Posts Tagged: crops
Farmers invited to tour cover crops in Sacramento Valley March 3
Farmers and ranchers are invited on a tour to learn how to use cover crops to build soil health. A full-day tour of several cover crop sites in orchards and annual crop fields in the Sacramento Valley is being offered on March 3 by the Western Cover Crop Council's Southwest Region Committee.
“The goal of this tour is to demonstrate ways to use cover crops effectively in annual crops and orchards in the Sacramento Valley,” said tour organizer Sarah Light, UC Cooperative Extension agronomy advisor.
“This tour will cover a range of topics, including cover crop selection, equipment needed to manage cover crops, considerations for cover cropping in the region, and the importance of building soil health,” said Light, who is also chair of the Western Cover Crop Council's Southwest Region Committee and a board member of the Western Cover Crop Council.
Cover crop species, cultivars and mixes including legumes, grasses and brassicas will be showcased in Colusa County, with farmers, UC Cooperative Extension specialists and researchers giving presentations.
The tour bus will depart from the Colusa County Cooperative Extension Office at 100 Sunrise Blvd., Suite E, Colusa, CA 95932 at 8 a.m. and return at 7:30 p.m.
Participants are currently limited to 50 farmers and ranchers. If space is available after Feb. 1, others may join. ?The $50 registration fee includes morning refreshments, transportation, lunch and dinner. To register or to see the agenda, visit https://surveys.ucanr.edu/survey.cfm?surveynumber=36190.
Lettuce growers hope weeding, research can counter devastating plant virus
Population explosion of insect vector contributed to $100 million in losses in 2020
While most Californians are wholeheartedly embracing the wet start to winter, one group is welcoming the rain more warily (and wearily) – lettuce growers in the Salinas Valley.
“It's a blessing, yes, we need the water,” said Tony Alameda, managing partner of Topflavor Farms, which grows a variety of produce in Monterey and San Benito counties. “But, oh gosh: with that water, here come the weeds, here comes the habitat, here comes all the other problems that go along with it.”
Weeds are overwintering havens for a tiny insect called the Western flower thrips, which in turn carries the impatiens necrotic spot virus (INSV) – a plant virus that caused $100 million in lost gross revenue for Salinas Valley growers in 2020.
The agricultural community called it “the biggest problem we've seen in a long, long time,” said Mary Zischke, facilitator of a task force convened by the Grower-Shipper Association to address INSV and a related affliction, Pythium wilt.
Widespread crop failure in 2020
Since INSV was first observed in the state in 2006, the virus – which poses no threat to people – triggered significant crop losses in 2019, leading up to a catastrophic 2020. As Alameda's lettuces began to show the telltale “bronzing” of the leaves, efforts to bag up or remove the infected plants had no effect on the virus' implacable spread.
“Nothing seemed to work,” he recalled, “and you just watch those fields collapse, week after week, until you're just like, ‘Ugh, there's nothing here to even harvest.'”
After “100% crop failure” that year in his prime fields at the heart of the Salinas Valley, Alameda tried to dodge the virus in 2021 – shifting lettuce plantings to San Benito County and instead using his most valuable land for unaffected crops such as cilantro, leeks and radishes. By decamping to San Benito, Alameda was able to harvest 70% of his usual lettuce yield.
Generally, growers enjoyed a reprieve from virus pressures in 2021. Even in this “good” year, however, about one-third of all lettuce plantings in the Salinas Valley had at least a low level of infection, according to Zischke.
“Since we were attributing a lot of our so-called good fortune – on having less damage this year – to the cooler weather, we know we can't count on that to get us out of this problem,” Zischke said. “All the models point to the fact that we're in a warming climate, so we were fortunate this year.”
More research needed on thrips
Heat waves were a major driver of the INSV disaster of 2020. Although researchers have established a link between warmer temperatures and population increases of thrips, science still has a lot to learn about those disease vectors.
“Thrips are something we're trying to understand as much as we can, but it's pretty tough because they're a little mysterious in the way they get around and where they overwinter,” said Richard Smith, a University of California Cooperative Extension vegetable crops and weed science farm advisor for the Central Coast region.
Smith – along with U.S. Department of Agriculture research entomologist Daniel Hasegawa and California State University-Monterey Bay plant pathologist JP Dundore-Arias – provided an INSV update during an Assembly agriculture committee hearing in December.
Recent studies have identified several weeds as key “reservoirs” of thrips, including malva, marestail, and hairy fleabane. The ubiquitous mustards, fortunately, appear to be poor hosts for thrips, although their pollen serve as potential food sources.
Controlling those weeds – which are beginning to spring up as the days lengthen – is a top priority during the winter months, according to Smith. Aggressive weed management in the preceding winter was an important factor in limiting the virus' spread in 2021.
