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.
Sloane M. Scheiber, Richard C. Beeson, and Heather Bass
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.
O. Gulsen, R.C. Shearman, K.P. Vogel, D.J. Lee, P.S. Baenziger, T.M. Heng-Moss, and H. Budak
Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] has the potential for increased use as a turfgrass species due to its low maintenance and water conservation characteristics. This study was conducted to estimate diversity and relationships among naturally occurring buffalograss genotypes based on the nuclear genome, using sequence-related amplified polymorphism (SRAP) markers. The 56 genotypes studied represented five ploidy levels collected from diverse geographic locations in the North American Great Plains. In addition, blue grama [Bouteloua gracilis (H.B.K.) Lag. Ex Steud.] and perennial ryegrass (Lolium perenne L.) were included as outgroups. Twenty-five combinations of forward and reverse primers were used. Ninety-five intensively amplified markers were scored and used to infer diversity and relationships among the genotypes. All buffalograss genotypes were discriminated from each other with similarity values ranging from 0.70 to 0.95. Principal component analysis (PCA) suggested that the 56 genotypes could be reduced to 50 due to high similarity levels among some of the genotypes. The distance between buffalograsses, blue grama, and perennial ryegrass were consistent with current taxonomical distances. This research indicates that SRAP markers can be used to estimate genetic diversity and relationships among naturally occurring buffalograss genotypes.
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.
Marsha Ann Bower, David H. Trinklein, and John M. Brown
Recent trends in greenhouse container production suggest using ebb and flow irrigation for water conservation and pollution control. A major problem in this system is management of soil borne pathogens. Some species of Trichoderma, a beneficial fungi, are known to control Pythium and Phytopthora in container production. This study investigates the potential of applying a Trichoderma conidial spore suspension in an ebb and flow irrigation system. Trichoderma conidia were collected from culture and placed in 101 l stock solution tanks at 10-2 and 10-4 colony forming units (CFU) per ml. Six inch container grown Dendranthema grandiflora `Delano', were irrigated as needed. To determine Trichoderma density in the root environment, soil samples were acquired from the container at 7 day intervals. Results showed that initial population densities of 10-4 CFU/ml were required to achieve adequate container populations to control disease after one irrigation. This study successfully demonstrated that Trichoderma could be dispersed through irrigation water into container plants in an ebb and flow system.
Dennis R. Pittenger, David A. Shaw, and William E. Richie
We conducted an evaluation of three commercial weather-sensing irrigation controllers to determine the climatic data they use, how easy they are to set up and operate, and how closely their irrigation regimes match landscape irrigation needs established by previous field research. The devices virtually controlled an existing reference irrigation system and used its system performance data as required in their initial setup. Reference standard treatments for cool-season turfgrass, trees/shrubs and annual flowers were calculated using onsite, real-time reference evapotranspiration (ETo) data and plant factors developed primarily from previous research. The reference irrigation system applied the correct amount of water to an actual tall fescue turfgrass planting whose water needs served as the reference standard treatment comparison for the cool-season turfgrass treatment. Virtual applied water was recorded for other plant materials and it was compared to the corresponding calculated reference standard amount. Results show each controller adjusted its irrigation schedules through the year roughly in concert with weather and ETo changes, but the magnitudes of adjustments were not consistently in proportion to changes in ETo. No product produced highly accurate irrigation schedules consistently for every landscape setting when compared to research-based reference comparison treatments. Greater complexity and technicality of required setup information did not always result in more accurate, water-conserving irrigation schedules. Use of a weather-sensing controller does not assure landscape water conservation or acceptable landscape plant performance, and it does not eliminate human interaction in landscape irrigation management.
Jinmin Fu, Jack Fry, and Bingru Huang
Deficit irrigation is increasingly used to conserve water, but its impact on turfgrass rooting has not been well documented. The objective of this study was to examine the effects of deficit irrigation on ‘Falcon II’ tall fescue (Festuca arundinacea Schreb.) root characteristics in the field using a minirhizotron imaging system. The experiment was conducted on a silt loam soil from the first week of June to mid-Sept. 2001 and 2002 using a mobile rainout shelter under which turf received applications of 20%, 60%, or 100% of actual evapotranspiration (ET) twice weekly. Neither soil water content (0 to 25 cm) nor tall fescue rooting between 4.1- and 50.1-cm depths was affected by irrigation at 60% compared with 100% ET. Despite consistently lower soil water content, tall fescue irrigated at 20% ET exhibited an increase in root parameters beginning in July or August. Tall fescue subjected to 20% ET irrigation had greater total root length and surface area on two of five monitoring dates in 2002 compared with that receiving 100% ET. Evaluation of tall fescue rooting by depth indicated that root proliferation at 20% ET was occurring between 8.7- and 36.3-cm depths. As evaluated under the conditions of this experiment, turfgrass managers using deficit irrigation as a water conservation strategy on tall fescue should not be concerned about a reduction in rooting deep in the soil profile, and irrigation at 20% ET may result in root growth enhancement.
D.R. Pittenger, Donald R. Hodel, and David A. Shaw
Non-turf ground-covers occupy a significant portion of the landscape, and understanding their water requirements is important when water conservationism being practiced. Six groundcover species (Baccharis pilularis `Twin Peaks', Drosanthemum hispidum, Vinca major Gazania hybrid, Potentilla tabernaemontani and Hedera helix `Needlepoint') representing a range of observed water needs were evaluated under different levels of irrigation based on percentages of real-time reference evapotranspiration.
Treatments of 100%, 75%, 50% and 25% of ETO were applied during 1989 while treatments of 50%, 40%, 30% and 20% of ETO were applied during 1990. Plant performance ratings in the first year indicated that 50% of ETO was the minimum treatment which resulted in acceptable plan aesthetics for all species except for Drosanthemum which performed equally well at each treatment. Significant differences in performance did occur among and within species at the different treatments. Results from 1990 will reveal which species might maintain aesthetic appearance at irrigation levels between 50% and 20% of ETO. These results will be presented and discussed in terms of their significance to species selection and total landscape irrigation management.
D.I. Leskovar, P. Perkins-Veazie, and A. Meiri
Water conservation strategies are being investigated for watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] production in the Winter Garden region of southwest Texas. Our objective was to determine how yield and fruit quality of a triploid (cv. Summer Sweet 5244) and hybrid (cv. Summer Flavor 710) watermelon were affected by irrigation based on evapotranspiration (ET) rates and timing of application during spring. Irrigation treatments included constant 1.0 and 0.5 ET, three with varying ET before or after fruit set, and one with cycles of 1.0 and 0.5 ET. Fruit quality characteristics were measured at the unripe, ripe, and overripe maturity stages. Water deficit before or after fruit set decreased yield and fruit number. Flesh color was not affected by irrigation at any maturity stage. Soluble solid content at the ripe stage increased only in triploids irrigated with constant 0.5 ET or with 0.5 ET applied after fruit set. Triploid plants exposed to frequent cycles of water deficit set more and smaller fruit than hybrids. These data suggest that triploid watermelon types may have a different acclimation response to drought stress than diploid hybrids.