Arizona's golf and sod industry generates $280 M year-1 in revenue and surpasses the vegetable, cotton and dairy industries. Despite the economic worth of turf, a need still exists to conserve the limited supply of potable water in this harsh Sonoran Desert environment. Mandatory water conservation programs have been developed for many sectors of the Arizona economy. To meet this challenge, the turfgrass industry and government bodies have begun to contribute to the development of research programs which reduce turfgrass water requirements and dependence upon potable water. Current research includes a) determining the minimum water requirements of higher quality turf under conditions of high temperatures and vapor pressure deficits; b) the turfgrass potential of grasses with lower water requirements than bermudagrass; c) the development of a statewide weather station network to predict daily turfgrass water use; and d) determine management strategies for turfgrass irrigated with wastewater effluent. The overall goal of these programs is to produce high quality and functional turf with 20 to 50 percent less water.
Charles F. Mancino
Tzu-Bin Huang and Karen E. Koch
Transpiration, respiration, dry weight gain, and water accumulation were measured to quantify the total carbon balance, total water utilization, carbohydrate cost for fruit growth, and water use efficiency in developing fruit of grapefruit (Citrus paradisi Macf). Rate of net carbon loss and net water loss (mg g-1FW hr-1) both decreased during fruit development. On a whole fruit basis, total carbon demand was reduced during the period of peak expansion, then increased rapidly during fruit maturation. In contrast, whole fruit rates of water loss and water utilization (loss plus accumulation) peaked at about 100 days after anthesis, then decreased toward fruit maturation. Carbohydrate cost for fruit growth was greatest (3.49 g sucrose g-1DW) at the early stage of fruit development (immediately following anthesis), whereas water use efficiency peaked (193 mg DM g-1 H2O) at the final stage of fruit development. The thickness of albedo and pectin content in fruit may contribute to the observed water conservation. Total estimated carbon cost of grapefruit development indicates approximately 120 g of sucrose would be necessary for production of a 450 g fruit (77 g DW) at 22 C.
Robert E. Call
The San Pedro River has been impacted by continued growth of Fort Huachuca Military Base. The San Pedro River, a riparian-migratory area, has had continuous water flow but now has intermittent water flow. The cause is cones of depression in the aquifer due to domestic well pumping. The aquifer is recharge with water from the river. Cooperative Extension has implemented Resource Conservation Audits for landowners in the lower San Pedro Valley. Also, outdoor classrooms are being constructed at three schools to educate children and community members. The goal of these programs is to educate landowners on water conservation through the use of native and adapted drought-tolerant plants, xeriscaping, irrigation efficiency, water harvesting, soil erosion, and composting. Site visits help landowners identify opportunities to reduce water use. Research-based informational brochures have been produced so landowners can plan and implement water-saving techniques on their properties. This program has been implemented using six members of the Border Volunteer Corp., part of Americorp program.
Jason J. Griffin, William R. Reid, and Dale Bremer
Successful establishment and growth of newly planted trees in the landscape is dependent on many factors. Weed pressure and water conservation are typically achieved with either organic mulches or chemical herbicides applied over the root ball of the newly planted tree. In the landscape, eliminating turfgrass from the root zone of trees may be more complicated than resource competition. Studies have shown that tall fescue (Festucaarundinaceae Schreb.) has allelopathic properties on pecan trees [Caryaillinoiensis (Wangenh.) K. Koch]. Well-manicured tall fescue turf in the landscape may have negative effects on the establishment and growth of landscape trees as well. A study was designed to examine the effects of popular turfgrasses on the growth of newly planted pecan and redbud (Cerciscanadensis L.). Results demonstrate that the presence of turfgrass over the root zone of trees negatively impacts tree growth. Through two growing seasons, every growth parameter measured on redbuds (caliper, height, shoot growth, shoot dry weight, root dry weight, leaf area, and leaf weight) was significantly reduced by the presence of turf. However, the warm season bermudagrass [Cynodondactylon (L.) Pers.] was less inhibitied than the cool season grasses. The affects of turfgrass on pecan growth was less significant; however, caliper, leaf area, and root dry weight were significantly reduced when grown with turf.
Sloane M. Scheiber, Richard C. Beeson, and Heather Bass
Native plants are often promoted as an approach for water conservation in urban landscapes. However, information regarding plant water needs is based primarily upon anecdotal observations of plant performance. Direct comparisons between native and introduced species using physiological measures of plant water stress are unavailable to support or refute such recommendations. Ligustrum japonicum and Myrica cerifera, representing an introduced and native species, respectively, were transplanted into a fine sand soil to evaluate establishment rates and growth characteristics under two irrigation regimes. Each species was irrigated either daily or every 3 days and received 1.3 cm of irrigation per event for 8 months after transplant. Predawn, midday, and dusk water potentials were recorded on three consecutive days monthly, with cumulative stress intervals calculated. Height, growth indices, shoot dry mass, root dry mass and leaf area were also recorded. Water potential was significantly influenced by day of water stress level. On days without irrigation, water stress was generally greater and affected growth. Myrica irrigated daily had the greatest growth, yet plants receiving irrigation every 3 days had the least growth and greater leaf drop. In contrast, for Ligustrum there were no differences between irrigation regimes in growth responses except for growth index.
