaction changed large pores into fine pore space. This is because soil compaction changes large pores into fine pore space. The increased fine pore space enhanced the water holding capacity of soil capillary and contributed to the less reduction of field capacity. The soil moisture control levels also affected the field capacity. Under same traffic level, the reduction of field capacity of high moisture treatment was much smaller than that of medium and low moisture treatments. The reason might be that traffic application at higher soil water content could generate more fine pores than at lower soil moisture. 49 Table 8 Changes in field capacity under different level of traffic intensity Traffic level Moisture level (%ofFC) Initial FC (%) Final FC (%) Changes (%) Heavy 80 66.5 59.5 7.0 Heavy 60 66.9 52.5 14.4 Heavy 40 68.8 53.4 15.4 Mediate 80 65.8 57.6 8.2 Mediate 60 68.1 55.5 12.6 Mediate 40 68.0 56.0 12.7 Light 80 63.0 60.0 2.9 Light 60 63.8 59.7 4.1 Light 40 67.8 60.2 7.6 4.2.3 Evapotranspiration 4.2.3.1 Effects of soil compaction and moisture stress on ET Evapotranspiration forms the foundation for planing, design and management of irrigation system. It is usually the starting point in irrigation scheduling for determination when to irrigate. Table 9 gives the weekly averaged Evapotranspiration rates of all treatments. The control treatment reflected the Evapotranspiration without stress. A l l other treatments reflected the Evapotranspiration under stress of soil compaction or both compaction and moisture stress. It can be seen that the average weekly Evapotranspiration rates rage from 0.6 mm/d to 2.5 mm/d, mainly depend on weather. Averaged over the 4-month measurement period, the control treatment had highest Evapotranspiration rate (1.7 mm/d). The average Evapotranspiration rates of other treatments were 1.4 to 1.5, 1.3 and 1.2 mm/d respectively for high, medium and low soil moisture treatments. It appeared that traffic levels did not significantly affect average Evapotranspiration rates. 50 Table 10 presented the total Evapotranspiration of all treatments over the 4-month measurement period. From table 10 it can be seen that the total Evapotranspiration decreased by 12.4 to 27.1, 11.9 to 25.5, and 15.1 to 29.2 percent for heavy, mediate and light traffic treatments respectively. Morgan et al. (1966) reported that Evapotranspiration declined as a result of soil compaction. O'Neil et al. (1982) found that the Evapotranspiration of Kentucky bluegrass decreased by 20% when water is unlimited. A later study by Agnew et al. (1985) also found a reduction of 21% in Evapotranspiration of Kentucky bluegrass over a 10-day measurement period. Our results basically agreed with previous reports, which support the conclusion that Evapotranspiration decreases under soil compaction, and the magnitude of reduction mainly depends on soil moisture condition. However, at same moisture level no significant differences in Evapotranspiration were found statistically among the different traffic treatments. Table 10 Changes in total Evapotranspiration due to traffic and soil moisture stress over study period Treatment Traffic level Moisture level (%ofFC) Total ET (mm) Changes (%) H H Heavy 80 187.3 12.4 H M Heavy 60 170.4 20.3 HL Heavy 40 155.9 27.1 M H Mediate 80 188.5 11.9 M M Mediate 60 164.0 23.3 M L Mediate 40 159.3 25.5 L H Light 80 181.6 15.1 L M Light 60 169.7 20.6 L L Light 40 151.5 29.2 C Control 60 213.8 0 51 s B _o '-In 8 I o o o g '-3 o t s >H H W 13 u bfl c3 VH <u ii ON o Cl o U c o CN CN cn X CN O *tJ T3 C H S H r - O O O N O N i — i f N c o c N l ^ O O O c O T t - i r i C N ' — ' O O r - - C N t-; OO 00 ON © o © o ^ m m c N o o ^ o o m L n ' ^ - c N r ^ O N O O c N © © ' © ' © < i — I ^ . - H ' O ^ J C N I - H ' - H ^ H ^ H I — i (S r-! r-~ oo © © © - H N W t N H O N ^ v o o N o o © i n i n i n t> 00 00 o CN CO © © O © .-I I - H ' r-H • — ' O v V O f - T T T t - C N V O - ^ - o o i n C N v o t > o o o o o c N > n c o 0 © © ' © T - H ' - H ' ^ H - , - H • — i c n o \ ^ j - - ^ - ^ H O o v o ^ - < t ^ c n 0 0 0 0 » — 1 » — i i — i i — 1 » — 1 » — 1 > — I ^ - < I — H C N T - < C N C N •—< 1/1 CN JO JO 0) ii ii fe P H fe •4 -_ 00 o I - H CN CN c3 ^ c3 i-| L-1 f-H }-H . - - a CL CL Q, « cd cd cd cd O ^ C N C N O ^ H - H C N O O ^ H C N C ! CN The comparison of ET between the different levels of moisture treatments showed in figure 16. In general the ET reduced as the soil moisture level decrease. At heavy and light traffic level, significant differences in ET existed among the three levels of moisture treatments. Under mediate traffic, the ET of the high soil moisture treatment was significantly different from those of medium and low moisture treatments. However, the ET of medium and low moisture treatments was not significantly different from each other. The results suggest that soil moisture is a more influential component to ET than soil compaction. E Heavy Mediate Light Traffic level Figure 16 Comparison of ET of different level of soil moisture treatments. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level 4.2.3.2 Estimating ET under compaction and moisture stress Owing to the difficulties of measuring ET in terms of accuracy and expense of the measurement, ET is commonly computed from meteorological data. A large number of empirical or semi-empirical equations have been developed for assessing crop ET from meteorological data. The crop coefficient ( K c ) approach is a global accepted method for estimating ET, because the K c varies predominately with the specific crop characteristics and only to a limited extent with climate (Allen et. A l . , 1998). In the crop coefficient approach the actual crop ET, ET C , is calculate by multiplying the reference ET, ET 0 , by a crop coefficient, Kc . The K c predicts ET C under standard conditions. When non-standard conditions, where limitations are placed on the crop growth, is encountered, the crop 53 will have different K c . The changing characteristics of K c due to soil compaction and moisture stress were not found in literature. Since the Kc can vary substantially over short periods, monthly averaged crop coefficients are usually used in irrigation scheduling. Table 11 presented the K c under soil compaction and moisture stress on a monthly basis. Reference ET was calculated based on the average meteorological data from 1961 to 1990 at Vancouver Airport. The K c of control treatment averaged from January to May, which represents conditions where no limitations were imposed, was 0.97. The average K c of the treatments with compaction and moisture stress ranged from 0.66 to 0.81, which were consistently lower than that of the control treatment. The reason is that both soil compaction and soil water shortage may reduce soil water uptake and limit crop ET. Under same moisture level, the crop coefficients were 0.79 to 0.81, 0.7 to 0.75, and 0.66 to 0.7 for heavy, mediate and light traffic treatments respectively. It appeared that the traffic intensity levels had little impact on K c . In considering the effect of soil moisture, it can be seen that the Kc decreased greatly with increased soil water stress. This is basically agrees with previous reports about Kc under soil water stress (Ervin et al., 1998, Carrow, 1995, Allen et al. 1998). Table 11 Crop coefficient under compaction and moisture stress Month Jan. Feb. March April May Avg.f Days 9 28 31 30 31 129 H H 0.69 0.89 0.83 0.82 0.67 0.79 H M 0.65 0.80 0.80 0.79 0.56 0.73 H L 0.73 0.73 0.71 0.73 0.48 0.66 M H 0.77 0.89 0.86 0.80 0.67 0.80 M M 0.70 0.76 0.72 0.78 0.54 0.70 M L 0.74 0.86 0.72 0.72 0.50 0.70 L H 0.84 1.00 0.91 0.76 0.56 0.81 L M 0.77 0.92 0.85 0.71 0.53 0.75 L L 0.78 0.87 0.68 0.70 0.44 0.68 C 0.92 1.30 1.12 0.93 0.58 0.97 f Weighted average based on the number of days in each time period 54 From this study, it is found that crop coefficient was reduced by both soil compaction and moisture stress. Therefore, to accurately estimate E T , it is necessary to adjust E T in according to both soil compaction and moisture stress. The environmental stress effects on E T can be incorporated into a stress coefficient, K s , and estimated by following equation: E T C = K s K c E T 0 (12) Where: E T C is actual E T ETo is reference E T K s is environmental stress adjustment coefficient K c is crop coefficient with nonstress When only soil compaction and moisture stress are presented, the K s can be separated into two components, the compaction adjustment coefficient ( K c s ) under nonlimited soil moisture and the moisture stress adjustment coefficient ( K w s ) , and can be expressed as: K s = K c s K w s (13) For soil water limiting conditions or compaction stress, K c s or K w s < 1. Where there is no compaction or soil water stress, K c s or K w s = 1. Based on the data from this study, the crop coefficients of compaction treatments under well irrigation ranged from 0.79 to 0.81 (mean 0.8). They vary very little with traffic intensity. This implies that the K c s could be regarded as a constant value. In the case of soil compaction stress but no soil water limiting conditions ( K w s = 1), using the average crop coefficient of 0.8, the K c s can be found from: K c s K w s K c = 0.8 or K c s = 0 . 