Publications Published in California Agriculture

1. Agroforestry is Promising for Previously Cleared Hardwood Rangelands. McCreary, Doug.
   California Agriculture: 2001
   Notes
   Livestock grazing is the primary economic use of most hardwood rangelands in the coastal foothills of California. But owners of these lands may be able to increase revenues by simultaneously producing two crops, trees and sheep. In 1993, we initiated an agroforestry project at the UC Hopland Research and Extension Center to study the ability of three pine species and one hybrid to grow on cleared hardwood rangelands that are grazed by sheep. This study also evaluated the response of planted seedlings to auger and fertilization treatments. After 8 years, tree survival has been high, growth has been vigorous and damage from sheep minimal. Monterey pine and KMX pine, a cross between Monterey and knobcone pine, had the most growth. These results suggest that some pine species are promising for planting on grazing lands in coastal foothills where oaks and other hardwoods have been removed.
   
   
   
2. Biodiversity is critical to future health of California's ecology and economy. Allen-Diaz, B.
   California Agriculture: 2000
   Notes
   Each individual organism plays a role in the birth-to-death cycle of this planet. Ecologists often refer to the web of life, describing the interconnectedness of all organisms and environments. Of California’s more than 4,800 native plant species, 29% are only found here. Each species is the repository of an immense amount of genetic information. Organisms provide direct economic value to humans in the form of marketable products such as food and medicine, as well as services like recreation, beauty and clean water. But civilization has been altering the Earth’s environment and the consuming resources at rates faster than during any known era in history. At the same time, we are poorly equipped to evaluate the environmental and economic trade-offs between species as traditional commodities, as providers of ecosystem services and as players with largely unknown roles in life on Earth. New institutional frameworks and incentives must be developed in the 21st century for making informed and wise choices about the environment. Such decision-making frameworks should ensure the protection of fundamental sources of food, clean water and habitat that are Earth’s life-support.
   
   
   
3. Blue oak enhance soil quality in California oak woodlands. Dahlgren, Randy A; Horwath, William R; Tate, Kenneth W; Camping, Trina J.
   California Agriculture: 2003
   Notes
   Blue oaks create islands of enhanced soil quality and fertility beneath their canopy. The quality of soil beneath the oak canopy is considerably better than that of the grasslands adjacent to the trees. We found evidence of improved soil quality under blue oaks for physical, chemical and biological soil properties. The type of vegetation (oak versus annual grasses) has a much stronger influence on soil organic matter and nutrient pools than does soil parent material. Removal of oak trees results in a rapid deterioration of soil quality with the majority of the loss occurring within 10 to 20 years after tree removal.
   
   
   
4. Long-term studies find benefits, challenges in alternative rice straw management. Bird, J A; Eagle, Alison J; Horwath, William R; Hair, Mike W; Zilbert, Eric E; Van Kessel, Chris.
   California Agriculture: 2002
   Notes
   California state legislation passed in 1991 mandated a phased reduction of rice straw burning in the Central Valley, to reduce air pollution. In 1993, UC Davis scientists launched an 8-year research project on the long-term effects of various alternative means of managing rice straw. Burning, incorporation into the soil, rolling, and baling and removing the straw were compared, with and without winter flooding. None of the various practices reduced California state legislation passed in 1991 (Connelly-Areias-Chandler Rice Straw Burning Reduction Act) mandated a phased reduction of rice straw burning. The final step of the phasedown started in September 2001, when the law allowed burning only for disease control. Under the current scenario, disease-control burning will be limited to 25% of the approximately 500,000 planted acres or 125,000 acres, whichever is less. In the future, further Rice straw management in California’s Central Valley has undergone profound changes over the past decade. Historically, rice growers routinely burned their field to dispose of rice straw for sanitation and seedbed preparation purposes. In 1989, when 400,000 acres of rice were grown in California, 95% of the resulting debris was burned in the field, creating air pollution in the Central Valley and statewide. grain yields on our experimental plots, but there was an increase in weeds when straw was incorporated, and in particular when the fields were not winter flooded. However, when straw is incorporated, nutrients are returned to the soil and less nitrogen fertilizer can be applied, resulting in lower production costs and less potential for water pollution. In addition, waterfowl on the Pacific Flyway benefit significantly from the wetlands created when fields are flooded during the winter.
   
