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In recent decades, air quality has improved near most cities but not in rural areas such as the San Joaquin Valley. Many studies using diverse exposure techniques have shown that ground-level ozone air pollution reduces plant growth and yield, from negligible impacts in some species to over 30% losses in others. We studied the interaction of ozone with weed competition from yellow nutsedge in Pima cotton and tomato in open-top field-exposure chambers at the UC Kearney Research and Extension Center in Fresno County. Ozone impacts on cotton (which is relatively sensitive) were compounded by weed competition, whereas tomato (which is less sensitive) competed well at all ozone concentrations. Our data suggests that crop-loss estimates obtained in single-factor experiments accurately reflect the serious risk of ozone to agriculture, but that more accurate yield predictions will require the consideration of interactions between the components of complex crop production systems, including weed competition.

Wind-blown fugitive dust is a widespread problem in the arid west resulting from land disturbance or abandonment and increasingly limited water supplies. Soil-derived particles obstruct visibility, cause property damage and contribute to violations of health-based air quality standards for fine particles (PM-10). These dry lands are often difficult to revegetate, yet they may require immediate stabilization. We evaluated the effectiveness of three types of mechanical wind barriers, which can be Installed more rapidly and more reliably than revegetation, in suppressing dust emissions. Wind fences, furrows and scattered roughness elements, such as plastic cones, are shown to reduce fugitive dust emissions in areas of the Mojave Desert that resisted revegetation.

Surface disturbance in arid regions — whether it results from abandoned agriculture, overgrazing or recreational activities — often sets the stage for windblown fugitive dust. Revegetation provides the most sustainable soil stabilization but is difficult to achieve in any given year. Widely varying environmental conditions and soil factors make direct seeding unreliable, and transplanting of nursery-grown shrubs does not assure plant establishment, even with supplemental irrigation. In occasional years plants can be successfully established, particularly Atriplex canescens, in the western Mojave Desert. Once vegetation becomes established, it successfully stabilizes the soil surface and reduces blowing dust. However, because successful establishment is infrequent, reliable mitigation of fugitive dust requires that other techniques be used as well.

UC ’s Kearney Research and Extension Center (KREC) lies at the heart of one of the most productive and diverse agricultural regions in the world. Also an area of environmental challenges, Kearney’s fi eld sites have supported decades of landmark research, addressing issues as diverse as air pollution effects, the development of exotic specialty crops, and the rapid molecular diagnosis of plant disease. First dedicated as the Kearney Horticultural Field Station in 1965, KREC is one of nine UC Research and Extension Centers (RECs). All are strategically located in key agricultural regions of the state, but Kearney is unique among them in its size and scope. Functioning as a small research campus, KREC encompasses 33 specialized laboratories and hosts the UC Kearney Agricultural Center (KAC), with 24 permanent resident faculty. In addition, 20 to 25 faculty from UC campuses and county UC Cooperative Extension (UCCE) offi ces conduct research at KREC each year. The center currently supports 90 research and extension projects in 130 different fi eld and laboratory locations. KREC also houses the UCCE Central Valley regional offi ce. The cutting-edge and practical research conducted at Kearney has helped San Joaquin Valley agriculture become a $16 billion industry, yielding roughly half of California’s farm production. This issue of California Agriculture commemorates the 40th anniversary of KREC with reviews and reports on recently completed research, much of which has immediate relevance to farmers, packers and shippers. Kearney has seen steady expansion, modernization and diversifi cation over its 40-year history. Its laboratories and greenhouse facilities rival those found on the UC campuses, and its postharvest facility is state-of-the-art. The center encompasses a variety of alluvial soil types, and more than 50 different crops are cultivated under commercial growing conditions. This combination of land, laboratories and greenhouses enables UC scientists to conduct studies in a carefully managed setting. Professional staff monitor cultivated crops and continually check the operation of sophisticated laboratory facilities. Collaborative environment. Located in the center of a remarkable agricultural region, Kearney fosters interactions with industry, government agencies, environmental and public policy groups, and university scientists. Whether on small research plots, in laboratories or on-site conference facilities, growers and scientists meet here daily in the collaborative spirit envisioned by the creators of the land-grant university system. Collaboration fosters Kearney scientifi c achievements

The California Ozone Deposition Experiment, using Instruments mounted In an airplane and on the ground, shows that agricultural land in the San Joaquin Vailey removes large amounts of ozone from valley air. The most active pathway Is uptake through sto-mata In plant leaves, the process leading to crop yield losses. Other pathways, Including ozone destruction on leaf, stem and soil surfaces, are slower but very important on a valley-wide basis. Ozone deposition to crops may have a slgnlflcant Impact on air qualify, and should be considered when farmland Is converted to urban uses that contribute more to ozone production and less to ozone removal.