8 / K c = 0.8 7 0.97 = 0.82 55 Under normal conditions, the crop coefficient varies very little before root zone depletion exceeds the readily available water (usually 50% of total available water for many plants). After water content drop below the readily available water, the crop coefficient begins to decrease in proportion to the amount of water remaining in the root zone. However, many studies indicated that the readily available water reduced under soil compaction. Unlike conditions without compaction, our observation demonstrated that crop coefficient under soil compaction began to decline at a higher soil water content (80%) of FC). To predict crop ET under soil compaction and water stress, it is necessary to find a relationship between K w s and soil water content. Figure 17 plotted observed crop coefficient VS moisture level. Correlation analysis indicated that the crop coefficients under soil compaction have a very strong association with moisture content (R = 0.902). The linear correlation equation is as follows: K w s = 0.003 9 r +0.5559 (14) Where 0 r is relative soil moisture (% FC) Therefore, under soil compaction and water stress the actual ET can be estimated by the reference ET (ET 0) multiplying crop coefficient under nonstress and adjusting by K c s and K w s (equation 3). K c s can be estimated with 0.82. 0.90 -0.85 • 1 0.80 • I 0.75 -§-•0.70 -I Vi..'.":'.': ""0.65-0.60 •y = 0:00 3x+ 0.5559 R* = 0.902 ' 20 40 .60 80 Soil moisture. (% FC) 100 Figure 17 Correlation between crop coefficient and soil moisture under soil compaction and water stress 56 4.3 Compaction impacts on drainage Adequate drainage for golf course is of great importance. It is not only essential to the health of the turf grass and its ability to withstand the concentrated traffic in a golf course, but also important to the profits of golf course because heavy rain or irrigation could cause cancellation of games if proper drainage is not provided. It has been found that soil compaction can lead to surface waterlogging or poor drainage problem. In an effort to understand the compaction impact on drainage, this section will provide an insight into two important soil physical parameters the hydraulic conductivity and drainable porosity, since both of them are most vulnerable to compaction events and most important for design and management of drainage system. Environmental concern is one of the greatest challenges facing the game of golf. Among the environmental issues, groundwater contamination by nitrate from soluble fertilizers brought most frequent concern in public (Sartain et al., 2000). Therefore, the impact of compaction on nitrate leaching will also be treated in depth in this section. Table 12 presented the significance levels of F-test for the hydraulic conductivity and drainable porosity. It can be seen that hydraulic conductivity and drainable porosity were significantly affected by both traffic intensity and soil moisture levels at probability level of 0.001. The T x M interaction only affects the hydraulic conductivity at probability level of 0.01. But it did not affect the drainable porosity significantly. Table 12 Summary of analysis of variables for traffic intensity, soil moisture levels and their interactive effects on some drainage parameters Variables Traffic intensity (T) Moisture levels (M) T x D HC 0.0002*** 0.0000*** 0.0101** DP 0.0000*** 0.0000*** 0.0543NS * significance at the 0.05 probability level ** significance at the 0.01 probability level *** significance at the 0.001 probability level NS Non- significance at the 0.05 probability level 57 4.3.1 Hydraulic conductivity Hydraulic conductivity is a measure of the ability of soil to conduct water. For drainage, the saturated hydraulic conductivity is used to compute the velocity at which water can move toward and into the drainlines below the water table. Its effective value is one of most important parameters in drainage. Table 13 summarized the measured mean hydraulic conductivity for all treatments. The results show that non-compaction treatment had a hydraulic conductivity of 1587 mm/hr, which exhibited an extremely high ability of water transmission. With soil compaction the hydraulic conductivity reduced less than 27.3 mm/hr. This demonstrated that soil compaction has a huge impact on hydraulic conductivity. In general, the hydraulic conductivity decreased with increased traffic intensity regardless of soil moisture levels with exception of one treatment (heavy traffic with medium soil moisture). Statistical analysis indicated that heavy and mediate traffic did not result in significant difference in hydraulic conductivity except for at medium soil moisture level, although there was a tendency that higher traffic leaded to lower hydraulic conductivity from value perspective. However, the hydraulic conductivity of light traffic treatments did significantly differ from those of heavy and mediate traffic treatments. Table 13 Summary of statistical analysis of hydraulic conductivity as influenced by traffic intensity and moisture levels (mm/hr) f Traffic intensity 40 Moisture f% of FC1 60 80 Heavy 3.2a 7.9a 0.1a Mediate 6.7a 4.7b 0.2a Light 27.3b 15.8c 3.3b Control - 1587NC -f Values followed by same letter within columns are not significantly different from each other at 0.05 probability level; n = 3 for each treatment; N C means not compared 58 Soil moisture levels also had a significant effect on hydraulic conductivity. Figure 18 compared the hydraulic conductivity of different levels of soil moisture treatments. For high soil moisture treatments, the hydraulic conductivity ranged from 0.1 to 3.3 mm/hr. The soil was almost impermeable. For medium moisture treatments, the hydraulic conductivity ranged from 4.7 to 15.8 mm/hr, which is a little higher than high soil moisture treatments. Based on the soil permeability classification by O'Neal (1953), the soil had a moderately slow permeability. For the low soil moisture treatments, the hydraulic conductivity varied from 3.2 to 27.3 mm/hr. The hydraulic conductivity was much higher, but still below the requirements of top layers or root zone materials of sports fields proposed by various countries (table 14). From the observed values of hydraulic conductivity, it was noticed that at same traffic level the hydraulic conductivity decreased with increased soil moisture level except for the medium moisture treatment with high traffic. Table 14 Minimal requirements of hydraulic conductivity of topsoil layer or root zone of sports field, as proposed by various country* Country Hydraulic conductivity Author (cm/d) Denmark 24-48 Petersen (1974) Germany 130 Deutcher Normenausschuss (1974) Netherlands 60 Stuurman(1970) Great Britain 240 Adams etal. (1974) United States 50-150 USGA(1973) 60 Schwartz & Kardos (1963), Beard 1973), Waddington et al. (1974) 120 Bingaham & Kohnke (1970) 120-240 Danialetal. (1974) 408 Brow & Duble * Sources: van Wijk, 1980; Ward, 1983. 59 30.0 -i Soil mDistune (% FC) Figure 18 Comparison of hydraulic conductivity of different level of soil moisture treatments. