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Tamara Wynne and Dale Devitt

Continued growth in the arid southwestern United States is placing greater demand on available water resources. Much of this growth is in sprawling metropolises where water is used outdoors to support urban landscapes ( Devitt et al., 2008 ; Litvak

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Fengyun Zhao, Yu Jiang, Xiufeng He, Huaifeng Liu, and Kun Yu

in the arid regions of Xinjiang has been developing rapidly, constituting 68% of China’s microirrigation area, which is the largest drip irrigation region in China ( Li et al., 2016 ). In recent years, drip irrigation technology has been extensively

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Rolston St. Hilaire, Dawn M. VanLeeuwen, and Patrick Torres

Urban areas in arid and semiarid regions continue to face water supply and demand challenges ( St. Hilaire et al., 2008 ). Some of the drivers of these challenges include accelerated population growth and enhanced economic activity of urban areas

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José Luis León and Enrique Troyo-Diéguez

The high cost of inputs and water deficit in arid lands demand the use of more drought tolerant species into the agricultue. The flora of the deserts offer a variety of fruits and vegetables that may diversify horticulture. `Cimarrón' wild plum tree or “ciruelo cimarrón” (Cyrtocarpa edulis Brand.:Anacardiaceae) is one of the species with potential importance in arid lands. C. edulis is an endemic tree of the meridional portion of the Baja California peninsula, occurring along arroyos and on gentle slopes in sandy soils. The flesh of the fruits is edible, with a slight acid tang, and is used locally. Actual exploitation is based on the fruit harvest in natural dry forest and xerophilous shrubs, where average density is near 100 trees/Ha. There is a growing interest in marketing the dried fruits, especially for the snack industry, hence, the need to develop a breeding program in order to establish it as a reliable fruit crop.

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Darrell Sparks

A multiple regression model (R 2 = 0.945) was developed from historical data, 1971-92, to predict pecan [Carya illinoensis (Wangenh.) C. Koch] production in an arid climate at high elevations. Dependent variables were year of production as a measure of production trend, number of degrees below 0.6°C following budbreak as a measure of late spring freeze injury, and number of degrees below 0.6°C preceding nut maturity as a measure of early fall freeze injury. Year of production was the dominant factor influencing production. Freezing temperature following budbreak had about two times more effect on production than freezing temperature preceding nut maturity. Pecan production under arid conditions at high elevations depends on fewer variables (three) than previously shown for humid conditions (eight variables).

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Abdullah A. Alsadon

Eleven onion (Allium cepa L.) cultivars were selected to evaluate their yield performance under the arid conditions of the Riyadh area in the Central region of Saudi Arabia during the 1996–97 and 1997–98 growing seasons. The selected cultivars were: Colossal PVP 234, Contessa, Dorado, Red Creole, Ring Master, Rio Sultan, RioTalat, Texas Grano 502, Texas Early Grano 502, Und Grande and Yellow Spanish. Yield (ton/ha) and yield attributes such as bulb diameter, length, weight and dry matter were assessed. Transplants grown in plastic trays for 45 days under greenhouse conditions were transplanted in the field on 7 Jan. 1997 and on 29 Dec. 1997 and harvesting was carried out on 19 May 1997 and on 15 May 1998 for the first and second season, respectively. Significant differences were observed between cultivars and among growing seasons, with significant interaction for yield and bulb weight. The top high yielding cultivars in the first season were Und Grande, Texas Early Grano 502, Colossal PVP 234, Contessa and Dorado. In the second season, Dorado, Red Creole, Contessa, Ring Master and Und Grande outyielded other cultivars. Under the conditions of this study, Contessa, Dorado, Red Creole, Texas Early Grano 502, and Und Grande had the highest yield attributes that made them recommended for growing in the arid regions. The yield and yield attributes of each cultivar will be discussed.

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David A. Bender and Frank J. Dainello

Trenched beds covered with plastic mulch was used to capture and retain precipitation for dryland cantaloupe production. Two trenches were formed in the fall in raised beds. Plastic mulch was laid over the beds and slitted at ca. 1 meter intervals over the trenches. Soil was placed over the slits, conforming the plastic to the shape of the trenches and channeling precipitation into the beds. Cantaloupes were seeded in the spring and grown with no supplemental irrigation. Planting moisture was significantly greater under the capture system than in unmulched beds. Seedling emergence time was reduced from 18 to 6 days and vine growth in the first 6 weeks was almost doubled. Total and marketable yields were doubled and fruit size significantly increased when water was limiting. Elevated soil temperatures under the mulch enhanced plant growth and yield even when moisture was not limiting. Combining a moisture capture system with supplemental irrigation could allow commercial production of cucurbit crops under limited water conditions in semi-arid areas.

