Natural Turf Surfaces Research Articles

The influence of playing surface on external demands and physiological responses during a soccer match simulation

ABSTRACT We investigated the effects of playing surfaces with different impact absorption characteristics on external demand and physiological responses. Fifteen participants completed a soccer match simulation on natural grass, synthetic turf and concrete surfaces. Accelerometry-derived PlayerLoadTM per minute (PL·min−1) and average net force (AvFNet) were used to quantify external demands at the centre of mass (CoM), upper-back, mid-back and hip. Heart rate, oxygen uptake, energy expenditure and RPE quantified physiological responses. The concrete surface exhibited the least impact absorption, with peak decelerations ~3.5x synthetic turf and ~10x natural grass (p < 0.001). Despite this, there was no differences in external demand between surfaces (surface: p ≥ 0.194; η2 p≤0.092). Both AvFNet and PL·min−1 (location: p < 0.001; η2 p≥0.859) were higher at the hip (613(91)N; 12.5(1.2)arb.u), reduced at the mid-back (521(67)N; 8.8(0.7)arb.u) and upper-back (502(60)N; 8.8(0.7)arb.u) when compared to CoM (576(78)N; 10.7(1.0)arb.u). Although playing surface did not influence the external demands, heart rate or oxygen uptake (p > 0.05), energy expenditure was highest on natural grass compared to synthetic turf (P = 0.034) and RPE was highest on synthetic turf compared to concrete (p = 0.026). Different playing surfaces can alter physiological responses to soccer-specific activity even when the external demands are similar.

Elite players’ perceptions of football playing surfaces: a mixed effects ordinal logistic regression model of players’ perceptions

ABSTRACTThe aim of this study was to determine potential explanatory factors that may be associated with different attitudes amongst the global population of elite footballers to the use of different surfaces for football. A questionnaire was used to capture elite football players’ perceptions of playing surfaces and a mixed effects ordinal logistic regression model was used to explore potential explanatory factors of players’ perceptions. In total, responses from 1129 players from 44 different countries were analysed. The majority of players expressed a strong preference for the use of Natural Turf pitches over alternatives such as Artificial Turf. The regression model, with a players’ country as a random effect, indicated that players were less favourable towards either Natural Turf or Artificial Turf where there was perceived to be greater variability in surface qualities or the surface was perceived to have less desirable properties. Player’s surface experience was also linked to their overall attitudes, with a suggestion that the quality of the Natural Turf surface players experienced dictated players’ support for Artificial Turf.

Comparison between Natural Turf and Artificial Turf on Agility Performance of Rugby Union Players

The purpose of this study was to investigate the difference in agility performance with natural turf (NT) and artificial turf (AT) surface in rugby union players on the repeated sprint, cut and turn movements and if any differences exist between holding the ball or not in relation to agility performance. Twelve tertiary rugby union players (mean ± SD age, 21.2 ± 2.0 years) participated in the study. Players underwent measurements of anthropometry (height, body mass). Running tests investigated were 40-meter sprinting, change of direction, and “L” run, with all tests for agility measured in two sets with ball and without ball respectively. Results indicated that subjects showed significantly better overall agility performance (P < 0.05) in sprinting (NT: 6.40 ± 0.26 seconds, AT: 6.24 ± 0.26 seconds) and turning (NT: 6.40 ± 0.44 seconds, AT: 5.96 ± 0.38 seconds) on AT than NT. Although the time counted of cutting on AT was faster than on NT (NT: 13.85 ± 0.61 seconds, AT: 13.55 ± 0.68 seconds), the result was not significant. The findings also indicated that running with the ball for 40 meters would not slow the players down as there was a counter effect on the ground surface and ball carrying, while the turning movement was affected by both effects.

Influence of Heat Treatment on the Bending Behaviour of LLDPE Monofilaments

Abstract It is known that artificial turf surfaces based on LLDPE monofilaments have the potential to replace natural turf surfaces used for several sport surfaces. Even though the production parameters have a strong influence on the behaviour of monofilaments and indirectly on the final product, the effect of heat treatment at different stages of the production lines is not studied in detail. Therefore, the influence of heat treatment during the production of monofilaments was investigated. This investigation includes a study of the mechanical properties such as tensile testing and bending behaviour and morphological analyses by employing DSC measurements. The results show that the applied heat treatment has a strong influence on the bending behaviour even though the classical studied morphology structures do not show significant changes. Heat treatment influences quite importantly the characteristics of the non-crystalline part of the monofilaments and results in better long-term properties, such as resilience, deformation recovery and fibrillation resistance.