   
   
5. Looking back 60 years, California soils maintain overall chemical quality. De Clerck, Fabrice; Singer, Michael J.
   California Agriculture: 2003
   Notes
   To learn whether soil properties important to production agriculture and environmental quality have changed significantly in the past half-century in California, we analyzed archival samples and samples collected in 2001 from the same locations. Comparisons of organic matter content, pH, electrical conductivity, total nitrogen, total carbon and plantavailable phosphorus showed significant changes since the mid-1900s. cross the state we found increases at the 95% confidence level for plant-available phosphorus, total carbon, pH, and percent clay, and increases at the 90% confidence level for percent silt and total nitrogen. We measured significant decreases at the 95% confidence level for electrical conductivity and percent sand. Based on this sample of 125 soils, we believe that California’s soil chemical quality has not decreased significantly over the past 60 years. However, increased clay percentages may be interpreted as a sign of accelerated erosion, which is a sign of decreased soil quality.
   
   
   
6. Minimum tillage practices affect disease and yield of lettuce. Jackson, Louise E; Ramirez, Irenee R; Morales, Israel; Koike, Steven T.
   California Agriculture: 2002
   Notes
   Vegetable growers have been experimenting with reduced tillage practices to increase soil organic matter, limit compaction, and reduce fuel and labor costs. We studied soil properties of different tillage practices and compared deep minimum tillage (chiseling and ripping) with shallow minimum tillage for lettuce on a farm in the Salinas Valley. We found that periodic deep minimum tillage is recommended for long-term retention of semipermanent, raised beds in lettuce production. Over a period of several years, deep minimum tillage increased lettuce yield and decreased symptoms of lettuce drop disease, as compared with shallow minimum tillage. Continuous shallow minimum tillage, despite a trend toward higher active and total organic matter in the surface layer of soil, is best used with intermittent deeper tillage to avoid disease and yield losses.
   
   
   
7. Modeling shows that alternative soil management can decrease greenhouse gases. Steven De Gryze, Maria Victoria Albarracin, Rosa Catala-Luque, Richard E. Howitt, Johan Six.
   California Agriculture: 2009
   
   
8. One-pass tillage equipment outstrips convential tillage method. Upadhyaya, Shrinivasa K; Lancas, Kleber P; Santos-Filho, Abilio G; Raghuwanshi, Narendra S.
   California Agriculture: 2001
   Notes
   For this study, we compared a new one-pass tillage implement called the Incorpramaster with a conventional tillage practice of stubble disking and land planning. Our randomized block experiment on the UC Davis campus evaluated the equipment’s energy and time savings. We found that the one-pass tillage equipment (OPTE) outperformed conventional land preparation methods in fuel consumption and speed. Fuel savings ranged from 19% to 81% with a mean savings of 50%. Time savings ranged from 67% to 83% with mean of 72%. The mean soil particle size created by the one pass tillage implement was comparable to that produced by conventional tillage methods.
   
   
   
9. Realistic payments could encourage farmers to adopt practices that sequester carbon. Richard E. Howitt, Rosa Català-Luque, Steven De Gryze, Santhi Wicks, Johan Six.
   California Agriculture: 2009
   DOI: 10.3733/ca.v063n02p91
   
   
10. Reducing fertilizer in sugarbeets can protect water quality. Kaffka, Stephen R; Kirby, Don; Peterson, Gary R.
    California Agriculture: 2001
    Notes
    Environmentally sensitive crop management requires applying only enough fertilizer to ensure economic crop yields. We found that sugarbeets grown in soils rich in organic matter in the Upper Klamath Basin can be fertilized at very low rates and used to remove more nutrients in harvested roots than are applied as fertilizer. Phosphorus levels in surface waters entering the Tulelake Irrigation District are high, and area soils contain large amounts of organically bound phosphorus.