Posts Tagged: almonds
‘Tis the season for baking lots of tasty treats. Breads, cookies, cakes, and candy are just a few that come to mind. What makes many of these treats so tasty is the addition of almonds or walnuts to the list of ingredients.
In California, we are lucky to be at the center of almond and walnut production. According to the California Department of Food and Agriculture's (CDFA's) latest Agricultural Statistics Review, more than 99 percent of the almonds and walnuts produced in the United States are grown in California.
Almond and walnut growers work tirelessly to supply enough nuts to not only satisfy domestic demand, but also for export. Worldwide, almonds rank as the largest specialty crop export. California is the top almond producer in the world, accounting for about 80 percent of all almonds grown. For walnuts, California ranks as the second largest producer in the world. To keep up with this demand, almond and walnut growers must be constantly aware of pests, diseases, and abiotic problems that can affect the tree and growing nuts.
The University of California Statewide Integrated Pest Management Program (UC IPM) has recently published revised Pest Management Guidelines for almonds and walnuts, helping growers prevent and manage pest problems with the most up-to-date information.
Revisions in the Almond Pest Management Guidelines include:
- A new section on bacterial spot, a new disease of almond in California found in the Sacramento and northern San Joaquin valleys
- A renamed section on fruit russeting, revised from the old powdery mildew section
- Significant revisions made to the management section of navel orangeworm, one of the major pests attacking California almonds
- Improvements on how to do dormant spur sampling section with easier-to-understand information on monitoring and thresholds
Revisions in the Walnut Pest Management Guidelines include:
- Updated information on the association between walnut twig beetle and thousand cankers disease
- New sections for Botryosphaeria and Phomopsis cankers, branch wilt, and paradox canker
- Significant changes to the walnut husk fly management section
Both the almond and walnut revised Pest Management Guidelines also include updated information on fungicide efficacy, weed management, and vertebrate management.
Authored by University of California specialists and advisors, the Pest Management Guidelines are UC's official guidelines for monitoring and managing pests in California crops. For more information on pest management in these or other crops, visit the UC IPM website.
The numbers are beginning to trickle in confirming UC Cooperative Extension advisor Brent Holtz' hunch. Chipping and returning expired almond orchards into the soil where they grew is not only environmentally sound, it is economically smart.
(View a three-minute video of the machinery in action at the end of this post.)
After about 20 years, almond orchards' productivity and vigor begin to decline. Most farmers remove the old trees and plant younger, more vigorous replacements to keep up almond production.
In the past, old trees were easily and cheaply disposed of: they were pushed into a pile and set on fire. Air quality regulations have all but eliminated the practice.
At first, grinding the trees and sending the chips to a co-generation plant was a farmer's preferred option. The companies that used biomass for electricity generation paid an acceptable sum – about $600 per acre – for the wood chips, which helped offset the cost of chipping and hauling the trees off the property.
However today, electrical utilities are looking for clean, renewable energy sources like wind and solar.
“Cogeneration plants burn wood biomass, which still releases carbon dioxide and methane into the atmosphere,” Holtz said. “Many are losing contracts and shutting down.”
Holtz sought another cost-effective alternative, and believes incorporating the wood into the orchard floor may be the answer. Although initially expensive, adding $400 per acre to the $600-per-acre cost of chipping the old trees, the organic matter and nutrients released by the woodchips over time appear to boost yield to a level that covers a chunk of the cost.
In preliminary research, Holtz found that almond orchards where old wood was incorporated into the soil were averaging about 1,800 pounds of meat nuts per acre, while the orchard where old trees had been burned averaged 1,600 meat nuts per acre.
“Almonds sell for about $2 to $3 per pound. To have a 200-pound average yield increase per acre, you've made up the cost of incorporating the wood in just one year,” Holtz said. “It would be even more affordable if farmers can sell carbon credits for the biomass that they sequester in the ground.”
Holtz recently demonstrated two approaches for incorporating almond trees into the soil. The first, which was also used in the study eight years ago at the UC Kearney Agricultural Research and Extension Center in Parlier, is a 50-ton rock crusher called the Iron Wolf. It lumbers down the tree row, grinding up whole trees in place, then reverses over the mangled wood to incorporate it into the ground.
“We thought this one-machine process was the answer,” Holtz said.
G & F Ag Services in Ripon, which has made a business of chipping and hauling almond wood to a co-generation plant, conceived another plan. It modified a manure spreader to spray ground-up wood chips across the orchard floor. Holtz worked with Manteca farmer Louie Tallerico to give the new process a spin.
“This required five different machines working together compared to one Iron Wolf. In this process, the trees have to be excavated by an excavator, then hauled to the wood chipper with a front-end loader. The trees have to be fed into the wood chipper, then the wood chips have to be spread on the orchard floor,” Holtz said. “Another machine, a disk or roto tiller, incorporates the chips into the soil.
The five machines combined are a tremendous time saver.
“The Iron Wolf could do about two acres per day,” Holtz said. “This process can do 15 or 20 acres per day.”
Tallerico opened his farm for a field day in October to demonstrate parts of the process to other farmers and industry representatives. Participants stood on layer of fresh-cut wood chip mulch where a full-grown almond orchard stood just weeks before. The spreader demonstrated the ease with which the wood chips are dispersed evenly across the orchard floor, and a tiller mixed the wood chips into the soil.
The Tellarico orchard will now be the site of research – funded by the California Almond Board – to be conducted by Holtz and a team of scientists interested in documenting the growth and development of the new almond orchard among the remnants of its predecessor.
