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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.

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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.

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Glenn D. Israel, Janice O. Easton, and Gary W. Knox

The Florida Cooperative Extension Service (FCES) teaches residents the importance of proper landscaping practices. FCES offers several educational programs that teach residents how to integrate energy and water conservation, pest management, and waste recycling practices into their home landscapes. In 1997, extension staff and volunteers planned and conducted environmental landscape management (ELM) programs resulting in >800,000 customer contacts. A survey was conducted to measure the adoption of recommended best management practices by program participants and nonparticipants. Results show that, of 39 practices examined, Master Gardener trainees increased the number of practices used by an average of 7.3, while educational seminar and publications-only participants increased by an average of 4.5 and 2.8 practices, respectively. Nonparticipants showed essentially no change. When practices are examined one at a time, the Master Gardeners made statistically significant increases in 28 of the 39 recommended practices. Educational seminar and publications-only participants made similar gains in 31 and 6 practices, respectively, and the nonparticipant comparison group made significant increases in 2 practices and decreases in 8. The results suggest that the publications-only strategy for delivering information to homeowners is less effective than strategies combining educational seminars or intensive training with relevant publications.

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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.

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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.

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Cathleen A. Peterson, L. Brooke McDowell, and Chris A. Martin

Heightened awareness of ecological concerns have prompted many municipalities to promote water conservation through landscape design. In central Arizona, urban residential landscapes containing desert-adapted plant species are termed xeriscapes, while those containing temperate or tropical species and turf are termed mesoscapes. Research was conducted to ascertain landscape plant species diversity, tree, shrub, and ground cover frequency; landscape canopy area coverage; and monthly irrigation application volumes for xeric and mesic urban residential landscapes. The residential urban landscapes were located in Tempe and Phoenix, Ariz., and all were installed initially between 1985 and 1995. Although species composition of xeric and mesic landscapes was generally dissimilar, both landscape types had comparable species diversity. Mesoscapes had significantly more trees and shrubs and about 2.3 times more canopy area coverage per landscaped area than xeriscapes. Monthly irrigation application volumes per landscaped surface area were higher for xeriscapes. Even though human preference for xeric landscape plants may be ecological in principle, use of desert-adapted species in central Arizona urban residential landscape settings might not result in less landscape water use compared with mesic landscapes.

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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.

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R. Louis Baumhardt, W. N. Lipe, David Rayburn, and C. W. Wendt

Mild temperatures during late winter have caused early budbreak in grapes which resulted in freeze injury and significant crop losses in 1980 and 1988. Evaporative cooling of grapevines with microsprinklers when the air temperature exceeded 10 °C (50 °F) used 100 liters/min/hectare of treated grapes (11 gallons/min/acre) and delayed budbreak for a period of 7 to 10 days. Methods of reducing the amount of water used while not reducing the cooling were evaluated. The average hourly difference between wet and dry bud temperatures, measured with thermocouples, were summed during the system operation time and compared as a function of air temperature, wind speed, global radiation, and relative humidity limits. Limiting the cooling system operation time as a function of air temperature, wind speed, or global radiation reduced cooling efficiency by approximately a one to one ratio. Limiting system operation to humidities less than 60% reduced the amount of water used by 33%, with only a 9% reduction in cooling efficiency. By changing the wetting interval employed in this research from 25 seconds every three minutes to 25 seconds every four minutes, total water conservation would increase to 50% with insignificant changes in cooling efficiencies. These system modifications would reduce water application requirements to 50 liters/min/hectare of grapes (5.5 gallons/minute/acre).

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Eric B. Bish, Daniel J. Cantliffe, and Craig K. Chandler

The demand for plug transplants by the Florida winter strawberry (Fragaria ×ananassa Duch.) industry may increase as water conservation during plant establishment becomes more important and the loss of methyl bromide fumigant makes the production of bare-root transplants more problematic. A study was conducted during the 1995-96 and 1996-97 seasons to determine the effect of container size and temperature conditioning on the plant growth and early season fruit yield of `Sweet Charlie' strawberry plants. Plants in containers of three sizes (75, 150, and 300 cm3) were grown in one of two temperature-controlled greenhouses (35 °C day/25 °C night or 25 °C day/15 °C night) for the 2 weeks just prior to transplanting into a fruiting field at Dover, Fla. Plants exposed to the 25/15 °C treatment had significantly higher average root dry weights at planting in 1995 and 1996 than did plants exposed to the 35/25 °C treatment. Plants exposed to the 25/15 °C treatment also had higher average fruit yields than the plants exposed to the 35/25 °C treatment (48% and 18% higher in 1995-96 and 1996-97, respectively). The effect of container size on plant growth and yield was variable. Plants propagated in the 150- and 300-cm3 containers tended to be larger (at planting) than the plants propagated in the 75-cm3 containers, but the larger container sizes did not result in consistently higher yields.

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Charles F. Mancino

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.