And because weeds recognize no boundaries, experts are also urging managers of non-agricultural lands to keep their properties as clean as possible, including industrial sites, equipment yards and the edges of roadways – namely U.S. Route 101, which runs through the center of the valley. Some growers have been volunteering to weed their neighbors' vineyards.
“We're encouraging everybody – as best they can – to knock down known weed hosts; that's really critical,” Zischke said.
Search for long-term solutions
Within the grower community, there is “nervous optimism” for the coming year, said Alameda, as he continues to hope for an innovation that would aid in the fight against INSV – whether a more targeted pesticide application or a beneficial insect that could deter the thrips.
However, both Alameda and Zischke pointed to the breeding of more resistant lettuce varieties as the ultimate solution to INSV – albeit one that is years away.
“We have a lot of different types of lettuce that we grow, so to move resistance into all the different types of lettuce we grow throughout the season … that's going to take time,” Zischke explained.
Research funding from the state and USDA – as well as projects supported by the California Leafy Greens Research Program – can help expedite that process. But, for Alameda, the INSV crisis underscores the need for more resources and farm advisors such as Smith, who has spent more than three decades cultivating relationships and building trust within Salinas Valley communities.
Alameda would like to see a renewed focus on bringing “bright, young, passionate people who live and breathe this stuff” to the region, so growers are better equipped to handle the inevitable next calamity.
“Hopefully this is a wakeup call to all,” he said. “This is a valued industry – you have to take care of it; it cannot be taken for granted. The ‘salad bowl of the world' cannot rest on its laurels.”
/h3>/h3>/h3>/h2>Researchers pinpoint which bird species pose food safety risk to crops
E. coli and Salmonella are rare in wild birds, Campylobacter more common
Concerns over foodborne risk from birds may not be as severe as once thought by produce farmers, according to research from the University of California, Davis, that found low instances of E. coli and Salmonella prevalence.
While the research found that the risk is often low, it varies depending on species. Birds like starlings that flock in large numbers and forage on the ground near cattle are more likely to spread pathogenic bacteria to crops like lettuce, spinach and broccoli, according to a study of food safety risk and bird pathogens from the University of California Davis. In contrast, insect-eating species were less likely to carry pathogens.
The findings, published in the journal Ecological Applications, suggest that current practice of removing bird habitats around produce growers' farms over concerns the animals could bring foodborne pathogens into their fields may not solve the problem.
“Farmers are increasingly concerned that birds may be spreading foodborne diseases to their crops,” said Daniel Karp, the senior author on the study and an assistant professor in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Yet not all bird species are equally risky.”
Only one foodborne disease outbreak in produce has been conclusively traced to birds: a Campylobacter outbreak in peas from Alaska. While the bacteria can cause diarrhea and other foodborne illness in humans, it's less of a concern to growers than E. coli and Salmonella, which have been responsible for multiple outbreaks across the nation.
In this study, researchers compiled more than 11,000 bacteria tests of wild bird feces and found that Campylobacter was detected in 8 percent of samples. But pathogenic E. Coli and Salmonella were only found in very rare cases (less than 0.5%).
In addition to the bacteria tests, researchers conducted roughly 1,500 bird surveys across 350 fresh produce fields in Western states and collected more than 1,200 fecal samples from fields. They then modeled the prevalence of pathogens in feces, interactions with crops, and the likelihood of different bird species to defecate on crops to determine risk.
Insect-eating birds pose lower risk
Based on the data, insect-eating birds, such as swallows, present a lower risk, while birds that flock near livestock, such as blackbirds and starlings, are more likely to transmit pathogens.
The data can help the agricultural industry determine risk and take action, such as separating produce crops from cattle lands. They also don't need to treat all birds the same.
“Maybe farmers don't need to be quite as concerned about all types of birds,” Karp said. “Our data suggest that some of the pest-eating birds that can really benefit crop production may not be so risky from a food-safety perspective.”
Removing habitat can backfire
This study and the authors' prior work indicate that removing habitat around farms may actually benefit the species that pose more risk and harm the beneficial, pest-eating ones that are less risky to food safety. This is because many prolific insect-eaters may visit crop fields to eat pests but need nearby natural habitats to survive. In contrast, many of the bird species that most commonly carry foodborne pathogens readily thrive on both cattle farms and produce farms without natural habitat nearby.
Other findings
Insect-eating birds that forage in the tree canopy pose minimal threat because they are less likely to carry foodborne pathogens and come into direct contact with produce. They can also be valuable parts of the ecosystem, particularly if they eat pests that can harm crops. Installing bird boxes could attract the pest-eaters, as well as help with conservation efforts.
