Skip to main content
Open Access Publications from the University of California

Volume 70, Issue 2, 2016

Conservation agriculture in California

Issue cover
Cover Caption: Complete contents, including news and editorial featuresRecent UC research demonstrates the potential of overhead irrigation as an alternative to furrow and drip irrigation on Central Valley crops such as wheat, corn and cotton (see article). Benefits of overhead irrigation include less soil disturbance, which complements conservation agriculture practices, and lower labor requirements. Shown here is an overhead system irrigating a carrot field in Arvin - Lamont, Kern County. Photo by Jeffrey Mitchell.

Research and Review Articles

Precision overhead irrigation is suitable for several Central Valley crops

Overhead systems are the dominant irrigation technology in many parts of the world, but they are not widely used in California even though they have higher water application efficiency than furrow irrigation systems and lower labor requirements than drip systems. With water and labor perennial concerns in California, the suitability of overhead systems merits consideration. From 2008 through 2013, in studies near Five Points, California, we evaluated overhead irrigation for wheat, corn, cotton, tomato, onion and broccoli as an alternative to furrow and drip irrigation. With the exception of tomato, equal or increased yields were achieved with overhead irrigation. Many variables are involved in the choice of an irrigation system, but our results suggest that, with more research to support best management practices, overhead irrigation may be useful to a wider set of California farmers than currently use it.


Accounting for potassium and magnesium in irrigation water quality assessment

Irrigation with treated wastewater is expected to increase significantly in California during the coming decade as a way to reduce the impact of drought and mitigate water transfer issues. To ensure that such wastewater reuse does not result in unacceptable impacts on soil permeability, water quality guidelines must effectively address sodicity hazard. However, current guidelines are based on the sodium adsorption ratio (SAR) and thus assume that potassium (K) and magnesium (Mg), which often are at elevated concentrations in recycled wastewaters, pose no hazard, despite many past studies to the contrary. Recent research has established that the negative effects of high K and Mg concentrations on soil permeability are substantial and that they can be accounted for by a new irrigation water quality parameter, the cation ratio of structural stability (CROSS), a generalization of SAR. We show that CROSS, when suitably optimized, correlates strongly with a standard measure of soil permeability reduction for an agricultural soil leached with winery wastewater, and that it can be incorporated directly into existing irrigation water quality guidelines by replacing SAR.


Community and home gardens increase vegetable intake and food security of residents in San Jose, California

As of 2013, 42 million American households were involved in growing their own food either at home or in a community garden plot. The purpose of this pilot study was to document the extent to which gardeners, particularly less affluent ones, increase their vegetable intake when eating from either home or community garden spaces. Eighty-five community gardeners and 50 home gardeners from San Jose, California, completed a survey providing information on demographic background, self-rated health, vegetable intake and the benefits of gardening. The gardeners surveyed were generally low income and came from a variety of ethnic and educational backgrounds. Participants in this study reported doubling their vegetable intake to a level that met the number of daily servings recommended by the U.S. Dietary Guidelines. Growing food in community and home gardens can contribute to food security by helping provide access to fresh vegetables and increasing consumption of vegetables by gardeners and their families.

A qualitative evaluation of UC CalFresh Plan, Shop, Save, Cook curriculum reveals additional outcomes

UC ANR Cooperative Extension (UCCE) conducted six focus groups in 2013 with CalFresh-eligible adults to determine how to improve the existing evaluation method for the Plan, Shop, Save, Cook nutrition education classes. Focus group participants (n = 54) cited many behavior changes that are captured by the existing method. During the focus groups, changes in cooking practices and types of food purchased emerged as two domains that are not currently captured. A small pilot study conducted on 22 of the 54 focus group participants suggests that using a telephone interview to survey participants is a feasible and practical approach to collect follow-up data on long-term behavior changes. More rigorous follow-up studies may guide the development of policies aimed at increasing diet quality and food security of adult CalFresh participants.

Low-input, low-cost IPM program helps manage potato psyllid

Potato psyllid is a pest of solanaceous plants throughout much of the western United States, including California, where it has increased and is now overwintering. The psyllid affects its plant hosts from direct feeding and by transmitting a plant pathogenic bacterium, Lso. Millions of dollars of damages have occurred in the U.S. potato industry, and a large acreage of crops is susceptible in California. Control is complicated because different crops have different pest complexes and susceptibilities to Lso; currently most growers use multiple pesticide applications, including broad-spectrum insecticides. Results of our field trials at South Coast Research and Extension Center indicate that the use of broad-spectrum insecticides actually increases psyllid numbers in both peppers and potatoes. We have developed a low-input IPM program, which in field trials produced encouraging results in peppers, potatoes and tomatoes compared to broad-spectrum insecticides. Economic analysis showed the low-input IPM approach was more cost effective than a standard insecticide program in tomatoes.

Editorial, News, Letters and Science Briefs