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Best Management Practices for
Landscape Water Conservation

Introduction
BMPs for Water Conservation in Landscape Design
BMPs to Improve Water Conservation through Proper Landscape Installation and Maintenance
BMPs for Landscape Irrigation System Water Conservation
BMPs for Turfgrass Water Conservation in Landscapes
Emerging and Existing Technologies for Landscape Water Conservation
The Economic Benefits of Landscape Water Conservation

Introduction

Clint Waltz, Extension Specialist — Turfgrass
Gary Wade, Extension Coordinator, Department of Horculture

Landscape water conservation Best Management Practices (BMPs) are practices that integrate plant selection, plant adaptation, irrigation, cultural and management practices, and a change in the acceptable expectations of plant performance under sub-optimal water conditions. The primary objective of these BMPs is to reduce landscape water use — not just during periods of drought, but throughout the entire growing season. Water conservation is an improvement in water use efficiency, not the temporary responses to periodic drought. BMPs are designed to be economical, practical, and sustainable while maintaining a healthy, functional landscape — a landscape that capitalizes on the environmental benefits of plant systems.

Georgia, like the rest of the United States, has a growing thirst for water. It is essential to human life, the health of ecosystems, and Georgia’s economic development. Figure 1-1 illustrates how Georgia’s demand for public supplied water, ground water, and surface water has increased over the past 50 years, from 130 million gallons per day (Mgd) in 1950 to more than 1,250 Mgd in 2000 (Fanning, 2003a).

Figure 1-1. Demands on Georgia's water supply and population increase since 1950.

Publicly supplied water is water withdrawn, treated, and distributed by public and private water suppliers for normal household uses, landscape maintenance, and commercial uses, including restaurants, hotels, retail stores, hospitals, prisons and colleges. In 2000, 98 percent of Georgia’s industries relied on their own water resources (Fanning, 2003a). Publicly supplied water is commonly referred to as “municipal” water supplied by local county or private utilities. Seventy-eight percent of the public supply water in Georgia comes from surface water, such as reservoirs and rivers, while 23 percent comes from ground water and aquifers.

Increasing demand for public water is directly related to increasing population (Figure 1-1), and an increase in the number of public and private water suppliers (Fanning, 2003b). From 1950 to 2000, Georgia’s population grew by 40 percent. Another 16-percent increase is projected by 2010 (Bachtel, 2003).

People relocating to Georgia are moving to urban areas for improved goods, services, schools and health care. Unfortunately, from the water supply standpoint, population is not evenly distributed throughout the state (Figure 1-2). In fact, more than half of Georgia’s population resides in 12 urban counties, while two-thirds of the population lives in just 40 of the state’s 159 counties (Bachtel, 2003).

Figure 1-2. Georgia's most populous counties, 2003. Dark blue counties account for 1/2 of Georgia's population, while dark blue + light blue counties account for more than 2/3 of Georgia's population. Population is highest in and around urban areas.

Table 1-1 shows population and water demand in 2000 and projected population and water demand in 2030 for five counties in northeast Georgia. Similar statistics can be obtained for most counties in and around urban areas in Georgia.

Unlike arid regions of the United States where annual rainfall may be less than 5 inches, most areas of Georgia receive 45 to 55 inches of rain annually (Table 1-2 and Figure 1-3). Summer drought is common in Georgia, however, when significant rainfall amounts may be 30 or more days apart. These periods of limited rainfall increase demand on pubic water supply systems.

Figure 1-3. To provide perspective of rainfall across Georgia, data for five locations were evaluated.

During the summer months, municipal water use outdoors increases between 30 percent to 50 percent, probably for outdoor recreational purposes (e.g. swimming pools), utility purposes (e.g. car washing and pressure washing), and for lawns and landscapes. Figure 1-4 shows a typical monthly demand cycle on a metro-Atlanta utility.

Figure 1-4. Daily water demand on a metro-Atlanta utility. Source: Cobb-Marietta Water Authority, 2000.

Population growth and increased demand for water in combination with seasonal drought has resulted in water restrictions or bans on outdoor irrigation in many areas of Georgia, even during years of normal rainfall. In 2004, the Georgia Department of Natural Resources (DNR) adopted guidelines for outdoor water use; visit www.state.ga.us/dnr/. These guidelines serve as a basis for local water purveyors and municipalities to regulate water use. Local restrictions may vary and may even be more restrictive than those of the state. Residents and professionals should become familiar with the DNR guidelines and, more importantly, their local outdoor water use rules and restrictions.

The state guidelines outline four drought response levels, each with specific restrictions and exemptions. The four levels and a few applicable restrictions include:

• Declared Drought Response Level One – Outdoor water use may occur on scheduled days within the hours of 12 a.m. to 10 a.m. and 4 p.m. to 12 a.m.
  • Scheduled days for odd-numbered addresses are Tuesday, Thursday, and Sunday.
  • Scheduled days for even-numbered addresses are Monday, Wednesday, and Saturday.
• Declared Drought Response Level Two – Outdoor water use may occur on scheduled days within the hours of 12 a.m. to 10 a.m.
  • Scheduled days for odd- and even-numbered addresses are same as Level One.
• Declared Drought Response Level Three – Outdoor water use may occur on the scheduled day within the hours of 12:00 a.m. to 10:00 a.m.
  • The scheduled day for odd-numbered addresses is Sunday.
  • The scheduled day for even-numbered addresses is Saturday.
• Declared Drought Response Level Four – No outdoor water use is allowed other than for activities exempted by the guidelines or the EPD Director.

Similarly, the “Georgia Drought Management Plan” was drafted by state government in 2003 (http://www.gaepd.org/Documents/index_water.html). It proposes “pre-drought strategies, implemented before drought, for the purposes of preparedness, mitigation and monitoring, and drought responses, which are short-term actions, implemented during drought, according to the level of severity.” Water use restrictions proposed by this plan can be addressed through the implementation of BMPs for water conservation in urban landscapes.

No doubt, water conservation is a concept that must be adopted as water resources become more limited. Water conservation should be institutionalized across all industries, including the green industry, production agriculture, pulp and paper, and manufacturing, just to name a few. Furthermore, the aesthetic, sociological, and environmental benefits of landscapes also must be recognized by water authorities and policy makers. Policies that value a landscape will not only reduce water consumption, they can accentuate the environmental and societal benefits.

Landscapes can have a positive influence on human behavior characteristics such as improved ability to concentrate and self-discipline (Taylor et al., 2001).

Views of “nature” have been correlated to more effective, self-disciplined lives in inner city girls who had an open view of natural settings or landscapes from their homes or apartments. This life style is thought to translate into improved academic achievement and fewer destructive tendencies such as juvenile delinquency and teenage pregnancy. While landscapes mitigate environmental concerns, the influences on the human psyche are just beginning to be understood.

Turfgrass, an integral component of the landscape, plays a significant role in reducing water runoff and mitigating stormwater problems in urban and suburban environments with significant areas of impervious surfaces such as parking lots, sidewalks, and driveways. A healthy turfgrass root zone will:

• Help improve soil structure and reduce soil compaction, leading to greater infiltration of rain or irrigation water into the root zone. These waters percolate through the soil and contribute to ground water recharge;
• Help improve soil processes that facilitate the biodegradation (breakdown) of various types of pollutants and air contaminants;
• Encourage soil-building processes through decomposition of organic matter and formation of humus, which contributes to easier lawn care with fewer fertilizer, pest control, or water inputs.

