July-September 2012

Cover: Cotton production has traditionally relied on multiple tractor passes during the growing season, but targeted UC research — applying technological innovations — is demonstrating that conservation tillage is a viable option for California growers. In a 12-year study of cotton grown in rotation with tomato, conservation tillage lowered the number of tractor passes by about half, reducing labor and fuel usage. In the study’s later years, lint yields were equivalent in the standard and conservation tillage plots. This innovative tomato transplanter (cover) tills strips of a Hollister field, rather than the entire surface. Photo by Jeffrey P. Mitchell

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California Agriculture, July-September 2012

Volume 66, Number 3
Long-term study: Conservation tillage saves soil, time and money

peer-reviewed research articles

Agricultural burning monitored for air pollutants in Imperial County; exposure reduction recommendations developed
by Martha Harnly , Kinnery Naik-Patel , Stephen Wall , Penelope J. E. Quintana , Diamon Pon , Jeff Wagner
pp85-90, doi#10.3733/ca.v066n03p85
Abstract
Air pollutants, notably particulate matter (PM) with aerodynamic diameter smaller than 2.5 micrometers (PM2.5), are emitted during agricultural burning. We studied a winter period in Imperial County when predominantly bermuda-grass stubble was burned. At four locations, PM2.5 levels were 23% higher from 4 p.m. on burn days to 8 a.m. the following morning than on days when there were no burns. On days when a burn was within 2 miles of a monitoring site, concentrations were 7 to 8 micrograms per cubic meter higher than on days when burns were farther away; measured levels lowered air quality, which potentially approached moderate. In monitoring five specific burns, we found that the levels of particulate matter with aerodynamic diameter smaller than 10 micrometers (PM10) were highly elevated and potentially hazardous directly downwind of one field. In addition, PM2.5 was composed primarily of carbon, and levels of naphthalene, a respiratory carcinogen, were elevated compared with upwind samples. In interviews, most community leaders, residents and farmers thought health educational efforts were needed. As a result, we developed fact sheets and have made recommendations for further actions to reduce people's exposure to smoke from agricultural burning.
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Income value of private amenities assessed in California oak woodlands
by Jose L. Oviedo , Lynn Huntsinger , Pablo Campos , Alejandro Caparrós
pp91-96, doi#10.3733/ca.v066n03p91
Abstract
Landowners in California were surveyed using a contingent valuation technique to assess its usefulness in estimating the monetary income value of private amenities from their oak woodland properties. Private amenities — such as recreation, scenic beauty and a rural lifestyle — are considered an important influence on rangeland owners, but few studies have attempted to place a monetary income value on them. Landowners were asked to estimate the maximum amount of earnings that they were willing to forgo before selling their property to invest in more commercially profitable, nonagrarian assets, and the proportion of the land price that they thought was explained by private amenities from their land. On average, landowners were willing to pay $54 per acre annually for private amenities, and they attributed 57% of the land price to them. Regression analysis revealed that the landowners’ willingness to pay per acre decreased as property size increased. This approach sheds light on how landowners value the benefits of land owner-ship and offers insights for outreach and policy development for privately owned oak woodlands.
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Radio-frequency identification could help reduce the spread of plant pathogens
by Andrea Luvisi , Alessandra Panattoni , Enrico Triolo
pp97-101, doi#10.3733/ca.v066n03p97
Abstract
A traceable declaration of health is now necessary for many plants, especially those being monitored for disease such as certified nursery stock. Radio-frequency identification (RFID) microchips placed in woody plants can be used to store and retrieve information on their health status through all phases of propagation and in the field. The microchip is linked to a database in which many other kinds of information, such as pesticide applications, can be collected and linked. Using a Web-based platform, information can be shared globally and accessed quickly. RFID technology can also be integrated with cell phones and netbooks for the easy recording of images and audio, which can be linked back to the chip and shared — or, with global positioning systems (GPS), used to create a virtual orchard or vineyard. There are myriad uses for this new technology, which is expanding rapidly and has been implemented successfully in the European livestock industry. Trials have shown its particular relevance to plant pathology, where it could be an important risk management tool.
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Standards vary in studies using rainfall simulators to evaluate erosion
by Mark Grismer
pp102-107, doi#10.3733/ca.v066n03p102
Abstract
Rainfall simulators are often employed to measure erosion rates, in order to estimate stream loading of sediment and nutrients in California foothill watersheds. The rainfall simulator enables the precise application of artificial rain with controlled drop sizes, intensity and duration. In addition to rain factors such as drop energy and intensity, several soil- and cover-related factors affect erosion rates. While computational models have evolved to quantify erosion based on field measurements taken by rainfall simulators, there has not been a consensus on the methodology to be deployed, especially in forested and remote landscapes. In addition, it is challenging to apply study results from small plots to entire watersheds. To guide future fieldwork on sediment loading to water bodies, we review key concerns related to rainfall simulator studies.
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Conservation tillage systems for cotton advance in the San Joaquin Valley
by Jeffrey P. Mitchell , Lyle Carter , Daniel Munk , Karen Klonsky , Robert Hutmacher , Anil Shrestha , Richard DeMoura , Jonathan Wroble
pp108-115, doi#10.3733/ca.v066n03p108
Abstract
Cotton production in the San Joaquin Valley has traditionally relied heavily on tillage for its presumed benefits to plant establishment, yields and insect management. Research in the 1960s and 1970s demonstrated the potential of precision or zone tillage, which foreshadowed the introduction of a variety of minimum tillage implements in the early 1990s. During a 3-year comparison study from 2001 to 2003, cotton yields in strip tillage plots matched or exceeded yields of standard tillage plots in all 3 years. In a 12-year study from 1999 to 2011, tillage costs were lowered an average of $70 per acre in 2011 dollars using no-tillage compared to standard tillage while achieving statistically comparable yields, provided that adequate crop stands were achieved. If bottom-line profitability can be maintained, conservation tillage may become increasingly attractive to cotton producers in the San Joaquin Valley.
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editorial, news, letters & science briefs

EDITORIAL: California agriculture profitable and growing
by Karen Klonsky
pp78, doi#10.3733/ca.v066n03p78
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Corrections
Editors
pp81, doi#10.3733/ca.v066n03p81b
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Letters
From our readers
pp81-84, doi#10.3733/ca.v066n03p81a
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Three ACE awards for California Agriculture
Editors
pp83, doi#10.3733/ca.v066n03p83
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First phase of Hilgardia Project under way
by Janet White
pp84, doi#10.3733/ca.v066n03p84
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General Information

About California Agriculture
by Editor
pp80, doi#10.3733/ca.v066n03p80
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Available from ANR: Protecting oak woodlands and A Planner's Guide for Oak Woodlands
Editors
pp116, doi#10.3733/ca.v066n03p116a
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COMING UP in California Agriculture: Implications of eliminating the Williamson Act
Editors
pp116, doi#10.3733/ca.v066n03p116b
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