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level Void ratio Figure 19 Relationship between steady hydraulic conductivity and void ratio under different level of soil compaction. The number of observations n = 30. 60 Statistically, under mediate and light traffic there were significant differences in hydraulic conductivity between high and medium soil moisture treatments. But the hydraulic conductivity of medium moisture treatments was not significantly different from those of both high and low moisture. Similar to the infiltration, the hydraulic conductivity also significantly related to the void ratio. Figure 19 showed their relationship, and a similar polynomial regression equation was obtained as follows: HC = 1859.3e3 - 8444.8e2 + 12515e- 6030.7 (15) Where HC is hydraulic conductivity (mm/hr) The polynomial regression has a correlation coefficient R 2 of 0.91. It could provide a good prediction of the hydraulic conductivity under soil compaction conditions. 4.3.2 Drainable porosity Drainable porosity is describe as the difference between the volumetric water content of unit volume of soil at saturation and its volumetric water content after drainage (Bouwer, 1979). It is needed for all nonsteady saturated flow methods in drainage design. The effect of soil compaction on drainable porosity was examined and shown in table 15. The results clearly shown that soil compaction caused a great reduction in drainable porosity. Comparing to no compaction treatment, the drainable porosity of heavy traffic treatment was reduced as much as 10 times. Even for the light traffic treatment, the drainable porosity was reduced more than 4 times. It was found that the drainable porosity decreased with increased traffic regardless of soil moisture levels. Under higher soil moisture levels (80% and 60% of FC), heavy and medium traffic intensity did not result in significant differences in the drainable porosity statistically. At low soil moisture (40% of FC), However, different traffic treatments resulted in significant differences in drainable porosity. The possible reason might be that the soil at higher moisture levels was easy to be compacted and was not very sensitive to different compacting forces. At lower soil moisture, however, the soil 61 had a higher ability to resist compaction force and responded to compacting forces differently. Table 15 Summary of statistical analysis of drainable porosity as influenced by traffic intensity and moisture levels (mm/hr) f Traffic intensity Moisture (% of FC) 40 60 80 Heavy 2.1a 2.1a 1.6a Mediate 2.6b 2.1a 1.7a Light 3.7c 3.1b 2.9b Control - 17.6NC | Values followed by same letter within columns are not significantly different from each other at 0.05 probability level; n = 3 for each treatment; N C means not compared The influence of soil moisture on drainable porosity was illustrated in figure 20. It can be seen that at same traffic level the drainable porosity increased with soil moisture level decreased. This can explained by the fact that lowering soil moisture can enhance the resistance to soil compaction. The changes in drainable porosity of soil moisture treatments ranged from 1.6 to 2.1, 1.7 to 2.6, and 2.9 to 3.7 at heavy, mediate and light traffic levels respectively. It appears that changes in drainable porosity with soil moisture levels were relatively small. Statistically, at mediate and light traffic levels the high and medium moisture treatments did not cause significant differences in drainable porosity, but there were significant differences between the low moisture and the high and medium moisture treatments. At high traffic level, the situation was slightly different. The drainable porosity of medium and light traffic treatment were significantly different from that of high soil moisture treatment. But they were not significantly different from each other. Figure 21 showed drainable porosity versus void ratio. Their relationship was given by following regression equation: 62 4 i 3 o > Q ! b b m H M L Traffic levels Figure 20 Comparison of drainable porosity of different level of soil moisture treatments under soil compaction. H = heavy traffic; M = mediate traffic; L = light traffic. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level 25.0 ^ 20.0 <JT> O o 15.0 OJ 10.0 b 5.0 0.0 y = 18.397x2 - 58.772x + 48.818 R 2 = 0 .9198 * Observations Regression 0.5 1 1.5 2 Void ratio 2.5 Figure 21 Relationship between steady drainable porosity and void ratio under different level of soil compaction. The number of observations n = 30. 63 DP = 18.397e2 - 58,772e + 48.818 (16) Where DP is drainable porosity. The regression has R 2 = 0.92. As shown in figure 21 this equation performs as well as regression equations (11) and (15). 4.3.3 Drainage water quality Nitrogen can be found in many different chemical forms. Of these different forms, nitrate (NO3") nitrogen has the most potential for movement into groundwater through drainage. Nitrate nitrogen can easily move though soil because it has a negative chemical charge, which can prevent strong binding with clay and organic matter. The nitrate ions are characterized by relatively high diffusivity (i.e. greater than 10"7 cm'V 1 in uncompacted soil; Liepic and Stepniewski, 1995). Information about effect of soil compaction on mobility of nitrate ions under turfgrass cultivation is still lacking. To examine the nitrate movement, drainage samples were collected for NO3" concentration analysis. Water samples were collected followed by each irrigation. Before May 29, most of the water samples were collected at different time, because each treatment had different irrigation schedule. For further comparison, all treatments were irrigated with same schedule after May 29. Water samples were collected and analyzed at the same time. Table 16 presented the NO3" concentration of all treatments for the whole measurement period. The data reflect the normal fertilization and irrigation practice in golf course. From table 16, it can be seen that the NO3' concentrations of all treatments were very low. The largest detected N 0 3 " concentration was 1.57 mg/L well below the maximum concentration of nitrate for drinking water standards (10 mg/L N 0 3 - N ) recommended by federal government. This is basically agrees with the results reported in literature (Petrovic, 1990; Kenna et. al., 2000; Johnston et. al., 1999) It was found that NO3" concentrations of non-compaction treatment were considerably low. This could be attributed to its higher N uptake due to greater top growth and massive root development. The data indicated that mediate and light traffic 64 co CN >—1 CO CN CO CN 1 o © o 0) Q o T - H o © o o o I O N CN IT) *—i © oo CO © O © CN o T — 1 O O © © © © © © © © © CO t - H CN r - T — 1 CN N O i n i n T - < CO T - H © © i n O N i n i n i n t-- © CN m >—i © © © © © © © © © © o © © © CO CO o © © © CO © o © © © © © © O © o © o CN oo N O © N O © CN t-- m N O N O i n © © © © © © CO r-- oo T - H CN CN © © © * *• * o CN © 00 CO O N © o CO © i n © © o © © © © © © © © © © N O © O N © O N O N O © CN © © © © © © 00 i n CO © CO © © © o CO © © © © © © o © © © © N O o © © © © T - H CN o © © © © T - H O © o © © © © o >> >> >> >> >> cd cd a cd Cd Cd cd cd cd ri cl > — 1 > I — > •Ju T - H © CO i n © CN O N CO JL, o O * — 1 <—i <—i I — 1 CN CN CN CN CN © © T - H 1 — 1 >n N O cd td •o > Cl treatments resulted in increase in N O 3 " concentration of leachate in comparison to non-compaction treatment, because compaction reduced the top growth and decreased the N uptake of turfgrass. This was in agreement with conclusions from agricultural field (Lipiec et al., 1995; Soane et a l , 1995). But the heavy traffic treatment reduced the concentration of nitrate in leachate in most cases. This could be explained by the fact that the soil under heavy traffic was severely compacted. Compaction of sandy soils, which are highly conductive to leaching, usually results in greater nitrate retention in topsoil (Lipiec et al., 1995; Agrawal, 1991). Thus less nitrate was detected could be because a greater amount of nitrogen might be retained in the topsoil. Figure 22 and 23 showed the average