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Open Access Publications from the University of California


California Agriculture is a quarterly peer-reviewed journal reporting research, reviews and news on California’s agricultural, natural and human resources.

Volume 58, Issue 1, 2004

Issue cover


How can Californians be overweight and hungry?

The United States is experiencing an epidemic of obesity in both adult and children, particularly among low-income populations. In fact, overweight has replaced malnutrition as the most prevalent nutritional problem among the poor. We examine this seemingly paradoxical relationship and explore the causes and consequences of overweight, obesity and food insecurity. In a UC Cooperative Extension Body Weight and Health Workgroup study of 561 low income Latino mothers and their young children, we found important differences in the association between family food insecurity and overweight status for mothers and their children. Forty percent of the women were overweight and 37% obese, and 22% of their children were overweight. Furthermore, U.S.-born mothers who were food insecure as children were more likely to be obese adults. Awareness and understanding of the link between food insecurity and weight gain will facilitate the efforts of schools, food assistance programs, the food industry and others in the community to provide effective nutritional programs.

Food insecurity prominent among low-income California Latinos

Food security is defined as access by all people at all times to enough food for an active, healthy life. In a study of 212 low-income Latino households in California, 45% were food insecure without hunger; 13% food insecure with moderate hunger; and 3% food insecure with severe hunger. Food insecurity was associated with a decline in household supplies of both nutritious and less nutritious foods. Among preschool children, the number of servings per day of all food groups was significantly correlated with household food supplies. A strong safety net to improve food security in low-income populations must include educational strategies and provision of nutritious foods to support a good diet at home and away from home.

Rural Latino families in California are missing earned income tax benefits

When properly accessed, the federal Earned Income Tax Credit (EITC) can boost a family’s yearly income by more than $4,000. A study in Kern and Madera counties indicated that many, perhaps most, qualified low-income Latino families living in rural California communities may not be receiving the EITC. About 80% to 86% of eligible households nationwide receive the EITC, compared with about 36% of eligible California families in the study. The primary reason appears to be lack of accurate information and limited access to tax-preparation assistance. UC Cooperative Extension advisors and staff are well situated to provide information about the EITC.

Project engages culturally diverse parents in Proposition 10 decisions

California’s Proposition 10, a tax on tobacco products passed in 1998, provides counties with funds to improve the health, education and school readiness of children up to age 5. A foundation-sponsored Civic Engagement Project (CEP) seeks to promote inclusive participation in Proposition 10 decisions by engaging a broad spectrum of parents and other community members. Based on our systematic evaluation of the CEP’s initial years of work, we describe six different civic engagement tools adopted by counties, strengths and weaknesses of each, and what we learned about the conditions under which they are most effective. The results illuminate a key public challenge — how to welcome culturally and linguistically diverse Californians as active and valued participants in local civic processes while obtaining meaningful guidance for decision-making.

Expanded production of labor-intensive crops increases agricultural employment

The production of labor-intensive fruit, vegetable and horticultural specialty crops increased in the 1990s, as did the employment of farmworkers: average annual employment or roughly the number of year-round equivalent jobs rose about 20%, to almost 400,000. Far more individuals, however, are employed on California farms during the year. Agricultural employers reported 1.1 million individuals (unique Social Security numbers) when they paid unemployment insurance taxes in 2001. We analyzed the jobs and earnings of these farmworkers in 1991, 1996 and 2001. About three individuals were employed for each year-round equivalent job in the 1990s, and there was a shift to farmers hiring workers via farm labor contractors. The findings suggest that it may be possible to employ a smaller total farm workforce, with each worker employed more hours and achieving higher earnings.

Irrigation and planting density affect river red gum growth

In a 6-year study, production of river red gum, an excellent fuel-wood source, was evaluated for responses to three levels of irrigation, fertilization and planting density. Irrigation and planting density had the greatest influence on tree growth. Irrigation in the fifth and sixth years produced greater wood volume and weight per tree. Tree size was greatest in the wide spacing of the lower planting density. Fertilizer had no effect on any of the treatments. Per acre volume and weight yields were greater at the higher planting density, while individual tree height, diameter, volume and weight was greater at the low planting density. Growers seeking total wood volume per acre can increase yields with the higher density planting and irrigation.