Jon Sammons and Daniel K. Struve
Water is quickly becoming one of the world's most precious resources. Micro- and cyclical irrigation are two effective ways that reduce irrigation volume without reducing plant quality. Development of a control mechanism to deliver timely and appropriate irrigation volumes combined with the advantages of micro- and cyclical irrigation will allow maximum water conservation and plant quality. For container-grown nursery plants, the interaction of container geometry and media physical properties dictate the volume of water available for plant uptake. The maximum amount of water a container substrate can hold under gravity is container capacity (CC). We managed season-long irrigation volumes by maintaining CC at three levels; 100% CC; 80% CC; and 60% CC, and used a set irrigation as a commercial control. The results showed similar plant growth for the 100% and set irrigation control groups through the growing season. However, the scheduled regime applied 50% more water than the group maintained at 100% CC. Our system increased water use efficiency without decreasing plant quality.
Susan D. Day, Paula Diane Relf, and Marc T. Aveni
A multi-faceted extension education program to reduce consumer contributions to nonpoint source pollution by encouraging proper landscape management was initiated in Prince William County, Va., and funded through the USDA-extension service. The program now is being replicated in several counties in Virginia, primarily in the Chesapeake Bay watershed. The program recruits participants through educational field days, advertisement and other means. Educational techniques include one-on-one assistance from Master Gardener volunteers and the use of Extension publications developed for this program. Publications developed include The Virginia Gardener Easy Reference to Sustainable Landscape Management and Water Quality Protection—a concise reference of Virginia Cooperative Extension landscaping recommendations that includes a calendar for recording fertilizer and pesticide applications, IPM, and other maintenance activities. The Virginia Gardener Guide to Water-wise Landscaping, was recently added to supplement the program in the area of water conservation. In Prince William County, over 700 people have participated. Most of those who complete the program report being more satisfied with their lawn appearance and spending less money. Participation also resulted in consumers being more likely to seek soil test information before applying fertilizer. Other effects include greater participation in leaf composting and grass clipping recycling and greater awareness of nonpoint source pollution.
Traci Armstrong, J.E. Wolfe III, J.C. Bradley, and J.M. Zajicek
Ornamental grasses are currently growing in popularity and are being used in parks, public plantings, and commercial landscapes. This study was developed to determine the esthetic appeal of 12 ornamental grasses and evaluate public attitude toward the use of these grasses in low-maintenance landscapes. Grasses were selected for this evaluation using the following criteria: recommendations of experts in the ornamental grass field; material used in the nursery trade; and recommendations in popular literature. Two field sites were prepared and planted in the Spring 1991 and 1992. Both sites were maintained and irrigated to enhance the survivability of the grasses. The survey was conducted on several dates in the Fall 1992. Participants responded to questions regarding ornamental grass use, and the need for research on water conservation in landscapes. In addition, participants were asked to rank the individual grass species as to their accept-ability for landscape use. The results of the survey indicate that visual aesthetics are a major factor in public acceptance of landscape materials. In addition, the majority of ornamental grasses tested in this study were acceptable alternatives for low-maintenance landscapes with native and introduced species equal in performance.
Sloane M. Scheiber, Maria Paz, Edward F. Gilman, Kimberly A. Moore, Sudeep Vyapari, and Richard C. Beeson Jr.
Landscape water consumption has become a prime target for water conservation and regulation. Imposing water restrictions during landscape establishment is detrimental to plants that have not developed sufficient root systems to compensate for transpirational water losses. Generally, municipalities regulate irrigation frequency but not application rate. Application frequency affects establishment rates of shade trees, but the effects on shrub establishment are not well documented. This study evaluated three irrigation frequencies during establishment of Ilex cornuta `Burfordii Nana' and Viburnum odoratissimumin a landscape. To simulate maximum stress, both species were transplanted into field plots in an open-sided, clear polyethylene covered shelter. Each species was irrigated either every 2, 4, or 7 days, and received 9 L of water per plant per event. Predawn, midday, and dusk water potentials were recorded at 28-day intervals and cumulative stress intervals calculated. Water potentials were taken the day prior to irrigation (maximum stress day) and the day of irrigation (minimum stress). Growth indices were also recorded. As days after transplant (DAT) increased, significant declines in cumulative water stress of Ilexwere found among treatments on the day of maximum stress. The 7-day treatment declined at a faster rate than the other treatments tested. No differences were found for Viburnum. No significant differences were found on the day of irrigation as DAT increased. Differences in canopy size were not significant among treatments for either species.
Richard A. Wit, Garald L. Horst, Donald H. Steinegger, and Blaine L. Blad
Depletion and contamination of traditional water supplies and population pressures are straining the water resources of the United States. This has placed increased emphasis on the need for water conservation through all phases of the use cycle. Objectives of this research were to: 1) Determine water use in residential, commercial, and institutional landscapes; 2) Evaluate landscape irrigation system performance; and 3) Evaluate feasibility of landscape irrigation scheduling. Beginning in 1991, water meters on 18 test sites in Lincoln, NE were read on a weekly basis. Water meter readings during the winter were used to develop a baseline on non-landscape water use. The “can test” method was used to evaluate landscape irrigation system precipitation rate and distribution efficiency. Four recording weather stations were used to estimate daily potential evapotranspiration (ETp). Lysimeters (20 cm dia. × 31 cm deep) were installed in two Kentucky bluegrass and one tall fescue landscape to estimate water use coefficients for calculating landscape evapotranspiration. Irrigation system Christiansen coefficients of uniformity ranged from .43 to .87 with scheduling coefficients ranging from 1.31 to over 15.14. Poor irrigation system performance characteristics made it difficult to schedule irrigation on estimated water use.