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.
D.I. Leskovar, P. Perkins-Veazie, and A. Meiri
Shawn T. Steed, Allison Bechtloff, Andrew Koeser, and Tom Yeager
Mulches have many positive benefits for the production of plants, ranging from weed suppression to water conservation. In this study, a novel method of using plastic film mulch for container-grown plants was evaluated. Plots of 25 japanese privet (Ligustrum japonicum) in #1 (2.5 qt) nonspaced containers were wrapped with 1.25-mil white or black plastic mulch over the top and sides of containers. Small plants were planted through the plastic and grown for 22 weeks with overhead irrigation. Water application amount was determined by moisture sensors placed in the substrate of each treatment. Plant growth, dry weights (DWs), weed fresh weights, weeding time, substrate electrical conductivity (EC), substrate temperature, total water applied, and mulch costs were determined. Black plastic (BP) and white plastic (WP) mulch reduced water applied by 82% and 91%, respectively, compared with the nontreated control (NT). Nontreated control plants grew faster and had greater DW at the end of the experiment. Mulched containers had fewer weeds and required less labor to remove weeds than the NT treatment. Substrate EC level was greater in BP and WP treatments than for the NT after 20 weeks, and plastic mulch did not result in different substrate temperatures. Plastic mulch added $4.94/1000 containers ($2.24 input cost and $2.70 removal cost) to production costs, not including disposal costs. This novel method of mulching nonspaced plants reduced irrigation water, herbicide applications, and weeding labor, but probably added 2–3 weeks to finish time.
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.
Shaoyun Lu, Zhongcheng Wang, Yuejing Niu, Zhenfei Guo, and Bingru Huang
Improving the drought tolerance of widely used bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon] is important for water conservation and producing quality turf with limited irrigation. Mutants of bermudagrass were generated using gamma-ray irradiation with an aim toward developing dwarf and drought-resistant bermudagrass. The objectives of this study were to compare morphological characteristics between radiation-induced mutants and the wild-type of bermudagrass and to determine antioxidant responses associated with changes in drought resistance in the bermudagrass mutants. Three mutant lines (7-9, 10-5, and 10-12) that exhibit slow growth and good turf quality were chosen for this study. Plants were exposed to drought stress by withholding irrigation in a greenhouse. Mutant lines had lower canopy height, shorter internodes, and shorter leaves than the wild type under well-watered conditions. Under drought stress, all three dwarf mutant lines maintained higher relative water content and lower ion leakage and malondialdehyde content than the wild type. Antioxidant enzyme activities decreased in response to the drought stress in the mutant lines and the wild type, whereas nonenzymatic antioxidants increased under drought stress. Compared with the wild type, higher enzyme activities and antioxidant contents were maintained in mutant lines under drought stress. Our results indicated that bermudagrass mutants induced by gamma radiation exhibited dwarf characteristics and improved drought resistance, which was associated with maintenance of higher levels of antioxidant enzyme activities and nonenzymatic antioxidant contents.
Gerard W. Wall and Guy McDonnell
, U.S. Water Conservation Laboratory, Phoenix, Ariz., and the NSF/DOE/NASA/USDA Interagency program on Terrestrial Ecology and Global Change (TECO II) (NSF-95-27 proposal no. IBN-9652614) (Gerard W. Wall, PI). Special thanks to Mr. Jose Olivieri for
Roger Kjelgren and Larry Rupp
We developed two courses, sustainable landscaping and landscape water conservation, to meet time-constrained students on campus and place-bound students off campus. Lecture material consisting of text, slides, drawings, and some video were assembled digitally using presentation software. Each course was broken into nine to10 units by topic matter, and each unit consisted of 50 to 100 individual “slides” containing visuals, text, and audio narration. The lecture material was then packaged for student consumption onto videotape and CD-ROM, and on the Web (without audio) and as hard copy. Students taking the course received a course reader of the lecture material in hard copy and CD format. Contact with the instructor was through e-mail and a threaded newsgroup on the Web. All testing was with take-home quizzes and an exam. These courses had 700 to 800 slides averaging 1 min of narration per slide, equaling 12 to 14 h of audio. Assembly time for 1 h of narration, or about 60 slides, was 20 to 30 h. These courses are taught live in a classroom, where the presentation time is doubled compared to audio narration, alternate years, and have been available every term on an arranged basis. Survey results of 40 students to date taking the course on an arranged basis, obtaining lecture material mainly through CD-ROM, showed that by a 6:1 margin, their learning experience was overall positive. However, by a 19:1 margin, students would have preferred to have taken the course with live classroom instruction. Developing digital courses such as these is only feasible if a faculty member has unequivocal and ample administrative and financial support, and is only cost-effective if there is sufficient student demand outside of conventional scheduling.