NO3" concentration in leachate over the measurement period before and after May 29. Before May 29, the averaged N O 3 " concentration in leachate generally increased with decrease traffic exception for the mediate traffic treatments at high moisture level (MH), which was slightly higher than heavy (HH) and light (LH) traffic treatments at same moisture level. The increase tendency was most evident for the treatments at low moisture level. The average N 0 3 " concentration in leachate after May 29 followed similar trends as before May 29. The only difference was that the average N 0 3 " concentration of treatment M M also was a little greater than treatment H M and L M were. However, their differences were very small. Moisture levels also had a significant impact on the average N 0 3 " concentration in leachate. As showed in figure 24 and figure 25, the average NO3" concentration in leachate over the measurement period exhibited a same pattern of high moisture > medium moisture > low moisture both before and after May 29. For high soil moisture treatments, the average NO3* concentration was less than 0.06 mg/L. Nitrate was almost undetectable. For the medium moisture treatments, the average N 0 3 " concentration ranged from 0.06 to 0.25 mg/L, which were little higher than high soil moisture treatments. For low soil moisture treatments, however, the average NO3" concentration increased to 0.16 - 1.22 mg/L, which were much higher than high and medium moisture treatments. But the nitrate concentrations were still very low. The NO3" concentration in drainage is dependent on the quantity of drainage water volume. For further comparison, the cumulative drainage water volume and 66 corresponding cumulative mass of nitrate presented in drainage water were showed in figure 26 to figure 31. The mass of nitrate was calculated based on nitrate concentration and drainage water volume. It was noticed that the trends of cumulative nitrate mass influenced by traffic intensity appeared to be not consistent at different soil moisture levels. At high soil moisture levels, the amount nitrate mass lost into drainage was extremely small and almost negligible. The mediate traffic treatment resulted in largest nitrate mass accumulation in drainage (see figure 27). This could be attributed to large amount of drainage generated by the mediate traffic treatments as showed in figure 26. The cumulative amount of nitrate mass resulted from heavy and light traffic treatments were not significantly different, although the value of mediate traffic treatment appeared to be little larger than that of heavy traffic treatment. For medium soil moisture level, the mediate traffic treatment also caused the largest amount of nitrate mass entered into drainage, although its drainage water volume was not lager than that of heavy traffic treatment. Unlike at high soil moisture level, the accumulated nitrate mass of light traffic treatment was lager than that of heavy traffic treatment at the medium moisture level. This is consistent with the trends of nitrate concentration discussed early. As figure 28 and 29 showed that the non-compaction treatment resulted in the smallest leaching in terms of drainage volume and nitrate mass. At the low soil moisture level, the pattern of drainage water volume was heavy traffic > mediate traffic > light traffic (see figure 30). However, the pattern of nitrate mass was just the opposite, namely heavy traffic < mediate traffic < light traffic (figure 31). The tendency is completely consistent with nitrate concentration. In relation soil moisture levels, it was noticed that the cumulative nitrate mass in drainage water followed the same pattern as that of the nitrate concentration (figure 32). That is, at same traffic level the largest amount of nitrate mass presented in drainage water was found in the low soil moisture treatments (40% FC), and followed by medium moisture treatments (60% FC). The high soil moisture treatments resulted in the least amount of accumulated nitrate in terms of mass. 67 H M L Traffic intensity Figure 22 N C V concentration in drainage water in relation to soil compaction before May 29 measurements H M L Traffic level Figure 23 N C V concentration in drainage water in relation to soil 29 measurements compaction after May 6 8 _ 1.80 3 1-60 £ 1.40 -\ .1 1-20 -I 1 1.00 § 0,80 § 0.60 H £ 0.40 £ 0.20 0.00 H M Traffic level Figure 24 Comparison of N03" concentration in leachate as influenced by soil moisture before May 29 measurements. H = heavy traffic; M = mediate traffic; L = light traffic. CTl £ O 4-1 (TJ i_ d) o C o u Qj j—i CO 1.00 0.90 0.80 0.70 0.60 0.50 -I 0.40 0.30 0.20 0.10 ^ 0.00 •y'V W H M Traffic level L Figure 25 Comparison of N03" concentration in leachate as influenced by soil moisture after May 29 measurements. H = heavy traffic; M = mediate traffic; L = light traffic. 69 4500 4000 _ 3500 % 3000 2 2 5 0 0 "I | 2000 'S 1500 H Q 1000 500 0 4/19 •H M L 5/9 5/29 6/18 Date Figure 2 6 Cumulative amount of drainage water of different level of traffic treatments with high moisture during measurement period 0.250 g . 0.200 0.000 6/18 Figure 27 Cumulative amount of nitrate in drainage water from different level of traffic treatments with high moisture during measurement period 70 60% of FC Date Figure 28 Cumulative amount of drainage water of different level of traffic treatments with medium moisture during measurement period 1.600 3 1.400 -I » 1.200 | 1.000 -I c CD 0.800 1 | 0.600 | 0.400 o 0.200 -I 0.000 4/19 5/9 5/29 6/18 Date H — - M L C Figure 29 Cumulative amount of nitrate in drainage water from different level of traffic treatments with high moisture during measurement period 71 40% of FC 4/19 5/9 5/29 Date 6/18 Figure 30 Cumulative amount of drainage water of different level of traffic treatments with low moisture during measurement period 9.000 nDate Figure 31 Cumulative amount of nitrate in drainage water from different level of traffic treatments with high moisture during measurement period 72 6/18 a £ , m m [U > n zs E O 9.0 8.0 -I 7.0 6.0 -I 5.0 4.0 3.0 2.0 1.0 0.0 4/1 light traffic r ~ r 9 5/9 5/29 Date 6/18 4.0 i 3.5 ra — 3.0 m 1 2.5 Mediate traffic / 4/19 5/9 5/29 6/18 Date m^Lf^7 UhtlVe a m ° U m ° f n i t r 3 t e m d r a m a 8 e W a t e r a S a f f e c t e d ^ d l f f e ™ < soil 73 The results of this section confirmed that soil compaction has a significant impact on drainage in golf course. The most pronounced effect of soil compaction on drainage was the poor drainage situation caused by drastic reduction of the hydraulic conductivity. This investigation clearly demonstrated that two most important soil hydraulic parameters to drainage design, the hydraulic conductivity and drainable porosity, are very sensitive to both traffic and soil moisture status when traffic applied. Even light traffic could reduce the hydraulic conductivity to such a degree the soil drainage became restricted. This study found that the reactions of hydraulic conductivity and drainable porosity to soil compaction can be adequately described by polynomial regression equations. The empirical equations concerning the hydraulic conductivity and drainable porosity obtained from this study may be useful to improve drainage system design in golf course. As appeared from the measurements showed in this section, soil compaction also affects the drainage water quality as characterized by the nitrate concentration or nitrate mass losses in drainage water. The general perceptible obtained from the measured NO3" concentration and nitrate mass losses were increase trends due to soil compaction. However, it appeared that severe compaction resulted in reduction in terms of both NO3" concentration and nitrate mass losses. 