The Effect of Stud Shape on Penetration Characteristics Through Synthesized Natural Turf in Football

The aim of this study was to provide information to footwear manufacturers to assist improvements in player performance and injury rates. Custom-made studs were dropped onto a synthesised natural turf surface using a bespoke instrument drop-rig. Ten drops were performed with each stud and the acceleration profile from contact to a depth of 30mm was recorded. Theoretical predictions were made based on the soil mechanics used in civil engineering. A difference/reverse Helmert contrast ANOVA revealed two significant differences in the rate of penetration and a regression analysis indicated that perimeter length made a significant contribution (p < 0.01) to predicting the negative jerk of the studs. There were no significant differences or relationships associated with time taken to reach a depth of 30mm. This study provides a plausible explanation for the somewhat expected differences in penetration behaviour. It also highlights a key development in establishing a methodology for this type of work.

One, two, three or four: Does the number of Clegg hammer drops alter ground hardness readings on natural grass?

The Clegg hammer is currently used to measure hardness of natural turf surfaces to inform performance and safety decisions. However, the number of Clegg hammer drops reported in natural grass testing varies from one to four drops, and the impact of the choice of the number of drops is unknown. The aim of this article is to determine whether significant differences exist between the four Clegg hammer drops on natural grass across a variety of conditions. Hardness readings (using a 2.25 kg Clegg hammer), soil moisture and botanical composition were recorded at nine different sites on seven football fields during an 18-week playing season. A total of 1255 hardness readings were collected for each of four consecutive Clegg hammer drops. Overall, there were significant differences between drop 1 and the other three consecutive drops, on all fields and on all sites. Deep soil moisture was the only factor that significantly influenced the hardness readings. The results of this study demonstrate that the decision regarding the number of drops recorded needs careful consideration as conclusions drawn on playability of a ground or the association with injury risk may vary considerably depending on the number of drops.

The effect of stud configuration on rotational traction using the studded boot apparatus

Due to its associated injury risk, rotational traction is a frequently measured natural turf surface property. The most commonly used equipment, the studded boot apparatus (SBA), consists of a circular stud configuration that does not replicate the stud pattern on a regular football boot and may under or over estimate the surface traction. The aim of this study was to establish potential differences in the rotational traction measured between the current stud configuration on the SBA and the stud configuration on the most commonly used Australian football boots. The original studded boot had significantly higher rotational traction than the moulded stud sole or bladed sole. Location, quality and time tested all interacted significantly with the rotational traction measured. The current SBA may not accurately represent the rotational traction experienced by football players, and consequently may not be the most appropriate configuration to assess the relationship between rotational traction and injuries.

Mechanical behaviour of natural turf sports pitches across a season

A study assessing the mechanical behaviour of six natural turf pitches of varying sporting level and surface construction was undertaken over a period of 10 months, spanning a sporting season (August 2010 to May 2011). Penetration resistance and shear resistance were measured with the GoingStick®, impact hardness and surface energy absorption were measured with the 2.25 kg Clegg Impact Soil Tester and the Dynamic Surface Tester device, respectively. The two sand rootzone pitches were more resistant to deformation and less variable in their impact behaviour (impact hardness and energy absorption) through the season than the native soil pitches containing greater proportions of silt and clay. Greater consistency was shown for penetration resistance and shear resistance on one of the sand rootzone pitches, with the other behaving similar to the native soil pitches for these parameters. The sand rootzone surfaces exhibited greater (P 0.05). The greater consistency of sand rootzone surfaces should be considered for the effect it may have on player and team performance, and injury potential. Analysis of data against Performance Quality Standard benchmarks indicated that all data on the sand rootzones exceeded preferred values for impact hardness, indicating these ranges may be obsolete for the modern elite natural turf surface.

