California Agriculture
California Agriculture
California Agriculture
University of California
California Agriculture

Current issue and featured articles

CAv071n02
April-June 2017
Volume 71, Number 2
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Peer-reviewed research and review articles

Field trials show the fertilizer value of nitrogen in irrigation water
by Michael Cahn, Richard Smith, Laura Murphy, Tim Hartz
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In Salinas Valley trials, lettuce and broccoli used irrigation water NO3-N as efficiently as fertilizer N, across different NO3-N concentrations and irrigation efficiencies.
Increased regulatory activity designed to protect groundwater from degradation by nitrate-nitrogen (NO3-N) is focusing attention on the efficiency of agricultural use of nitrogen (N). One area drawing scrutiny is the way in which growers consider the NO3-N concentration of irrigation water when determining N fertilizer rates. Four drip-irrigated field studies were conducted in the Salinas Valley evaluating the impact of irrigation water NO3-N concentration and irrigation efficiency on the N uptake efficiency of lettuce and broccoli crops. Irrigation with water NO3-N concentrations from 2 to 45 milligrams per liter were compared with periodic fertigation of N fertilizer. The effect of irrigation efficiency was determined by comparing an efficient (110% to 120% of crop evapotranspiration, ETc) and an inefficient (160% to 200% of ETc) irrigation treatment. Across these trials, NO3-N from irrigation water was at least as efficiently used as fertilizer N; the uptake efficiency of irrigation water NO3-N averaged approximately 80%, and it was not affected by NO3-N concentration or irrigation efficiency.
Yield in almond is related more to the abundance of flowers than the relative number of flowers that set fruit
by Sergio Tombesi, Bruce D. Lampinen, Samuel Metcalf, Theodore M. DeJong
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Maximizing healthy populations of productive spurs is key to optimizing yields in commercial almond orchards.
Almond tree yield is a function of the number of flowers on a tree and the percentage of flowers that set fruit. Almonds are borne on spurs (short proleptic shoots that can have both leaves and flowers). Almond tree spur dynamics research has documented that previous year spur leaf area is a predictive parameter for year-to-year spur survival, spur flowering and to a lesser extent spur fruiting, while previous year fruit bearing has a negative impact on subsequent year flowering. However, a question remained about whether yields are more dependent on flower numbers or relative fruit set of the flowers that are present. The aim of the present work was to compare the importance of flower abundance with that of relative fruit set in determining the productivity of a population of tagged spurs in almond trees over a 6-year period. Overall tree yield among years was more sensitive to total number of flowers on a tree rather than relative fruit set. These results emphasize the importance of maintaining large populations of healthy flowering spurs for sustained high production in almond orchards.
Lessons learned: How summer camps reduce risk factors of childhood obesity
by Gretchen L. George, Lucia L. Kaiser, Constance Schneider
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Results suggest that youth in summer nutrition and fitness camps may lose more weight than those in non-nutrition-themed camps.
The purpose of this article is to present findings related to parent- and youth-reported outcomes from a nutrition- and fitness-themed summer camp targeting low-income families and to identify lessons learned in the implementation, evaluation and sustainability of a summer program. The Healthy Lifestyle Fitness Camp, offered through UC Cooperative Extension (UCCE), was a summer camp program for low-income youth at high risk for obesity. From 2009 to 2012, UCCE nutrition staff in Fresno County collaborated with the camp staff to provide a 6-week nutrition education program to the campers and their parents. Anthropometry and dietary data were collected from youth. Data about food preferences and availability were collected from youth and parents. As reported by parents in pre- to immediately post-camp surveys, Healthy Lifestyle Fitness campers consumed fruits and vegetables promoted at camp more often, relative to a comparison group of youth in a nearby non-nutrition themed camp. Summer programs may be an effective tool in the reduction of childhood obesity risk factors if implemented appropriately into the community and through the utilization of supportive partnerships such as UCCE and local parks and recreation departments.
Using InVEST to assess ecosystem services on conserved properties in Sonoma County, CA
by Van Butsic, Matthew Shapero, Diana Moanga, Stephanie Larson
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A low-cost, spatially explicit method for documenting ecosystem services can help guide land conservation efforts.
Purchases of private land for conservation are common in California and represent an alternative to regulatory land-use policies for constraining land use. The retention or enhancement of ecosystem services may be a benefit of land conservation, but that has been difficult to document. The InVEST toolset provides a practical, low-cost approach to quantifying ecosystem services. Using the toolset, we investigated the provision of ecosystem services in Sonoma County, California, and addressed three related questions. First, do lands protected by the Sonoma County Agricultural Preservation and Open Space District (a publicly funded land conservation program) have higher values for four ecosystem services — carbon storage, sediment retention, nutrient retention and water yield — than other properties? Second, how do the correlations among these services differ across protected versus non-protected properties? Third, what are the strengths and weaknesses of using the InVEST toolset to quantify ecosystem services at the county scale? We found that District lands have higher service values for carbon storage, sediment retention and water yield than adjacent properties and properties that have been developed to more intensive uses in the last 10 years. Correlations among the ecosystem services differed greatly across land-use categories, and these differences were driven by a combination of soil, slope and land use. While InVEST provided a low-cost, clearly documented way to evaluate ecosystem services at the county scale, there is no ready way to validate the results.
Soil nitrate testing supports nitrogen management in irrigated annual crops
by Patricia A. Lazicki, Daniel Geisseler
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Soil NO3 testing can help growers use N fertilizers efficiently.
Soil nitrate (NO3) tests are an integral part of nutrient management in annual crops. They help growers make field-specific nitrogen (N) fertilization decisions, use N more efficiently and, if necessary, comply with California's Irrigated Lands Regulatory Program, which requires an N management plan and an estimate of soil NO3 from most growers. As NO3 is easily leached into deeper soil layers and groundwater by rain and excess irrigation water, precipitation and irrigation schedules need to be taken into account when sampling soil and interpreting test results. We reviewed current knowledge on best practices for taking and using soil NO3 tests in California irrigated annual crops, including how sampling for soil NO3 differs from sampling for other nutrients, how tests performed at different times of the year are interpreted and some of the special challenges associated with NO3 testing in organic systems.

