Even on the west side of the San Joaquin Valley, where average rainfall is a mere 7 inches per year, farmers can reap the benefits of winter cover crops without the expense of irrigation, University of California research has found. Growing a winter cover crop helps retain soil nitrogen – keeping it from leaching into groundwater – improves water infiltration, reduces runoff, increases soil organic matter and boosts long-term soil fertility.
Moreover, a vigorously growing cover crop can smother winter weeds, reducing or eliminating the need for herbicides or tillage between crops.
“Despite the many and varied benefits of cover cropping that are increasingly seen by farmers in other parts of the country, the vast majority of Central Valley farmers currently do not use them,” said Jeff Mitchell, UC Cooperative Extension specialist in the Department of Plant Sciences at UC Davis. Mitchell, a cropping systems expert, is based at the Kearney Agricultural Research and Extension Center in Parlier, Calif.
The costs and benefits of winter cover crops are being examined in an ongoing trial at the UC West Side Research and Extension Center in Five Points, Calif. Initiated in 2000, the trial is led by Mitchell, William Horwath, a professor in the Department of Land, Air and Water Resources at UC Davis, and Dan Munk, UC Cooperative Extension advisor in Fresno County, a cotton and soils expert.
Mitchell said the West Side trial addresses valley farmers’ primary concern about cover crops – water.
“When water is short, as it has been in many recent years, farmers wonder how inserting an extra crop that doesn’t bring an immediate return on investment makes sense,” Mitchell said. “But our work over the last 12 years has demonstrated that cover cropping ‘on the cheap’ – relying only on rainfall for irrigation – supplies many benefits and doesn’t cost much.”
Rainfall during the November to March winter growth period in Five Points averages 7 inches, slightly less than the 30-year average annual rainfall of 7.6 inches for the site. Winter rainfall has varied considerably during the trial, from a low of 2.9 inches in 2003 to a high of 11 inches in 2006.
From 2000 to 2010, a cover crop mix of triticale, ryegrain and pea was grown at a seed cost of $55 per acre (2012 dollars). In 2011 and 2012, the researchers used a mixture of fava bean and “tillage radish” for the cover crop, at a cost of $50 per acre.
Tillage radish is a large-rooted winter annual being marketed for its ability to improve soil condition. It’s thick, tuberous roots break up the soil surface. When it is killed in the spring and the roots decompose and shrivel, it leaves behind channels that help with aeration and water infiltration.
Over the course of the UC trial, an average of 3,400 pounds of dry biomass per acre was produced by the cover crops each year with rainfall alone. Productivity generally related to the amount of rain, with as little as 65 pounds of dry biomass per acre in 2007, when rainfall was 5.2 inches, and 6,400 pounds in 2005, when 10.1 inches of rain fell.
The timing of rainfall was also important. Rain is needed early to establish the crop and late in the season to sustain its growth when the temperature warms.
Over time, growing cover crops results in a significantly higher amount of carbon in the top foot of soil. Following eight years of cover cropping, soil carbon values in the standard tillage cover crop system, in which the cover crop was treated as a green manure and incorporated into the soil at a depth of 10 inches, was 12.2 tons of carbon per acre. Where cover crops were combined with conservation tillage, the researchers measured 12.8 tons per acre. In areas managed with conservation tillage and no cover crop, 11.7 tons per acre of carbon was in the top foot of soil. Under standard tillage and no cover crops, currently the common practice in the San Joaquin Valley, soil carbon came in at 9.9 tons per acre.
In addition to improving soil quality, farmers are investigating whether storing extra carbon in the soil will make them eligible for selling carbon credits under California Assembly Bill 32, the Global Warming Solutions Act.
“Sequestering carbon in farmland could be a means of mitigating global warming from greenhouse gas emissions,” Mitchell said. “We are working with farmers to develop a record of performance so they can document their potential for storing more carbon using conservation tillage and cover crops.”
The UC Conservation Agriculture Systems Initiative challenges Californians to look 100 years, or even 500 years, into the future and imagine how today’s common agricultural practices will have impacted the environment and society.
The United Nations estimates world population in 2300 will be about 9 billion. There is likely to be significant development in the ensuing 300 years that reduces the amount of land for farming.
“We have to be able to do more with less,” said Jeff Mitchell, UC Cooperative Extension cropping systems specialist, echoing a common theme repeated by speakers at the launch of the UC Conservation Agriculture Systems Initiative (CASI) Jan. 27. “The global demand for food will be immense.”
Mitchell, other researchers and many innovative farmers have documented in more than 14 years of field research that changes in traditional farming practices – employing such technologies as precision irrigation, integrated pest management and conservation tillage – cut costs $75 to $150 per acre, reduce dust and diesel fuel emissions 60 to 80 percent, and prevent evaporation of about 4 inches of water per season from the soil surface.