“We basically didn't know which birds were problematic,” said lead author Olivia Smith, a postdoctoral researcher at Michigan State University who was at University of Georgia when the paper was written. “I think this is a good step forward for the field.”
Additional co-authoring institutions include James Cook University, UC Berkeley, UC Riverside, University of Kentucky, University of Texas, Virginia Polytechnic Institute and State University, Washington State University, BioEpAr, The Nature Conservancy and Van Andel Institute.
The research was funded by the United States Department of Agriculture and the National Science Foundation.
/h3>/h3>/h3>/h2>Can California native plants be used as cover crops to benefit farmers and native ecosystems?
In late February, in an almond orchard in the Sacramento Valley, the fall-planted cover crop mix of grasses, brassicas and legumes had barely produced a green fuzz above the soil surface, and it was unclear when it would bloom. Unfortunately, this scene is becoming more frequent across California, as climate change causes more prolonged droughts and rain-dependent winter cover crops can barely grow, which delays or reduces bloom, essential for supporting pollinators. Fortunately, California native plant species have evolved with drought and have developed many strategies to survive and reproduce in those conditions.
Would it be possible to capitalize on the over 9 million acres of cropland in California for drought resilience and habitat restoration by utilizing more native species as cover crops? Our team at the UC Sustainable Agriculture Research and Education Program (UC SAREP) spent some time considering various native plant species and their potential ecological and operational attributes as cover crops. For a full list of species and their attributes, see https://ucanr.edu/sites/covercrops/.
Many native species are so well adapted to drought that they will still germinate and bloom during extremely dry years, for example, annuals like Tidy Tips (Layia platyglossa) and California poppy (Eschscholzia californica). Alternatively, perennial bulb species like Prettyface (Triteleia ixioides) and Bluedicks (Dipteronstemon capitatus) become dormant during the dry summer, retaining their bulbs below ground and re-growing when the rains return. These species could perhaps fit well in no-till orchard systems. Summer dormancy is important for tree nut growers because they usually need clean ground under the trees during harvest. Moreover, the costs to terminate and reseed would potentially be eliminated. While these species are well-known by Native Americans for their edible bulbs, at this point in time, we are not aware of any cover cropping trials having ever been conducted with these species.
Another species with strong reseeding and more availability is the annual Lacy Phacelia (Phacelia tanacetifolia), which offers an intriguing historical precedent for developing a native species for cover cropping purposes. Native to California, it was introduced into Europe in 1832 by Germans. It is very attractive to pollinators and experienced a boom there in the early 1990s. European beekeepers and farmers have been using Lacy Phacelia as a cover crop ever since, and it has recently been gaining traction on California farms as well. California has many species of phacelia, with another, described as being even more attractive to native bees, being the annual Great Valley Phacelia (Phacelia ciliata). Besides supporting native bees, other native plant species can contribute nitrogen to the soil, such as annual Lupine (Lupinus spp.) and perennial Deerweed (Acmispon glaber), which are legumes and form an association with nitrogen-fixing bacteria in their roots.
Cover crops are not usually considered marketable crops. However, we should not preclude the potential for some plants that are useful as cover crops to provide a harvestable product as well. Native perennial fiber plants such as Indian hemp dogbane (Apocynum cannabinum), narrow leaf milkweed (Asclepsias fascicularis), and common nettle (Urtica dioica) could offer the opportunity to cultivate summer cover crops that have a market value, especially in cases where farmers are already willing to irrigate their cover crops to improve their development and amplify the benefits. Bowles Farming in the San Joaquin Valley is experimenting with growing these three species for fiber production. All three also attract native bees and important butterfly species such as monarchs (as long as farmers avoid spraying insecticides).
While we believe that some native species could open new opportunities for farmers as cover crops, we still have insufficient studies testing the effects and viability of these species. Organizations like the NRCS Plant Materials Center at Lockeford and the Xerces Society are conducting practical studies with native species, creating plant guides and working with farmers to expand their use. In addition, researchers Lauren Hale of the USDA Agricultural Research Service and Anil Shrestha of California State University, Fresno, are using a 2021 UC SAREP small grant to study the effects of native species mixes on water demand and weed populations in San Joaquin Valley grape vineyards. Hale suggests that below-ground ecosystems may benefit as much from native plants as above-ground ecosystems. Says Hale, “Because plants and their microbiomes have evolved together for millennia, it seems logical that native plants would promote a good response from the native soil microbiota.”
