Rotational and tank-mix programs incorporating biofungicides demonstrated comparable powdery mildew control to conventional synthetic-only treatments under moderate disease pressure (all photos by T. Tian.)
The sulfury smell on our shirts in the spring signals a new season and the battle with powdery mildew (PM), arguably the most important and expensive disease to control in the vineyard. The causal pathogen, Erysiphe necator, has a high productive rate and short generation time. Since it infects succulent tissues of grapevines, including young shoots, green berries and rachis, preventative practices like fungicide sprays typically begin at bud break and last until veraison or even beyond. Insufficient PM management results in scars on the berry, compromising fruit quality, reducing market value and increasing risks of bunch rot during fruit ripening. Given the large canopy of vines grown in the San Joaquin Valley and favorable weather conditions for PM development, fungicide applications become a must.
Successful PM control relies on effective fungicide rotation and thorough spray coverage. In conventional vineyards, we depend heavily on sulfur and synthetic fungicides. While sulfur is affordable and resistance has not been observed, its residual effects can wear off within five to seven days, requiring frequent applications to keep the vineyard clean. Synthetic fungicides, on the other hand, convey benefits of high efficacy and long residual effects. However, their site-specific modes of action increase the risk of resistance with repeated use of the same active ingredient. Widespread resistance of FRAC 11 fungicides (QoIs) in PM has been confirmed in California vineyards, particularly in table grapes. The resistance of FRAC 3 (DMIs) is often suspected, though we still lack sensitive and reliable molecular methods to quickly confirm field observations. Note that poor spray coverage accelerates resistance development because fungi that survive the sublethal exposure have a greater chance to develop natural tolerance and genetic mutations.
In addition to sulfur and synthetic fungicides, biofungicides became popular in the last few decades. Though they have mainly been used in organic systems, there is increasing interest in adopting biofungicides for PM control in conventional vineyards, aligning with California Department of Pesticide Regulation’s Sustainable Pest Management Roadmap for California. Biofungicides can be roughly separated into four categories: plant extracts and oils, mineral-based oils and compounds, bacterial or fungal strains, and metabolites of fungi or bacteria. Compared to synthetic fungicides, they offer shorter reentry and preharvest intervals. They are subject to a lower risk of resistance development, owing to their diverse mechanisms. While their residual activity is generally shorter, biofungicides are ideal complementary tools in conventional programs for enhanced disease control and resistance management.
While their residual activity is generally shorter, biofungicides are ideal complementary tools in conventional programs for enhanced disease control and resistance management.
Results from Field Trials (2022-24) From 2022 to 2024, we examined the efficacy of incorporating biofungicides into PM control in table grape vineyards. These trials involved rotating or tank-mixing biofungicides with synthetic fungicides applied between bloom and two weeks post-veraison. The efficacy of those programs was compared to a conventional synthetic program that used wettable sulfur, sulfur dust, copper and mineral oils prior to bloom, and synthetic fungicides afterward. All fungicides were used at label rates. The incidence and severity of PM in clusters were evaluated pre-veraison and at veraison.
Trial 1: Plant extract rotation
In the first trial, a plant extract-based product was integrated into a synthetic fungicide rotation. The conventional synthetic program involved pre-bloom applications of wettable sulfur followed by rotational applications of Luna Experience (fluopyram + tebuconazole), Switch (cyprodinil), Vivando (metrafenone) and Torino (cyflufenamid) every 14 days between bloom and veraison. In the other treatment, Problad Verde (Banda de Lupinus doce), a plant extract product, was applied at bloom and veraison to replace synthetic fungicides without changing the spray interval. Both programs demonstrated comparable efficacy in reducing PM incidence and severity in a Flame Seedless vineyard under moderate disease pressure (Fig. 1).
Figure 1. The efficacy of two fungicide program on powdery mildew control in a Flame seedless vineyard in 2022. The control vines were not sprayed after bloom. The incidence and severity of powdery mildew in clusters were evaluated at veraison.
Trial 2: Bacillus-based rotation
The second trial evaluated the rotation of Bacillus-based products with synthetic fungicides. The conventional synthetic program utilized copper, sulfur and mineral oils pre-bloom, followed by a 14-day rotational schedule of Luna Experience, Switch, Vivando and Elevate 50 WDG (fenhexamid). In the other treatment, synthetic fungicides were replaced by Double Nickel (Bacillus amyloliquefaciens) and Aviv (Bacillus subtilis) at bloom, bunch closure and veraison. Considering the potentially shorter residual activity of the Bacillus products, the spray interval for this treatment was reduced to seven days (e.g., Switch applied seven days after Double Nickel at bloom). Compared to the conventional program, adding Double Nickel and Aviv to the rotation offered a small improvement in PM control (Fig. 2). It may be associated with the additional spray in the second treatment. Thus, in the second year of the experiment, we tested a similar program but kept the spray interval the same for both treatments. Results suggested comparable PM control efficacy between those two programs (Fig. 2).
Figure 2. The efficacy of two fungicide programs on powdery mildew control in a Thompson seedless vineyard in 2023 (first year) and 2024 (second year). The control vines were not sprayed after bloom. The incidence and severity of powdery mildew in clusters were evaluated at veraison in the first year. In the second year, additional evaluation was conducted two weeks prior to veraison (pre-veraison).
Additional tank-mix trials
In the two other trials,one or two fungicides, including Oxidate 5.0 (hydrogen peroxide and peroxyacetic acid), Cinnerate (cinnamon oil and potassium oleate) and Instill O (copper sulfate pentahydrate), along with Avivand Double Nickel, were tank-mixed with synthetic fungicides in each spray. The spray interval was every 14 to 21 days between bloom and veraison. These tank-mix programs demonstrated comparable efficacy in reducing PM incidence and severity to the conventional synthetic program. No phytotoxicity was observed. However, these findings are preliminary. The viability of Bacillus bacteria in specific tank mixes with synthetic fungicides as well as potential phytotoxicity issues requires further investigation.
Overall, our findings suggest incorporating biofungicides into conventional fungicide programs, either through rotation or tank mixing, can achieve similar PM control efficacy as programs relying solely on synthetic fungicides post-bloom. Integrating fungicides with complementary mechanisms may offer benefits, such as reducing the risk of fungicide resistance development and providing greater flexibility in preharvest fungicide applications. We are continuing our research and looking forward to providing the industry with updated information on effective PM management strategies.
The author would like to thank Consolidated Central Valley Table Grape Pest and Disease Control District and industry collaborators for funding support.
Discussion of research findings necessitates using trade names. This does not constitute product endorsement, nor does it suggest products not listed would not be suitable for use. Some research results involve use of chemicals which are currently registered for use or may involve use which would be considered out of label. These results are reported but are not recommended by UC for use. Consult the label and use it as the basis of all recommendations.