Furthermore, recent research (Bandaranayake et al., 2003) indicates that turfgrass systems help rid the atmosphere of greenhouse gases, like carbon dioxide (CO₂), which contribute to global warming. Turfgrasses, like all plants, use the carbon requiring process of photosynthesis to produce their own “food.” Studies have shown golf course putting greens and fairways store nearly a ton of carbon (C) per acre per year, with effects lasting for 31 to 45 years (Elstein, 2003). Interestingly, these data are comparable to carbon sequestration rates of lands placed in federal Conservation Reserve Programs. Because of the high productivity and lack of soil disturbances in turfgrass systems, golf courses, home lawns, athletic fields, and other grassed areas serve as effective, long-term “traps” for CO₂ while providing aesthetic, economic, and recreational benefits.

To meet Georgia’s growing demands for water resources, the focus must be on how to use water more efficiently without sacrificing environmental quality. This objective can be achieved through proper plant selection and installation, and the use of landscape management practices that accentuate a plant’s natural ability to survive despite a temporary deprivation of required resources (e.g. nutrients and water).

By employing proper techniques in landscape design, installation, and routine maintenance, water use in the landscape can be more efficient and, therefore, reduce the amount of water used. The purpose of this publication is to provide BMPs for landscape design, planting installation, effective use of irrigation systems, proper turfgrass maintenance, and guidance of irrigation practices. When combined, all these practices become an integrated approach to achieve landscape water conservation. The practices presented in this publication can be used by landscape professionals, homeowners, water purveyors, municipalities, and state regulatory agencies to improve water use efficiency while maintaining a healthy and attractive landscape.

Literature Cited

Bachtel, Douglas C. 2003. The Georgia County Guide, 22nd Edition. Center for Agribusiness and Economic Development, College of Agricultural and Environmental Sciences, The University of Georgia, http://www.agecon.uga.edu/~coutyguide.

Bandaranayake, W., R. Follett, and Y. Qian. Assessing soil carbon sequestration in turfgrass systems using long-term soil testing and the CENTURY simulation model. Agronomy Abstracts.

Elstein, D. 2003. Are golf courses holding the carbon? Turfgrass as a “sink” for CO₂. Agriculture Research, June, page 10.

Fanning, Julia A. 2003a. Water Use in Georgia by County for 2000 and Water-use Trends for 1980 -2000. Information Circular 106, Georgia Department of Natural Resources, Environmental Protection Division. http://ga.water.usgs.gov/pubs/other/ggs-ic106/pdf/ggs-ic106.pdf

Fanning, Julia A. 2003b. Water Use in Georgia, 2000; and Trends, 1950-2000. Proceedings of the 2003 Georgia Water Resources Conference, April 23-24, 2003, The University of Georgia, Kathryn J. Hatcher, editor, Institute of Ecology.

Northeast Georgia Regional Development Center Projected Water Demand, 2000 and 2030. Cited in the Athens Banner-Herald, January 25, 2004.

Taylor, A. F., F. E. Kuo, and W. C. Sullivan. 2001. Views of nature and self-discipline: Evidence from inter city children. Journal of Environmental Psychology 21: available online: http://www.idealibrary.com.

BMPs for Water Conservation
in Landscape Design

David Berle, Extension Horticulturist
Gary Wade, Extension Coordinator, Department of Horticulture

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	Select plants that match the existing light conditions; they will grow better and require less water.
	Match surface and soil drainage conditions to plant moisture requirements.
	Select plants that grow well in the temperature ranges of the area.
	Select plants that are regionally adapted to the average rainfall of the area.
	Preserve established vegetation growing on a site; it has an extensive root system and requires less irrigation water than newly planted trees and shrubs.
	Space plants according to their mature size to reduce competition for water.
	Concentrate seasonal color in small, high impact areas to reduce overall water requirements.
	Avoid constructing raised beds under trees due to root competition for available water.
	Develop a landscape plan BEFORE designing an irrigation system.
	Incorporate shade trees into the landscape to reduce evaporative water loss.
	Select and group plants according to their water needs and drought tolerance.
	Divide the landscape into water-use zones.
	Avoid small, irregular-shaped island plantings in turfgrass areas because they are difficult to irrigate.
	Consider irrigation sprinklers when designing turfgrass areas and planting beds.
	Move or eliminate plants not suited to the existing site conditions and irrigation.
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Introduction

Conserving water should be a goal when establishing new landscapes, as well as when retrofitting existing landscapes. When designing a new landscape, you need to make many decisions, including how the landscape will be used, how it should look, what trees and shrubs already exist, which plants are appropriate, and what colors and textures to use. All of these decisions will have an impact on the appearance of the landscape, as well as how much water will be required to maintain it.

Landscaping of commercial sites is different from residential landscaping. Not only do budgets vary, but goals for appearance and maintenance are often different. For example, apartment complexes and shopping centers focus on drawing in visitors while minimizing maintenance. Home landscape design focuses more on creating environments and outdoor spaces that meet the needs of the client.

Homeowners often try to duplicate commercial designs with showy flower beds, entrance plantings, and large turfgrass areas. These practices may work well on a larger property, but they look out of place on a residential scale and can result in wasted water resources.

Regardless of land use, a water-conserving landscape design should re-evaluate traditional landscape practices while incorporating sound water management practices. This does not require special skill or knowledge, only a new way of thinking that considers the overall effects of design decisions on water use.

Be aware of design-related mistakes that can directly influence the water requirements of a landscape. Re-thinking design techniques will help reduce water use without sacrificing the quality or beauty of the landscape design.

Site Characteristics Affecting Water Use

Select plants that match the existing light conditions; they will grow better and require less water.

When observing a landscape plan, it is easy to imagine the big circle labeled “oak” as a mature specimen. Oak trees can grow to heights of more than 50 feet and cast a large shadow. However, if the oak is planted at the same time as the rest of the landscape plants, it is not likely to cast much of a shadow during its first years. The ultimate goal may be to have shade-loving plants growing under a grand oak tree, but establishing a shaded environment may take several years. In this situation, select plants that might prefer some shade but will tolerate full sun while waiting for the shade tree to grow.

The reverse is true when planting under existing shade trees. Mature trees such as pecans and oaks not only cast a large shadow, they also have roots that compete aggressively with nearby plants for nutrients and water. Contrary to popular belief, most tree roots extend out well beyond the limbs of the tree.

All plants require a certain amount of sunlight to grow properly and flower. Some require more than others. Plants listed as requiring full sun generally need 6 to 8 hours of full, direct sun. Although the plant may grow with less light, plant form, leaf shape, and flowering habit will likely be affected. Sun-loving plants grown under shaded conditions tend to have bigger leaves, spindly stems, and fewer flowers. Plants adapted to full sun in cooler temperature zones often must have a certain amount of shade just to survive in warmer climates. A good example is the rhododendron (Rhododendron catawbiense), which flourishes in full sun in the northern United States but must have some shade in Georgia to grow.

Shade-loving plants grown in full sun, however, require additional water to survive and may not grow properly. If they receive more than 4 hours of direct sunlight, they may wilt or even exhibit leaf scorch. Match the light conditions of the site to the light requirements of plants to reduce the need for supplemental water.