Angela O'Callaghan*, Florence Brown, Denise McConnell, and Robert Morris
Southern Nevada Master Gardeners (MGs) donate 50 hours annually to educational and service projects. These volunteers respond to community needs by developing and staffing horticultural projects under UNCE supervision. In Las Vegas, 20 such projects exist. Some are more energy and information intensive than others. Mojave Guides are docents at the Desert Demonstration Garden, a part of the Las Vegas Springs Preserve, not Extension. They commit to a shift at the garden, providing information to visitors. While they are directly supervised by garden staff, the hours they contribute are Master Gardener hours. These volunteers receive training in desert flora from gardens staff and participate in seminars on selected topics. The MG Orchard Team operates a teaching orchard at the Center for Urban Water Conservation in North Las Vegas. These volunteers maintain hundreds of fruit trees and grape vines. They receive training on topics related to fruit trees and orchard management. This project began in 1996. Since 2002, they have been formalizing their organization using the logic model and SWOT analysis. Many members work weekly at the orchard and take the produce to a local farmers market. This raises funds for the orchard and is an opportunity to teach the community about desert horticulture. Project PLANT volunteers work at the Red Rock National Recreation Area visitor center and grounds. They are docents who also learn about and maintain the native plants there, and prevent infestations of invasive weeds which threaten the area. Their monthly meetings include training on topics related to the project. These projects are successful because of the MGs themselves. They grew out of interest and continue because the volunteers have drawn commitment from others.
Erin James and Marc van Iersel
Water conservation is increasingly important for growers in the United States, but there is little information on the use of alternative irrigation systems, such as ebb and flow, for the production of bedding plants. The objective of this study was to quantify the growth of Petunia ×hybrida Hort. Vilm.-Andr. `Blue Frost' and Begonia ×semperflorens-cultorum Hort. `Ambassador Scarlet' grown in an ebb and flow system in three soilless media and fertilized with P at 0, 50, or 100 mg·L-1 in the fertigation solution. After 5 weeks, plants grown with 50 or 100 mg·L-1 P had greater dry weight, height, and width than plants grown with 0 mg·L-1 P. Begonias grown with 50 or 100 mg·L-1 P had 38% more flowers than did those grown without P. Petunias flowered 4 to 7 days earlier when no P included in the fertilizer. Growing media had little effect on the plants. Begonias grown in Metro-Mix 220 had more inflorescences than those grown in Metro-Mix 366Coir. Changes in electrical conductivity (EC) and pH of all three media were similar over the course of the experiment. The EC dropped during the third and fourth week and rose again in the fifth week. The pH of the leachate from all three media dropped by an average of 1 unit during the experiment. The results indicate that petunias and begonias may be grown successfully with ebb and flow irrigation, using a variety of fertilizers and growing media. However, P must be included in the fertigation solution for optimal plant quality.
Catherine K. Singer and Chris A. Martin
Mulches applied to landscape surfaces can moderate soil temperatures by changing the surface heat energy balance and conserve soil water by reducing evaporation rates. In the Southwest, decomposing granite is commonly used as landscape mulch. However, organic mulches, such as pine residue mulch and shredded tree trimmings, are becoming more available as industry by-products. Recent impetus toward water conservation and recycling forest and urban tree waste into urban landscapes has increased the need to better understand how such mulch types effect the temperature, moisture. and light quality of drip-irrigated landscapes typically found in the Southwest. We compared effects of three mulches, two organic (composted ponderosa pine residue and shredded urban tree trimmings) and one inorganic (Red Mountain Coral decomposing granite), turf grass, and bare soil applied to 14 drip-irrigated landscape research plots on below-ground soil temperatures at depths of 5 cm and 30 cm, temperatures at the mulch-soil interface, mulch surface temperatures, diel mulch surface net radiation, and albedo. Below-ground soil temperatures were more buffered by organic mulches, and mulch-soil interface temperatures were lower under organic mulch than inorganic mulches. Inorganic mulch daytime surface temperatures were lower than organic mulch surface temperatures. Nighttime net radiation values were less negative over organic mulches than inorganic mulches and albedo was significantly higher for the inorganic mulch and bare soil treatments. These results provide evidence to show that organic surface mulches have higher resistances to heat transfer than inorganic mulches, which could improve landscape plant water and nutrient use efficiencies by lowering high summer root zone temperatures.
In the past decade, there has been a growing trend toward conservation and management of wildlife and the environment. Growing suburban development has increased displacement of native animals from their natural habitats; thus, there is an ever-increasing need to manage not only existing forests and large land holdings for wildlife but also developed land areas. The idea of “backyard habitat” gardening and the “green movement” in golf course design address these issues of wildlife habitat and provide design solutions that hail the growing need for natural habitats. The same principles also can be used in commercial landscape design and ultimately in reclaiming grazing pasture land for dual habitat by farm animals and native wildlife. Just as the “American Lawn” provides minimal support for wildlife due to its lack of diversity, the manicured pasture of the American farm can also be limiting for wildlife. Providing areas of cover for nesting and protection can benefit the “kept” and “unkept” animals inhabiting the area. Furthermore, the biophilic landscape provides a psychologically healthy biosphere for the personnel working on the farm. In designing landscape plans with the primary goal of aesthetic enhancement of university experimental research farms, the principals of water conservation, integrated pest management, and providing wildlife cover and food are applied to develop an aesthetically pleasing design that also provides habitat for displaced wildlife. The intent of the project is to explore the possibilities in designing successful habitats for wildlife while preserving the ultimate goal of livestock production. Implementing successful ecologically sound landscapes enable the land-grant university to teach the public the benefits of wildlife conservation and the importance of its incorporation to all aspects of land use.