How Living Algae is Transforming Sustainable Agriculture: The Chlorella vulgaris Breakthrough
Soil is the source and catalyst for all life-nourishing substances that plant and animal life need for sustenance, and the more life in soil, the better crops and animals who consume them will thrive.
The use of biostimulants in agriculture has gained significant traction due to their potential to enhance yields, improve soil health and reduce dependency on chemical fertilizers. Biostimulants like humic and fulvic acids, protein hydrolysates, compost and inoculants, and kelp or seaweed extracts have surged in usage across all crop types and continents. Research proves that all of them bring some benefits, but none of them deliver all the known benefits derived by biostimulants since extensive research began in the 1970s, except for one: live cell green algae, namely Chlorella vulgaris, literally Latin for “common green.”
Chlorella vulgaris is the most ubiquitous freshwater algae found globally, and there is evidence that it was used by ancient cultures in Africa, Mesoamerica and Asia to increase crop production because growers knew that increased fertility would occur by planting near freshwater river deltas and lakes after flooding events.
Microscope image of Chlorella vulgaris, photo courtesy of Andrew Shuler, Enlighted Soil Corp.
These living green microscopic organisms, capable of surviving in soil, are a building block of life and what sets this biostimulant apart from all others because it stimulates the biology that is already in soil.
Extensive research worldwide and field trials have proven that this is of paramount importance in the potency and efficacy of biologicals for significantly boosting soil organic matter (SOM) and microbial biomass, enabling every scientifically recognized benefit attributable to biostimulants to be realized:
Improved SOM, plant fertility and microbial mass
Increased leaf chlorophyll content resulting in increased photosynthetic capacity
Enhanced plant growth and increased yield across a wide variety of crops
Reduced dependence on chemical fertilizers (NPK)
Enhanced plant resistance to abiotic stresses such as drought, heat and salinity
Potential increased resistance to plant pathogens due to improved plant vigor
Soil biodiversity is the key to improving nutrient cycling and plant fertility for increasing productivity while saving on inputs and increasing profits. Published research has shown live green algae, uniquely Chlorella vulgaris, to be a particularly effective biostimulant, having a significant impact on soil microbial activity, plant growth and overall farm ROI.
A Breakthrough in Living Biostimulant Technology
Historically, the challenge of maintaining live algae viability during storage and transport has hindered their widespread use. Green algae, like most plants, are usually dependent on photosynthesis to maintain life. They die when placed in dark storage.
Living organisms feed themselves in one of two ways: producing their own food via photosynthesis, like green plants and algae, or by finding it outside of themselves, like animals and bacteria. Those that photosynthesize are called autotrophs (auto = self, troph = feeding), while those organisms that scavenge or hunt for food are called heterotrophs (hetero = other). There is a third category known as mixotrophic, an organism that can switch between autotrophic and heterotrophic metabolism.
Scientists with EnSoil Algae™ have now introduced a breakthrough formulation of mixotrophic Chlorella vulgaris, which can photosynthesize in light and consume organic material in darkness. This allows them to remain viable during transport and storage for 6 to 12 months. This patent-pending technology does not use any commercial or laboratory gene-altering techniques. It does not rely on genetic modification, as the heterotrophic pathway is already present in green algae. This technology activates that pathway to produce mixotrophic chlorella.
Moreover, live cell green algae is an endophyte acting as a transport vehicle for soil microbes and chlorophyll. A research study by Dr. James White of Rutgers University demonstrated a symbiotic relationship between EnSoil Algae™, plants and endophytic soil bacteria. Algae cells attract and carry bacteria into plant roots, delivering chlorophyll and promoting growth of root hairs.
Reducing Synthetic NPK, Increasing Yields and Crop Quality
One of the most important benefits of living green algae is that it can be used to lower synthetic nitrogen inputs. “Where will the nitrogen come from,” people ask? The answer is that living green algae amplifies nature’s process of extracting nitrogen from the air and converting it into ammonium compounds in the soil. One gram of healthy soil contains some 10 billion bacteria, fungi and other organisms that work together to make this conversion. Live cell green algae accelerate the process of nitrogen fixation.
In addition, rhizospheric bacteria produce weak acids that solubilize soil-bound phosphorus, making it available to plant root systems. This especially happens when these bacteria are stimulated by Chlorella vulgaris. Soil testing using the Haney Soil Test after the first application has even demonstrated excess nitrogen after harvesting, nitrogen that is available for the next season.
Squash in field, photo courtesy of Clemson University
This means growers can reduce their use of synthetic NPK fertilizers to produce quality crops with higher nutrient density. Known as phytochemicals, such as carotenoids, polyphenols and alkaloids, these nutrients are critical for healthy function of organs, strengthening the immune system and preventing chronic disease.
And because EnSoil Algae™ is applied at lower rates and at a much lower cost than synthetic NPK, growers can realize savings of 20% to 50% in fertilizer costs. This enables them to increase their profitability in year one while improving the health of their soil, increasing yields and improving the nutritional content of their crops.
Biostimulants like Chlorella vulgaris make sense because they can lead to significantly improved agronomic and economic outcomes. They enable growers to realize a much better return on investment that compounds over time as increased SOM and organic nutrient cycling improve water retention, plant health and resiliency. This allows for reduction in irrigation and crop protection inputs.
To learn more, download the 72-page Growers Report with research data and trials across a wide variety of crop types, soils and regions. Or come meet Jessica Murison, jessica@ensoilalgae.com at the Progressive Crop Consultant Conference in Visalia, September 24th and 25th.
EnSoil Algae™ is a product of Enlightened Soil Corp., a South Carolina public benefit corporation, ensoilalgae.com.
New irrigation calculators based on local weather data aim to simplify water scheduling for California avocado growers seeking to boost efficiency (photo by Ali Montazar, UCCE.)
At the recent UCCE Avocado Irrigation Workshop in San Diego County, industry experts, crop consultants and growers gathered to address one of the most pressing challenges in avocado farming: irrigation efficiency. The meeting presented Danny Klittich of Mission Produce Inc. shared firsthand insights from groves across the state, highlighting common issues and emerging solutions as well as opportunities for crop consultants to assist growers.
“I think one of the biggest challenges in avocado growing is water management,” Klittich said, “and trying to manage how many hours are applied and the frequency with which it is applied, and then doing that without the tools in the field to have any feedback is difficult.”
He noted many growers are still making irrigation decisions based on rigid routines rather than real-time data. “[Some growers are] just doing six hours twice a week or 24 hours once a week, and not having some type of soil moisture sensor or tree sensor to really have feedback. Is it too much? Is it not enough?”
New Tools for Growers
To address these pain points, new tools and resources are being developed to help growers simplify their decision-making and become more precise.
“The California Avocado Commission is funding a project with Cooperative Extension to build out a simple irrigation calculator based on weather data to give a better estimate for people,” Klittich said. “So they can know how many hours they need to irrigate without having to go do all the math, pulling data out of CIMIS, trying to figure out what all the different correction factors and things are. Just really simplifying things.”