Match surface and soil drainage conditions to plant moisture requirements.

The amount of water in the soil can either be a problem or an asset in terms of plant survival. Determining the movement of water across the site surface and into the ground is critical to plant selection. For instance, dry areas may benefit from water redirected from sidewalks, gutters, or foundation drains during rain, but using drought tolerant plants in dry areas may be the best solution.

If poor soil drainage is the problem, make corrections prior to planting. Soil drainage is determined by topography, soil texture, and the presence of sub-surface hardpans. Removing and replacing the existing soil is often tried; this often proves unsuccessful because quality topsoil is hard to find, and the interface of the new and existing soil is critical to drainage. Depending on soil texture, amending a native soil with too little sand can actually reduce the soil drainage. For example, improving drainage of a clay soil with sand would require a sand content greater than 70 percent.

Mounding soil to create raised beds improves soil drainage, but if the drainage problem is caused by topography, a raised bed may not work. Any time new soil is added, take care to mix the two soils together to prevent drainage problems caused by layering effects. If a hardpan is causing the problem, using a piece of machinery to break up the impermeable layer will improve drainage. French drains, subsurface drainage systems, or other engineered systems are often required to correct drainage problems. These practices can be incorporated into the design by means of a false creek bed or gravel walk, but they can add considerable expense to a landscape project. It is easier and cheaper to select plants adapted to specific drainage situations than to remedy serious drainage problems. When drainage work beyond surface grading is required, consult with someone experienced in successfully treating such problems.

Select plants that grow well in the temperature ranges of the area.

The United States has been divided into zones for both cold hardiness and heat tolerance. Reference books and plant labels frequently list the cold hardiness zone for ornamental plants (www.usna.usda.gov/Hardzone/ushzmap.html). Nursery growers, retailers, and landscape designers use the cold hardiness information as a guide to indicate how well an ornamental plant performs in a given location. Figure 2-1 shows the hardiness zones in Georgia. This information is based on the average date of the last and first frosts of the season. A heat zone map has recently been developed, which classifies plants according to their tolerance of temperatures above 86 degrees F. Figure 2-1. USDA plant hardiness zone map for Georgia.

Cold and heat tolerance directly affect a plant’s water requirement. For example, a plant listed for hardiness zone 7 will survive in zone 8, but it will require more water and possibly more shade to survive. In a large parking lot, radiant heat temperatures soar well above the average air temperature of the area. As a result, the transpiration rate increases and plants require more water than normal. Although most ornamental plants will tolerate higher air temperatures, root growth is often stunted when the soil temperatures get extremely warm. Stunted root growth translates into poor plant development.

Figure 2-1. USDA plant hardiness zone map for Georgia.

Select plants that are regionally adapted to the average rainfall of the area.

Every region of the country is known for growing certain plants. Some plants are natives to the area, others are not. Some plants are salt tolerant. Others grow well in heavy clay soils. Plants suited to the regional conditions will grow better and use less irrigation water.

Much debate in recent years has been over the use of native versus non-native plants in the landscape. Some government agencies and municipalities have gone so far as to mandate the exclusive use of native plants on public lands. While there are many philosophical arguments for and against the use of native plants, from a water conservation point of view, a plant’s parentage does not matter. Selecting the best plant for the specific site conditions, regardless of its parentage, provides the best outcome.

Sometimes, a new variety discovered or developed in a particular region will be better suited to that region than the native species. Look for regionally adapted cultivars that have been evaluated for your area. A good example is red maple, the cultivar Acer rubrum ‘October Glory,’ which was selected because it is more heat tolerant than most of the other available cultivars.

Design Principles Affecting Water Use

Preserve established vegetation growing on a site; it has an extensive root system and requires less irrigation water than newly planted trees and shrubs.

Whenever possible, preserve native vegetation and avoid disturbing it. Existing plants have well-established root systems that have adapted to the moisture extremes of the region. Mature trees also provide immediate shade that would take many years for newly planted trees to provide. It is important to identify valuable plants prior to site work and to install protective barriers to preserve the native vegetation, which can later be incorporated into the new landscape design.

Space plants according to their mature size to reduce competition for water.

Densely planted shrubs are not only unattractive but require more water and maintenance. Densely planted shrubs encourage moisture-related problems around foundations and crawl spaces by reducing air flow. Over-crowding also increases the water requirements of plants since they compete for available moisture. Additionally, the dense canopies are havens for insects and diseases. The foundation of a building, with its “green necklace” of plants wrapped around it, is the most commonly over-planted area (Figure 2-2).

Figure 2-2. "Green necklace" around foundation of building.

Many clients want an “instant landscape” and insist on spacing plants closer than their mature size indicates. Changes to the landscape plan are often made during installation because smaller plants just “look too far apart.” It is not uncommon to see foundation shrubs such as dwarf yaupon holly (Ilex vomitoria ‘Nana’) planted as close as 24 inches, even though its mature width can reach 48 inches. A good reference book, Manual of Woody Landscape Plants, lists the mature spread of plants and is a useful guide in determining proper spacing.

Concentrate seasonal color in small, high impact areas to reduce overall water requirements.

Most annuals used in seasonal color displays are shallow-rooted plants and have high water requirements. Showy color beds have become a common practice in today’s landscape. They draw attention, and add excitement and visual interest into the landscape. The vivid color, not the size, of the planting attracts attention.

Concentrating color in small, highly visible areas saves water, time, and money. Tall, colorful plants, such as canna lilies (Canna sp.) can be used to make a planting stand out. Bold colors such as red and orange help smaller flower beds attract attention. Perennial plants, flowering shrubs, or shrubs with colorful foliage can be used in or around a flower bed to add height and depth to a small planting. Herbaceous perennials and shrubs tend to have more extensive root systems than annuals, are less costly to maintain, and are more water efficient than shallow-rooted annuals.

Locate flower beds where they will provide the greatest impact yet be close to available water sources. Another alternative to large in-ground flower beds is to use large containers placed in high impact locations. By using containers large enough for adequate root growth and by carefully selecting plants for container conditions, high-impact color can be achieved that requires less water than in-ground beds.

Avoid constructing raised beds under trees due to root competition for available water.

Creating raised beds under trees can be harmful to tree roots and ultimately results in root competition for moisture. Large trees have extensive root systems that compete with adjacent plants for water and nutrients.

A common remedy is to create a raised bed under the tree by adding several inches of new soil over the existing grade. This practice is harmful to the tree because it restricts the amount of oxygen and nutrients reaching the tree roots. When placed around the trunk, it may also promote wood decay. If the tree survives, its roots will eventually grow into the added soil and compete once again for water and nutrients.

Develop a landscape plan BEFORE designing an irrigation system.

Irrigation systems work more efficiently and use less water if designed after the planting plan has been deter-mined. In the rush to complete a new home or commercial building, irrigation systems are often installed prior to developing a landscape plan. This is particularly true in subdivisions that have covenants requiring the installation of a certain amount of turfgrass, plants, and an irrigation system. After moving in, the homeowner decides to supplement the initial landscape planting and finds that existing sprinklers are not located properly and timers do not have expansion capacity.

