Crop and Soil Science Department, University of Georgia, 1109 Experiment Street, Griffin, GA 30223.
Science-based, holistic, site-specific water conservation practices can reduce water use on turfgrass sites without adversely affecting turfgrass performance. However, when water use is decreased below a certain threshold, performance declines. Water conservation measures that reduce turfgrass performance essentially decrease its economic, environmental, recreational, and aesthetic values, which can in turn adversely impact many “stakeholders” ---including the local economy and those affected by increased wind erosion, water erosion, or fire hazard. On larger turfgrass sites, considerable costs are associated with some water conservation strategies---especially when the quality of an alternative irrigation water source is poor or redesign of the landscape and/or irrigation system is involved.
Science-based, holistic, site-specific water conservation practices can reduce water use on turfgrass sites without adversely affecting turfgrass performance. However, when water use is decreased below a certain threshold, performance declines along with its economic, environmental, recreational, and aesthetic values.
Turfgrass, water conservation, BMPs for water conservation.
The question “Can we maintain turf to customers’ satisfaction with less water?” suggests several points:
In the midst of a water crisis, the general public, politicians, and water regulatory agencies may focus only on water savings that can be achieved by implementing immediate water saving measures without regard to potential short or long term consequences to all that may be affected. However, if water conservation measures are severe enough to compromise turf recreational use, economic impact, environmental/functional benefits, or aesthetics, then more than the perceived direct “customer” may be adversely affected (Beard and Green 1994; Gibeault 2002; Cathy 2003). The focus of this paper is to address the points posed by the question in the paper’s title.
In recent papers (Balogh and Watson 1992; Ervin and Koski 1998; Richie et al. 2002; Bastug and Buyuktas 2003), the relationships between turfgrass evapotranspiration (ETc) and turf quality were explored along with discussion of past research as reviewed by Kneebone et al. (1992) and Kenna and Horst (1993). Several conclusions can be reached based on the various studies relating ETc versus turf performance:
In general, the landscape coefficient (KL), for cool-season grasses (0.70 to 0.95) are higher than for warm-season turfgrasses (0.65 to 0.85) when the irrigation regime is at 3 to 7+ days between events, which would allow moisture stress within the surface zone. At these KL values, the turf could maintain acceptable quality and growth, but as the KL value was decreased below these general ranges using a similar irrigation schedule, turf performance rapidly declined (Meyer and Gibeault 1987; Carrow 1995; other references listed in this section).
Irrigation scheduling can influence the KL value versus turf performance. When a grass was irrigated more heavily (KL 0.75 to 1.00 for tall fescue, Festuca arundinacea Shreb., 7 day schedule), the irrigation frequency could be extended; but with a 2 to 3 day schedule, a KL of 0.50 maintained good quality (Fry and Butler 1989; Richie et al. 2002). The concept of deep, infrequent irrigation scheduling is limited by the surface drying versus turf performance relationship, especially in arid regions. In arid regions, where most water addition is by irrigation, it is important to determine the deepest and least frequent irrigation schedule that will allow maximum water conservation without an unacceptable decline in turf quality resulting from too severe drying at the surface (Brede 2000). Extending the irrigation interval too far will result in more water to maintain the same quality level compared to a less frequent irrigation using less water. In a semi-arid or humid climate, deep rooting is important to take advantage of natural precipitation events. But, in an arid climate, rooting to a depth that allows a reasonable interval between scheduling events without excessive surface drying is all that is needed and not the deepest rooted grass.
Carrow (1995) reported turfgrass ETc was 40 to 60 % less in a humid environment compared to the same cultivar in an arid environment, but similar KL values were reported in both environments. ETo (potential evaporation estimate) under the humid climate was less, accounting for the differences in observed ETc. Additionally, irrigation intervals in arid or semi-arid climates were normally within the range of 3 to 7 days, but Carrow (1996) reported irrigation frequencies of 5 to 20 days due to lower ETc, allowing more opportunity to capture natural precipitation rather than to irrigate.
If a daily irrigation regime was followed, KL for cool-season grasses is reported to be 0.88 to 1.09 (Aronson et al. 1987; Bastag and Buyuktas 2003). Thus, allowing no drought stress on the turfgrass can result in high ETc. Dormant turf would have only evaporation losses, similar to any ‘mulch’.
Within the broad categories of cool and warm-season grasses, species differences are apparent.
Within a species, there can be 20 to 60 % range in ETc (Kjelgren et al. 2000).