Synthetic grass cricket pitches and ball bounce characteristics

The use of synthetic grass cricket pitches is becoming more common at club and sub-elite levels which constitute the majority of cricket participants but there is sparse data on ball bounce characteristics on these surfaces. ObjectivesTo compare the speed, angle and consistency of ball bounce on two types of synthetic cricket surfaces, the Traditional and the All-Seasons, and compare these ball bounce characteristics with published data for natural turf pitches. DesignGroup-based comparison. MethodsHigh speed motion analysis was used to capture data from balls projected onto the cricket pitches from a bowling machine at three speeds: slow (47kmh−1), medium (72kmh−1) and fast (104kmh−1). Both ends of the cricket pitches were assessed and two types of balls were used: 2-piece and 4-piece leather cricket balls. Digitisation was used to determine the ball speed and angle pre and post bounce and then to calculate the ratios of ball speed and angle. Consistency was determined by the coefficient of variation. ResultsThe All-Seasons synthetic surface generated a lower speed ratio and a higher angle ratio than the Traditional synthetic surface. The speed ratio for the Traditional surface fell within the range reported for natural turf, whilst the value for the All-Seasons surface was outside the range. Both synthetic surfaces produced angle ratios greater than those for natural turf surfaces. ConclusionsDifferences were detected between the different synthetic cricket surfaces and also when compared to natural turf. This variability may have implications for skill development as well as safety.

Is the level of uniformity of hardness and traction associated with injury risk on community level Australian Football fields?

Introduction: Ground hardness and traction have been the two surface properties most frequently associated with an increased injury risk, particularly in sports played on natural turf surfaces. In more recent times, there has been speculation that uniformity across the playing surface may have a greater impact on injury rates than the absolute hardness and traction measures. Currently, no evidence exists to support or refute this assertion. The aim of this paper is to investigate if level of uniformity of hardness and rotational traction on community level Australian Football fields is related to the number of injuries sustained.

Advancing natural turf to meet tomorrow’s challenges

The majority of outdoor sports surfaces are natural turf and they remain the elite-level standard for a number of sports. A natural turf surface is susceptible to environmental and physical stress and has a limited resistance to wear. A number of technological advances have increased the quality and durability of natural turf surfaces including: sand rootzones; drainage; irrigation; agrochemicals; turfgrass breeding; turf reinforcement; supplementary lighting; ventilation; and advanced stadium architecture. These advances have resulted in an increase in resource consumption and where resources are restricted natural turf viability, performance, and safety is limited. This paper examines these challenges and others facing natural turf by reviewing the state of the art and signposting future research required to ensure performance, safety, and sustainability from natural turf surfaces. More development is required for lower-cost technologies for recreational-level facilities. Synthetic turf surfaces can be used to reduce the intensity of use of natural turf but sustainable natural turf construction and management must focus on resource consumption reduction and resilience to climate change for the continued provision of high performance, safe surfaces for sport. Furthermore, greater user-awareness of resource consumption and the consequences of reduced consumption are important for adoption in the future of more sustainable practices.

Development of a simplified dynamic testing device for turfed sports surfaces

The response of natural turf surfaces to loading changes with the force and loading rate applied. Quantification of surface behaviour to athlete loading is complicated by the lack of devices that replicate forces, stresses and loading rates of athletes that can be specifically used on natural turf. To address this issue, a vertical dynamic impact testing device, the DST, was developed. The DST consists of a compressed air-driven ram that vertically impacts a studded test foot on to the surface using data from biomechanical studies. The vertical dynamic stress of athlete foot strike during running is replicated, using peak force and mean boot contact area data. The ram pressure is adjustable to allow variation of the stress applied upon impact, potentially replicating a range of athlete–surface interactions. Initial laboratory testing indicated that the device was sensitive to changes in soil condition due to variations in impact data. Total penetration time and distance, and surface energy absorption were all significantly greater in prepared ‘soft’ soil treatments ( p &lt; 0.05). The loading rate in the first 50 ms after impact was significantly greater in the ‘hardest’ soil treatment ( p &lt; 0.05). Future research work will determine in situ behaviour of actual playing surfaces, compare device loading rates to those of athletes, and assess surfaces to a range of stresses.

Biomechanical Response to Changes in Natural Turf During Running and Turning

Integrated biomechanical and engineering assessments were used to determine how humans responded to variations in turf during running and turning. Ground reaction force (AMTI, 960 Hz) and kinematic data (Vicon Peak Motus, 120 Hz) were collected from eight participants during running (3.83 m/s) and turning (10 trials per condition) on three natural turf surfaces in the laboratory. Surface hardness (Clegg hammer) and shear strength (cruciform shear vane) were measured before and after participant testing. Peak loading rate during running was significantly higher (p < .05) on the least hard surface (sandy; 101.48 BW/s ± 23.3) compared with clay (84.67 BW/s ± 22.9). There were no significant differences in running kinematics. Compared with the "medium" condition, fifth MTP impact velocities during turning were significantly (RM-ANOVA, p < .05) lower on clay (resultant: 2.30 m/s [± 0.68] compared with 2.64 m/s [± 0.70]), which was significantly (p < .05) harder "after" and had the greatest shear strength both "before" and "after" participant testing. This unique finding suggests that further study of foot impact velocities are important to increase understanding of overuse injury mechanisms.