For additional information:
UC SAREP List of California Native Species for Potential Use as Cover Crops: https://ucanr.edu/sites/covercrops/
Xerces Society lists of pollinator-friendly native species for California: https://xerces.org/pollinator-resource-center/california
NRCS California Plant Materials Center plant guides: https://www.nrcs.usda.gov/wps/portal/nrcs/publications/plantmaterials/pmc/west/capmc/pub/
UC SAREP Cover Crops Database: https://sarep.ucdavis.edu/covercrop
Soil health practices show economic and ecological benefits, say farmers
A group of California organic farmers is sharing information about their efforts to combine reduced tillage with the use of cover crops, which they have been planting on their vegetable farms for decades to protect soil while adding carbon and diversity to their production systems.
“Every one of the pioneering farmers has seen tremendous benefits from the practices,” said Jeff Mitchell, UC Cooperative Extension vegetable crops specialist. “These are the very growing practices that we have demonstrated over two decades of research to benefit soil health, environmental conservation and the bottom line on plots near Five Points in Fresno County.”
The organic farmer research project is funded with a Natural Resources Conservation Service Conservation Innovation Grant (CIG) and aims to develop crop production system alternatives for vegetable crops. The farmers are seeing evidence of the ecological benefits, and also benefits that promote the public good.
“Consumers prefer food that is grown in ways that improve soil health as well as environmental health and human health,” Mitchell said. “Farmers must not become obsolete by ignoring ever-evolving buyer demands and environmental imperatives. Make changes, or you'll lose markets.”
The need for California farmers to adjust to changing times was to have been part of the dialogue at a public field day in March at Teixeira & Sons Farm in Firebaugh. It was postponed due to COVID-19 concerns. The event was to showcase Mitchell's data and the experiences of long-time cover crop farmer John Teixeira of Firebaugh.
Teixeira began cover cropping 30 years ago in one of his organic fields. He wanted to build fertility, organic matter and water holding capacity in the soil. Ever since, he's been growing cover crops ahead of tomatoes and several other commodities. This past winter, he grew a mixture of common, hairy and purple vetch, white oats, biomaster peas and bell beans. Teixeira estimates that it provided over 5,000 pounds per acre of dry biomass, which is supporting his 2020 tomato crop with elevated biological activity in the soil.
Mitchell's study in Five Points has tracked impacts of winter cover cropping coupled with no-till since 1999. Over the 21 years, some 37 tons of organic matter, or about 15 tons of carbon, have been added to the soil. These inputs averaged about 3,700 pounds per acre of organic matter, or 0.8 tons of carbon annually. Year-to-year variability has been high, ranging from 8,800 pounds in 2000 when supplemented by irrigation, to 54 pounds in 2007 when, as in most years, the cover crops were grown with rainfall only. Cover crops were typically seeded by Nov. 15 each fall and terminated around March 15.
Several key soil-health indicators improved over the years, including aggregation (or soil structure), porosity and water-holding capacity. Work at the Five Points site conducted by UC Merced professor Teamrat Ghezzehei and Ph.D. student Samuel Araya, has shown 20% higher water-holding capacity in the system with cover crops and no-till compared to the standard bare system.
Earlier results from the study field have shown that when the cover crop and other crop residues are converted to a mulch and left on the soil surface, as much as five inches of water that would normally evaporate during a typical summer crop period stays in the soil.
Mitchell is coordinating the group of organic farmers who are conducting cover crop, tillage and mulch experiments. The farmers cultivate vegetables up and down the Central Valley from Meridian and Guinda in the north, to Dixon, Hollister, Madera, Five Points and Buttonwillow in the south.
“They are an incredible group of people,” Mitchell said. “They have taken soil, farm and human health goals to dramatically important lengths.”
As organic farmers, they have always been in the forefront of soil care and attention to soil biology, Mitchell said, but they're now working together to implement such innovations as virtually year-round soil cover, reduced disturbance tillage, and integration of grazing animals into their fields. Their objective is to enhance the health of their soils, the health of their farms, and the quality of the vegetables that they produce.
Tom Willey, one of the project's farmers from Madera, puts it this way, “What we're attempting to do is up our game on natural systems mimicry on our farms, break through the barrier of over-dependence on tillage in organic systems.”
Eric Brennan, a USDA Agricultural Research Services organic systems horticulturist in Salinas, and integral partner in the effort, has studied cover crops in the Salinas Valley.
“Cover cropping regularly, every winter if possible, is one of the ‘lowest-hanging fruit' practices that vegetable farmers can use to improve soil quality and nutrient management in their production,” Brennan said.
Mitchell believes it's time for broad adoption of practices to promote soil health.
“Everyone used to talk about ‘barriers to adoption' when it came to cover crops. Now the question will more aptly be, ‘What happened to those folks who didn't change and adopt?'” Mitchell said.