Planning for future irrigation needs is easy if done before installing the irrigation system. Larger timers can be used to accommodate future zones. PVC sleeves can be placed under paved surfaces to provide easy access for future water lines, and control valves can be placed in an in-ground box adjacent to areas for future planting. The irrigation system should fit the landscape plan instead of dictating the landscape design.

Incorporate shade trees into the landscape to reduce evaporative loss.

Large trees provide shade, reduce stormwater runoff, stabilize soil, reduce evaporative water loss, and reduce summer air conditioning needs. Place shade trees on the south and west sides of a building to block the sun but at least 20-30 feet away from the building, so the tree will not cause future damage from falling limbs or brushing against the building.

Consider grouping several shade trees together to create a shaded bed for plants. It may take several years to turn a sunny area to shade, so wait until the trees have grown enough to provide shade before planting underneath them. Most oaks and maples are excellent choices for shading the landscape. Several different species and cultivars are adapted to Georgia. A listing of plants can be found on the Georgia Cooperative Extension website at: http://pubs.caes.uga.edu/caespubs/pubcd/B625.htm.

Select and group plants according to their water needs and drought tolerance.

Grouping plants with similar water requirements in the landscape allows more precise irrigation design and water management. All plants require a certain amount of water to grow to maturity. Some plants, such as yucca (Yucca filamentosa), can tolerate periods of limited rain-fall. Others, like viburnum (Viburnum sp.) and rhododendron (Rhododendron catawbiense), require a steady supply of either rain or irrigation to survive. Some plants, such as Bald cypress (Taxodium distichum) and Virginia sweetspire (Itea virginica), can tolerate standing water for extended periods. When making a final plant selection, list the plants and group them according to irrigation needs. Look for alternatives when moisture-requiring plants are specified for non-irrigated areas. Understanding the individual needs and tolerances of plants will help in selecting and grouping plants in the landscape.

Divide the landscape into water-use zones.

Divide the landscape into three water-use zones: high, moderate, and low. High water-use zones are highly visible areas of the landscape, such as the entrance to the property or building. In these zones, plants are irrigated as needed to promote optimum growth and aesthetic appearance.

Moderate water-use zones are transition zones, bridging the high and low water-use zones. In these areas, established plants are watered only when they show signs of moisture stress. Plants that require some irrigation during periods of limited rainfall, such as dogwoods (Cornus florida), azaleas (Rhododendron sp.), and hydrangeas (Hydrangea macrophylla), could be planted in moderate water-use zones. Low water-use zones are low impact areas or background areas viewed from a distance. Beds of mulch or drought tolerant plants would be used in low water-use zones because they are not irrigated once established.

Avoid small, irregular-shaped island plantings in turfgrass areas because they are difficult to irrigate.

Isolated islands of individual trees or shrubs in the middle of turfgrass are difficult to irrigate properly and contribute to a disorganized design. Because turfgrass is a tough competitor for water and nutrients, landscape plants perform better if planted in larger groupings with a sufficient amount of mulch around them. The bed line of the mulched area can then be used to tie the plants together visually and help create unity in the landscape. For a large solitary tree, provide an adequate amount of mulch to cover as much of the tree root zone as possible. The mulched area should match the width of the root ball at planting time, and then gradually expand as the tree canopy expands. Make allowances in the landscape plan for extending the mulch area, either by leaving enough room for expansion or by planning to incorporate the trees into larger mulched beds as they grow.

Grouping plants is not only a good design practice, it also reduces water use by allowing more efficient irrigation layout. Mulched areas under grouped plants are a better environment for root growth. To create order in the landscape, arrange plants in groups of three, five, or seven. Group plants with similar colors, textures, or shapes. This helps unify the landscape. Mulched areas with wide, curved bed lines create a more natural or informal look in the landscape. When carefully selected and spaced properly, plants within mulched areas can be watered separately from adjacent turfgrass areas. This helps conserve water.

Consider irrigation sprinklers when designing turfgrass areas and planting beds.

Limitations of irrigation sprinkler patterns can affect the water available to irrigate a landscape. For example, most irrigation sprinkler heads water in a circular pattern, so lawn areas should be designed with smooth, flowing curves to match the available irrigation distribution patterns. Sharp-angled, irregularly shaped, and small rectangular areas often receive too much or too little water, because irrigation sprinkler heads are not designed to cover every possible shape that can be drawn on paper. While irrigation should not dictate the entire design, consideration of available sprinkler patterns will help prevent misuse of water. Designing turfgrass areas that match available sprinklers can also help reduce problems such as watering sidewalks and streets, or accidentally watering adjacent mulched areas.

For herbaceous plants and shrub installations, it makes sense to arrange the plants according to height in order to take advantage of the upward angle of most irrigation sprinklers. A large plant located along the edge of a bed will block the stream of water, preventing the plant behind it from receiving the proper amount of water. Plantings adjacent to buildings often require sprinklers to be placed on risers in the back of the planting in order to prevent irrigation water from contacting the building. An alternative in this situation is to install drip irrigation.

Move or eliminate plants not suited to the existing site conditions and irrigation.

When landscapes are designed and installed without regard to site conditions or water conservation practices, problems can occur. Some plants may require frequent watering to survive, while others are over-watered. When this happens, it may be necessary to relocate some plants and replace others. Most landscape plants can be successfully transplanted when they are dormant. If plants are too large to move, they may have to be left in place to fend for themselves or removed if they become unattractive. Unattractive plants can be cut down to the ground and treated with an herbicide to prevent re-sprouting. Then a more appropriate plant can be placed in its spot.

BMPs to Improve Water Conservation through
Proper Landscape Installation and Maintenance

Robert Westerfield, Extension Horticulturist
Gary Wade, Extension Coordinator, Department of Horticulture

Research has shown that proper selection, installation and maintenance of ornamental plants can greatly increase their survivability and performance in the landscape. Follow sound planting and care procedures for ornamentals to help conserve water in the landscape. Properly sited plants that have been carefully planted and maintained usually require less irrigation and are less prone to diseases and insects. The following BMPs will help conserve moisture and will also promote overall health and vigor of the ornamental plants.