Dynamic behaviour of soils used for natural turf sports surfaces

The modulus and damping properties of soils in compression are a function of soil type, water content, stress history and loading rate. To model human–surface interaction with natural turf sports surfaces, stiffness and damping properties must be determined at dynamic loading rates. Two contrasting soil types, a Sand and a Clay Loam, commonly used in sports surfaces were loaded uniaxially to 2 kN at loading rates between 0.6 and 6 kN s−1 in modified dynamic soil testing apparatus. Soils were compacted prior to loading but initial cycles resulted in viscoplastic deformation, with strain accumulation with repeated cycles of loading. Ultimately a resilient, viscoelastic steady-state equilibrium with loading was established. Resilient modulus and damping ratio varied with soil type, water content, stress history and increased significantly with loading rate. The resilient modulus of the Sand soil, typical of modern free-draining sand construction natural turf sports surfaces, was significantly greater than that of a Clay Loam soil more characteristic of traditional natural turf surfaces; reducing water content caused an increase in modulus and a decrease in damping ratio in the Clay Loam soil. Determination of these properties provides initial data for the modelling natural turf surface behaviour in terms of both ball and human interactions, with further research required to determine the effect of both grass roots and leaves on mechanical behaviour.

Natural Turf Surfaces

It is well documented that health and social benefits can be attained through participation in sport and exercise. Participation, particularly in sports, benefits from appropriate surface provisions that are safe, affordable and high quality preferably across the recreational to elite continuum. Investment, construction and research into artificial sports surfaces have increased to meet this provision. However, not all sports (e.g. golf, rugby and cricket) are suited to training and match-play on artificial turf without compromising some playing characteristics of the games. Therefore, full sport surface provision cannot be met without the use of natural turf surfaces, which also have an important role as green spaces in the built environment. Furthermore, a significant number of people participate in outdoor sport on natural turf pitches, although this is a declining trend as the number of synthetic turf surfaces increases. Despite natural turf being a common playing surface for popular sports such as soccer, rugby and cricket, few biomechanical studies have been performed using natural turf conditions. It is proposed that if natural turf surfaces are to help meet the provision of sports surfaces, advancement in the construction and sustainability of natural turf surface design is required. The design of a natural turf surface should also be informed by knowledge of surface-related overuse injury risk factors. This article reviews biomechanical, engineering, soil mechanics, turfgrass science, sports medicine and injury-related literature with a view to proposing a multidisciplinary approach to engineering a more sustainable natural turf sport surface. The present article concludes that an integrated approach incorporating an engineering and biomechanical analysis of the effects of variations in natural turf media on human movement and the effects of variations in human movement on natural turf is primarily required to address the longer-term development of sustainable natural turf playing surfaces. It also recommends that the use of 'natural turf' as a catch-all categorization in injury studies masks the spatial and temporal variation within and among such surfaces, which could be important.

Testing natural turf sports surfaces: The value of performance quality standards

The performance of a sports surface is quantified for a number of reasons and by a range of methods. Four categories of surface performance testing are proposed: category 1, to determine compliance with minimum standards; category 2, to assess the overall quality of surfaces across different tiers of sport; category 3, to inform management intervention (construction and maintenance); category 4, to inform research into sports surface engineering, equipment development, the biomechanics of sports performance, and sports injury. The majority of testing in the UK falls into category 1, particularly for synthetic surfaces. Performance quality standards (PQSs) are a system for the quantification of natural turf surface performance and are suitable for category 1 testing but in this study the suitability of the PQS approach for category 2 and category 3 testing was considered in the objective statistical analysis of data from football (soccer) and cricket in the UK. Analysis determined that a PQS is suitable for category 2 testing but that a weighting system for individual components should be developed. Development of a system of decision support based upon PQS data will enable PQS systems to be used for category 3 approaches, although a coherent decision support system is not currently available. The limitation of this type of testing for category 4 was also considered.