News and opinion

EDITORIAL
California's working landscapes offer opportunities for economic growth
by Glenda Humiston
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Building sustainable livelihoods around our farms, ranches, forests and rivers.
PROFILE
How to study cannabis
by Jim Downing
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Van Butsic is pioneering the study of how California's richest crop affects rural landscapes.
NEWS FROM THE RECS
Coexisting with chaparral
by Jim Downing
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Long-term studies at Hopland Research and Extension Center find no simple answers for reducing fire risk while conserving biodiversity.
NEWS FROM THE RECS
After fire, the roles of rabbits and wildflowers
by Hazel White
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The dark ash left by a chaparral fire is rich in ammonium nitrogen; can the ecosystem absorb it before winter rains wash it away?
NEWS
Apps for Ag winner launches community-building app in Davis
by Hazel White
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GivingGarden will connect neighbors through a produce-sharing service. It's superlocal, like NextDoor, but devoted solely to food and gardening.
NEWS
Research highlights
Editors
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Recent scientific articles from the Agricultural Experiment Station campuses.

Early view articles

PEER-REVIEWED
Forage seeding in rangelands increases production and prevents weed invasion
by Josh S. Davy, Katherine Dykier, Tony Turri, Elise Gornish
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In a seeding study in the California foothills, annual ryegrass and soft brome performed well in the short term, and Flecha tall fescue, several hardinggrass varieties and Berber orchardgrass worked well in the long term.
Increasing forage productivity in the Sierra foothill rangelands would help sustain the livestock industry as land availability shrinks and lease rates rise, but hardly any studies have been done on forage selections. From 2009 to 2014, in one of the first long-term and replicated studies of seeding Northern California's Mediterranean annual rangeland, we compared the cover of 22 diverse forages to determine their establishment and survivability over time. Among the annual herbs, forage brassica (Brassica napus L.) and chicory (Cichorium intybus L.) proved viable options. Among the annual grasses, soft brome (Bromus hordeaceus) and annual ryegrass (Lolium multiflorum) performed well. However, these species will likely require frequent reseeding to maintain dominance. Long-term goals of sustained dominant cover (> 3 years) are best achieved with perennial grasses. Perennial grasses that persisted with greater than 50% cover were Berber orchardgrass (Dactylis glomerata), Flecha tall fescue (Lolium arundinaceum) and several varieties of hardinggrass (Phalaris aquatica L., Perla koleagrass, Holdfast, Advanced AT). In 2014, these successful perennials produced over three times more dry matter (pounds per acre) than the unseeded control and also suppressed annual grasses and yellow starthistle (Centaurea solstitialis L.) cover.
PEER-REVIEWED
Volunteer educators bring their own ideas about effective teaching to a 4-H curriculum
by Steven Worker
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Pragmatic and structural constraints shaped the pedagogical choices volunteer educators made, as did their professional identification and comfort with engineering.
Youth programs implemented during out-of-school time often rely on volunteers. These volunteers are responsible for selecting and adapting curriculum and facilitating activities, so their pedagogical practices become primary contributors to program quality, and ultimately, youth outcomes. To describe volunteers' pedagogical practices, I conducted a qualitative case study at three sites where volunteer educators were implementing a design-based 4-H curriculum. The curriculum advanced youth scientific literacy by supporting scientific inquiry in conjunction with planning, designing and making shareable artifacts. Through detailed observations, videos and focus groups, I identified six common pedagogical practices, though educators differed widely in which ones they used. Pragmatic and structural constraints shaped their choices, as did their professional identification as engineers, or not, and their relative comfort with engineering. To support volunteer educators in implementing a learner-centered educational program, curricula designers might be more specific in recommending and explaining pedagogical practices, and program managers might better train volunteer educators in those preferred practices.
PEER-REVIEWED
Modeling identifies optimal fall planting times and irrigation requirements for canola and camelina at locations across California
by Nicholas George, Lucia Levers, Sally Thompson, Joy Hollingsworth, Stephen Kaffka
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Sufficient rainfall and appropriate soil temperatures during the canola planting window occur statewide on average 1 in 3 years, but camelina is significantly more drought and cold tolerant.