This sort of objective data, plus favorable economic analyses and access to high-technology conservation equipment, are important factors in motivating farmers to change their practices, but they are not the only factors, Mitchell said. The Institute is committed to not only demonstrating and communicating the documented benefits of conservation agriculture but also identifying the drivers behind behavior change. The goal is converting 50 percent of California crop acreage to conservation practices by 2028.
“The cornerstone of sustainability is behavior change,” said Ron Harben of the California Association of Resource Conservation Districts, one of the Initiative’s founders. “Simply providing information has little or no effect on what people do.”
In parts of the U.S. and the world, conservation agriculture is common practice. World leaders in conservation agriculture include Brazil, Argentina and Paraguay, Western Australia and Canada. Within the next ten years, Mitchell reported, more than 85 percent of the cropland in the three South American countries is expected to be converted to conservation agriculture. Adoption rates are also quite high in parts of South Dakota, Nebraska, the Pacific Northwest, and areas throughout Alabama and Georgia. Yet implementation in California is still low.
In 2010, conservation tillage systems accounted for about 14 percent of the acreage in silage and grain corn, small grains for hay, silage and grain, tomatoes, cotton, dry beans, and melons in the nine-county Central Valley region. This was an increase from about 10 percent in 2008. Minimum tillage practices were used on about 33 percent of crop acreage in 2010, up from about 21 percent in 2008.
Mitchell said the implementation trends around the world, in the U.S. and in California “lend a certain inevitability” to its wide adoption in the San Joaquin Valley.
“This is not just about making a profit and optimizing yields,” Mitchell said. “By minimizing soil disturbance, preserving surface residue and including a greater diversity of crops in the rotation we are improving the soil resources and deepening the soil in an improved condition.”
The keynote speaker at the CASI launch was Hanford dairy farmer Dino Giacomazzi, a long-time innovator in conservation agriculture. Giacomazzi discovered conservation agriculture not long after taking over day-to-day operations of the Giacomazzi dairy from his father.
“It’s less work for more money,” Giacomazzi said. “Why aren’t people doing it? What’s the holdup?”
Perhaps in answer to his own question, Giacomazzi shared the reaction of his father to the new system being used on their farm. In their last conversation, the elder Giacomazzi lamented that, “Everything I’ve ever done, you’ve undone,” his son related at the meeting.
Dino Giacomazzi said many farmers’ tendency to be “enthralled” with tradition, their fierce independence, aversion to risk and fear of derision from neighbors contribute to their resistance to change. But accepting change is what is needed to adapt to a rapidly changing world.
Giacomazzi said the new Institute will play an important role in supporting farmers as they convert to conservation practices.
“This can’t be just a launch,” Giacomazzi said. “We must make this happen. Stay in touch.”
A video of the complete CASI January 27 launch meeting will soon be available at the Institute’s website http://ucanr.org/CASI.
A farm advisor who has been instrumental in developing profitable niches for farmers was named "Outstanding Agricultural Educator" with a 2012 Pedro Ilic Award, for his dedication to small-scale farming.
Paul Vossen, UC Cooperative Extension advisor in Sonoma and Marin counties, accepted the award on March 5 at the California Small Farm Conference in Valencia.
"Paul has contributed tremendously to the success of the growing California olive oil industry," said Shermain Hardesty, who presented the award and is director of UC's small farm program. "Paul helps farmers connect with consumers who are willing to pay the price premiums necessary for their high-quality products. And he was one of the first to recognize 'local' as a marketing attribute."
Vossen is one of the founders of the UC Davis Olive Center. He was also instrumental in the first organic production manuals published by the university, which were for apples and olives. He conducts field research on specialty crops, including tree fruit, berries and vegetables, to share with farmers in his region and throughout California.
"Paul Vossen has passion, energy and enthusiasm for his profession and his clientele," they wrote. "He easily moves from teaching farm workers to discussing olive oil production with an olive grower visiting from Spain."
Vossen knew and worked with the award's namesake, Pedro Ilic.
"One of the really neat things about Pedro was that he was so passionate about the small farmer, and I really think that's why this award lives on," he said. "He was such a hard worker and so dedicated to the small farmer."
Ilic's untimely death in 1994 prompted the UC Small Farm Program to annually honor those who carry on his legacy of personal commitment to small-scale and family farming. Ilic was a UC Cooperative Extension farm advisor in Fresno County and one of the original advisors of the Small Farm Program when it was established in 1979.
DAVIS -- What new invasive species threaten California’s plant ecosystems? How do you educate people and organizations about the threat of invasive species? And, how can you help detect and exclude them?
An all-day conference April 24 at UC Davis will answer those questions. The event runs from 8 a.m. to 5 p.m. in the UC Davis Conference Center, at 550 Alumni Lane, across from the Mondavi Center for the Performing Arts.
Themed “Educating the Public about New Invasive Species Threatening California’s Plant Ecosystems,” the conference will include such topics as “New Pests Threatening California,” “Case Histories” and “Other Perspectives on Communication,” said coordinator Kris Godfrey, associate project scientist with the Contained Research Facility at UC Davis.