4.4 Effects of soil Compaction on turfgrass In preceding sections the theme was compaction effects on irrigation and drainage. However, one of the most fundamental concerns for golf course managers is the influence of soil compaction on the performance of turfgrass. A few publications on this subject, which are available in literature, have not led to definite conclusions. In fact, many reports appear contradictory (Watson, 1953; Harper, 1953; O'Neil et al., 1982; Agnew et al., 1985). This section continues to discuss this subject and focus on the responses of turfgrass to soil compaction in terms of shoot and root growth as well as visual quality. Significant levels of F-test for the turfgrass growth parameters evaluated are given in table 17. Shoot and root growth of turfgrass were assessed with clippings yield and dry root weight. The clipping yield (CY) was affected significantly by both traffic (T) and 74 soil moisture levels (S) at probability level of 0.001. And the interaction of T x M also had significant effects on the C Y . For the root response, the dry root weight (RW) was significantly affected by traffic intensity at probability level of 0.05. But both soil moisture and the interaction of T x M had no significant effects on the RW. With respect to the turf quality (TQ), traffic intensity only had significant effects on TQ at probability level of 0.05. However, both soil moisture levels and the interaction of T x M strongly affect the TQ at the probability level of 0.001. This result does not comply with the results of Agnew et al. (1985) and O'Neil et al. (1982), who stated that compaction had a greater detrimental effect on turf quality than the soil moisture levels. However, it in general agrees with conclusions by Watson (1950) and Harper (1953). Table 17 Significance levels of F values for turf growth parameters as influenced by traffic intensity (T) and soil moisture levels (M) parameters T M T x S C Y 0.0242 * 0.0000 *** 0.0001 *** RW 0.0013 ** 0.1251 NS 0.3001 NS TQ 0.0000 *** 0.0000 *** 0.0000 *** * significance at the 0.05 probability level ** significance at the 0.01 probability level *** significance at the 0.001 probability level NS Non- significance at the 0.05 probability level 4.4.1 Shoot growth The mean comparisons of dry weight of accumulated clippings shown in figure 33. At high soil moisture level, significant differences were found among different levels of traffic intensity. The higher the traffic intensity, the lower the clippings yield. For the mediate moisture level, the clippings yield of heavy traffic treatment was significantly lower than that of mediate and light traffic treatment. However, there was no significant difference between the mediate and light traffic treatments. Moreover, it was observed 75 that the clippings yield of light traffic treatment was little higher than that of no compaction treatment, although statistically there was no significant different between them. This confirmed that light coil compaction might be beneficial to the top growth of turfgrass. For low soil moisture level, different levels of traffic intensity did not result in differences in clippings yield statistically. This implies that soil moisture dominated the stress of turfgrass under lower moisture content. 80 60 40 Soil Moisture (% of FC) Figure 33 Comparison of clippings yield under different level of soil compaction. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level Figure 34 shown the accumulative clippings affected by soil moisture. It further illustrated how soil moisture levels influence the top growth of turfgrass. The interesting result is that under heavy traffic, low soil moisture treatment resulted in higher clippings yield. This means that for an intense use golf course control of soil moisture to a certain level actually help shoot growth of turfgrass. This is important because many golf course superintendents attempt to apply more water to maintain high soil moisture status in their compacted site to stimulate shoot growth. Our study indicated that this is not the case. 76 • i 1 T 1 j 3/10 3/30 4/19 5/9 5/29 6/18 Date • ' i i , 1 3/10 3/30 4/19 5/9 5/29 6/18 Figure 34 Comparison of accumulative clippings of the treatments with different levels of soil water content 77 With mediate traffic, it appeared that medium and low soil moisture treatments made no difference in top growth. But high moisture treatments still resulted in lowest clippings yield. Contrary to high traffic intensity, clippings yield of light traffic enhanced as soil moisture increase. 4.4.2 Root growth The turfgrass root response to soil compaction are primarily a result of reduced aeration, high soil strength, altered soil water status, or combination of these factors. The net result of these interacting effects is drastic reduction in depth, extent, and total quantity of the roots produced by turfgrass. As showed in figure 35, the Kentucky bluegrass had a massive root system without soil compaction. With soil compaction, the root growth dramatically changed (see figure 37). Total quantity of root biomass of turfgrass was reduced by as much as 47 to 75 percent compared to no compaction treatment. It was observed that the vast majority of root distributed within the top 10-cm soil under soil compaction. Below top 10-cm soil, a little root was found only in the soil profile of light traffic treatments. Nearly all the root of the heavy and mediate traffic treatments was dead back as showed in figure 36. Figure 38 compared the dry root weight under different traffic intensity. It can be seen that mediate traffic treatment resulted in less root biomass regardless of soil moisture levels. However, no significant differences in root biomass were found between heavy and light traffic treatments. As regard to the soil moisture levels, interestingly, the medium soil moisture treatments resulted in the lowest root biomass value regardless of applied traffic intensity (see figure 39). One of possible reasons is that maintaining high soil water content can decrease the soil mechanical impedance and probably help rooting. Traffic under low soil water content, on the other hand, results in lower soil compaction due to its greater resistance ability. Traffic at medium soil moisture level, however, may neither decrease the penetration resistance to a sufficient degree, nor make soil dry enough to resist the compaction force. However, in the viewpoint of statistics, different soil moisture treatments resulted in no significant differences in dry root weight. 78 Figure 35 View of root system of Kentucky bluegrass without soil compaction Soil moisture of this treatment was maintained above 60% of field capacity. Figure 36 View of the profile of root growth of Kentucky bluegrass under severe soil compaction. Soil moisture of this treatment was maintained above 60% of field capacity. Figure 37 Effect of different level of soil compaction on root growth of Kentucky bluegrass. Soil moistures of these treatments were maintained above 60% of field capacity. 79 80 60 ' 40 Soil Moisture (% of FC) Figure 38 Comparison of root growth of different traffic treatments. H = heavy traffic; M = mediate traffic; L = light traffic. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level. H - M L Traffic level Figure 39 Comparison of root growth of different soil moisture treatments. H = heavy traffic; M = mediate traffic; L = light traffic. Bars marked with same letter within each group are not significantly different from each other at 0.05 probability level. 