demographic covariates. In the southwestern United States, high temperatures in summer pose serious health threats to humans. Landscape designers and architects place trees strategically to alleviate high temperatures in urban areas. In Phoenix, AZ, summer
Kristen Hanson, Tilak Mahato, and Ursula K. Schuch
species in containers filled with soil and exposed to solarization in a double tent ( Stapleton et al., 2002 ). At present there are no studies for the semiarid southwestern United States region comparing solarization inside and outside of a high tunnel
Emmanuel Alves Dos Santos Hecher, Constance L. Falk, Juliette Enfield, Steven J. Guldan, and Mark E. Uchanski
eastern and midwestern parts of the United States, little work has focused on the southwestern part of the country. With limited water and a dry climate, farmers in the southwestern United States are under pressure to divert agricultural land and water to
Mark E. Uchanski, Dawn M. VanLeeuwen, Steven J. Guldan, Constance L. Falk, Manoj Shukla, and Juliette Enfield
southwestern United States has predominately sunny days. Even during winter, New Mexico receives 70% to 75% of the possible sunshine ( New Mexico Climate Center, 2019 ). Due to geographic location and limited cloud cover, the Southwest receives more sunlight
States and the best fruit is produced in the southwestern United States with similar climate conditions as Xinjiang area in China. CHALLENGES AND OPPORTUNITIES Limited commercially available cultivars, lack of cultivar trials, and limited research
Shengrui Yao and Robert Heyduck
without many known pests or diseases in the southwestern United States ( Yao, 2013a ). They have a 2-month blooming period that attracts many insects, and function as a sanctuary for beneficial insects ( Grasswitz and Yao, 2017 ; Yao, 2018 ). All jujube
Jose G. Peña
The United States pecan industry experienced dynamic production changes during the last 25 years. Production in Georgia, the leading state, experienced serious problems during the late 1980s and early 1990s as a result of orchard crowding, old orchards, high incidence of diseases, and other problems. During the same 25-year period, plantings and production shifted to the southwestern United States to new production centers in Texas, New Mexico, Arizona, and California under a drier, more-favorable growing environment. Although the southeastern region continues to lead the nation in annual pecan production due to the high number and concentration of orchards with improved varieties, production in the southwestern region eventually may dominate the industry.
S. Miyamoto and J. Benton Storey
Irrigated pecans in the southwestern United States have been planted in every soil imaginable, and tree performance has become highly soil-dependent. Desperate attempts to deal with this poor soil selection has led to advancements in soil management, consisting primarily of physical measures, such as chiseling and trenching. Chemical amendments appear to have played a secondary or supplemental role. Meanwhile, soil structural degradation, mainly compaction and aggregate destruction, began to cause poor water penetration, die-back of deep roots, and resultant loss of tree vigor. These problems have been dealt with primarily by chiseling. In the future, spiking and sodded-floor management are likely to become increasingly important. Scientific examination of soil management practices has lagged, but has provided some rationale and targets for soil management. H should play an increasingly important role in refining these measures and in establishing a comprehensive soil management program in which the soil is viewed as a plant growth medium and an integral component of cost-effective orchard management.
S. Miyamoto, J. Henggeler, and J. Benton Storey
Irrigated production of pecans in the southwestern United States started with notoriously inefficient flood irrigation along river basins. Today, most surface-irrigated orchards are laser-leveled, and many orchards in upland areas are under sprinkler or drip irrigation. Technical and scientific knowledge for improving water management also has evolved from studying drought effects on tree performance to an improved understanding of water relations, salt effects, evapotranspiration processes, and the distribution of water and salts in irrigated fields. Yet, many growers still experience difficulties with water management and may benefit from maintaining the soil water suction above saturation but below 30 to 40 cb until shuck opening. The soil salinity should be kept below 2.5 dS·m−1, and irrigation water should be applied to essentially the entire root zone for optimum tree growth. Due to extreme soil variability existing in most irrigated fields of the southwestern region, these guidelines alone are not adequate. Soil profiles, root distributions, water quality, and irrigation methods may have to be examined to improve water management.
Overcoming environmental stresses during seedling establishment is crucial to successful vegetable production. In the irrigated production areas of the southwestern United States, stress most often is related to unfavorable temperature, soil or water salinity, or poor soil structure; it is frequently difficult to separate the effects of these stresses because they may all be present to some significant degree. Growers use a variety of techniques to ameliorate these conditions. Advances in seed technology have improved seedling establishment under unfavorable temperatures, particularly for lettuce. The use of sprinkler irrigation for stand establishment has become a widespread practice; sprinkling moderates soil temperature, minimizes salinity in the zone of germination, and reduces soil crusting. By modifying bed configuration, growers have been able to increase soil temperature to stimulate germination. Modifying seed placement and furrow irrigation patterns can create zones of lower salinity. Various chemical and physical treatments have proven effective in reducing soil crusting. The use of transplants-has expanded for many crops, both as a means to circumvent seedling establishment problems, as well as a technique to obtain earliness.