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New UC study helps growers estimate cover crop costs and potential benefits
Cover crops offer many potential benefits – including improving soil health – but not knowing the costs can be a barrier for growers who want to try this practice. To help growers calculate costs per acre, a new study on the costs and potential benefits of adding a winter cover crop in an annual rotation has been released by UC Agriculture and Natural Resources, UC Cooperative Extension and the UC Davis Department of Agricultural and Resource Economics.
Led by UC Cooperative Extension farm advisors Sarah Light and Margaret Lloyd, the cost study is modeled for a vegetable-field crop rotation planted on 60-inch beds in the lower Sacramento Valley of California. Depending on the operation, this rotation may include processing tomatoes, corn, sunflower, cotton, sorghum and dry beans, as well as other summer annual crops.
“This cost study can be used by growers who want to begin cover cropping to determine the potential costs per acre associated with this soil-health practice,” said Light, a study co-author and UC Cooperative Extension agronomy advisor for Sutter, Yuba and Colusa counties.
“Based on interviews with growers who currently cover crop on their farms, this cost study models a management scenario that is common for the Sacramento Valley. In addition, growers who want to use cover crops can gain insight as to what standard field management practices will be from planting to termination.”
At the hypothetical farm, the cover crop is seeded into dry soil using a grain drill, then dependent on rainfall for germination and growth.
“Given the frequency of drier winters, we included the cost to irrigate one out of three years,” said Lloyd.
A mix of 30% bell bean, 30% field pea, 20% vetch and 20% oats is sown in the fall. Depending on winter rainfall, soil moisture and the following cash crop, the cover crop is terminated in mid to late spring. The cover crop is flail mowed and disced to incorporate the residue into the soil.
The study includes detailed information on the potential benefits and the drawbacks of cover cropping.
Another consideration for growers is that multiple programs such as CDFA's Healthy Soils Program, various USDA-funded programs (EQUIP, the Climate-Smart Commodities, etc.), and Seeds for Bees by Project Apis m. offer financial incentives for growers to implement conservation practices, such as cover crops.
“This study can provide growers with a baseline to estimate their own costs of using winter cover crops as a practice. This can be useful to calculate more precise estimates when applying for some of these programs and/or weigh the costs per acre with expected benefits in terms of soil health, crop insurance premium discounts or other benefits provided by the cover crops,” said Brittney Goodrich, UC Cooperative Extension agricultural and resource economics specialist and study co-author.
“Last year, the USDA's Pandemic Cover Crop Program gave up to a $5/acre discount on crop insurance premiums for growers who planted a cover crop, and there is potential this will get extended going forward,” Goodrich said.
A list of links to resources that focus specifically on cover crops is included in the study. Five tables show the individual costs of each cultural operation from ground preparation through planting and residue incorporation.
The new study, “2022 - Estimated Costs and Potential Benefits for a Winter Cover Crop in an Annual Crop Rotation - Lower Sacramento Valley,” can be downloaded from the UC Davis Department of Agricultural and Resource Economics website at coststudies.ucdavis.edu. Sample cost of production studies for many other commodities are also available on the website.
This cost and returns study is funded by the UC Davis Department of Agricultural and Resource Economics.
For an explanation of calculations used in the study, refer to the section titled “Assumptions.” For more information, contact Don Stewart in the Department of Agricultural and Resource Economics at destewart@ucdavis.edu, Light at selight@ucanr.edu, or Lloyd at mglloyd@ucanr.edu.
Drip-irrigation study sees ‘huge’ reduction in water, fertilizer use for sweet corn
Study by UCCE advisor in Imperial County also shows 5% increase in yield
A new study suggests that drip irrigation for sweet corn can significantly conserve water, reduce fertilizer use and boost crop yield in the low desert of California – and likely in other areas of California with similar conditions.
Although Imperial County is California's top sweet corn-producing county, with about 8,000 acres planted on average each year, irrigation methods for this crop have been rarely studied in this region (or anywhere else in the state), according to Ali Montazar, UC Cooperative Extension irrigation and water management advisor for Imperial, Riverside and San Diego counties.