80 4.4.3 Turfgrass quality Visual quality of turfgrass integrates several components with shoot density, color and uniformity of turfgrass being of primary importance (Carrow et al., 1992). In this study, the visual quality of the turfgrass resulted from the different treatments was rated regularly throughout the experimental period. Quality ratings were based on shoot density, color and uniformity using a 1-9 scale, where 1 = turfgrass dead or completely dormant, 5 = minimally acceptable turf quality, 9 = ideal turf quality. Table 18 summarized the evaluated results for all treatments. Before traffic applied, there were no differences in turfgrass quality detected. After traffic applied 4 weeks, only the heavy traffic treatments with high soil moisture level exhibited differences in turf quality. Until the 18 th of March there were noticeable reductions observed in turf quality for all other treatments. The evaluation results indicated that only the light traffic with medium and low soil moisture treatment after the 13 r d of May resulted in below acceptable quality ratings. A l l other treatments had acceptable quality throughout the study period. The evaluations indicated that in terms of quality the response of turfgrass to different traffic was similar to clippings yield. Ratings of mediate traffic treatments were consistently lower than that of heavy and light traffic treatments after treatment for four weeks. At high and medium soil moisture levels, the quality ratings of heavy traffic treatments were lower than that of light traffic treatments. But at low moisture level, heavy traffic treatment rated higher than light traffic treatment with exception on 18 th of March. With respect to the influence of soil moisture levels, similar tendency was also found as the clippings yield. That is, under heavy and mediate traffic high soil moisture treatments resulted in lower turf quality ratings. Under light traffic, however, the ratings of turf quality increased as soil moisture increase. The results again confirmed that contrary to one would hope to help to stimulate turfgrass growth, maintaining high soil moisture content through frequent irrigation in intense use golf course actually reduces 81 turf quality. The results of this study suggest that control of soil moisture level is as important as traffic control for turfgrass growth in intense use golf course. Table 18 Mean quality rating valuesf of all treatments across three replications Date 80% 60% 40% H M L H M L C H M L 1/20 9.0a 9.0a 8.7a 8.7a 9.0a 9.0a 9.0a 9.0a 8.3a 8.7a 2/18 7.8a 9.0b 9.0b 8.8a 9.0a 9.0a 9.0a 9.0a 9.0a 9.0a 3/18 5.8a 5.7a 8.8b 7.3a 6.8a 8.8b 8.8b 6.8a 7.5b 8.3c 4/15 6.5a 5.8a 8.8b 8.0ab 7.5a 8.5b 8.2ab 8.0a 7.7a 7.8a 5/13 7.0a 7.2a 8.5b 7.3ab 6.3a 7.5b 7.8b 6.2a 4.8b 4.8b 5/31 8.0a 6.5b 8.2a 6.2a 6.0a 7.8b 7.0c 5.0ab 5.8a 4.5b t Values followed by same letter within rows of each moisture group are not significantly different from each other at 0.05 probability level; n = 3 for each treatment 82 5 Summary and conclusions This study attempts to get a better understanding of soil compaction influences on irrigation and drainage on golf course fairway. Soil compaction does not directly affect the irrigation and drainage. Instead, it acts by changing the soil and plant properties, which in turn influence the irrigation and drainage. It is for this reason that this study focuses on investigating some soil physical, mechanical, hydrological properties and turfgrass growth that are most important to irrigation and drainage design and management, rather than the irrigation and drainage system themselves. To achieve the objectives of this study, a soil compaction experiment under turfgrass cultivation was carried out in greenhouse. The study first attempt to examine and characterize the state of soil compaction under the interaction of different level play intensity and soil water content. Four soil physical parameters were used in this study including soil bulk density, total porosity and void ration as well as penetration resistance. The study proved that the degree of soil compaction is dependent on both traffic intensity and soil water content. Under wet soil condition, even mediate traffic could cause severe soil compaction. Restricting traffic under wet soil condition is very important for the control of soil compaction. The second step of this study was to explore how different level of soil compaction affect irrigation under golf course fairway conditions. Three parameters that are of fundamental importance to design and management of irrigation system were investigated. Results from infiltration measurements were presented first, which showed dramatic reduction in infiltration rate due to soil compaction. The relationship between the steady infiltration and the degree of soil compaction in terms of void ratio was established for prediction. The influence of soil compaction on field capacity was then discussed briefly. Particular attention was devoted to the interactive effects of traffic and soil moisture on turfgrass ET because this topic was not adequately covered in the turfgrass literature. Based on the analysis of measured data, an equation for determining crop coefficients under soil compaction and water stress was proposed for estimation of turfgrass ET with meteorological data. 83 To assess the impact of soil compaction on drainage, two important drainage parameters hydraulic conductivity and drainable porosity that must be determined in design of drainage system were examined and discussed in detail. Relationships between hydraulic conductivity, drainable porosity and the degree of soil compaction characterized with void ratio were formulated for prediction. In addition, special attention was also given to the water quality of drainage, since no information was found in literature about effects of soil compaction on drainage water quality under turfgrass cultivation. Analysis was made on the basis of concentration and mass of nitrate. The turfgrass growth under environmental stress is the fundamental concern for golf course management because of the incompatibility between highly desired play rounds and viability of turfgrass under compaction. Therefore, the final step of this study was to further examine the reaction of turfgrass growth to different level of soil compaction. Top growth, root growth and quality of turfgrass were included in this study. A summary of the major conclusions derived from this thesis study is as follows: 1) In terms of bulk density, total porosity or void ratio, the state of soil compaction not only is largely influenced by traffic intensity, but also is closely related to soil water content. Hence control of traffic and soil moisture is equally important for minimizing soil compaction. 2) In this study, penetration resistance of soil under different traffic and soil moisture levels followed an evident pattern in which the degree of compaction was clearly distinguished. It proved that the penetration resistance as measured with a recording cone penetrometer is a simple and convenient measure to judge the state of soil compaction. 3) Compaction affects nearly all properties and functions of soil. However the most significant changes are soil hydraulic properties (e.g. infiltration, hydraulic conductivity and drainable porosity). When soil is very wet, even light traffic could reduce the water conductivity to such a degree that the soil becomes almost 84 impermeable. This suggests that restriction of traffic at high soil moisture is very important for minimizing water transmission problem in soil. 4) Soil compaction greatly reduced the infiltration rate and field capacity. This implies that light irrigation (light application rate and low irrigation quota) may be suitable for compacted turf site. However, this does not necessarily mean frequent watering is needed, because the turfgrass water requirement is also reduced. Furthermore, Maintaining high soil moisture level actually not helpful to turfgrass growth for highly compacted soil. 5) The study found that ET of turfgrass decreased by 12 to 29 % as a result of compaction, depend on the level of soil moisture maintained. This may be attributed to its reduced shoot and root growth. Despite the clear effect on turfgrass ET, statistically there appeared to be no significant differences among different level of traffic treatments at same soil moisture level. With respect to the influence of soil moisture, it was found that the effects of soil moisture on ET are more evident than compaction. 6) This investigation clearly demonstrated that two most important soil hydraulic parameters to drainage design, the hydraulic conductivity and drainable porosity, are very sensitive to both traffic and soil moisture status when traffic applied. The reactions of hydraulic conductivity and drainable porosity to soil compaction can be adequately described by polynomial regression equations. The empirical equations obtained from this study may be useful to improve drainage system design in golf course. 