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	Plant woody ornamentals and herbaceous perennials in the fall and winter; there will be less demand for water and nutrients by the top, allowing more energy and food for root growth. While the crown of a plant shuts down for winter, the roots continue to grow. A plant installed during cooler temperatures suffers less stress because this allows the plant time to develop a strong root system before dry, hot weather hits.
	Prepare the planting bed properly by deep tilling to a depth of 8 to 12 inches. When planting individual plants, dig a wide planting hole to provide a favorable rooting environment. A large planting hole and deep tilling will allow roots to expand more easily and the plant will develop a strong root system, better able to sustain the plant during times of drought.
	Add appropriate amendments to the planting bed, when necessary, to improve the physical properties of the soil, such as water retention, water infiltration, or drainage and/or to enhance the mineral content and microbial activity. Soil amendments (e.g. organic matter, compost) contribute to an overall healthier plant environment, allowing easier root development and fewer soil related problems.
	Avoid placing granular general-purpose fertilizers in the planting hole. These products can dehydrate and damage the roots of plants. Only slow-release fertilizer should be added to the planting hole if fertilizer is needed. General purpose fertilizer can be applied to the planting surface as indicated by a soil test after roots have become established.
	Give special care to seasonal color beds because of their high demand for water and maintenance. Plant seasonal color on well amended, raised beds to develop a healthier and more water efficient landscape.
	Apply 3 to 5 inches of mulch on the soil surface after planting to conserve soil moisture and help maintain a uniform soil temperature, while preventing weeds that compete with plants for light, water, and nutrients. Fine-textured mulches prevent evaporative water loss better than coarse-textured mulches. For best water efficiency, mulch out to the drip line of plants but do not pile mulch deeply against the trunks of trees and shrubs.
	Wait until you see moisture stress symptoms before irrigating. An abnormal gray-green color or obvious wilting indicate that a plant needs water. Water only when plants truly require it to help develop a deep, strong root systems and prepare plants to survive during drier periods.
	Irrigate at night or early in the morning to conserve moisture and to avoid evaporative loss of water. Water between the hours of 9 p.m. to 9 a.m. to conserve moisture and help prevent disease problems.
	Water deeply to encourage strong, healthy root systems that are water-efficient. Avoid light, frequent irrigation that encourages shallow rooting. Infrequent but thorough watering is the best formula to a healthy landscape. Water long enough to penetrate the soil to a depth of 6 to 8 inches.
	Test soil to provide the best gauge for fertilization requirements of the landscape. A healthy landscape is more water efficient. Proper nutrition enables plants to better use available water and to conserve it during dry periods. Over-fertilization increases plant stress during times of drought.
	Use slow-release fertilizers to provide a more even uptake of nutrients by the plant, resulting in a more uniform, water-efficient growth rate. Slow-release fertilizers are actually more cost efficient, decrease the chance of root burn, and allow the plant a season’s source of nutrition.
	Avoid over-fertilization. Over-fertilization can cause excessive plant growth and additional water requirements.
	Avoid fertilizing during periods of limited rainfall or high temperatures. Additional fertilizer can cause root burn and other damage on drought stressed plants.
	During times of prolonged drought, cut back annual and perennial flowers several inches to reduce moisture loss. Reduction in the plant’s overall canopy will cut down on water loss through transpiration.
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Installation

Plant woody ornamentals and herbaceous perennials in the fall and winter; there will be less demand for water and nutrients by the top and more energy and food available for root growth.

Correct planting procedures are essential to establishing a water efficient landscape. Fall is the ideal time to plant most woody trees, shrubs, vines, and ground covers as well as herbaceous perennials. Temperatures are moderate and less stressful to plants than the hot temperatures of late spring and summer. Plants require less frequent irrigation and are less likely to suffer sun scorch or heat-related stress. In addition, fall-planted ornamentals continue to develop a strong root system even after their tops have gone dormant. Fall and winter establishment will benefit the plant tremendously the following spring as the well-established root system can readily funnel water and nutrients to the above-ground growth. Ornamental plants that have a cold requirement (e.g. flowering bulbs) or are sensitive to frosts and freezes, such as annuals, are best planted according to recommended planting dates.

Prepare the planting bed properly by deep tilling. When planting individual plants, dig a wide planting hole to provide a favorable rooting environment.

An ideal soil for optimal plant health contains air space for good drainage and good water holding capacity. It contains some organic mineral matter that supplies nutrients and improves soil structure and texture. A poorly drained and compacted soil can stunt root systems and may result in wasted water through runoff and evaporation. A poorly drained soil can also lead to disease problems later, shutting down a plant’s ability to function properly.

Deep tilling the entire planting bed to a depth of 8 to 12 inches is one of the best and most cost effective ways to improve the planting site. Tilling will break up and loosen the existing soil, allowing easier plant root penetration and water infiltration. Deep tilling will help establish a plant more quickly with a healthier root system that can handle moisture extremes.

When planting solitary plants in undisturbed soil, make the planting hole as large as possible. Dig the hole at least twice the size of the diameter of the root ball. Set the top of the root system level with the soil surface, or slightly higher if the soil is prone to settling. Planting too deeply will result in root suffocation, and shallow planting may result in root death from dehydration.

Before planting balled-and-burlapped plants, cut the wire or cord around the trunk and pull back the burlap from the top one-third of the root ball. These can serve as an impediment to root growth if left in place. When planting container grown plants that are root bound, use a knife to make four to six shallow, vertical slits around the root ball and spread out the root system within the planting hole. This will allow water to readily penetrate the root ball while encouraging new root growth.

Add appropriate amendments to the planting bed, when necessary, to improve the physical properties of the soil. This improves water retention, water infiltration, drainage, and enhancement of mineral and microbial content.

Most Georgia soils are low in organic matter, so it is usually beneficial to incorporate an organic amendment such as compost during the tilling process. Apply at least 4 inches of the amendment on the soil surface and thoroughly incorporate it into the native soil to a depth of 12 inches.

There are two broad types of soil amendments: organic and inorganic. Organic amendments come from something that is or was alive. Inorganic amendments are either mined or man-made. Examples of organic amendments are compost, peat moss, manure, and biosolids.

Organic amendments improve the water retention, oxygen infiltration, and nutrient-holding capacity of a soil. They also provide good environments for beneficial fungi and bacteria, earthworms, and other living organisms that improve nutrient availability and aeration of the soil.

Examples of inorganic amendments are vermiculite, perlite, pea gravel, shale, and sand. They are typically used to improve soil drainage. Unlike organic amendments, these products have little nutritional value.

Hydrogels are synthetic polyacrylamide or starch-based organic compounds capable of holding several hundred times their weight in water. They improve the water-holding capacity of soil while improving soil aeration as they swell and shrink according to fluctuation in soil moisture. In the landscape industry, they are used in containerized plantings and seasonal color beds, but their effectiveness and economic viability for use in shrub and tree planting remains questionable.

Other considerations when selecting soil amendments include:

• carbon to nitrogen (C:N) ratio;
• how long the amendment will last in the soil (coarser type amendments typically will last longer than fine ones);
• cost and availability;
• salt content and effect on soil pH.

Avoid placing granular general-purpose fertilizers in the planting hole; they can dehydrate the roots of plants.

Granular general-purpose fertilizers such as 10-10-10, 8-8-8 or 16-4-8 are chemical salts and may burn the tender roots of newly planted ornamentals. They may actually dehydrate the roots and cause the plant to demand more water in the planting hole. Use general-purpose fertilizers on the soil surface once the plant is established. Spread the fertilizer away from the base of the plant out to the drip line area. Do not pile the fertilizer to one side of the root system as this might burn roots as well.

In general, fertilizers are not a necessary ingredient in the planting hole. The plant will have enough stored energy in its roots to get established. One exception to this rule is seasonal color plantings. It’s a common practice in the landscape industry to place slow-release fertilizer in the planting hole beneath annuals and perennials. This assures a season-long supply of nutrients and results in stronger growth compared to broadcast application.

Give special care to seasonal color beds because of their high demand for water and maintenance.

Seasonal color beds are short-lived, shallow-rooted, and demand a uniform supply of water and nutrients for optimum growth. Amended beds are essential to promote good health and water transfer for annuals. On new beds, add 4 inches of organic matter to the soil surface and incorporate it to a 12-inch depth.

Raise the planting bed approximately 10 to 15 inches above grade to assure good drainage and improve the visual appeal of the planting. Raised beds assure good infiltration and movement of water in the soil, prevent possible waterlogged conditions, and result in a healthier rooting environment.