Contributions of the inside and outside leg to maintenance of curvilinear motion on a natural turf surface

Little is understood of the mechanisms of locomotion if human subjects are not moving in a straight path. The identification of contributory variables to curved motion would also underpin other non-linear actions such as cutting and turning. The performance of such tasks has relevance to both success in sports and exercise, and accident avoidance in an occupational setting. Comparison of ground reaction force values in successive footstrikes would allow an understanding of the contribution of each limb's movement to motion in a curved path. For ecological validity to field games, two natural-turf covered force platforms were located outdoors in a field. Six males (age 25+/-4.73 years; mass 79.7+/-7.17 kg) wearing standard six-stud soccer boots performed straight and curved trials (radius 5m) at velocities of 4.5 and 5.5 ms(-1). Ground reaction force measures were collected on successive footstrikes at 500 Hz, whilst kinematics of the lower extremity were measured at 50 Hz. Results for two successive footfalls showed greater average total force in straight motion (3.53BW versus 3.08BW), with the outside leg contributing most to the movement pattern in curvilinear motion. Ballistic airtime was reduced from straight to curvilinear motion, creating a greater proportional foot contact time during curved running. This, with lowered total force values, suggested a lower centre of gravity during curved motion to minimise drift towards the tangent of the curve. In curved motion, all vertical force measures were greater for the outside leg, with anterior-posterior forces showing the outside leg provided greater propulsion forces and impulse. Improvement in performance in curvilinear motion should therefore be focused at the outside limb.

Ground reaction force measures when running in soccer boots and soccer training shoes on a natural turf surface

There are differences in ground reaction force when wearing soccer boots compared with training shoes on a natural turf surface. Two natural-turf-covered force platforms, located outdoors in a field, allowed comparison of performance when six-studded soccer boots and soccer training shoes were worn during straight fast running (5.4 m s-1 ± 0.27 m s-1) and slow running (4.4 ms-1 ± 0.22 m s-1). Six male soccer players (mean age: 25 ± 4.18 years; mean mass 79.7 ±9.32 kg) struck the first platform with the right foot and the second platform with the left foot. In fast running, the mean vertical impact peak was significantly greater in soccer boots (2.706 BW) than in training shoes (2.496 BW) when both the right and left foot were considered together and averaged (P = 0.003). Similarly, the mean vertical impact peak loading rate was greater when wearing soccer boots at 26.09 BWs-1 compared to training shoes (21.32 BWs-1;P = 0.002). Notably, the mean vertical impact peak loading rate of the left foot (boots: 28.07 BWs-1; shoes: 22.52 BWs-1) was significantly greater than the right foot (boots: 24.11 BWs-1; shoes: 20.11 BWs-1) in both boots and shoes (P = 0.018). The braking force was greater for the left foot (P = 0.013). In contrast, mean peak vertical propulsion forces were greater for the right foot (P > 0.001) when either soccer boots or training shoes were considered. Similar significant trends were evident in slow running, and, notably, in both soccer boots and training shoes medial forces were greater for the left foot (P = 0.008) and lateral forces greater for the right foot (P = 0.011). This study showed the natural turf ground reaction force measurement system can highlight differences in footwear in an ecological environment. Greater forces and impact loading rates occurred during running activity in soccer boots than in training shoes, with soccer boots showing reduced shock attenuation at impact. Such findings may have implications for impact-related injuries with sustained exposure, especially on harder natural-turf surfaces. There were differences in the forces occurring at the right and left feet with the ground, thus suggesting the use of bipedal monitoring of ground reaction forces.