In addition to this calculator, he mentioned ongoing efforts to improve crop coefficients and other input variables that influence irrigation calculations. “I think that’s really where we’ve doubled down.”
For growers ready to invest more deeply, Klittich pointed to the availability of more advanced platforms. “There are so many great paid services that incorporate multiple-sensor packages, where you can purchase multiple sensors and then utilize those for making crop decisions.”
Understanding Soil’s Role
Klittich also emphasized how soil characteristics complicate irrigation planning. “Soil has an obvious interaction with irrigation. It’s how much water we can hold in the root zone. But also, there are innate problems with soil, with limiting layers and percolation rates. All of those have to be taken into account when we’re designing our irrigation management plan.”
Importantly, he clarified water use doesn’t necessarily change with soil type. What changes is how much water the soil can store. “A healthy tree on sandy soil and a healthy tree on heavy soil use the same amount of water. The problem is we can just hold less water in the sand than we can in the heavy soil.”
Actionable Recommendations
For consultants advising growers on next steps, Klittich’s advice is straightforward: Start with basic feedback tools.
“If you don’t have any soil moisture sensing technology, there’s huge return on investment to having just one sensor in the field to tell you if the soil’s too wet or too dry and how deep your irrigations are going,” he said. “I think that is a must in every operation.”
He also encouraged growers to make use of existing public data. “Every grower has access to the CIMIS stations that are a California statewide system. However, there’s not always a station close by, but you can use that data to then influence your irrigation calculations.”
Combining those tools can significantly improve accuracy. “Getting an idea from CIMIS of how much you might need to irrigate and then using a soil sensor to make sure that you didn’t irrigate too much or too little can really make a huge difference above just guessing six hours, eight hours, because the weather was what it was last week.”
Check out the full conversation with Klittich in a recent MyAgLife YouTube video.
BioLumic is a U.S.- and New Zealand-based agricultural biotechnology company using light signaling as a programming language for plants.
Champaign, Illinois – July 15, 2025 – BioLumic, the only agricultural biotechnology company that programs seed traits using light, today announced the appointment of Dr. Howard-Yana Shapiro, distinguished senior fellow at CIFOR-ICRAF, and Dr. Jeremy Hill, chief science & technology officer at Fonterra Co-operative Group Limited, to its Scientific Advisory Group.
Dr. Shapiro and Professor Hill join founding members Professor Mark Tester – internationally renowned for pioneering the science of salt-tolerant crops – and Dr. John Bedbrook, former DuPont Vice President and inventor on more than 50 plant-biotech patents. Together, the four advisors bring a uniquely diverse mix of agronomic and biotechnology discovery for world-leading innovations.
“Bringing on Howard and Jeremy strengthens an advisory team with a proven track record of scaling breakthrough science from lab bench to global impact,” said Steve Sibulkin, CEO of BioLumic. “Their insights will accelerate the impact of our light-signal xTraits™ platform, helping ensure it delivers meaningful value for farmers, industry, and the planet—while advancing a more resilient food system.”
BioLumic’s patented xTraits™ platform delivers precisely timed UV-light signals to activate plants’ own gene-expression pathways. The result is double-digit gains in yield, quality, and resilience in a fraction of the time and cost of conventional trait development, and all without altering DNA. Advanced programs in corn, soybeans, rice, and forage crops are already under way with multiple partners, including food production companies, charitable entities, and leading seed companies.
New Scientific Advisory Group Members:
Dr. Howard-Yana Shapiro is a 50-year crop-science pioneer who led global agriculture initiatives at Mars, Inc., and founded the African Orphan Crops Consortium, which is working to improve 101 nutrient-dense crops critical to food security across Africa. He has driven scientific efforts that combine biodiversity, nutrition, and equitable access to high-performing crops.
“I am excited to support BioLumic’s pioneering work in using light to naturally enhance plant performance,” said Shapiro. “Harnessing the power of biology and light opens up powerful new pathways for crop productivity and resilience traits.”
Professor Jeremy Hill brings decades of experience in science, technology, nutrition and sustainability across the entire farm-to-consumer dairy value chain. As Fonterra’s Chief Science & Technology Officer, and former President of the International Dairy Federation, he helped lead the development of international greenhouse gas and nutrition frameworks for agriculture and food systems. In 2020, Prof. Hill was awarded the Member of the New Zealand Order of Merit for services to the dairy industry and scientific research in the Queen’s Birthday Honours.
“BioLumic’s innovation sits at the nexus of science, sustainability, and food system transformation,” said Hill. “I look forward to contributing to BioLumic’s efforts to shape the future of sustainable agriculture.”
BioLumic’s Scientific Advisory Group brings deep expertise across plant science, trait commercialization, global food systems, and sustainability.
About BioLumic
Founded in 2013, BioLumic is a U.S.- and New Zealand-based agricultural biotechnology company using light signaling as a programming language for plants. Its patented xTraits™ technology unlocks non-GMO genetic expression traits to enhance yield, composition, and crop resilience through a one-time, light-based seed application. BioLumic traits are scalable, fast to develop, and easily integrated into existing seed systems. Learn more at www.biolumic.com or contact info@biolumic.com.
The California Walnut Conference, the annual gathering for walnut growers and handlers, is returning with a new date and location for 2026. The event will take place February 19, 2026, at the Turlock Fairgrounds, marking a new chapter in its continued evolution and growth.
The annual California Walnut Conference is presented by West Coast Nut magazine in partnership with the California Walnut Commission (CWC). Together, these organizations have built a forum for information, networking, and solutions for walnut growers and handlers and industry suppliers.
“We know this event has become important to the walnut industry and allied community and hope this more centralized location and new date will help make the conference accessible to additional growers and handlers,” said Jason Scott, Publisher and CEO of West Coast Nut and JCS Marketing Inc.
This year’s conference will include a full day of seminars covering topics important to walnut growers and handlers, including research, production practices, trade developments, advocacy, and market dynamics. Continuing education will be offered eligible sessions.
“The California Walnut Conference is a cornerstone of our efforts to bring the industry together,” said Robert Verloop, Executive Director and CEO of the California Walnut Board and Commission. “We changed the location to Turlock in order to make the conference more accessible for all growers. It provides the opportunity for knowledge-sharing, collaboration, and dialogue that is essential to moving our industry forward into the future. With the challenges and opportunities ahead, this conference helps ensure we are aligned and working toward a strong and sustainable future for California walnuts.”
Based on overwhelming interest from last year, the Poster Board Research Sessions will be expanded in 2026. These sessions feature key findings from walnut industry-funded research in areas such as pest management, irrigation, fertility, varieties and rootstocks, and overall crop production. Researchers will be on hand to engage directly with attendees, answer questions, and provide insights into practical applications for growers.