A slow-release fertilizer added to the planting hole gives a uniform nutrient supply throughout the season and a healthy fibrous root system that makes best use of available water. Additional fertilizer may be needed to provide nutrition throughout the growing season.

Apply 3 to 5 inches of mulch on the soil surface after planting to conserve moisture and help maintain a uniform soil temperature, while preventing weeds that compete with plants for light, water, and nutrients. Fine-textured mulches prevent evaporative water loss better than coarse-textured mulches.

Mulches have many benefits in the landscape. They hold moisture in the soil, prevent weeds, inhibit certain soil-borne foliar diseases, insulate the roots of plants from temperature extremes, and provide a protective barrier around the plant to keep lawn mowers or string trimmers away. They also provide a pleasing background contrast for plants.

Common mulches include pine straw, pine bark nuggets, hardwood chips, and cypress shavings. Fall leaves are also a good mulch, provided they are shredded prior to use. Grass clippings are not good mulch unless they are composted first, because they tend to mat down and inhibit the flow of water and nutrients into the soil. They may also introduce weeds into the planting bed.

Inorganic mulches such as rock, gravel, or marble are good soil insulators, but they are not good choices for Georgia landscapes because they absorb and radiate heat in the planting bed, increasing water loss from plants.

Apply mulches 3 to 5 inches deep. When mulching trees, remember that the root system of a mature tree may spread two to three times the canopy width, so mulch as large an area as possible.

Landscape fabrics are sometimes used under organic mulches to prevent weeds and to serve as an added barrier to moisture loss. Make sure these fabrics are free from soil on top as weeds may germinate. Do not use landscape fabrics in areas that tend to stay wet for long periods of time.

Irrigation

Watch for moisture stress symptoms before deciding to irrigate. An abnormal gray-green color or obvious wilting are good indicators that a plant needs moisture.

Most healthy established woody ornamental plants in the landscape can survive weeks without supplemental irrigation. In fact, over-watering during periods of limited rainfall and the root rot which results has killed more plants than drought.

The best guide in determining when to water is the plant itself. Wilting or a pale grayish-green color are the most common symptoms of moisture stress. Some plants, such as annuals and herbaceous perennials, may need water more often than woody ornamentals because of their limited root system. By targeting irrigation to only those plants in the landscape that need water, you not only save water, time, and money, you also avoid potential disease or insect problems from over-watering.

The best time to irrigate is at night or early in the morning to conserve moisture and to avoid evaporative loss of water.

Irrigating during mid-day results in evaporative water loss and inefficient use of water. Irrigating between 9 p.m. - 9 a.m. avoids evaporative water loss.

Deep watering encourages strong, healthy, water-efficient root systems. Avoid light, frequent irrigation that encourages shallow rooting.

Frequent, light irrigations encourage shallow rooting. As a result, roots dry out more quickly and the plant’s demand for water increases.

When irrigating, apply enough water to wet the soil to a depth of 8 to 10 inches to promote deep root growth. Remember to change irrigation frequency and amount according to changes in rainfall patterns. Make certain automated systems have a rain sensor that prevents them from operating during rain.

Apply water slowly using a hand-held hose, drip or trickle irrigation, micro-sprinklers, or an ooze hose. The amount and frequency of irrigation depend on the type of plant, the soil type, and the time of year. Plants in sandy soils normally require more frequent irrigation than those growing in clay soils.

Fertilization

A soil test provides the best gauge for fertilization requirements of the landscape. A healthy landscape is more water efficient.

Soil sampling through the local county Extension office is the best and most affordable way to assess the fertilizer needs of plants. In addition, a soil test is the only scientific way to determine whether lime is needed to adjust soil pH. Applying lime without a soil test may cause nutritional problems. Plants cannot use fertilizer properly unless the pH is adjusted correctly.

Proper nutrition promotes optimum plant growth and resistance to diseases, insects and environmental problems. Plants receiving proper nutrition also will be more water efficient. They have a healthier, larger root system that can better sustain the plant during periods of limited rainfall.

Slow-release fertilizers provide a more even uptake of nutrients by the plant, resulting in a more uniform growth rate. Excess nitrogen or high nitrate fertilizers cause rapid growth and an increased demand for water.

Because slow-release fertilizers are coated and release nutrients over time, plants grow at an even rate instead of in bursts of new growth. This results in a more water-efficient plant. There is also less chance of salt injury from slow-release fertilizers, as the protective coating only releases a small amount at a time.

Slow-release fertilizers may also be more cost effective than traditional soluble fertilizers because they supply nutrients over an extended period.

Avoid over-fertilization. Excessive fertilizer can be harmful to the plant’s water efficiency and health, and to the environment.

Fertilizers are salts, and excess amounts can damage plants by drawing water from the roots. Plant cells in the roots begin to dehydrate and collapse, resulting in plant roots being “burned” or dried out to a point where they cannot recover.

Over-fertilizing can cause water quality problems as excess fertilizer enters storm drains, and eventually streams and rivers, through run-off and leaching. Leaching is the effect of nutrients being washed through the lower soil layers and into the groundwater supply.

The frequency of fertilization depends on the type of plants, the age of the plants, and the type of fertilizer used. In general, most established woody ornamentals need only one application of slow-release fertilizer per year. Annuals benefit from light, monthly applications of a water-soluble fertilizer or the use of a slow-release fertilizer product. Newly planted ornamental trees and shrubs may benefit from light additions of fertilizer applied in three applications during the growing season (March, May and July).

Avoid fertilizing during periods of limited rainfall or high temperatures.

Plants absorb fertilizer when they are actively growing. Fertilize most plants during the early spring from the time they break dormancy until they taper off in their growth in fall and go dormant. It is a good idea to irrigate immediately after an application of fertilizer.

During periods of drought, reduce the amount of fertilizer applied and the frequency of application in non-irrigated areas as plants may be stressed and do not need to increase their canopy from nutrient uptake.

Pruning

During times of severe drought, cut back annual and perennial flowers to reduce moisture loss.

If irrigation is impossible because of public watering restrictions, cutting back herbaceous annuals and perennials that are wilting will reduce the water loss from leaves by taking pressure off the root system. Be sure to provide mulch to help keep moisture in the soil.

Maintain pruning equipment in good order to improve the health and water efficiency of plants.

Dull hand-pruners will not cut cleanly and will cause cut branches to be frayed. Frayed branches will not recover as quickly as those cut cleanly by sharp blades and will allow more water loss. In addition, poorly cut branches may be a site for disease penetration that can weaken the plant.

Learn to sharpen tools properly with a stone, and keep them clean and oiled. Buy the best tools you can afford.