Montazar conducted a study in the Imperial Valley over two crop seasons, 2020-21 and 2021-22, to demonstrate and quantify the potential benefits of switching to drip irrigation from the more common furrow irrigation method. The study, available in a recent issue of UC Agriculture and Natural Resources' Agricultural Briefs, will be published in a future issue of Vegetables West.
“I'm hoping with this project we can encourage growers to adopt it, because it seems very promising,” said Montazar, noting that drip irrigation is a “new practice” for sweet corn in California.
Among the 11 commercial sweet corn fields in the study over the 2021-22 season, the six that were under drip irrigation used, on average, 37% less water than the five under furrow irrigation. In absolute terms, the drip-irrigated fields saw an average water savings of 2.2 acre-feet per acre; for Montazar, who has studied drip for a variety of crops in the Imperial Valley, that was an astonishing result.
“I've worked with drip on processed onions, lettuce, alfalfa, spinach … we've never seen a figure like 2.2 acre-feet per acre, that's huge,” he said, attributing the dramatic drop-off to the high volume of water required to furrow-irrigate the sandy soil in the Imperial Valley.
More efficient irrigation also means less fertilizer is needed – a boon to the environment and Salton Sea water quality, as well as growers' bottom line. With fertilizer prices continuing to rise, sweet corn growers using drip could see a substantial 25% cost savings on fertilizer expenses – about $150 per acre less – compared to furrow irrigation, according to Montazar's study.
And by relieving plants of the stress from over- and under-irrigated conditions, drip irrigation helps keep soil moisture at its “sweet spot” – resulting in a 5% increase in marketable crop yield for sweet corn in the study.
“When we have a better, more efficient irrigation system, we can maintain soil moisture at a desired level, over time and space,” Montazar explained.
Because the benefits of drip appear to be linked to soil conditions (sandy loam, and other light soils), Montazar believes that this irrigation practice could deliver relatively similar water and fertilizer savings and improved crop yield in other regions across California, regardless of climactic differences.
“If you use drip in any part of the state, you have the benefits of drip – more uniform water application, more uniform fertilizer – that's not related to the desert,” he said. “That's part of the system's potential.”
Montazar plans to follow up on his preliminary study with additional research on sweet corn and drip irrigation during the 2022-23 crop season.
Avocado growers to get irrigation tools, strategies from UC ANR’s Montazar
CDFA grant supports research to optimize water use for iconic California crop
California growers, who account for more than 90% of avocado production in the U.S., will soon be getting some help in weathering the extreme fluctuations of climate change.
Ali Montazar, a University of California Cooperative Extension irrigation and water management advisor, recently received a grant to develop tools and strategies that optimize growers' irrigation practices across Southern California – the state's avocado belt. California avocados are valued at more than $411 million, according to the National Agricultural Statistics Service.
“This region faces uncertain water supplies, mandatory reductions of water use, and the rising cost of water – while efficient use of irrigation water is one of the highest conservation priorities,” Montazar said. “Water is the most critically important input to avocado production.”
At the California Avocado Commission's suggestion, Orange County was added to the study to better capture the range of climates and cropping systems across the region, Montazar said.
He hopes to develop “crop coefficients” that avocado growers can use to determine the optimal irrigation for their crop based on a host of factors: soil type and salinity, canopy features, row orientation, slopes, soil and water management practices, and more.
“Growers are unclear on how much water the crop actually needs under those conditions,” Montazar said.
He will incorporate data from the actual water use in the experimental orchards – including information from the newest soil moisture and canopy temperature sensors – to help ensure growers do not under- or overwater their crops. Overirrigating contributes to a devastating disease, avocado root rot, caused by the plant pathogen Phytophthora cinnamomi.
Another component of the grant supports outreach in disseminating these resources and best practices to the broader agricultural community.
“Developing and adopting these tools and information may have a significant impact on water quality and quantity issues and bolster the economic sustainability of avocado production not only in the well-established production region of Southern California, but also in Kern and Tulare counties where new avocado plantings are growing,” Montazar said.
Preliminary findings and recommendations are expected at the end of 2022.
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.”
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.