The Walnut Industry Resource Center—first introduced in 2025—will return with even more nonprofit and government partners offering cost-share programs, educational materials, and grower-focused resources aimed at improving profitability and sustainability on the farm.
Don’t miss this opportunity to connect directly with handlers, processors, and the California Walnut Board and Commission staff to learn more about how the industry is working together to boost demand and increase prices for California walnuts.
Exhibitor and sponsorship registration opens this month. Interested businesses and organizations are encouraged to act quickly to reserve space. For sponsorship or exhibitor opportunities, contact sales@jcsmarketinginc.com.
Attendee registration will also open this month. Growers, handlers, and industry professionals can register at myaglife.com/events.
For more details or to register for this free event, visit myaglife.com/events or walnuts.org.
An integrated approach to spider mites is always recommended, including the use of beneficial insects, particularly fostering six spotted thrips populations, according to Todd Burkdoll, field market development specialist for Valent (photo courtesy UC Statewide IPM Program.)
As summer temperatures soar into triple digits across California’s Central Valley, the annual battle against spider mites has intensified. Growers with a history of infestations face a high risk once again, prompting early action.
“There’s a 95% chance that orchards that had spider mites last year have them again this year,” said Todd Burkdoll, field market development specialist for Valent. “Scouting for overwintering females, if you find adults out there, they’re laying eggs, and those eggs will hatch, and then it goes from one to two to four exponentially really fast. Get on them early, get those females under control.”
Burkdoll recommends an integrated pest management (IPM) approach that combines vigilance, targeted materials and biological control.
He emphasizes early detection. “When in doubt, scout,” attributing that advice to the late John Palumbo.
For chemical control, Burkdoll favors an insect growth regulator (IGR). “I like to go with an IGR [like] Zeal. It’s very specific. It’s basically a mite growth regulator and sterilizes the females, so the eggs that she lays are sterile. The eggs that are already laid, they turn black and die, and the nymphs don’t go from one to the next. So it’s a pretty effective tool.”
Despite its efficacy, proper application is critical. “The only Achilles heel is you have to get good coverage. You can’t spray and pray, go across the field three, four miles an hour and expect it to work, because to the degree you get coverage is to the degree you will get killed, period.”
He quoted the late Madera County Farm Advisor George Levitt: “If you don’t get good coverage, you’re not going to get control. Speed does not kill. Slow down, do it right the first time and you won’t have to go back and try to play catch‑up later on.”
Burkdoll expects moderate to heavy mite pressure in tree fruit, almonds and vineyards in 2025 and stressed the value of biological controls in IPM. “An integrated approach to spider mites is always recommended, and involved in that approach will be the use of beneficial insects, particularly fostering six spotted thrips populations.”
He cautioned against overuse of broad-spectrum insecticides like pyrethroids and organophosphates, saying they harm both pests and beneficial species. “They kill most arthropods, spiders, predatory mites, six spotted thrips… If you can back off on those or wait till the last minute or use something else that isn’t as broad-spectrum or a more targeted approach, that’s always an advantage in the long term.”
For dormant-season mite management, Burkdoll noted selective use of pyrethroids, especially when mixing up chemistries, to avoid resistance. “Going out there broad-spectrum with pyrethroids early season is putting you on a treadmill for other pests. You’re going to have to spray again and again. So using IPM, mixing up chemistries, using different modes of action, and they have to work; you have to have something that works.”
He recommends following UC guidelines for mite management rooted in decades of research. “Older chemistries that have been around, they’ve been thoroughly tested, gives you a pretty good ballpark of what you can use. Just mix up the modes of action. Don’t use the same group number.”
The 2025 Crop Consultant Conferencereturns September 24-25 at the Visalia Convention Center, bringing together California’s leading PCAs, CCAs, researchers and industry professionals for two days of learning, networking and innovation in the heart of Central Valley agriculture.
Hosted by Progressive Crop Consultant, MyAgLife and Western Region Certified Crop Advisers, the Crop Consultant Conference is California’s premier event for crop consultants committed to advancing sustainable, profitable farming. Attendees can look forward to a packed agenda that includes expert-led sessions, CEU opportunities, novel research and practical field-ready strategies designed to meet today’s challenges head-on.
Comprehensive, Flexible CEU Opportunities
One of the conference’s greatest strengths is its dual-format CEU education program. Attendees can earn continuing education units (CEUs) for CA DPR, CCA, FREP, NDA and AZDA through both in-person and online sessions, providing the flexibility busy ag professionals need.
Beginning April 1, 2025, a new expert-led online session launches on the first of each month, covering topics like tree nut economics, advanced irrigation management and more. In-person sessions during the conference will offer extensive CE credit opportunities, with online access to additional courses extended through Dec. 31, 2025.
“This flexibility allows PCAs and CCAs to balance their work schedules while advancing their knowledge and skills,” said Jason Scott, CEO of JCS Marketing, Inc. “And with registration priced at just $345, it’s an incredible value, translating to pennies per CE credit.”
Practical Knowledge and Cutting-Edge Innovation
This year’s program emphasizes practical, immediately actionable insights. Topics will include soil health, pest and disease management, regulatory updates, climate-smart farming practices and the latest advancements in ag technology.
“This strategic location in Visalia allows participants to connect directly with innovations shaping the future of crop consulting,” Scott said.
Attendees will have full access to the conference trade show, showcasing the newest products, services and technologies in agriculture. It’s a rare opportunity to see the tools that can enhance consulting practices and client results firsthand.
A Full Conference Experience
Beyond earning CEUs, participants will enjoy breakfast and lunch both days, a lively networking mixer and ample opportunities to build connections with industry leaders, decision-makers and peers.
“This event is more than just lectures; it’s a platform for collaboration, innovation and professional growth,” Scott said. “It’s where future-forward crop consulting happens.”
High Demand: Register Now
Given the conference’s comprehensive educational offerings, affordable pricing and outstanding networking opportunities, both registrations and sponsorships are expected to sell out quickly.
“This is your chance to be part of a transformative experience that will elevate your professional knowledge and expand your industry network,” Scott said.
Secure your spot today and join us in Visalia this September for the 2025 Crop Consultant Conference.
Almond shells are lightweight but bulky, making them difficult and costly to spread due to the high volume needed per acre. Given limited impacts on soil fertility and yield, this practice is most practical for alfalfa fields located close to almond shell sources (all photos courtesy S. Light.)
Almond shells were applied as a mulch to an established alfalfa field in Yolo County over a two-year period. The intent of the study was to see if alfalfa could serve as a sink for almond shell byproducts after processing without affecting stand productivity. Alfalfa is deep-rooted and fixes nitrogen, which may allow for application of high-carbon materials like almond shell mulches.