In California, Brassica oilseeds may be viable crops for growers to diversify their cool-season crop options, helping them adapt to projected climate change and irrigation water shortages. Field trials have found germination and establishment problems in some late-planted canola, but not camelina at the same locations. We used computer modeling to analyze fall seedbed conditions to better understand this phenomenon. We found seedbeds may be too dry, too cold, or both, to support germination of canola during late fall. Based on seedbed temperatures only, canola should be sown no later than the last week of November in the Central Valley. Camelina has broader temperature and moisture windows for germination and can be sown from October to December with less risk, but yields of camelina are lower than canola yields. In areas without irrigation, growers could plant canola opportunistically when seedbed conditions are favorable and use camelina as a fallback option.
PEER-REVIEWED
Land access and costs may drive strawberry growers' increased use of fumigation
by Julie Guthman
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The phaseout of methyl bromide and increasing regulation of other fumigants did not decrease overall fumigant use in California strawberries. Here are some likely reasons why.
2016 marked the year of the final phaseout of methyl bromide for use in strawberry production. During the long phaseout period, one replacement fumigant met so much public opposition it was taken off the market, while restrictions on use of other fumigants increased. As part of a larger study on the challenges facing the strawberry industry, I tracked fumigant use through California's pesticide use reporting system from 2004 to 2013. During the last few years before the phaseout, I interviewed 74 growers in the four main strawberry production regions about how they were now managing soilborne pests. As a general trend, growers had increased their use of chloropicrin and switched from broadcast fumigation to bed fumigation, and many were experimenting with organics. At the same time, significant percentages of growers were reluctant to change fumigation regimes or adopt nonchemical options of pathogen control. Some were unable to adopt less chemical-intensive methods because of land access conditions and land costs. Given these land-related obstacles, policymakers ought to consider strategies that will incentivize transitions to nonchemical alternatives and mitigate the financial risks.
PEER-REVIEWED
Automated lettuce thinners reduce labor requirements and increase speed of thinning
by Elizabeth Mosqueda, Richard Smith, Dave Goorahoo, Anil Shrestha
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Automated thinners were as accurate in thinning lettuce as manual thinning, produced comparable yields, and were more than three times faster than thinning crews.
Salinas Valley lettuce growers are adopting automated lettuce thinners to improve labor efficiency. We conducted field studies in 2014 and 2015 to compare the time involved in automated and manual thinning of direct-seeded lettuce and any differences in lettuce quality and yield. We recorded the number of doubles (two closely spaced plants) left behind after thinning, time taken to remove the doubles, final crop stand, efficiency in weed removal, crop yield and disease incidence. Using an automated thinner in place of manual hoeing reduced the thinning labor requirement from 7.31 ± 0.5 person-hours per acre to 2.03 ± 0.5 person-hours per acre. Automated thinning left more doubles than manual thinning, resulting in additional time to remove them, but was overall more labor-efficient and had no impact on yield or disease incidence.
PEER-REVIEWED
Remote sensing is a viable tool for mapping soil salinity in agricultural lands
by Elia Scudiero, Dennis L. Corwin, Ray G. Anderson, Kevin Yemoto, Wesley Clary, Zhi “Luke” Wang, Todd H. Skaggs
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Remote-sensing modeling produces an accurate regional salinity map of the western San Joaquin Valley, useful for growers and state agencies.
Soil salinity negatively impacts the productivity and profitability of western San Joaquin Valley (WSJV) farmland. Many factors, including drought, climate change, reduced water allocations, and land-use changes could worsen salinity conditions there, and in other agricultural lands in the state. Mapping soil salinity at regional and state levels is essential for identifying drivers and trends in agricultural soil salinity, and for developing mitigation strategies, but traditional soil sampling for salinity does not allow for accurate large-scale mapping. We tested remote-sensing modeling to map root zone soil salinity for farmland in the WSJV. According to our map, 0.78 million acres are salt affected (i.e., ECe > 4 dS/m), which represents 45% of the mapped farmland; 30% of that acreage is strongly or extremely saline. Independent validations of the remote-sensing estimations indicated acceptable to excellent correspondences, except in areas of low salinity and high soil heterogeneity. Remote sensing is a viable tool for helping landowners make decisions about land use and also for helping water districts and state agencies develop salinity mitigation strategies.
Editor Jim Downing talks about what's in the current issue of California Agriculture journal — almonds, nitrogen management, chaparral and biodiversity, cannabis cultivation and more.

 

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