Thus, controlled research studies confirm that water conservation can be achieved to a point before turfgrass quality starts to decline; thereafter, decreasing water results in reduced turf quality. The resulting reduction in turf quality or cover implies a potential for reduction in recreational use, environmental/functional capabilities, and economic use/value of the site, which in turn may adversely affect the direct customer, owners, local economy, and local environment (Beard and Green 1994; Cathy 2003). The real issue then becomes how to maximize water conservation on turfgrass areas while maintaining economic viability.
Only two broad approaches to site-specific water conservation are possible: rigid regulations or by holistic, science-based methods. For other environmental issues, a Best Management Practices (BMPS) approach has been successfully used and accepted by society and regulatory agencies: for example, BMPs for protection of surface and subsurface waters from pesticides and nutrients (also called IMP or integrated plant/pest management) or BMPs for sediment abatement. In terms of turfgrass water conservation, a BMPs approach must be adopted by the turfgrass industry and encouraged by regulatory groups. To ensure that a site-specific water conservation program is successful in water savings, while incorporating recognition and adjustments for other impacts, a sound water conservation program should include several attributes.
Even with a BMP approach, during severe water constraints, more rigid regulations are used for all water users, including the turfgrass industry.
Vickers (2001) noted key steps to a successful water conservation program on a regional or state-wide basis as: a) identify conservation goals, b) develop a water-use profile and forecast, c) evaluate planned facilities, d) identify and evaluate conservation measures, e) identify and assess conservation incentives, f) analyze benefits and costs, g) select conservation measures and incentives, h) prepare and implement the conservation plan, i) integrate conservation and supply plans, modify forecasts, and j) monitor, evaluate, and revise program as needed. However, best management practices (BMPs) for turfgrass water conservation that can be applied on a site-specific basis are essential. There are a number of components or strategies that should be integrated into an overall turfgrass water conservation plan, at the site-specific level (Gibeault and Cockerham, 1985; Carrow and Duncan, 2000a; Carrow et al. 2002a, 2002b). Within each “broad strategy”, there are many options to consider when selecting the BMPs for water conservation for a particular site. However, except for the “water audit” approach, which deals only with the irrigation system, comprehensive, in-depth plans have not been available to turf managers (Irr. Assoc. 2003a). Recently, Carrow et al. (2004), in conjunction with the Golf Course Superintendents Association of America, developed a comprehensive, water conservation BMPs document (template) for individual golf courses dealing with: the planning process; detailed options for different water conservation strategies; and information on benefit/cost assessment. Components of a site-specific water conservation program for golf courses are denoted in Table 1.
Assessment of benefits and costs of implementing water conservation measures on all stakeholders is essential to understand implications. The immediate owner or manager of a turf site will naturally assess the direct costs involved to implement water conservation measures. For the homeowner, rebate or water cost incentives may help offset the cost of landscape design and plant material changes, irrigation system alterations, and rain sensors (WRA 2003). For large scale facilities, such as a golf course, the implementation costs may be considerable for changes in landscape design/plant material, irrigation system design and operation, using alternative irrigation water resources (i.e., wastewater piping costs, water/soil amendments), more frequent cultivation, training, and monitoring. Vickers (2001) and WRA (2003) Smart Water provide much discussion on direct and indirect benefits of reducing water consumption, but limited discussion concerning potential for adverse effects to: a) facility costs to implement changes required by a plan, and b) some potential adverse environmental impacts if overuse of water on turf resulted in adverse in-stream flow, over-pumping of groundwater, reduced wetland effects, and one mention of fire hazard from native grasses. In contrast, Cathey (2002), Beard and Green (1994), and Gibeault (2002) note a broad array of benefits that turfgrass and the turf industry contribute to society (Table 2), and present a good discussion with case studies of adverse effects when water conservation measures are taken to the extreme, especially without consideration of other environmental impacts.
Table 1. Components of site-specific turfgrass water conservation programs (Carrow et al. 2004)
A. Initial Planning and Site Assessment.
B. Identify, evaluate, and select water conservation strategies and options.
C. Assess benefits and costs of water conservation measures on all stakeholders.
As noted earlier, careful application of water conservation strategies can reduce turfgrass water use, but after a point turfgrass performance and associated benefits will start to decline. Therefore, as a part of an overall water conservation plan, actual water conservation/savings must be balanced by potential effects that may arise---economic, functional/environmental, recreational use of the site, and aesthetics---not just on the specific site but also on the local and broad economy and environment. A couple examples illustrate this point when removal of turf is carried too far:
Table 2. Benefits that turfgrass sites contribute (after Beard and Green 1994; Cathey 2002, Gibeault 2002).