Additional References

Web sites:

http://www.caes.uga.edu/departments/hort/extension/index.html

http://ohioline.osu.edu/lines/hygs.html

http://www.hgic.umd.edu/

http://www.gaurbanag.org

Books:

Georgia Gardener’s Guide, by Erica Glasener and Walter Reeves
Your Florida Landscape, by Dr. Robert Black and Dr. Kathleen Ruppert
Month by Month Gardening in the South, by Don Hastings and Chris Hastings
The American Horticultural Society – Pruning and Training, by Christopher Brickell and David Joyce

BMPs for Landscape Irrigation System
Water Conservation

Rose Mary Seymour, Department of Biological and Agricultural Engineering
Kerry Harrison, Extension Engineer

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	Base the irrigation system design on the site landscape design, water use zones, and water use of the matured landscape.
	Divide irrigation zones according to water supply amount available.
	Use appropriate applicators for the plant materials and to fit the irrigated area for each zone.
	System design should fit the site’s soil type, topography, and climate.
	System design should consider the time available for applying irrigation.
	Installation should follow the irrigation design specifications and component manufacturer’s specifications.
	Upon completion of the irrigation system installation, conduct a field performance audit to determine distribution uniformity and precipitation rates for each zone.
	Use a separate or secondary meter for the irrigation system.
	Size meters, pipe, and pumping systems for optimal performance.
	Use lower trajectory sprinklers to minimize wind and evaporative losses.
	Include rain shutoff and other sensor devices as appropriate for site conditions.
	Provide a system controller that has flexibility and capacity.
	Use soil moisture sensing based or real-time weather based control for irrigation management.
	Use the short cycle feature for low permeability soils or steep slopes to prevent runoff.
	Perform a thorough irrigation system inspection annually.
	Repair or replace damaged or worn components in a timely manner, preferably before the next irrigation application.
	Conduct a field performance audit on an irrigation system every 5 years.
	As plants grow and mature, trim or remove vegetation that blocks applicator pattern to preserve the intended distribution of irrigation water.
	Carry out a regular winterization of the irrigation system if it will not be used for an extended period of time in the winter.
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Introduction

The water conservation practices in this chapter can reduce water waste from landscape irrigation systems. Along with providing efficient water use and uniform distribution of water in the landscape, irrigation systems must have economic installation costs and operating costs, and be simple to operate and adjust. There are many local codes and state laws that the irrigation installer and designer must know to create an efficient design and to install an irrigation system correctly. Many of the codes, laws, rules, and regulations do not pertain directly to water use efficiency, but some do, and those will be discussed.

The water conservation practices in this chapter are considered the primary responsibility of landscape irrigation designers, installers, and commercial landscape maintenance personnel. The landscape industry also has a responsibility to provide education to customers and to assist the customer or owner/operator in operating an irrigation system efficiently. Practices and suggestions are included for providing customers with tools and information that will enable them to do their part in efficient irrigation practices.

Irrigation system design, installation, and maintenance should be performed by licensed, certified and, when appropriate, bonded professionals. While Georgia does not have certification requirements for irrigation professionals, the Irrigation Association (IA) (http://www.irrigation.org) has a national certification program. To become certified, irrigation professionals can contact the IA or the Georgia Irrigation Association (http://www.gairr.org). Contact information for these two sources can be found at the end of the chapter. Certification indicates that a contractor or maintenance company is competent and takes a professional approach to providing services.

Irrigation System Design

Base the irrigation system design on the actual site landscape design, water use zones, and water use of the matured landscape.

Efficient irrigation design begins with a good landscape design. The landscape design should be the basis for the irrigation system design whether the landscape is put in place before the irrigation system or after. Unfortunately, it is much too common for a new development with similar lot sizes to install irrigation systems with a “one size fits all” approach. While this approach usually costs less in design and installation costs, it is the surest way to create poor efficiency and uniformity of irrigation systems because of the variability from lot to lot in soils, topography, landscape design, and microclimate influences.

Irrigation system design should include specifications of the manufacturer, model number, and nozzle size for each applicator. A drawing of the system layout with all valves, irrigation zones, control equipment, and points of connection labeled should also be included. The layout should include key landscape features such as trees, fences, and buildings so the installer and owner/operator can easily locate components of the system according to the layout.

In the design documents provided to the customer, the designer should diagram the area of each irrigation zone, the location of all points of connection, control sensors, valves and sprinkler applicators, and areas where drip irrigation will be used. Other information to have in the design document for each irrigation zone is water-use zone and plant materials, soil types, root zone depths used for design, estimated precipitation rates, expected distribution uniformity, area square footages, and gallons per minute flow rate for each valve and applicator. Figure 4-1 is an example of a good and simple design diagram to provide an owner/operator.

Figure 4-1. This "as-built" diagram would be adequate for owner/operator maintenance and management of the irrigation system. The specifications of gallons per minute information will be needed for sizing replacement nozzles correctly.

Group plant materials into water-use zones in the landscape design. A water-use zone is an area of the landscape with all the plants having similar water requirements. If the landscape is laid out in water-use zones, then the irrigation system can be designed to allow independent control of irrigation for the different water use zones. Figure 4-2 shows a landscape design layout.

Figure 4-2. Landscape design layout.

The water-use zones are designated as high, moderate and low use zones. Once plants are established, the low water-use zones should not need irrigation. However, these plants will need irrigation during the establishment phase. The moderate and high water-use zones will need similar irrigation coverage and uniformity of application, but will be run on different schedules that suit the needs of the plant material for each water-use zone. For more information on water-use zones, refer to Chapter 2 of this publication or to Georgia Cooperative Extension Bulletin B-1073 at http://pubs.caes.uga.edu/caespubs/pubcd/B1073.htm.

Irrigation systems in landscapes are presumed to have a lifetime of 15-20 years. Base the water supply and irrigation zone layout on the water needs of the mature landscape, so the system will be able to apply sufficient water for the lifetime of the system. It is much easier and less stressful to plants to run a larger irrigation system less frequently, and for shorter periods of time, while the landscape is young rather than trying to add additional water capacity or re-zone the system as the landscape matures and ages.

During the design process, consider the mature landscape, shrubs, and trees so irrigation equipment is not blocked or hindered. Take this into account as the applicators are put in place in the design. Figure 4-3 shows an example of an irrigation system design that did not plan for the landscape design correctly. The irrigation head is completely blocked for part of its application arc by a tree.

Figure 4-3. Poor design and/or installation of the applicator location wastes water because the sprinkler pattern is blocked by a tree 35 inches from the applicator.

Divide irrigation zones according to water supply amount available.

Water for irrigation can be pumped from an on-site well or storage, or it may come from a municipal supply line. Whatever the source, the water supply delivers a limited volume and pressure where the irrigation system is connected. An irrigation zone is a set or grouping of irrigation applicators isolated from the rest of the irrigation system by a control valve. The valve is used to start or stop irrigation. The area covered by an irrigation zone is limited by the amount of water that can be delivered to the zone from the water supply. A large contiguous area may be divided into two or more irrigation zones since the water supply does not have a sufficient flow rate to irrigate the whole area at the required operating pressure.

Use appropriate applicators for the plant materials and to fit the irrigated area for each zone.

Many kinds of irrigation application devices can be used in landscapes. Irrigation zones may be differentiated in the design process because different application devices or different management is needed from one area to the next. Keeping different kinds of application devices separated into different irrigation zones allows each zone to be operated in a way that is consistent with the application rate for similar application devices.

The two main categories of irrigation application devices are sprinkling type applicators or micro-irrigation applicators. Sprinkling application devices spread water in a broadcast manner over the whole area to be irrigated, mimicking rainfall, while micro-irrigation devices do not broadcast water over an entire area. To spread water evenly over an area, sprinkle application devices must have overlap of their water streams. Micro-irrigation application devices, also called drip irrigation, apply water directly to the root zone areas of plants, minimizing the wetted area of the soil surface. They do not have overlapping wetting patterns.