The first year, almond shells were applied in October 2021 to a three-year-old stand at 4 to 8 tons per acre. By spring 2022, the almond shells had mostly decomposed. Almond shells were applied to the same test plots in November 2022 at 12.5 tons per acre. Additional field treatments included gypsum at 2 tons per acre per year and an untreated control. In addition to yield, test plots were evaluated for stand vigor, percent cover (bare soil, alfalfa, weeds) and weed pressure. Soil fertility and soil health measurements were also collected during this trial, including aggregate stability, compaction, soil moisture and soil cracking.
Outcomes of Mulch Application on Crop and Soil Metrics The almond shell mulch did not reduce stand vigor as measured by the number of alfalfa plants per square foot. Alfalfa yields were likewise not significantly reduced (P>0.05), though they trended lower in almond shell plots for the first spring cutting (Fig. 1 and 3) and then evened out and were slightly higher than control plots in late summer for both years of this study (Fig. 2 and 4). Almond shells are high in C and low in N. Amendments with a high C:N ratio can tie up N as they break down. The slight reduction in spring yields might be due to initial spring tie-up of N for feeder roots from the almond shell application.
Figures 1-4. Alfalfa yields were not significantly different between the almond shell and control treatments (P>0.05), though trended slightly lower in the spring harvest followed by increased yields in midsummer where almond shells were applied to established alfalfa stands the previous fall in both 2022 and 2023. Gypsum likewise showed trends for higher alfalfa yields, indicating benefits to soil health at our study site with relatively high clay soils.
For soil health metrics, almond shell applications showed benefits of reduced soil cracking (Fig. 5) and soil compaction in the top three inches of soil (Fig. 6). Soil cracking is common in clay soils and can tear feeder roots apart in perennial crops like alfalfa. Soil compaction, a common problem in alfalfa due to equipment traffic during multiple harvests, can lead to yield and stand loss, poor water infiltration and reduced microbial activity. Our study shows almond shells provide an opportunity to mitigate surface soil compaction once the alfalfa has established. There were no changes to other soil health metrics like aggregate stability and bulk density after two years of this trial, nor did the almond shell mulch suppress weeds at rates applied.
Figure 5. One measure of soil health is the degree of cracking as soils dry. Applications of almond shell as a mulch to alfalfa growing on a relatively high clay soil significantly reduced levels of cracking.Figure 6. Soil compaction is measured using a penetrometer, which collects pressure (pounds per square inch (PSI)). Less pressure was needed to penetrate soil in the top 3 inches in plots that had almond shells applied as a mulch (not incorporated).
Apart from electrical conductivity (EC), which measures salinity levels in soil, soil measurements were not significantly different by treatment. Gypsum is a highly soluble salt, and EC was higher in the gypsum plots compared to the almond shell and control plots. Even though differences were not statistically significant, there were some interesting trends in soil measurements. Specifically, almond shells have about 30 pounds of potassium per ton (36 lb K₂O/ton), which can eventually leach into the root zone with rain or irrigation as almond shells decompose. In this project, there was more potassium in soils with almond shell mulch compared to gypsum or control plots. In addition, plots with almond shells had more total carbon and total organic matter. Soil samples were collected in the top foot of soil and shells were applied to the soil surface. It is likely the soil sampling depth affected our ability to measure differences in soil K and C. Other measurements like cation exchange capacity, magnesium, calcium and total N were not different by treatment.
Soil water measurements were collected in this trial. Infiltration measurements were taken for the first four inches of water applied. Infiltration measures the rate at which water moves into the soil. Infiltration was fastest in plots with almond shells for all 4 inches of water. However, the differences were only statistically significant for the 4th inch of water (Fig. 7). In a heavy rain event, rapidly moving water into the soil is advantageous for preventing runoff and retaining water in the fields. Saturated hydraulic conductivity measures the rate that water flows through saturated soil. Though not statistically significant, almond shell plots also had a faster saturated hydraulic conductivity (faster water flow rate) compared to other treatments.
Figure 7. Water infiltration was measured for the first 4 inches of water. This simulates how long it takes water to move into the soil during a heavy rain event. The almond shell plots had the fastest water infiltration (fewest minutes required per inch) for all measurements. The 4th inch of water is shown.
Volumetric water content was measured in the top 6 inches of soil. The total differences in soil water content at any point in the season were negligible for on-farm irrigation decisions. However, some interesting trends were observed. In rainy months, almond shell plots had higher water content after rain events, likely because of increased infiltration and hydraulic conductivity. However, in the summer months, almond shell plots had slightly less water in the top 6 inches of soil. These are the months when the yields trended slightly higher in the almond shell plots. Alfalfa is a crop that yields relative to water applied; this reduction in water content is likely due to the increased alfalfa yield in plots with almond shell application.
Cost Considerations and Logistical Factors of Shell Application Almond shells are both bulky and very lightweight, making them challenging to spread compared to other amendments. However, shells are a dry material, and transportation costs are not lost to water weight as with other soil amendments like compost. Good soil coverage requires a high volume of shells per acre, and multiple truckloads per field will be needed. This increases hauling and spreading costs. For the Sacramento Valley where this field trial was conducted, freight costs are $10 per ton within 50 miles and spreading costs are $15 per ton. These costs are high given the lack of measurable differences to soil fertility and yield. Thus, this practice is best suited for established alfalfa fields located near a source of almond shells to reduce freight costs.
Mulching is considered a soil conservation practice under both federal and state guidelines. However, mulch must be applied to a 2-inch depth and at a rate to achieve 70% soil coverage. At the highest application rate in our study (12.5 tons/acre), the depth of the mulch was under 1 inch.
Almond shell mulch rests on the soil surface of an alfalfa field. Researchers observed benefits such as reduced soil cracking and improved water infiltration without significant changes in soil fertility or productivity.
Key Takeaways In our study, almond shell mulch in an established alfalfa field showed benefits of reduced soil cracking, reduced soil compaction and increased water infiltration without negatively affecting overall stand health and yields at the rates of almond shells applied. Alfalfa has deep roots and fixes N, making it a resilient crop for diverting high-C almond shell waste byproducts from nearby orchards to alfalfa stands, improving organic matter recycling in the region. Since almond shells are not incorporated, any N tie-up would be slow and only in the soil surface. Incorporating almond shells to alfalfa stands prior to planting or applying shells to first-year stands is not recommended due to issues with tying up N with a high C:N product that could affect stand establishment and plant growth. This project was an initial evaluation and did not quantify the optimum application rate to alfalfa fields.
Funding was provided by the California Alfalfa and Forage Research Foundation. Thank you to our grower collaborator for supporting this work.
The original version of this article first appeared in the April/May 2025 issue of Hay & Forage Grower.
Figure 3. Recently released CB77 has a slightly larger, whiter seed compared to CB46. More lygus stings are visible in CB46 (photo courtesy B. Huynh.)