Several potential water conservation strategies with options can be used in BMPs for a turfgrass site (Table 1) (Carrow et al.2004):
An important strategy for water conservation is to use alternative non-potable water sources---runoff collected in ponds, effluent (wastewater), poor quality ground water, seawater or seawater/blends (Carrow and Duncan 2000b). As recreational areas shift to poorer water quality, more salt-induced problems are anticipated that will require extra alternative irrigation water beyond the normal irrigation rate for salt leaching. Monitoring of soil moisture and salt levels at multiple depths will become more commonplace by mobile and/or installed moisture and salt sensors. The necessity of using grasses with higher salt tolerance will alter management not only because the grass is new, but because salt-induced problems must be managed (Carrow and Duncan 1998).
The environmentally friendly term water harvesting is not often used in relation to golf courses or other turf sites, yet it is a common practice. Many golf course irrigation lakes also serve as landscaping features and catch excess runoff, preventing the loss of substantial amounts of water from the site and preventing sediment into streams or rivers. Catchment features are usually part of an overall stormwater control and reuse plan mandated by governmental policies. A recent survey of Georgia golf courses indicated that as much as 67 percent of irrigation water came from such non-potable, runoff lakes (Florkowski and Landry 2002). Water harvesting is usually thought of as treating watersheds to enhance runoff collected for future use (Thomas et al. 1997; Todd and Vittori 1997; Waterfall 1998). In the case of golf courses, the landscape is purposely contoured to collect the excess runoff from rainfall, while allowing good infiltration of water into the soil under normal conditions. Some golf courses with large adjacent housing developments are investigating the potential for collecting drainage and runoff from these areas, using their own facility to treat the non-potable water to standards acceptable for turf use, and irrigating the golf course with the water. This practice saves local government the expense of treating the water.
Development and use of turfgrasses with superior drought resistance/low water use is a primary means of decreasing water needs on turfgrass sites (Kenna and Horst 1993). Cynodon spp. are widely used in the warm-season zones and most cultivars exhibit superior drought resistance; but superior drought resistance in many other commonly used species, especially cool-season grasses, is less evident—and will remain so until breeders focus on this as a priority. Some turfgrass breeders are now placing more emphasis on drought resistance, particularly the most important component which is drought avoidance via a greater genetic-based root tolerance to soil stresses that limit root development/maintenance and by shoot characteristics that contribute to an inherent low water use (Duncan and Carrow, 1999). Under more limited irrigation regimes, other stresses besides drought are enhanced and will require attention by breeders and turf managers: namely, high temperature tolerance for cool-season grasses, wear tolerance, salinity tolerance in the case where poor water quality is used, and pests that are favored by reduced growth rates. In addition to assessing and developing drought resistant cultivars among “traditional” species, non-traditional species bred for superior drought resistance and/or other stress resistance traits will become more common place (Brede 2000; Duncan and Carrow 2001; Loch et al. 2003).
On homesites, Xeriscape principles are often promoted as water conserving. Interestingly, Vickers (2001) notes that “beyond” Xeriscape is a move to natural landscape. Behind this movement appears to be groups that promote only natural landscape plants and use water conservation as the environmental reason, but without a balance of what other adverse human and ecological environmental effects may result--- fire hazard, dust hazard, etc.---or what about the non-native garden and food crop plants? However, Welsh (2003) states that as the original “Xeriscape concept matured and spread, the principle of limited turf use was increasingly scrutinized by horticulturists and turf experts. Today’s Xeriscape movement incorporates a more holistic approach to reducing turf irrigation…through the principles of Xeriscape, turf irrigation can be reduced while the many benefits of turfgrass can still be derived….many turfgrasses are drought-tolerant and can survive extreme drought conditions”. These contrasting views illustrate that all “Xeriscape landscape design” concepts are not equal---which one is used for water conservation purposes has a dramatic effect on the potential for environmental and human hazards. Landscape design focus must not be one-dimensional by focusing on minimizing the turf area, but must apply all of the Xeriscape principles (Cathy 2003) of planning and design, soil improvement, appropriate plant selection, practical turf areas, efficient irrigation design and scheduling (including the human factor), mulching, and appropriate maintenance. Additionally, any adverse environmental effects of proposed landscaping changes should be considered---wind erosion/dust, water erosion/sedimentation of water features, fire hazard, etc.