“The public needs to become more aware of the threat of invasive species,” said Godfrey, formerly with the California Department of Food and Agriculture. "The goal of this conference is to bring together biologists, social scientists, and communication experts to discuss how to educate all segments of society about the threat of invasive species and how to assist in their exclusion and detection.”
Conference attendees will learn about developing and delivering effective and consistent messages about invasive species to a variety of audiences, Godfrey said. They also will learn how to access the resources available to conduct effective outreach programs on invasive species.
Speakers will examine pest plants and plant pests that are likely to enter California in the near future, the pathways of introduction and likelihood of entry, and examples of successful outreach programs that resulted in changes in behavior by segments of society. “Methods to overcome barriers to communication with various segments of the population and possible new methods of communication” will also be discussed, Godfrey said.
Registration is free for UC personnel and $25 for non-UC personnel.
Invasive pest topics on the agenda include the golden spotted oak borer, Asian citrus psyllid, European grapevine moth, Japanese dodder, sudden oak death, and zebra and quagga mussels.
Among the speakers:
- "Predicting the Next Pest Invaders and How To Prevent Their Introduction," Joseph DiTomaso, UC Davis Department of Plant Sciences
- “New Pest Plants,” Doug Johnson, California Invasive Plant Council, Berkeley
- “New Arthropod Pests,” Kevin Hoffman, California Department of Food and Agriculture, Sacramento
- ”New Plant Pathogens,” Richard Bostock, UC Davis Department of Plant Pathology
- ”Zebra and Quagga Mussels,” Ted Grosholz, UC Davis Department of Environmental Science and Policy
- “European Grapevine Moth,” Lucia Varela, UC Cooperative Extension, Sonoma County
- ”Asian Citrus Psyllid/Huanglongbing,” Beth Grafton-Cardwell, UC Riverside Department of Entomology
- “Sudden Oak Death and Buy-Where-You-Burn Campaigns,” Janice Alexander, UC Cooperative Extension, Marin County, Novato.
- “Japanese Dodder, “Ramona Saunders, Sacramento County Agricultural Commissioner’s Office
- “Newspaper Perspective,” Matt Weiser, Sacramento Bee
More information, including the full agenda and updates on the conference, is available at http://crf.ucdavis.edu. Conference registration is online at https://registration.ucdavis.edu. For additional information, contact Kris Godfrey at firstname.lastname@example.org or (530) 754 2104.
The conference, supported with a grant from the UC Davis College of Agricultural and Environmental Sciences’ 2011 Spring Programmatic Initiative, is a cooperative project of the UC Davis College of Agricultural and Environmental Sciences, the UC Davis departments of Plant Pathology, Entomology, Plant Sciences, and Food Science and Technology, the California Center for Urban Horticulture at UC Davis, the UC Statewide Integrated Pest Management Program, and the UC Riverside Department of Entomology.
- Contact: Pat Bailey, UC Davis News Service, (530) 752-9843, email@example.com
The study is published in the early edition of the week of Feb. 20 Proceedings of the National Academy of Sciences.
“Many disease-causing microbes can evade one defensive action by a host plant, but we believe that most microbes would have difficulty overcoming a combination of two immune-system defenses,” said the lead researcher Abhaya Dandekar, professor in the Department of Plant Sciences at UC Davis.
He and his colleagues tested this hypothesis on Xylella fastidiosa, the bacteria responsible for Pierce's disease in grapevines. Strains of the bacteria also attack and damage other host plants, including citrus, stone fruits, almonds, oleander, and certain shade trees, such as oaks, elms, maples and sycamores.
The findings further strengthen UC Davis’ standing as a world leader in the science of plant improvement through advances in genetics, genomics, plant breeding and biodiversity.
First noted in California near Anaheim around 1884, Pierce's disease in grapevines is now known to exist in 28 California counties. From 1994 to 2000, the disease destroyed more than 1,000 acres of northern California grapevines, causing $30 million in damages. There is currently no known cure for Pierce’s disease.
In grapevines, Xylella fastidiosa is carried from plant to plant by half-inch-long insects known as sharpshooters. The bacteria infect and clog the plant’s water-transporting tissue, or xylem. Grapevines with Pierce's disease develop yellow and brown leaves and die within a few years.
To block such infections, the researchers engineered a hybrid gene by fusing together two genes that are responsible for two key functions of the plant’s innate immune response: recognizing Xylella fastidiosa as a bacterial invader and destroying its outer membranes, causing the bacteria to die.
The researchers then inserted this hybrid gene into grapevines.
They found that sap from plants genetically engineered with the hybrid gene effectively killed Xylella fastidiosa in the laboratory. And grapevines engineered to carry the hybrid gene had significantly less leaf scorching and xylem clogging, indicating resistance to Pierce’s disease.
The Los Alamos National Laboratory, New Mexico, and the U.S. Department of Agriculture collaborated on the project. Funding came from the state Department of Food and Agriculture’s Pierce’s Disease Program, the U.S. Department of Energy and the U.S. Department of Agriculture.