7) This study found that NO3" concentration in leachate increased as a result of soil compaction. It could be resulted from reduced N uptake of turfgrass due to less shoot and root growth under soil compaction. However, the detected NO3" concentration under soil compaction was still extremely low, well below the drink water requirement. 85 8) The study revealed that favorable soil water content for turfgrass growth depends on extent of traffic. At heavy traffic intensity, maintaining low soil moisture is more desirable to turfgrass growth. With mediate traffic, maintaining medium soil water content may be better. For light traffic, maintaining high soil moisture is more favorable. 9) The evaluation of top growth and quality of turfgrass showed that soil moisture levels had greater effects on turfgrass growth than soil compaction. This implies that control of traffic and soil water content is equally important in the management of soil and water in golf course. 10) It was observed that root biomass of turfgrass was reduced by as much as 47 to 75 percent under soil compaction condition when compared to non-compaction. From turfgrass growth perspective, soil compaction is more detrimental to root growth than to shoot growth. 86 6 References Adams, W.A. and R.J. Gibbs. 1994. Natural turf for sports and amenity: Science and practice. C A B International, Wallingford U K . Agnew, M . L . and R.N. Carrow. 1985. Soil compaction and moisture stress preconditioning in Kentucky bluegrass. I. Soil, Aeration, water use and root response. Agron. J. 77:872-878. Agrawal, R.P. 1991. Water and nutrient management in sandy soils by compaction. Soil Tillage Res., 19:121-130. Allen, R.G., L.S. Pereira, D. Raes and M . Smith. 1998. Crop evapotranspiration -Guidelines for computing crop water requirements. Irrigation and Drainage Paper No. 56. FAO, Rome, Italy. Amoozegar, A . and G.V. Wilson. 1999. Method for measuring hydraulic conductivity and drainable porosity, p. l 149-1205. In: R.W. Skaggs and J. Van Schifgaarde (ed.) Agriculture drainage. Agron. Monogr. 38. ASA, CSSA, and SSSA, Madison, WI. Arvidssion, J. 2000. 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Greening your BC golf course: a guide to environmental management. USGA. 1993. U S G A recommendations for a method of putting green construction. USGA Section record 26(2): 1-3 Valoras, N . , W.C., Morgan, and J. Letey, S.T. Richards, and. 1966. Physical soil amendments, soil compaction, irrigation and wetting agents in turfgrass management. I. Effects on compatibility, water infiltration rates, Evapotranspiration and number of irrigation. Agron. J. 58:528-531. Van Wijk, A . L . M . 1980. A soil technological study on effectuating and maintaining adequate playing conditions of grass sports field. Agric. Res. Rep. 903. PUDOC, Wageningen. Waddington, D.V. 1992. Soils, soil mixtures, and soil amendments. P.331-384. In: D.V. Waddington, R.N. Carrow and R.C. Shearman (eds.): Turfgrass Monogr. Ward, C.J. 1983. Sports turf drainage: A review. J. of Sports Turf Research Institute. Vol . 59:9-28. 94 Watson, J.R. 1950. Irrigation and compaction on established fairway turf. U S G A J. Turf Manage. 3(4):25-28. W. Graham Argyle and Associates Inc. et al. 1991. Golf course development in the lower mainland. Whalley, W.R., E. Dumitru and A.R. Dexter. 1995. Biological effects of soil compaction. Soil and Tillage Research 35:53-68. 95 Appendix A Computed reference ET and measured daily ET Meteostation: Vancouver Airport Weather Station Hemisphere: North Latitude: 49.183 degree Longitude: 123.167 degree Elevation: 3 m Anemometer height: 2 m Atomspheric pressure (P): 101.265 KPa Psychrometric contant (Gamma ): 0.067 KPa/deg Solar constant (Gsc): 0.082 MJ/m 2min Albedo (alpha): 0.23 Stefan-Boltzmann constant (Sigma): 4.903E-09 MJK" 4/m 2day Adjust Coefficient (kRs): 0.19 96 e i s o 1 J ^ 1 E i~ OI 22 oo co oo m NO CN o C O cn CN C O cn O N VO ro ro Tt in CO CN © in Tt O N r~- o <n O O m o Tt Tt NO o C O NO in CN CN r- CN O N O N o Tt CO ro ro CN ro in CN in Tt tr-NO ' ro CN CN r- C O r- O N p m NO O O CN cn NO  CN NO ON NO © © © © © O © o O O o O O O o o o O O © © O © © © © © © O N fN o NO CN NO CN C O «n Tt m r--(N NO ro ro C O C O CN Tt © ro © VO in NO NO o O N r~~ NO T> NO C O CN CN O N O N CN C O CN C O C O 00 rO © O N O N • O N O N © o o NO o NO C N — p CN CN O N CO ro NO Tt Tt Tt © © o © © o o 1-H O O 1 " © o © © 1 © CN in o O N CN O N oo O N o C O in o cn O N Tt o O N in in cn m Tt O N m ro Tt NO CN CN ro O N Tt </~J cn Tt o C O «n CN CN CN m CN C O o r- ro Tt in CN r- Tt ro O N oo O N rO N O NO NO NO NO C O r- Tt NO NO r~- NO NO C O ro Tt r- vO NO in NO NO CN NO O N r~- VO CN © in © O co o © © CN o —* o ^ CN o o o Tt Tt o o © o" o CO © CN ro O NO ro Tt in o m ^ Tt NO O Tt Tt Tt CN in o NO C O © C O CN C O C O —i NO C O oo OS O </-) ro Tt C O o O Tf NO C O ro r- m o CN m O O © O N NO m r~- VO C O © CO in in ro NO NO NO O N cn O O N o • C O O N O N in ON © C O © NO CN Tt NO —' ^ ro — r-CN ~* CN CN CO — Tt Tt •~1 ^ CN CN CO CN CO Tt <N NO NO NO ON O N ro o o Tt Tt CN in CN CN NO ro ro r- Tt Tt Tt Tt r- Tt Tt r- m CN m © vo O in o I T ) o NO CN C O CN ON m CO CN o o © © CN ro m r- O N <N in 00 CN CN CN ro CO Tt Tt m ir> NO r- r~- C O O N p —| CN ro Tt m NO C O O N © —i CN in NO C O N O NO NO NO NO NO NO NO NO NO NO NO NO NO t>- C O C O C O 06 C O C O C O N O O ro Tt NO cn in C O r~~ CN C O O N in C O C O Tt Tt © in r- r- O N in r- O N </-> m O O CN cn ON Tt ON C O O N ro NO © O N © in C O in in o O CN O o CN »—« —• CN C O CN  O N CN ro in CN ro Tt Tt in CN in NO © NO in 00 Tf r- NO tN CN Tt CN fN CN cn CN CN CN CN ro CN CN CN in in CN CN CN cn CN CN in" CN Tt in (N C O co C O o r- VO NO o Tt O N vo cn CN CN Tf NO o Tt o Tt CO CO Tt m C O m © VO CO © oo C O O N co in C O o CN «/-» C O Tt r~- O Tt r~- Tt C O CN NO © Tt C O ro CN VO NO © o O —-H •—< _ —H CN CN CN C N cn ro cn Tt Tt Tt m m m NO NO C O oo ON Ov © © —i C O C O C O C O C O C O C O C O C O C O C O C O C O C O C O C O C O C O C O C O C O 00 00 co oo C O C O 00 O N O N O N Tt ( N m CN oo r- 0\ CN 00 O N in C O NO O N NO C O m Tt O N C O CN o CN O N CN © Tf C O CO C O ro O N NO CS © r- in CN t-» cn O N NO cn O N r- VO NO N D NO NO C O O N Tt r~- © (N Tt in p- C O © T T *n CN CN co ro Tt in NO NO r- C  O N O CN CO Tt NO r~- co © © © © © © © ^ 00 C O C O C O C O C O C O C O C O C O C O O N O N ON" O N O N O N O N O N C O o CN Vj oo _, Tt r-~- , Tt C O CN NO O m O N Tt O N Tt O N Tt O N in © NO CN C O © NO CN in NO NO O^ NO C O C O C O O N O N O o O CN CN CO CO Tt in in NO VO C O C O O N o o o O o o o o o o o O O l t o C O \o m oo NO Tt O N vo CO o r- Tt r- Tt © r- ro O N m _ r-~ <N C O Tt O N o o O N O N O N O N o\ oo C O C O C O r- r- r~- r~- NO NO NO m m m Tt Tt CO m cn CN CN © Tt Tt co CO co cn cn cn cn cn cn cn cn cn cn cn cn cn cn cn m cn cn cn cn CO ro m ro ro ro o o 1 o O i ©' o ©' o o o i o o i o o o o o o o o o © i © i © i o o © o © i © © co ro m cn m m cn to cn cn CN CN CN CN CN CN CN , o © © © O N Ov O N O N C O ro ro ro ro ro m m ro cn cn CO CO ro ro ro CO CO CO CO CO cn CO m ro CO CO CN CN CN CN CN o o o © o o o o O o o o O O O o o o o © © © © © © © © O © © © oo o Tt r- C O r-- oo in Tt ro ro O N O N in r- NO in C O VO Tt O N TT C O C O Tt m C O CO CN 0\ CN ro ro O NO Tt r- O N in m Tt ro r- P- cn cn o o o — o —i o — 1—' o O O —— CN CN cn CN © —^  o —-< CN CN CN Tt cn CN o o o o © ©' © o o o o o O o O O O o o O © o © © © O © o © © © C O Tt ro CN CN O N C O O N CN C O Tt —- ro O N Tt —. ro in o m O N m CN ro © o m O N in Tt in CN r- NO r- O O N CO r-~ O C O NO m m t- O N NO Tt vo Tt NO NO m in NO NO NO NO NO NO O O r- NO in m in NO NO NO m m vn CO Tt in © © o © © o o o o o o o o o o o o O O © © © © © © © © O ©' o o o C O Tt ro O N oo O N C O VO cn 00 Tt in NO r- C O CO © in CO Tt CN O N C O O N VO C N NO © CN cn cn C N O N ON cn C O o o o CN cn Tt cn ro Tt in NO cn ro ro O N m CN © NO NO r~~ C O C O C O C O C O C O C O C O C O C O C  C O C O O O C O C O C O oo C O cc C O © © © © © © o o o o o o o o © o o o © © © © © © © © © o O © © c Q Vi cal E rolo X rolo ai o u c CJ •g 2 H sO E i <r. 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VO i n v o C N C N O i n i n ON c n r--ON 0 0 T t © T t © © cn CO T t cn m T t ' C N ON VO i n VO CN ON c n T t © T t T t T t ,—i ON cn ON C N VO VO © P- i n ON t C N NO cn i n © o o © OO ON © *—%; C N cn C N C N , — ' o i C N C N © © C N NO cn cn 0 0 C N © i n C N cn C N cn © i n o o t— C N 0 0 o q ON !