On larger, more complex sites, such as golf courses, during construction or renovation planning stages many decisions can be made that will either foster water conservation or greatly limit it---such as grass choices, irrigation system design/piping and zoning, contouring, and area of well-irrigated turf on the site. Numerous design “looks” can be achieved with mulch materials; use of alternative, drought-resistant grasses that are left unmowed in non-landing areas; incorporation of native low growing ground covers, shrubs, and trees that require minimal irrigation and possess unique looks; using higher mowing heights on parts of the fairway or adjacent roughs that may receive little or limited irrigation; utilization of features such as rock, sand bunkers, and non-irrigated mounds. Customers (golfers) seem to accept brown turf when it is mowed high or left unmowed, but may not accept as much discoloration or lower plant density on the closely mowed high-use areas. Since golf courses must compete for local and, in some locations, national and international customers, the visual aspects on the close-mowed playing area influences play and the associated tourist industry---i.e., Asian golfers may not come to the Australian Gold Coast if it does not have competitive quality to alternative golf locations. In other instances with less play demand and competition for customers, dormant, semi-dormant, or lower quality turf may be very acceptable on large expanses of many golf courses. Irrigation level on the high use areas also influences the degree of traffic that a golf course or recreational field can tolerate. Contouring is another important design factor, especially avoiding excessive slopes, mounds, and berms that are difficult to irrigate even with an excellent irrigation system. Also, contouring should foster water harvesting.
Irrigation system design and irrigation scheduling (see next section) are essential for water conservation on irrigated sites. One critical design challenge is to deal with spatial variability, which can be very complex on turf sites with many microclimates resulting from the diverse terrain, soil, and plants (Table 3). Spatial variability must be determined, and adjustments made through landscape design, irrigation system design, and site-specific irrigation scheduling. Even a home landscape can be much more variable than most agricultural fields and golf course sites are very complex in terms of variability. Specific types of variability (Table 3) must be individually identified and quantified. This is an area that the author believes will receive more attention in the future so that more precise design of irrigation systems and their operation can be achieved, while also maximizing sensor placement.
In recent years as “water conservation” has become a looming reality, there has been a marked increase in entrepreneurial activity to improve irrigation design and scheduling aspects through better hardware, develop software to communicate between controllers and sensors, and improved irrigation concepts. The author’s current research is focused on identification and characterization of landscape and soil variabilities; categorizing similar microclimates; and using sensor technology to integrate real-time information by microclimate type into irrigation scheduling by combinations of atmospheric and soil-based means. Within agriculture, the equivalent of incorporating these issues would be the ‘precision agriculture’ or ‘integrated approach to irrigation management’ approaches described by Buss (1996).
Irrigation system design is an important component of water conservation on turfgrass sites in order: a) to apply water in an efficient manner so as to limit water losses by runoff, leaching past root systems, or unnecessary evaporation from water standing on the surface; b) to allow adequate irrigation of areas as needed within the time constraints imposed by night time irrigation, salt leaching, water control authorities, etc.; and c) to make site-specific or precision water applications accurately on individual, microclimate areas, according to their needs. In this latter aspect, control of water application on a site-specific basic will often include control of the water rate and depth of percolation for maintaining root viability; and on areas with poor water quality to ensure salt movement downward, while preventing capillary rise back into the root zone. Many of the fundamentals of good irrigation design are known and have been applied to a certain extent, especially in more arid and semi-arid locations (Irrigation Association 2003a, 2003b). However, for maximum water use-efficiency, full incorporation of these principles must be “the norm” for the next generation of irrigation systems and renovations of existing systems. Water must be applied on a precision basis in a BMPs water conservation plan---and this cannot be accomplished with a poorly designed irrigation system. Highly automated irrigation systems will initially cost more, but in the long term save water/money and allow true implementation of environmental stewardship principles by the turf facility.
Table 3. Spatial variability that influences irrigation scheduling and water-use efficiency.
Variability across the landscape due to:
Good design, zoning, and hardware reduces landscape and soil variability but when the system is not properly designed or operated it becomes another source of variability.