Black-eyed peas, also called cowpeas, are a bean speciesnative to Africa in the Vigna genus of legumes. Cowpeas were introduced to the United States as early as the 16th century by Spanish colonists and through the trans-Atlantic slave trade. “Blackeyes,” as they’re called locally, are grown by California growers on approximately 8,000 acres each year to produce a nutrient-rich food for consumers. Most production in California goes to the dry bean sector for canning and bagging. A small amount of the crop is produced for fresh consumption, similar to green beans or snap peas, and may be sold at farmers markets.
Blackeyes are an important crop in the San Joaquin and Sacramento valleys, where diverse crop rotations are common. A relatively drought-tolerant crop, blackeyes are usually flood or furrow irrigated. Growers rarely fertilize with nitrogen since blackeyes efficiently fix nitrogen from the air due to the plant’s symbiotic relationship with a root-inhabiting Rhizobia bacteria species. Additionally, blackeyes are moderately tolerant of salinity and can grow in conditions where yield declines would be expected for other summer annuals like corn and tomatoes. These characteristics of blackeyes can be an economic incentive to grow them in some years and will be important in California, particularly under hotter and drier conditions expected with climate change. Plant Breeding for the Future
As California shifts toward drier and more extreme weather, blackeyes, like most cultivated plants, will experience new pressures that growers will be first to manage. Heat stress and drought vulnerability, emerging and invasive insect pests, increased weed competition and the evolution of endemic and invasive diseases are some of these pressures. Plant breeding that considers these stresses will help the industry stay ahead of the curve.
UC has a long history of variety development for the California blackeye and garbanzo industries. For blackeyes, the current standard varieties are CB46 and CB50, which were released in 1990 and 2009, respectively. CB46 is high-yielding and has Fusarium wilt race 3 resistance, but it is susceptible to virulent and aggressive races of root-knot nematodes, Fusarium wilt race 4, aphids, lygus and late-season diseases known collectively as ‘early cut-out.’ Additionally, the market now prefers larger seed and whiter grain than what CB46 provides. CB50 is high-yielding, has larger seed size than CB46 and is resistant to Fusarium wilt races 3 and 4 and root-knot nematodes.
To support plant breeding efforts, new breeding lines and cultivars are trialed at research facilities and then on commercial farms to evaluate material across environmental conditions. New materials are evaluated against commercial standards for yield, quality and pest resistance. The cultivars and advanced lines that have been trialed across regions and years are described in Table 1. UCCE farm advisors have collaborated for more than 10 years with UC Riverside plant breeders to test improved lines and, over the last five years, have conducted 21 trials across seven locations in the Central Valley.
Table 1. Descriptions of California blackeye cultivars and new breeding lines.
The variability in precipitation and average air temperature down the Central Valley can influence blackeye phenotypic traits. For example, in Five Points (southern San Joaquin Valley) from 2020 to 2025, the mean annual precipitation was 7.6 inches, whereas Davis (southern Sacramento Valley) had a mean annual precipitation of 17.1 inches. Similarly, average daily air temperature in June, July, August and September over the same five-year period in Five Points was 78 degrees F but was 73 degrees F in Davis. It is important to test experimental lines across regions to understand how they will perform in different environments.
California growers who serve on the California Dry Bean Advisory Board have identified high yield, seed quality and disease resistance as top priorities for plant breeding efforts. They have also emphasized the importance of regional acclimation. The following are some highlights from research funded by the California Dry Bean Advisory Board, USAID Feed the Future Innovation Lab for Legume Systems Research and California Crop Improvement Association, made possible through the generous support of numerous growers, bean harvesters and bean handlers.
Regional Trial Results
Yield results from 2020 to 2024 trials are summarized for the Sacramento and San Joaquin valleys (Table 2), where average yields ranged from 1,091 to 3,582 pounds per acre. The lowest yield occurred in 2020 and the highest in 2024, both in the Sacramento Valley. Interestingly, yields in the San Joaquin Valley were 27% lower than in the Sacramento Valley in 2024. While yields are usually higher in the San Joaquin Valley, the lower yields may have resulted from a prolonged heat wave and above-average nighttime temperatures, which caused significant crop losses.
Table 2. Annual blackeye bean cultivar and advanced breeding line yield (lb/ac) in the Sacramento and San Joaquin valleys.
Seed size is an important quality factor in blackeye production related to consumer preferences. Average seed size, reported as the weight of 100 seeds, for the last five years of trials is shown in Table 3. Seed size ranged from 20.0 grams per 100 seeds for CB77 (2020, Sacramento Valley) to 27.8 grams for CB50 (2024, Sacramento Valley). CB5 and CB50 consistently have the largest seed size across sites from year to year, while the experimental lines tend to have smaller seed size, similar to CB46 and CB77. Over the last five years, average seed size in the San Joaquin Valley was approximately 7% smaller than in the Sacramento Valley.
Table 3. Annual blackeye bean cultivar and advanced breeding line seed size (100 seed weight in grams) in the Sacramento and San Joaquin valleys.
An important insect pest of blackeyes is lygus, which kills fruits before they develop, resulting in direct yield loss. Lygus feeding, called “stings,” also damages and discolors seeds after pods develop (Fig. 1), which reduces yield and diminishes the quality of the beans. The results for lygus damage, shown as the percent of seed with lygus stings, are shown in Table 4. The average lygus damage ranged from 2% for CB77 (2020, Sacramento Valley) to 43% for CB5 (2021, Sacramento Valley). Average lygus damage in the Sacramento Valley over the last five years was 20%, while in the San Joaquin Valley it was 7%. Importantly, under the heavy lygus pressure in the Sacramento Valley, the five-year average lygus damage was lower for experimental line 07KN-74 and newly released CB77 compared to the commercial cultivars CB5 and CB46. This demonstrates a high yield potential and reduced need for insecticides to control lygus with the newer material. With little development of new insecticides for use in dry beans, the importance of insect-resistant varieties cannot be overstated.
Figure 1. Lygus susceptible (left) and lygus tolerant cowpea (right) (photo courtesy Rachael Long, UCCE.)Table 4. Annual blackeye bean cultivar and advanced breeding line lygus damage (% of seed damaged) in the Sacramento and San Joaquin valleys.
New material is also evaluated for disease resistance (data not shown). The evolution of Fusarium wilt provides an example of why plant breeding is critical to disease management. CB5 is an older blackeye variety that is susceptible to Fusarium wilt race 3. CB46 was released as a commercial variety with Fusarium wilt race 3 resistance. However, after years of production, CB46 started showing susceptibility to Fusarium wilt race 4. CB50 was then introduced as a new variety with resistance to both Fusarium wilt race 3 and race 4. During trialing, advanced breeding lines are grown alongside traditional cultivars (like CB5, CB46 and CB50) to quantify how new material compares to varieties already on the market. Lines are evaluated over multiple years to capture variability in pest pressure, weather and other yield-limiting conditions.