The biomechanics of soccer: A review

This review considers the biomechanical factors that are relevant to success in the game of soccer. Three broad areas are covered: (1) the technical performance of soccer skills; (2) the equipment used in playing the game; and (3) the causative mechanisms of specific soccer injuries. Kicking is the most widely studied soccer skill. Although there are many types of kick, the variant most widely reported in the literature is the maximum velocity instep kick of a stationary ball. In contrast, several other skills, such as throwing-in and goalkeeping, have received little attention; some, for example passing and trapping the ball, tackling, falling behaviour, jumping, running, sprinting, starting, stopping and changing direction, have not been the subject of any detailed biomechanical investigation. The items of equipment reviewed are boots, the ball, artificial and natural turf surfaces and shin guards. Little of the research conducted by equipment manufacturers is in the public domain; this part of the review therefore concentrates on the mechanical responses of equipment, player-equipment interaction, and the eff ects of equipment on player performance and protection. Although the equipment has mechanical characteristics that can be reasonably well quantified, the player-equipment interaction is more difficult to establish; this makes its efficacy for performance or protection difficult to predict. Some soccer injuries may be attributable to the equipment used. The soccer boot has a poor protective capability, but careful design can have a minor influence on reducing the severity of ankle inversion injuries. Performance requirements limit the scope for reducing these injuries; alternative methods for providing ankle stability are necessary. Artificial surfaces result in injury profiles diff erent from those on natural turf pitches. There is a tendency for fewer serious injuries, but more minor injuries, on artificial turf than on natural turf pitches. Players adapt to surface types over a period of several games. Therefore, changing from one surface to another is a major aetiological factor in surface-related injuries. Heading the ball could lead to long-term brain damage. Simulation studies suggest the importance of ball mass, ball speed and player mass in affecting the severity of impact. Careful instruction and skill development, together with the correct equipment, is necessary for young players. Most applications of biomechanical techniques to soccer have been descriptive experimental studies. Biomechanical modelling techniques have helped in the understanding of the underlying mechanisms of performance, although their use has been limited. It is concluded that there are still many features of the game of soccer that are amenable to biomechanical treatment, and many opportunities for biomechanists to make a contribution to the science of soccer.

Nitrogen Loading from Coastal Watersheds to Receiving Estuaries: New Method and Application

In this paper we develop a model to estimate nitrogen loading to watersheds and receiving waters, and then apply the model to gain insight about sources, losses, and transport of nitrogen in groundwater moving through a coastal watershed. The model is developed from data of the Waquoit Bay Land Margin Ecosystems Research project (WBLMER), and from syntheses of published information. The WBLMER nitrogen loading model first estimates inputs by atmospheric deposition, fertilizer use, and wastewater to surfaces of the major types of land use (natural vegetation, turf, agricultural land, residential areas, and impervious surfaces) within the landscape. Then, the model estimates losses of nitrogen in the various compartments of the watershed ecosystem. For atmospheric and fertilizer nitrogen, the model allows losses in vegetation and soils, in the vadose zone, and in the aquifer. For wastewater nitrogen, the model allows losses in septic systems and effluent plumes, and it adds further losses that occur during diffuse transport within aquifers. The calculation of losses is done separately for each major type of land cover, because the processes and loss rates involved differ for different tesserae of the land cover mosaic. If groundwater flows into a freshwater body, the model adds a loss of nitrogen for traversing the freshwater body and then subjects the surviving nitrogen to losses in the aquifer. The WBLMER model is developed for Waquoit Bay, but with inputs for local conditions it is applicable to other rural to suburban watersheds underlain by unconsolidated sandy sediments. Model calculations suggest that the atmosphere contributes 56%, fertilizer 14%, and wastewater 27% of the nitrogen delivered to the surface of the watershed of Waquoit Bay. Losses within the watershed amount to 89% of atmospheric nitrogen, 79% of fertilizer nitrogen, and 65% of wastewater nitrogen. The net result of inputs to the watershed surface and losses within the watershed is that wastewater becomes the largest source (48%) of nitrogen loads to receiving estuaries, followed by atmospheric deposition (30%) and fertilizer use (15%). The nitrogen load to estuaries of Waquoit Bay is transported primarily through land parcels covered by residential areas (39%, mainly via wastewater), natural vegetation (21%, by atmospheric deposition), and turf (16%, by atmospheric deposition and fertilizers). Other land covers were involved in lesser throughputs of nitrogen. The model results have implications for management of coastal landscapes and water quality. Most attention should be given to wastewater disposal within the watershed, particularly within 200 m of the shore. Rules regarding setbacks of septic system location relative to shore and nitrogen retention ability of septic systems, will be useful in control of wastewater nitrogen loading. Installation of multiple conventional leaching fields or septic systems in high-flow parcels could be one way to increase nitrogen retention. Control of fertilizer use can help to a modest degree, particularly for optional uses such as lawns situated near shore. Conservation of parcels of accreting natural vegetation should be given high priority, because these environments effectively intercept atmospheric deposition. Areas upgradient from freshwater bodies should be given low priority in plans to control nitrogen loading, because ponds intercept much of the nitrogen transported from upgradient.