> ON o o ON ON o o OO © ~" T—1 *-* »—i ' 1 ON P » p - p - © C N VO r - © T t ^ H © C N ON m cn © O I - H © © C N © ON - H © © '—i C N C N C N C N C N ^ H C N C N C N C N —< C N © C N ON c n ON ON ON i n ON ON C N i n p - T t VO VO 0 0 © T t i n T t c n i n c n T t T t v q c n T t c n P - © © c n c n © c n i n *—1 c n ON — H T t m © f ~ v o © T t i n c n c n NO c n T t i n v q c n m VO 0 0 0 0 C N S O o o m ON T t r - ON VO o o r - c n ON VO c n 0 0 VO v q r - i n i n NO P-; VO X> X> CD CD PH PH — o o © i n S3 13 • H * H i D . Q . Q . a . 9 * 9 , 9 ' 9 ' 9 ' c 3 ' c 3 ' J 3 j a j S j H « j H j ^ C N i n ' ^ . 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A ' _ L ^ _ t o » n r A v D ^ S S v i o i 2 r t ^ S S ^ r t ^ * - - - N N M « 2 2 r t r t o CN T t CN OI O) Ol CO CO I CN CN CN O I S CN SIS C N i u cu 0 -fl E 3 D g o JS > a i _ ^ 0<S CO u > A 0 "o D) > 2 g •I * to £ CO X C N i CO CO CO I C N X o cd i i •*-» >• IU Q A C O s C N i r—I £ kH c Q < H i n o i r i o o m m o o o o o o o o o o o o o o o w - i o o o o o •vt T f - H tN - ON NO > « o o > « o o > n u - i u - i i r ) 0 0 o o o o o o o o o o o o o o o o o o t ^ t - - T f T f r c ) r t r \ l ^ - i O CN CN l o m i r i o i n i n o c o o o o o o o o o o o o o o o o o o o o o T j - C O C N C O ^ H - H ' - H OO NO O O O O O U - i U - i c N O O O O i O i r i O O O O O i O i ^ O O O O ' - O O i r i O I C l T f (N| C O fN - H ON t~~ ON fN ON 00 CN C O i - H ^ H T f ^ H C O i r ) > 4 0 o o o v i o i n o o o o > « o u - ) 0 0 0 0 i r i i r i 0 i o o o > - o u - i o o i n T f CN CO CN ^  — 00 f N T f T f .—• i n o C N C N H (N| H _ (NJ RT m i n c N C N i O O O O O O O O O O O O O O u n O O O O O O i O O O co cN i n oo oo Tt m T t i n i vo i n m i - o i o i - o m i o c o o o o o o o o o o o o o o o o o o o o o IT) T f CN CN CN - H U - ) O W - i O O i r ) O U - N O O O O O O O O O O O O O O O O O O O O \ D T f CN m CN > n O > n u - i O i O i o C N O O O O O O O O O O O O O O O O O O O O t— VN CN CN CN ^ H i r i l O i n O O U - i i n c N O O O O O O O O O O O O O i O O O O O O O <*0 T f CN CO CN —' O CN C N i r i i n o o o m o m o o o o o o o o o o o o o o o i n o o o o l o i o c o c o c N - H - H T J - i n N O CO C O u - i o o i n o m i n i n o o o o o o o o o o o o o o o o u - i o o o m i n co co CN •—< —i m en I H t s CN — • n o v N > n i n i n i o c o i n u - ) 0 0 0 0 0 > n < r N O > n i n o o o o o o > n o C N C N ^ C N i — < T f NO CN >n CO CN Un i n T t 00 NO t~-CN - H i n i n i n o i n i n i n o i n o o o o o o m o m o o o o o i n i n o ' n o o M CN - H CN - H i n CO T f T f N O O N T f - H O N O N T f ^ H i~H o m o o i n i n o m o i n o o o o m i n m o i n o o o i n i n o i n o o C N N O T f c o c N - H - H oo T f T f m T t r- o T f C N O O CO CN r-i r-l C C C X > - O - O - O - O X > J 0 , O . O . O . O _ O *-1 kn in kn k. i - k- in u u u Ui k» ^ ^ ^ - ^ ^ O O ^ ^ ^ O O O C N ^ ^ J H ^ N O O O ^ r-H — ( CN CN CN CN ^ . - H ^ . - H O I C N C N C N C N a ii CO a >H iS rt <rt o 0) o > ccj a ccj g >-  Q Q U o i3 c n c n CN i c n c n h-1 c n CN rt) HO tT3 CN CN c n CN rt h-1 c n c n o I S <u tf c n o o o o o o o o o o o o o o o o o o o o o o o o o o o o c n VO O O C N O O O O O O O O O O O O O O O O m O O O O O O O O m oo o o o o o o o o o o o o o o o o o o o o o o o o o o o o cn oo O O c n C N O O O O O O O O O O O O O O O O O O O O O O O O cn C N • O O C N C N O O O O O O O O O O O O O O O O O O O O O O O O cn C N " O O O O O O O O O O O O O O O O O O O O O O O O O O O O m o o o o o m o o o o o o o o o o o o m o o o o o o o o 00 vo O C N C N O O O O O O O O O O O O O O O O O O O O O O O O O C N r-Tt O C N O O O O l O O O O O O O O O O O O O m O O O O O O O O CN VO m o o o o o o o o o o « o o o o o o o o t o o o o o o o > n o rt i n r> cn Tf rt O C N O O O O O O O O O O O O O O O O O O O O O O O O i O O CN 00 O N O rt CN Tf o m o o o o o o o o o o o o o o o o o o o o o o o o i o o C N C N t*» O C N cn Tf o o m m o i o i n o o o o o o o o o o o o o o o o o o o o o Tf cn rt rt rt W I O C N m c N O O O O O O O O O O O O O O O O O O O O O O O CN CN — o o m o m o o o o o o o o o o o o o o o o o o o o o o o VO VO rt CN C C C X I X J X I H Q H O H O H O H O J O H O H O X ) *H * I *-I >H >- >H I H <H 1- 1- I H I H I H cs as cs UJ o o (L> cu <u <u u to a ii u i 2 r t r t r t r t r t r t r t r t i 2 i 2 i 2 i 2 CN CN CN cn rtrtrtrtCNCNCNCN rtrtrtCNCNCNCNCN a rt tf 0) l-i MH • p—I X ) o O > I H CD tf (20 g tf I H Q Q E—1 c n C N CN CN CD tf •3 <D CN CN c n CN i c n c n CN O ! <tf I T — < K CN i 55 t—1 o o o o o o o o o o o o o o o m o o o o o o o o o o o OO - H CN CN CN CN o o o o o m o o o o o o o o o v i o o o o o m o o o o o CN T t VO rt ON CN CN T f CN CN o o o o o m o o o o o o o o o m o o o o o i r i o o o o o CN CN rt 00 O N o o o o i n i n o o u - i i o o o o o i n o o o i o o o o o o o i n i n r~- r-- oo ON oo <n vo T t r— T t >o m ON C N C N rtm rtrnrt oo o t--o o o o o o o o i n i n m o o o m o o o u - i i n o o o o o o o O oo rt T t m r ^ oo T t rt Ttvo in o oo oo ( M r t r t rtCN rtCNrt c n r t C N C N C N C N o o o o o o o o o m o o o o o o o o o o o o o o o o o oo vo cn oo T t T t r-~ r-- r~- r-- r~ r~- r~-O O O O O O O O O O O O O O O O O i O O O O O O O O O O o cn cn cn CN CN o o o o o o o o o o o o o o o o o m o o o o o o o o o o o CN i n CN CN o o i o o o o o o o o o o o o o o o m o o o o o o o o o cn rt i n m oo i n cn rt CN o o o o o o o o o o o o o m o o o o o o o o m o o o o o i n m rt T t oo m i n CN CN O O O O O O O O O O O O O O W - i O O O O O O O i O O O O O cn cn o m vo m CN rt C N o o o o m m o o o o o o o o o o o o o o o o m o o o o T t c N c n c N i n m oo oo O N r-~ C N C N r t r t ( M r t r t O CN o o o o o m o o i n o o o i n o o o o o o o i n o o o o o o r-- m o r- T t o r-- O N O N c n V O O N T T m m O N O O m o o o i n o o o o i n o o i n o o o o m o o i n i n o o m o o CN r - m vo c n O T t T f cnTt ON O N l > rt ^ ^ r-t rtrt rt r n i n o i n o o m o o o i n o o o i n o o m i n o o o o o o o o o o r~ vo C N cn o r- ON r-- m ON cn VO « r- N oo rt r-i r-i r-* r-i r-i r-i rtrt — ( N | VO I H I H I H I H I H I H I H I H I H I H I H I H I H > ^ ^ > ^ > ^ > ^ > ^ > ^ ; > , > ^ > , > ^ > ^ > ^ > J 5* 5* | | | | | | | | | | | | | r^H r^H r^-t r C - l r ^ H f = - ( F=H f^H P—H r = H r=-H rtrtrtrtrtCNCNCNCN rtrtrtrtCNCNCNCNCNcn a a CD a CD kH M-H • T-H T 3 O <u o > kH CD 13 CD 00 cd a kH Q Q CD U o o IU cn k-1 CN cn cn C N i—) IS . CN CN i CN i i—i i - i cn cn o IS kH H-» CD 13 CD o o m o o o o o o o o o o m o o o o o o o o o o o m o cn C N cn T f T f o o o o o o o o o o o o o o o o o o o o o o o o o m o m f - cn i n ON oo o o m o o o o o o o o o o o o o o o o o o o o o o m o Tf NO <«0 CN — CN O O O i r i O O O O O O O O O O O O O O O O O O O O O O O T f cn 00 ON o o o o o o o o o o o o o o o o o o o o o o i n o o o o C N C N 00 —i —i C N o o o o o o o o o o o o o o o o o o o o o o o o o o o 00 ON cn ND o o m o o o o o o o o o o i n o o o o o o o o o o o o o CN i n T f CN cn CN o o m o o o o o o o o o o o o o o o o o o o o o o o o CN CN ON —< CN *—1 o o o o o o o o o o o o o u n o o o o o o o o o m o o o NO ON m ON ON O o o o o o o o o o o o o o o o o o o o o o o o o o o o i n ND oo o T f T f TT cn o o o o o » n o o o o o o > n o o o o o o o o o o o > n o o T f oo ON c-~ cn m m cn o o o o o o o o o o o o m o o o o o « * n o o o o o m o o oo oo r— C N cn cn m T f o o o o o o o o o o o o o o o o o o o o o o o o o o o r - cn cn T f CN CN o o o o o o o o o o o o o o o o o o o o o o o o o o o CN CN o o o o o o o o o o o o o o o o o o o o o o o o o o o T f r-~ £ £ £ £ £ £ OH OH 0 , 0 , £ £ £ i? £ £ £ £ I? £ £ S & S ST I N CN CN CN ^ ^ H ^ ^ H f M f S l f ^ ^ f S , ^ Appendix E Comparison of visual quality of turfgrass under different degree of soil compaction Fig. D Comparison of turfgrass quality of all treatments. H = heavy compaction, M = mediate compaction, L = light compaction, C = no compaction, 1 = high soil moisture, 2 = medium soil moisture, 3 = low soil moisture. 115 

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