Research Outcomes
Recently developed varieties show resistance to disease and aphids, while new breeding lines show great promise for nematode or lygus resistance. Recently, CB77 was publicly released as an improved variety with similar yield and quality to CB46 but with resistance to cowpea aphid (Fig. 2). It also has a brighter white color than CB46 (Fig. 3). The California Crop Improvement Association currently holds foundation seed of CB77 and will distribute it to growers who successfully apply to grow certified seed for commercial production.
Figure 2. CB77 with resistance to cowpea aphid (left) and CB46, which is susceptible to cowpea aphid (right) (photos courtesy Rachael Long, UCCE.)
Lines N2 and 07KN-74 will be ready for public release within a year. Line N2 is a root-knot nematode-resistant line with high yields in the San Joaquin Valley. Root-knot nematodes damage roots, which diminishes water uptake and yield. As fumigants are phased out through regulatory processes, host resistance and alternative strategies for reducing root-knot nematode damage must be taken into consideration. Line 07KN-74 is a lygus-tolerant variety with moderate yield, similar to or slightly lower than the commercial standard CB46. This article summarizes the plant breeding and trialing efforts to improve blackeyes for the California industry. Yield, quality and pest resistance are important traits for plant breeding efforts, and this article summarizes years of data across multiple locations in the Central Valley. These evaluations are ongoing and provide growers with first-hand information on how new genetic material performs under commercial farming conditions. Growers who are interested in learning more or hosting on-farm trials should contact the authors, who would be glad to help make those arrangements.
Figure 1. A demonstration of one flux tower monitoring station and some of the instrumentation set up above the canopy and within the flux tower’s footprint.
In California, avocado (Persea americana Mill.) is primarily grown in southern and central parts of the state along the coast where 88% (USDA-NASS 2023) of the avocados are grown in the United States. These regions have semi-arid Mediterranean climates and currently face uncertain water supplies, mandatory reductions of water use and rising cost of water, and thus, efficient use of irrigation water is one of the highest conservation priorities. Moreover, due to increasing salinity in water sources and the fact that avocado trees are sensitive to salinity, effective irrigation is more critical to ensure optimal yield and high-quality avocado fruits. Many avocado growers have developed irrigation practices that enable good profitability; however, the continual increase in water costs and water restrictions due to drought and climate change has placed pressure on the industry to further enhance water use efficiency. Accurate information on crop water use along with irrigation best management practices are the immediate needs of the avocado industry under the current fluctuations in water availability, reliability and quality to sustain the profitability and sustainability of production. Hass is the predominant avocado variety in California, accounting for nearly 95% of the planted area (Hass Avocado Board 2020). This article summarizes some findings from our recent three-year study conducted on Hass avocado crop water use (actual evapotranspiration or crop water consumption) and crop coefficients.
Experimental Sites and Measurements The data used in this analysis are from the research conducted at Hass avocado orchards in four avocado sites in southern California, here referred to as site A (San Pasqual Valley, Escondido), site B (Via Vaquero, Temecula), site C (Orchard Hills, Irvine) and site D (West Saticoy, Ventura) (Table 1). The sites consisted of a wide range of climates, slopes and elevations, soil texture and conditions, tree spacings, soil types and conditions, and water sources, offering a good representation of the Hass avocado production systems in California.
Table 1. General information about experimental avocado sites.
A combination of eddy covariance and surface renewal equipment (flux tower, Fig. 1) was utilized to measure actual crop water consumption at each avocado site over a three-year period (2022-24). Several other sensors and equipment were used to monitor soil and plant water status, soil salinity and chloride, and high-resolution images were captured by unmanned aerial systems to evaluate canopy features.
Weather Variables Monthly average meteorological data over three years from 2022-24 were compared with the 10-year average (1995-2024) (Fig. 2). The data demonstrated all regions had a dry 2022 winter, a wet 2023 winter and a near normal (10-year average) 2024 winter. Overall, more variations were observed in the monthly maximum temperatures than the minimum values over the study seasons compared with the mean 10-year corresponding temperature data. A similar tendency was found across the experimental regions over the period. Except the fall, the entire 2022 season was warmer compared to the 10-year average. August 2022 had the highest mean daily maximum temperature for the recorded period of three years at 38.1 degrees C (100.6 degrees F) in the San Pasqual Valley and 34.8 degrees C (94.6 degrees F) in the Via Vaquero area. September 2022 had the highest mean daily maximum temperature over the three-year period at 30.9 degrees C (87.6 degrees F) and 28.3 degrees C (82.9 degrees F) in the Orchard Hills and the West Saticoy regions, respectively.
Figure 2. Monthly mean daily maximum and minimum air temperatures over the study period compared to the 10-year average and monthly total rainfall over the study period compared to the 10-year average in regions 1-4 (A-D). Data from CIMIS stations of Escondido SPV# CIMIS 153, Temecula East III# CIMIS 237, Irvine# CIMIS 75 and Camarillo# CIMIS 152 were used for this analysis, representing sites A-D, respectively.
Salinity Effects Salinity within the soil profile varies over the season and between the seasons affected by rainfall, irrigation management, leaching practices, irrigation water quality, and soil types and conditions. The bulk electrical conductivity values measured by CropX sensor at site A (Fig. 3) demonstrated a decline from 388 µS/cm on June 23, 2022 to 95 µS/cm on Feb. 8, 2023 at this site. The salinity noticeably diminished after the wet winter 2023 in comparison with summer 2022 when a salt-affected condition was observed at some of the avocado sites. The avocado sites occasionally could experience salt accumulation more than the threshold while wet winter and appropriate leaching practices may have a significant impact on maintaining salt and chloride issues (Fig. 4). This may negatively influence the crop coefficient values under circumstances. The threshold ECe (electrical conductivity of the saturation extract, dS/m−1) for Hass avocado is reported to be 2.0 dS/m−1.
Figure 3. Half-hourly bulk electrical conductivity data from CropX sensor at 20 cm depth at site A. The data is reported for a 16-month period (June 9, 2022 through Oct. 8, 2023). A wet winter was observed in the 2023 season. The ECe value measured on two different dates (Sept. 17, 2022 and May 4, 2023) at the same depth was 1.69 dS/m−1 and 0.84 dS/m−1, respectively.Figure 4. Soil profile ECe observed values in different sampling points at site C from the survey conducted in September 2022 and April 2023 (after the wet winter 2023). The threshold ECe for ‘Hass’ avocado is reported to be 2.0 dS m-1.