Autoguidance system operated at high speed causes almost no tomato damage

This project explored the effectiveness of an autoguidance system based on a real-time kinematic global positioning system (RTK GPS) accurate to the centimeter (about halfinch) in agricultural production. Our objectives were to determine the effect of spacing between cultivator disks or knives and forward tractor speed on plant damage, and of deep tillage operations on drip-tape damage. Two sets of split-plot field experiments were conducted (with processing tomato transplants and direct-seeded tomatoes) in a Yolo loam field on the UC Davis campus. No significant plant damage occurred even at 7 miles per hour (mph) forward speed and cultivator disk spacing of 2 inches from the plant line. In an additional split-plot test, there was no significant damage to drip tape when the fertilizer shank was operated 2 inches from the drip tape at 3.5 mph. This system allows for automatic steering of the tractor and implements along a path close to buried drip-tape and/or plants without damaging them, even at high operational ground speeds.

Drip irrigation evaluated in Santa Maria Valley strawberries

About 4,000 acres of strawberries are grown in the Santa Maria Valley using drip irrigation. In order to help growers irrigate more effectively, we conducted studies to determine crop evapotranspiration; irrigation system performance; patterns and levels of soil salinity; soil moisture content around drip lines; and irrigation water quality. We also developed canopy growth curves. Results at 13 sampling locations showed maximum canopy coverage of less than 75%. Crop evapotranspiration ranged from 12.2 inches to 15.6 inches. Irrigation system evaluations revealed that most of the distribution uniformities were greater than 80%, considered acceptable. The electrical conductivities of the irrigation water ranged from 1 deciSiemens per meter (dS/m) to 2.36 dS/m; levels over 1 dS/m could result in yield reductions in strawberries. However, 79% of the samples had electrical conductivities equal to or less than 1.5 dS/m. Levels of soil salinity in the vicinity of drip lines ranged from 1 dS/m to 3.5 dS/m. This information can help growers calculate crop water needs and estimate irrigation set times.

In vitro gas production provides effective method for assessing ruminant feeds

An animal’s feed intake, and how well that feed is digested, determine the feed’s production performance. The in vitro gas production technique is a relatively simple method for evaluating feeds, as large numbers of samples can be incubated and analyzed at the same time. This method has been applied successfully at UC Davis for a variety of purposes in feed evaluation, including calculating organic matter digestibility, the metabolizable energy of feeds and kinetics of their fermentation; determining how feed value is affected by added fat, anti-nutritive factors and rumen modifiers; quantifying the energy value of feed mixtures (rations); monitoring microbial change in the rumen; synchronizing nutrient digestion; and selecting forage nutrient targets for agricultural biotechnology. More than half of the nutrients consumed by ruminant animals leave the animal unutilized and undigested, and are excreted in feces, urine and gases. The in vitro gas production method can be used to examine animal waste components that impact the environment and develop appropriate mitigations.

Tomato pomace may be a good source of vitamin E in broiler diets

Dried tomato pomace, a byproduct of tomato processing, is an excellent source of ?-tocopherol (vitamin E), which is used as an antioxidant in broiler meat. In a feeding study, there were no significant differences in body weight and feed per gain in chicks given diets with or without tomato pomace. Tomato pomace could be used as a source of ?-tocopherol in broiler diets to decrease lipid oxidation (fat deterioration) during heating and long-term frozen storage of dark meat, and to prolong shelf life. Because tomato byproducts contain high levels of unsaturated fatty acids, the pomace must be defatted without losing vitamin E to minimize its oxidation potential. Although we found no evidence that introducing a high-fiber feed ingredient significantly limited broiler growth, more research is needed to enhance its practical applications.