Irrigated sites can be over-watered because people do not irrigate according to plant needs, including Xeriscapes---in Phoenix Xeriscapes actually used 30% more water than conventional landscapes. This illustrates the critical point that it is people who over-irrigate (Vickers 2001). Means must be developed to couple irrigation applications to true plant water needs. The best designed irrigation system will not efficiently apply water unless it is properly programmed. Irrigation scheduling is normally by experience of the turf manager using indicator spots or problem areas where drought symptoms are first observed to aid in deciding when to irrigate. Many golf courses and some other turf sites have an on-site weather station where estimated ETo data is available; but ETo data must be adjusted for each microclimate site, since grass, soil type, radiation, wind, and other environmental or management conditions will differ from the weather station site. For example, each microclimate adjustment is made by multiplying a Landscape Coefficient (KL) by the ETo to obtain an estimated turf ET (ETc). Unfortunately, the KL factor differs with grass, season, weather front, and microclimate soil/atmospheric conditions, while the ETo does not take into account the soil (current soil moisture level by depth) nor plant (depth of viable root system, current level of stress) conditions.
Irrigation scheduling of the future will involve real-time information from within an irrigation zone to provide more site-specific guidance (Sudduth et al., 1999). One approach will be soil sensors that are now capable of monitoring soil moisture in 50-100mm zones at multiple depths down to 1 m in a real-time mode with remote transfer of the data for ease of use (Moller et al., 1996; Charlesworth, 2000). Precision application of irrigation for prevention of moisture stress and for salt control, requires precise information on current conditions by soil depth. A common question that arises with soil moisture sensors is whether a soil measurement represents the area due to spatial variability across a landscape and within the soil. Comments related to this question are:
Another emerging technology is the possible use of plant-based monitoring of plant stress for use in irrigation scheduling using the precision agriculture concept (Frazier et al. 1999). Currently, the most effort is in measuring light reflectance from the turf canopy within the 350 to 1100 nm wavelength region, which includes the visible/ PAR (photosynthetically active radiation) region of 400-750 nm (Geuertal et al. 2000). Loss of color and/or leaf area can increase reflectance within certain wavelengths that may be used in models to estimate overall plant stress, irrigation need, or perhaps a nutrient stress, such as N. Other approaches may become possible such as using a wider wavelength range of 350 to 2500 nm where several “water bands” occur; use of the infrared thermal region of 8000-14000 nm; fluorescence reflectance; digital imaging data; and others. However, even with an accurate plant-based method, the question of how much water to apply is a major problem.
Various management practices can substantially affect water-use efficiency, especially practices that maximize water infiltration and turfgrass root development and maintenance (Carrow 1994). Cultural operations may alter the soil conditions to reduce water loss from runoff, leaching or excess evaporation and to improve soil water retention. Although a particular turfgrass may have the genetic potential to be drought resistant, but without proper management, it may exhibit low water-use efficiency.
Educational efforts will need to be developed for various audiences concerned with water conservation and management on turfgrass areas as well as policy makers, water management authorities, turf students, facility officials and members, crew members, etc. The challenge for Extension specialists and research scientists will be to produce in-depth informational packages containing both scientific principles and specific practicum for turf managers and consultants in the industry (Carrow et al. 2001). Turf mangers will be more likely to embrace new technology if they have ready access to good education opportunities from well-trained consultants and specialists.
A water conservation plan conserves water on a continuous basis, whereas a contingency plan deals with water-conserving measures in time of severe shortages. At the turfgrass facility level, it is essential that owners, members and officials assist in formulating these plans, understand their implications, and adopt the plans. Facility policies must include water conservation.
In addition to the practices already outlined, other practices include: a) monitoring a water conservation program to assess success by documenting water use (for example, by water meters) and relating it to turfgrass performance; b) periodic site water audits can identify leaks, irrigation head malfunctions, design limitations, irrigation scheduling problems or other wasteful water use, and c) indoor water conservation plans for any buildings on a facility (Vickers 2001).
Considerable information exists about many aspects of turfgrass water conservation practices, which could be implemented rapidly to achieve water savings on most sites. Incorporating new developments in grasses, technology, concepts, and scientific knowledge would produce additional water savings over time. Many turfgrass managers already follow some water conservation practices at their sites, but full implementation is often hindered by certain challenges:
In summary, water conservation will become increasingly necessary on many turf sites, regardless of the climatic zone. Considerable knowledge already exists about many practices within this complex "soil-plant-water source-climate-man" system that can be implemented rapidly to achieve a certain degree of water conservation or water-use efficiency without sacrifice of turf performance. In addition to the current state of science, turf managers will be presented with a host of new tools for better water management and ongoing changes in equipment, chemicals and practices. In-depth, continuing education will become necessary as new technology and new grasses must be integrated into ‘BMPs for water conservation’ to be truly efficient, properly implemented, and carefully monitored; but this paradigm will require whole-hearted involvement by all owners/facility officials and the turf manager associated with a turfgrass facility.
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