Daily Crop Water Use While a similar crop water use pattern was found over the course of the measurement seasons in experimental sites, daily crop water consumption was generally greatest at site A. Variable daily crop water use was observed on each site over the season/s. For instance, it varied from 0.03 in d−1 to 0.18 in d−1 with an average of 0.11 in d−1 in the 2023 season at site A (Fig. 5a). Considering the tree spacings at this site, the crop water use ranged between 6.7 and 40.5 gallons per tree with an average crop water need of 24.6 gallons per tree in 2023. The values were, as expected from the weather data, lower in late fall and winter when conditions were cooler, and the days were shorter. Uniform daily crop water consumption over the summer months occurred more frequently than other months, specifically during the winter and part of the spring when the weather conditions were more unstable.
The observed daily actual crop water use and Spatial CIMIS ETo (reference ET) in each of the experimental sites were used to compute the daily actual Kc values at each site over the study seasons. The trends in daily Kc values were similar across experimental sites over the study period, with more Kc variability during late fall and winter months when compared with spring and summer months (Fig. 5b). During late-fall and winter, the weather is more unstable with more cloudy and rainy days and wet soils. More fluctuations in actual Kc values are expected under such circumstances. The daily Kc value varied from 0.61 to 1.10 with a mean of 0.75 at site A over the 992-day study period.
Figure 5. Daily actual crop water uses (a) and actual crop coefficient values (b) and 15-day average values at site A over a 992-day period (April 2022 to December 2024).
Seasonal Crop Water Use and Crop Coefficient Values Considerable differences were found in the seasonal crop water use measured across experimental sites and seasons (Fig. 6). The largest difference was 11.4 inches between site A and site D during 2024. However, the seasonal crop water use difference between avocado sites C and D was 2.1 and 2.4 inches in 2023 and 2024, respectively. Overall, greater crop water consumption was observed in each of the avocado sites in 2024.
The greatest seasonal crop water consumption was determined at an avocado site (site A) with the features of coarse sandy loam soil texture, 44% south facing slope, average elevation of 758 feet above mean sea level, plant density of 120 trees per acre, average canopy coverage of 88.7% and tree height of 23.2 feet (Fig. 6). In contrast, the least seasonal crop water use was observed at an avocado site (site D) affected by coastal climate with the features of loamy soil texture, 3% southwest facing slope, average elevation of 164 feet above mean sea level, plant density of 254 trees per acre, average canopy coverage of 75.9% and tree height of 12.5 feet.
Figure 6. Seasonal crop water use measured at the avocado sites in 2023 and 2024. The comparison demonstrates that the seasonal consumptive water use at avocado sites varied from 28.1 inches (affected by coastal climate) to 40.4 inches (an inland valley) over the two growing seasons of 2023 and 2024. Considering the tree spacings at the avocado sites, the seasonal crop water requirements may vary from about 3,000 gallons per tree (high density orchard affected by coastal climate) to about 9,000 gallons per tree (low density orchard under growing conditions of inland valley).
The results demonstrated there is considerable spatial and temporal variability in crop coefficient values of avocado orchards (Fig. 7). At site A, the average monthly Kc value varied between 0.70 in July-August and 0.85 in January. The south facing high slope along with the large canopy coverage are likely the most influential drivers in the environmental conditions of this avocado site, which tends to receive higher direct sunlight and light interception resulting in high crop coefficient values over the season. The monthly actual Kc value varied from 0.55 in July to 0.73 in January at site D, located at a low elevation. This specific site was more affected by the coastal fog influence than the others that could be a major reason for less crop water needs over the season.
Figure 7. Mean monthly actual crop coefficient (Kc) values at the experimental avocado sites. The observed daily actual evapotranspiration and Spatial CIMIS ETo on each site were used to compute the monthly mean Kc values over the study period. Standard deviation of the corresponding Kc values is shown on the bars.
The maximum difference was found between the monthly Kc values of site A and site D, ranging from 11.5 % greater in April to 27.0 % greater in July. Greater differences were observed during the June-September period when lower Kc values determined than in the other months of the year. A similar trend was found at site B with the lower difference values. Inversely, more differences (the values are relatively low) were obtained in the winter months at site C that could be caused by the green ground cover between tree rows during the winter at this site.
The results illustrated summer has the lowest crop coefficient values, increasing gradually from late September to a maximum in mid-winter, again gradually reducing during spring to a minimum in mid-summer. To be more precise, the findings revealed greater Kc act values of avocados during flower bud development and flowering through fruit set growth phases than the fruit development phase. Potential reasons for such a trend are:
• Avocado leaves have a thick waxy cuticle that may reduce water loss through leaf surface and stomata. Young leaves, flowers and young fruit do not have a fully developed cuticle and may lose more water. Researchers reported that during flowering, as some of the floral parts have stomata, the evaporative surface of the avocado tree canopy increases by up to 90%, leading to an increment of the total tree transpiration rate.
• Avocado requires high energy in fall and winter for oil accumulation in fruit and floral development, and the trees may transpire at a higher rate compared to grass (ETo) during these months for photosynthetic activity throughout the growing season.
A mean daily crop water use of 0.13 and 0.15 in d−1 was found for spring and summer (over the three study seasons), respectively, whilst the value for winter and fall was similar (0.08 in d−1) at avocado site A with maximum values. Considering the tree spacings at this avocado site, the average daily crop water requirements are estimated 29.2 and 33.7 gallons per tree in spring and summer and 17.7 gallons per tree in fall and winter. In a winter with normal or wet rainfall conditions, precipitation most likely provides sufficient water to compensate for avocado tree water needs. The study verifies this for 2023 and 2024 at all avocado sites.
Considerable spatial and temporal variability were found in crop water consumption and crop coefficient values of avocado orchards. Several factors impact the variability of these measures in avocados, including climate, slope and row orientation, elevation, height of trees, trees canopy coverage that provides a good indication of canopy size and the amount of light interception, irrigation management practices and salinity and/or soil differences. If avocado orchards are located in similar climatic regions, it appears slope and row orientation along with canopy coverage percentage are likely the most influential drivers on avocado crop water use. It needs to be noted that in the Northern Hemisphere, midday and daily total solar radiation is mostly greater on southern slopes than on northern slopes and the slope aspect influences incoming light intensity and as a result consumptive water use.
The seasonal crop water uses provided in this article are the seasonal water consumption measured for avocado orchards across avocado experimental sites. Excess irrigation can be considered beneficial water use for salinity and choloride management in avocado orchards. The amount of additional irrigation water to effectively drain salt from the crop root zone depends on the soil conditions, effective rainfall and quality of irrigation water. However, the total irrigation water that needs to be applied in an individual orchard over the season depends on seasonal crop water requirements, effective rainfall, water distribution uniformity and salt leaching requirements. Heat waves are another driver that may impact the total applied water in avocado orchards.
The USDA Agricultural Marketing Service and the California Avocado Commission jointly supported this research.
References
Hass Avocado Board and the CIRAD Market News Service. 2020. World avocado production prospects: California in transition.
U.S. Department of Agriculture National Agricultural Statistics Service., 2023. Quick Stats. Available online at: https://quickstats.nass.usda.gov/.
