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San Diego avocado growers look to Cooperative Extension experts to manage water costs
San Diego County used to be home to nearly 25,000 acres of avocado trees but today there are about 14,000. The drastic decrease is largely due to rising costs associated with avocado production, namely the cost of water.
On September 28, avocado growers gathered at the San Diego County Farm Bureau offices for an Avocado Irrigation Workshop facilitated by Ali Montazar, University of California Cooperative Extension irrigation and water management advisor for Imperial, Riverside and San Diego counties.
“All of our information being developed right now is focused on [irrigation] efficiency. Growers want to know how much water they need and what tools they should use to be more efficient,” explained Montazar.
“The sophisticated research in avocado irrigation that Dr. Ali Montazar is conducting is the first of its kind that the University of California has carried out specifically in avocados. His presentation allowed us attendees the opportunity to see and learn about the technology he is employing – from soil moisture sensors to the California Irrigation Management Information System level equipped station.”
Burr is hopeful that Montazar's research will help avocado growers accurately determine the evapotranspiration in an avocado grove or water use specific to avocados, critical parts of how growers select tools to determine irrigation runtimes.
“His presentation that showed his research finding of the avocado Kc (crop coefficient), while very early into his project, was really interesting. It indicates the possibility that we may need to vary the Kc for different times in the growing season, but he is just beginning a two-to-three-year project that will hopefully deliver solid data on what the Kc for avocados is,” said Burr.
Colorado River uncertainty looms
San Diego's avocado production is primarily managed by small farms. According to Montazar, this adds a level of complexity to water management because there is a greater emphasis on irrigation tools and strategies being user-friendly and cost-efficient.
“We don't know the future,” said Montazar. “But we need to be prepared for all consequences. The Colorado River is experiencing a significant water shortage, and this could impact the water supply source for San Diego County from the Imperial Irrigation District Transfer in the future. It is wise to consider enhancing irrigation efficiency as the most viable tool to manage limited water supplies in Southern California.”
Water has always been an issue. In the 1970s, California's water program paved a way for an additional 98,000 acres of agricultural land.
According to a 1970 study analyzing the cost of avocado production in San Diego County, water costs “averaged 3½ acre feet per acre at $60 an acre foot,” which came with the assumption that water costs would remain relatively low and affordable for a long time.
Unfortunately, that is no longer the case. The county of San Diego gets the majority of its water from the Colorado River, which is concerning given five-year projections of the river reaching critically low reservoir levels by 2027.
In fact, beginning in 2023, the San Diego County Water Authority will be raising the rates for water, prompting growers to invest in more efficient irrigation practices (Table 1).
Table 1. Cost for untreated and treated water in San Diego County in 2022 and 2023.
NOTE: An acre-foot is about 325,900 gallons of water.
Training growers on irrigation a top priority
There are no loopholes or short cuts when it comes to irrigation because irrigation is the key to tree health. Ben Faber, Cooperative Extension subtropical crops advisor for Ventura and Santa Barbara counties, points out that tree health is how growers stay in business.
“You can mess up your fertilization program, and you can mess up your pesticide program, but if you mess up your irrigation program, you're out of business,” he said.
According to Faber, efficient irrigation requires a strong grasp on salt management.
“We import water that has a lot of salt in it. So, you've got to figure out how to put the right amount of water on the root zone without causing root health problems,” said Faber.
This process requires meticulous care, as anything that gets below the root zone can cause groundwater contamination – something growers do not want to be responsible for.
While the latest irrigation technology, such as smart controllers, could help growers, Faber said that training and educating farm managers should be the priority.
As Faber puts it, managing irrigation should be “like brushing your teeth” – something that growers do naturally and competently. Many growers are over-irrigating or wasting time trying to resuscitate dying trees. It's important to learn the needs of the tree and, in some cases, it might be best to stop watering all together.
The first step to water efficiency is acquiring knowledge and identifying needs. Because an over-irrigated tree looks just like an under-irrigated tree, it's crucial that growers learn to recognize the difference and plan accordingly.
This is where Cooperative Extension advisors and researchers come in. Opportunities like the Avocado Irrigation Workshop are ideal for growers looking for answers or support.
For more information and to learn about future workshops in San Diego County, visit https://cesandiego.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.
Growers refine date palm irrigation with UC ANR research
California's $86 million date industry produces more than half of the nation's dates. Most of the fruit is grown in the arid Coachella Valley. Despite efforts by growers to conserve water, data was lacking on date palms' actual water use to refine the best irrigation management for the crop until a recent research project led by Ali Montazar, UC Cooperative Extension irrigation and water management advisor for Imperial and Riverside counties.
“California dates are grown in the hottest and most arid climate in North America and require substantial amounts of water in order to bring a successful crop to fruition,” Albert Keck, Coachella Valley date grower and chairman of the California Date Commission, wrote in a letter of support for this project. “In addition, there is scant modern research specifically and technically focused on growing dates in North America.”
Montazar said there is a lack of irrigation management information on date palms worldwide.
“The information developed in this study is expected to have a worldwide impact,” he said.
To determine the evapotranspiration rate and crop coefficients for California date palms, Montazar teamed up with scientists at UC Davis, California Department of Water Resources, USDA Agricultural Research Service, and USDA Salinity Laboratory.
The experiment was carried out in six date orchards in the Coachella and Imperial valleys. The sites represent various soil types and conditions, irrigation management practices, canopy characteristics, and the most common date cultivars in the region.
“The findings of the project indicate that there is considerable variability in date palm consumptive water use, both spatially and temporally,” Montazar said. In other words, the amount of water the trees use varies considerably depending on each site's growing conditions.