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Figure 4-4. Spray applicators are pop-up style heads that will let the applicators recede below the turfgrass when irrigation stops.		Figure 4-5. These two rotor applicators have over-lapping radius of throw to get a more even broadcast application of the irrigation water.

Sprinkle applicators can be sprays or sprinklers. Spray applicators do not have any movement of the water streams that form the pattern, or wetted area, of the spray, and have no moving parts in the spray head. Figure 4-4 is a picture of spray applicators operating in a landscape. Sprinklers have moving water streams broadcasting water over an area that forms the pattern of the sprinkler. Sprinkler types include rotor, impact, and rotator style movements of the water streams. Figure 4-5 and 4-6 picture a rotor and rotator applicator, respectively. Most sprinkler or spray applicators can be housed in pop-up canisters that recede below the soil level when not applying water. They may also be placed on top of a riser, a vertical length of pipe, to provide broadcast application above taller plants. Table 4-1 has a summary of some key characteristics of sprinkle type applicators. Note that the water application rates and pattern sizes of the different sprinkling applicators vary considerably. The differences in the various applicator types require that they be managed differently and that they be laid out in a design differently. Their differences make them suitable for different kinds of landscape areas.

Figure 4-6. The pop-up rotator applicator has several individual small moving streams rather than the one large stream of a rotor applicator.

Micro-irrigation devices include drip emitters, inline emitters in rigid lateral pipe, drip tape, micro-sprinklers, and micro-sprays. The most common micro-irrigation device in landscapes is the drip emitter, which is in-stalled along a lateral pipeline laid on the surface of the ground. Drip emitters are positioned along lateral pipelines where needed to drip water over the root zone of individual plants. Figure 4-7 shows a drip emitter that has been installed into a lateral pipe. Semi-rigid poly-ethylene pipe laterals have inline emitters embedded at regular intervals such as 12 inches within or along one side of the pipe. Drip tape is a flatter, more flexible polyethylene hollow “tape” with emitting devices evenly spaced along the tape. Drip tape and inline emitter piping can be buried or be placed at the soil surface. Micro-sprays and micro-sprinklers have low volume application rates similar to drip emitters, but the low volume of water is spread out over a larger area than with drip emitters. Micro-sprinklers are similar to micro-sprays except they have moving parts and water streams. Figure 4-8 is a picture of a micro-spray that is not applying water. Neither micro-sprays nor micro-sprinklers are designed to have overlapping water patterns like other sprinkling application devices. These micro-sprays or micro-sprinklers are needed where soils have a low water holding capacity and high permeability, so that the water applied does not move below the root zone without adequately refilling a large area of the root zone.

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Figure 4-7. A drip emitter connected to a pipe lateral at each plant will provide water directly to the soil surface. This emitter and lateral are on the ground surface and would usually be covered by a layer of mulch.		Figure 4-7. This is a micro-spray applicator positioned above a mulch layer by a plastic stake driven into the soil. Micro-sprays and micro-sprinklers must be above the mulch layer so the mulch will not inhibit their water spray or sprinkling patterns.

Some plant materials such as herbaceous perennials and woody plants are more amenable to drip irrigation, while turfgrass areas will be better suited to the broadcast application of sprinkler irrigation. The appropriate system for herbaceous annuals depends on their spacing and growth habit. Where there are steep slopes and plant materials other than turfgrass, drip irrigation is a better system since it will apply water slowly and prevent runoff. For turfgrass on steep slopes, low application rate sprinklers are preferred.

The designer should choose applicators such that impervious surfaces are not irrigated. Spray applicators come in many shapes to accommodate difficult spaces. Both sprays and sprinklers can have arcs that are less than 360 degrees to prevent watering impervious areas. Most sprinklers and sprays come in standard one-quarter, one-third, half, three-quarter, and full circle arcs. There are also sprinklers and sprays with adjustable arcs for spaces that need more or less than the standard arc sizes. When these partial or adjustable arc applicators are used, the flow rate of the nozzle should be proportionately less than a comparable full circle nozzle flow rate based on the ratio of the reduced arc area to the full circle area.

For more information on different kinds of applicators, please refer to Georgia Cooperative Extension Service Bulletin 894 at http://pubs.caes.uga.edu/caespubs/pubcd/B894.htm.

Any irrigation device requires a certain operating pressure and flow rate. The operating pressure results from the static pressure at the upstream start of the irrigation system minus the pressure losses in the delivery lines and equipment of the irrigation system. Static pressure is the pressure measured when there is no flow, i.e. reading a pressure gauge just behind or at a closed valve is the static water pressure at that valve.

Where a municipal water supply is the irrigation source, new land development downstream along the municipal supply can mean reduced static pressure in the upstream pipes. For this reason, the system design should factor in a 10 percent reduction in static pressure of the water supply to accommodate future expansion of the supply system.

To ensure adequate pressure for all applicators, analyze pressure losses due to distribution and topography for each irrigation zone throughout the system to ensure applicators at locations with the least pressure are adequately pressurized. Careful choices in the layout of distribution lines can reduce the amount of pressure difference among the applicators within an irrigation zone, which will provide a more uniform distribution of water to the applicators.

If the actual operating pressure is higher than appropriate for the applicators, the system uniformity will be compromised. Pressure regulators are needed where excess pressures would occur. High pressures are common at the base of steep slopes.

System design should fit the site’s soil type, topography, and climate.

A good design includes obtaining direct knowledge of site conditions and not relying only on plot plans to generate a design. Taking measurements on site to verify actual pressure and flow rate is necessary for proper sizing of equipment. Also, base design on the soils at the site with adaptations made for soil variability around the site. While at the site, the designer should record possible microclimate variations. Important things affecting microclimate include the topography, shade from buildings and other structures, impervious areas, and soil conditions. The plant materials, the soil type, and micro-climate influences will dictate different water needs for different areas. The soil type and site topography influence how the irrigation water will infiltrate into the soil and the potential for runoff problems around the site.

Precipitation rate is defined as the depth of water applied per hour. This rate of water applied is comparable to rainfall rate. Ideally, an irrigation zone’s precipitation rate would not exceed the ability of the soil to absorb and retain the water applied during one application. For sprinkler zones in high clay content soils, heavily compacted soils, or on steep slopes, it may not be feasible to have a precipitation rate less than the basic infiltration rate. At such sites, low application rate is important, but flexibility of the control equipment is also needed to prevent runoff. The irrigation system controls should allow for intermittent water application for a series of cycles during one application event. Irrigation can be applied for repeated short intervals, switching the water between several irrigation zones. This allows the water to infiltrate between irrigation cycles, preventing the runoff that would occur with one long application period.

Typical weather conditions affect the changes in water needs with changing seasons. Hotter, drier, and windy climate conditions will mean higher water use for the plants in a landscape. Climates where maximum temperatures are not as high or do not persist will have lower water needs for plants. Because humid air is already close to saturation with water vapor, humid conditions limit the transpiration rate of plants. As a result, plants use less water in humid conditions than they would at the same temperature and sunlight levels in a drier climate.

Topography can also affect the pressure within the system. The site topography must be considered in laying out irrigation zones. Steep areas can be isolated for better management in irrigation zones separate from zones for flatter areas. This allows for better pressure control and better irrigation management for topography differences. Flat areas at the base of a steep area may receive some runoff from the steep area and will need less irrigation water.