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Thayne Montague, Roger Kjelgren, and Larry Rupp

Gas exchange and growth of transplanted and nontransplanted, field-grown Norway maple (Acer platanoides L. `Schwedleri') and littleleaf linden (Tilia cordata Mill. `Greenspire') trees were investigated in an arid climate. In the spring of 1995, three trees of each species were moved with a tree spade to a new location within a field nursery and three nontransplanted trees were selected as controls. Predawn leaf water potential, morning-to-evening stomatal conductance and leaf temperature, leaf-to-air vapor pressure difference, midday stomatal conductance and photosynthetic rate, and growth data were collected over a 2-year period. After transplanting, weekly predawn leaf water potential indicated that transplanted trees were under greater water stress than were nontransplanted (control) trees. However, predawn leaf water potential of maple trees recovered to control levels 18 weeks after transplanting, while that of transplanted linden trees remained more negative than that of controls. In 1995, stomatal conductance and photosynthetic rates were lower throughout the day for transplanted trees. In 1996, gas exchange rates of transplanted maple trees recovered to near control levels while rates for transplanted linden trees did not. Sensitivity of stomata to leaf-to-air vapor pressure difference varied with species and with transplant treatment. Each year transplanted trees of both species had less apical growth than did control trees. Although gas exchange and apical growth of transplanted trees was reduced following transplanting, recovery of gas exchange to control rates differed with species.

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Thayne Montague* and Lindsey Fox

Recent droughts and depleted water tables across many regions have elevated the necessity to irrigate field-grown (FG) nursery trees. At the same time, ordinances restricting nursery irrigation volume have been implemented, often without regard to plant water requirements. This research investigated growth of seven FG tree species (Acer buergeranum, A. campestre, A. × freemanii `Autumn Blaze', A. truncatum, Quecus muehlenbergii, Q. polymorpha, and Q. robur) subjected to three reference evapotranspiration (ETo) irrigation regimes (100%, 60%, and 30% ETo) in a semi-arid climate. During Spring 2002, nine containerized (11.3 L) trees of each species were field planted in a randomized block design. Each year trees were irrigated through a drip irrigation system. During the first growing season, all trees were irrigated at 100% ETo. Irrigation treatments began Spring 2003. Growth data (shoot elongation and caliper increase) were collected at the end of the 2003 growing season. Species growth data were subjected to analysis of variance. If treatment differences were found, means were separated by Fisher's least significant difference. Shoot growth was influenced by irrigation regime for each species except A. campestre and Q. robur. For each of the five remaining species, the greatest shoot growth increase was generally not associated with the greatest irrigation regime. In a similar manner, caliper increase was influenced by irrigation regime for each species. The 100% ETo irrigation regime produced the greatest caliper increase for A. buergeranum, A. truncatum, Q. polymorpha, and Q. robur. For remaining species, the greatest caliper increase was generally not associated with the greatest irrigation regime.

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Ahmed ElObeidy*

One of the major steps in responding to imminent water shortages in the Middle East is improving water use efficiency. Drought-resistant crops would be an effective technology to curb rising demands of water. Columnar Cactus species characteristics fit with most of the requirements of a drought tolerant crop with very high water-use efficiency. Cereus cacti have physiological and morphological methods of exploiting environments that would soon desiccate other plants. Four Cereus species were introduced into UAE deserts and could be ideal for establishing crop plantations in the arid environment. The introduced fruiting cacti are Cereus hexagonus, C. pachanoi, C. peruvianus, and C. validus. Plants were propagated by cuttings in the greenhouse. Cuttings developed roots within 2*&8211;4 weeks of planting. The propagated plants were acclimatized and transplanted into the field in the desert. C. peruvianus was the most promising in the new environment in terms of its high adaptability and healthy growth in the new environment. C. pachanoi grew very fast, averaging up to a fifteen centimeter a month of new growth. C. pachanoi was recommended as a rootstock for other species. C. validus could not survive the new environment.