He estimated the water needs for date palms planted in different soil types in the low desert region.
“Growers will be able to use the science-based information and tools developed by this project to determine their date palm water needs and optimize the efficiency of water and fertilizer use in their groves,” Montazar said.
The peer-reviewed article “Determination of Actual Evapotranspiration and Crop Coefficients of California Date Palms Using the Residual of Energy Balance Approach” is published in the journal MDPI Water at https://www.mdpi.com/2073-4441/12/8/2253.
“With a large quantity of new date plantings in the region, coupled with increasingly limited water resources in the Colorado River Basin Watershed, the knowledge anticipated to be developed by this research project has the potential to yield large dividends through not only improved water use efficiency, but also best management practices and crop quality,” said Keck of the California Date Commission.
Although the research focused on Coachella Valley dates, Montazar said the results are likely to be useful to growers who have orchards with similar varieties, irrigation practices, and canopy and soil features in other locations.
Montazar's co-authors are Robert Krueger of the USDA-ARS National Clonal Germplasm Repository for Citrus and Dates; Dennis Corwin of USDA-ARS U.S. Salinity Laboratory; Alireza Pourreza UC Cooperative Extension specialist based at UC Davis Department of Biological and Agricultural Engineering; Cayle Little of California Department of Water Resources; Sonia Rios, UC Cooperative Extension advisor in Riverside County; and Richard L. Snyder UC Cooperative Extension specialist emeritus in the UC Davis Department of Land, Air and Water Resources.
The date palm irrigation project was funded by the CDFA Specialty Crop Block Grant Program.
A nutty idea: A little stress could be good for walnuts
When it comes to watering walnuts, most California growers believe you need to start early to keep trees healthy and productive throughout the long, hot summer. But according to striking results from a long-term experiment in a walnut orchard in Red Bluff, growers can improve crop production if they hold off irrigation until later in the season and directly measure their trees' water needs.
The findings from researchers at the University of California may help farmers optimize water use.
“It's a game-changer,” said walnut grower Hal Crain, who welcomed researchers on to his orchard to test irrigation optimization. “It's clear to me you can improve nut quality and yield by applying water based on what the tree wants and needs, rather than just watering when it's hot outside and the soil is dry. That's a big deal for walnut growers and for the entire agricultural industry.”
Changing the paradigm
Crain is a second-generation farmer whose family has been growing walnuts in Butte and Tehama counties for 55 years. Like most walnut farmers, Crain had always started irrigating in early to mid-May when the days grew warmer and the trees sprouted leaves.
“That's standard practice for probably 90 percent of California's walnut growers,” said Crain, walking amid his trees on a sunny afternoon. “The theory is that when you irrigate early, you preserve the deep moisture in the soil that trees need to survive the heat of summer.”
But that's not how it works, the research shows. Instead, trees that grow in saturated soil early in the season don't develop the deep roots they need to thrive.
“With all the water right there at the surface, the lower roots suffer,” explained Bruce Lampinen, UC Cooperative Extension orchard management specialist with the UC Davis Department of Plant Sciences. “Trees end up with a very shallow root system, which doesn't serve them well as they try to extract moisture from the soil later on.”
Lampinen has long suspected that walnuts were getting too much water in the spring.
“A lot of the symptoms we see like yellowing leaves and various diseases can all be explained by overwatering,” said Lampinen.
So Lampinen did what scientists do: He set up an experiment. Five years ago, with funding from the California Walnut Board and the U.S. Department of Agriculture, he joined forces with Ken Shackel, a plant sciences professor with UC Davis, and Allan Fulton, an irrigation adviser with UC Cooperative Extension. Together, they led a team of scientists testing irrigation on Crain's ranch.
“Hal is an exceptional partner,” Fulton said. “Farmers have a lot to accommodate when they host an experiment like this, with researchers going in and out of the orchard at all hours. He had to work around our people and the timing of our water treatments. He's always eager to experiment with technology and learn new things, and he shares what he learns with other growers. Hal completes the circle.”
Tough nut to crack
When is the best time to irrigate? Researchers say the trees hold the answer. Scientists use pressure chambers, which are air-pressure devices that measure a leaf or small shoot to gauge how hard the plant is working to pull moisture from the soil.
“Just because the soil looks dry doesn't mean the plant is suffering,” said Shackel, who specializes in plant physiology. “Pressure chambers let you ask the tree how it's feeling — sort of like taking a human's blood pressure — which is a much more accurate way to measure a plant's water needs.”
For the last five years, the team has been applying different water treatments to five blocks of trees. One block is getting standard, early irrigation. Crain's orchard managers begin irrigating the other blocks when the trees reach different levels of water stress based on pressure-chamber readings.
The trees that experience moderate stress are doing the best. Their irrigation usually starts in mid-to-late June, several weeks later than when standard watering begins.
“You can tell just by looking at that block that the trees are healthier,” said Crain, standing beneath a canopy of lush, green trees. “And, we're starting to see greater yields and better nut quality.”
Translating the research
The research is helping scientists advise farmers on irrigation.
“My biggest take-away is knowing when to start watering is a really important factor to the health of your trees,” Lampinen says.
Pressure chambers — sometimes called pressure bombs — can cost more than $3,000, and high-tech versions are under development.
“I tell growers a pressure bomb would pay for itself even if you just used it once a year to determine when to start watering,” Lampinen said.
Crain is certainly convinced.
“When you irrigate based on your trees' needs, you optimize water,” Crain says. “I'm not using less water overall, but the water I do use is producing more food. That's good news for everyone.”
This story was originally published in the Fall 2018 issue of Outlook Magazine, the alumni magazine for the UC Davis College of Agricultural and Environmental Sciences.
