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Open Access Publications from the University of California

Volume 71, Issue 4, 2017

Issue cover
Cover Caption: Satellite imagery to model root-zone soil salinity in the western San Joaquin Valley. They found 30% of mapped farmland to be strongly or extremely saline. In the map section shown on the cover, soil salinity ranges from non-saline (dark green) to extremely saline (red). Image credit: USDA-ARS and University of California Riverside.

Research and Review Articles

Volunteer educators bring their own ideas about effective teaching to a 4-H curriculum

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.

Modeling identifies optimal fall planting times and irrigation requirements for canola and camelina at locations across California

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.

Ownership characteristics and crop selection in California cropland

Land ownership is one of the primary determinants of how agricultural land is used, and property size has been shown to drive many land use decisions. Land ownership information is also key to understanding food production systems and land fragmentation, and in targeting outreach materials to improve agricultural production and conservation practices. Using a parcel dataset containing all 58 California counties, we describe the characteristics of cropland ownership across California. The largest 5% of properties — with “property” defined as all parcels owned by a given landowner — account for 50.6% of California cropland, while the smallest 84% of properties account for 25% of cropland. Cropland ownership inequality (few large properties, many small properties) was greatest in Kings, Kern and Contra Costa counties and lowest in Mendocino, Napa and Santa Clara counties. Of crop types, rice properties had the largest median size, while properties with orchard trees had the smallest median sizes. Cluster analysis of crop mixes revealed that properties with grapes, rice, almonds and alfalfa/hay tended to be planted to individual crops, while crops such as grains, tomatoes and vegetables were more likely to be mixed within a single property. Analyses of cropland ownership patterns can help researchers prioritize outreach efforts and tailor research to stakeholders' needs.

Remote sensing is a viable tool for mapping soil salinity in agricultural lands

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.

Forage seeding in rangelands increases production and prevents weed invasion

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.

Cow cooling on commercial drylot dairies: A description of 10 farms in California

California summers are hot, compromising the welfare and productivity of dairy cows. To minimize negative effects, producers use shade, fans and sprayed water. However, little is known about how those heat abatement strategies are provided in commercial conditions, nor their effectiveness. Ten dairies with drylots, a common housing system in California, were assessed for strategies provided, and the cows' responses to heat load were observed for 3 days in the afternoon. Dairies were diverse in all aspects. Shade varied in terms of placement (at corral and feed bunk or at corral only) and amount (28 to 74 square feet, or 2.6 to 6.9 square meters, per cow). The quantity of water used to spray cows ranged from 0 to 6.8 gallons (0 to 25.6 liters) per hour per cow. Across dairies, there was a range in the cows' shade use (47% to 98% of herd) and feeding activity (7% to 33% of herd). Respiration rates ranged from 65 (normal) to 95 breaths per minute (very hot) and were positively related to inactivity. Our results indicate that there are opportunities to improve cooling, and consequently dairy cattle welfare, in drylots.

News and Opinion

Measuring our impact, setting our course

UC ANR is a network of change agents who care about the health and welfare of people, communities and natural resources.

Building climate change resilience in California through UC Cooperative Extension

A survey of UC ANR academics found opportunities for expanding the role of climate change in extension work.

Desert REC: Educational outreach and crop breeding

Located in the Imperial Valley, this research station runs UC ANR's biggest agricultural outreach program and hosts the largest public carrot breeding program in the Americas.

Research highlights

Recent scientific articles from the Agricultural Experiment Station campuses

Teaching volunteer educators to tinker

Steven Worker is helping to improve out-of-school-time pedagogy.