“In the previous study, three years after incorporating the old trees into the soil we started to see the nutrient benefit,” Holtz said. “This was done at Kearney, where we incorporated a peach orchard that had about 30 tons of organic matter per acre. Almond trees are larger, so here we have 86 tons of organic matter being returned to the soil.”
In the new study, the scientists will determine whether the nutrient benefits found in early research still hold true, whether the wood chips in the soil stunt the new orchard or boost its growth, whether the new orchard suffers from replant disease, and the fate of good and bad nematodes (tiny soil-borne worms) in the new orchard.
“We will also study the carbon budget and continue the life cycle assessment of almond with this practice, to better understand the benefit of these processes,” Holtz said.
Research by UC Davis and UC Agriculture and Natural Resources scientists found that almonds have a relatively small carbon footprint, which could be further reduced with advanced management practices.
Two related articles published in the current issue of Journal of Industrial Ecology examine the environmental impact of this agricultural industry. Co-author Alissa Kendall, an associate professor in the UC Davis Department of Civil and Environmental Engineering, and her colleagues noted that certain practices substantially reduce greenhouse gas emissions and energy use, including the strategic use of co-products, and the choice of water source and irrigation technology.
"Our research shows that 1 kilogram of California almonds typically produces less than 1 kilogram of CO2-equivalent emissions, which is a lower carbon footprint than many other nutrient- and energy-dense foods," said Kendall.
“These results include the use of almond co-products — orchard biomass, hulls and shells — for renewable power generation and dairy feed,” said Kendall. “Under ideal circumstances, which are feasible but not in place today, California almonds could become carbon-neutral or even carbon-negative, largely through the improved utilization of orchard biomass."
David Doll, UC ANR Cooperative Extension advisor in Merced County, agrees.
“As California farmers improve their nitrogen and water use efficiencies, they will reduce the carbon footprint,” Doll said. “This will happen as we continue to transition into a nitrogen budgeting system, which will reduce over-applications of nitrogen. Furthermore, on the other end, research conducted by Cooperative Extension has shown that the entire biomass of an orchard can be incorporated back into the soil, which increases the amount of total carbon sequestered.”
“Only a full life cycle-based model like the one we developed for this research will allow us to accurately assess whether incorporating the biomass into the soil or using it for power generation instead results in a lower net carbon footprint,” said Sonja Brodt, academic coordinator in the UC ANR Sustainable Agriculture Research and Education Program, noting that there will be some trade-off.
The first article, "Life Cycle-based Assessment of Energy Use and Greenhouse Gas Emissions in Almond Production, Part I: Analytical Framework and Baseline Results," is authored by Kendall, Elias Marvinney, a graduate student in the UC Davis Department of Plant Sciences; Brodt and Weiyuan Zhu, a UC Davis graduate student in horticulture and agronomy.
Marvinney is lead author of the second article, "Life Cycle-based Assessment of Energy Use and Greenhouse Gas Emissions in Almond Production, Part II: Uncertainty Analysis through Sensitivity Analysis and Scenario Testing," in collaboration with Kendall and Brodt.
This research was supported by grants from the Almond Board of California and the CDFA Specialty Crop Block Grant Program.
Brodt and Marvinney will host a webinar to discuss their life cycle assessment analyzing the environmental impacts associated with walnuts, prunes, peaches, almonds and pistachios. The researchers are quantifying energy use and greenhouse gas emissions in orchard crop production both within and beyond the farm. To join the webinar, visit https://uc-d.adobeconnect.com/orchard-lca at noon on Wednesday, July 29.
The University of California Global Food Initiative aims to put the world on a path to sustainably and nutritiously feed itself. By building on existing efforts and creating new collaborations among UC's 10 campuses, affiliated national laboratories and the Division of Agriculture and Natural Resources, the initiative will develop and export solutions for food security, health and sustainability throughout California, the United States and the world.
Holtz has been pioneer in ag burn alternatives throughout his 26-year-career with UCCE, and going back still further on his family almond farm near Modesto. Beginning in the early 1990s, Holtz and his father experimented with chipping almond prunings instead of burning them, long before air quality regulations required wide implementation of the practice.
When Holtz heard a four-acre stone fruit orchard was slated for removal at the UC Kearney Agricultural Research and Extension Center in Parlier seven years ago, he took the opportunity to study the impact of grinding up and incorporating the whole trees before planting a new orchard.
“When an orchard is pushed out, there is about 100 tons per acre of organic matter that is taken out of the system,” Holtz said. “My previous research showed positive results from organic matter. Our San Joaquin Valley soils are typically critically low in organic matter. Why remove it if it is good for the soil?”
A local company was contracted to grind up and incorporate the trees using an Iron Wolf, essentially a 50-ton rototiller, in selected research plots. (See video below.) At first, Holtz was concerned that the Iron Wolf left “firewood-sized” chucks of wood in the plots, pieces much larger than he had studied before in his wood chipping research. But the worry turned out to be unfounded.
In comparison plots, trees were pushed together and burned. The ashes later were spread out on the soil. All the plots were fertilized at the normal rate.
Over the years, Holtz has compared laboratory analyses of the nutrients available to the trees in the soil and nutrients in the leaves. Initially, the burn treatments had more nutrients available. The second year, nutrient availability was about equal. Leaf analyses in the third year began to show a higher level of nutrients in the leaves of trees growing in the area where old trees had been ground up and incorporated. In the fifth and sixth years, Holtz didn't see any differences in growth, but data suggests slightly higher yields where the trees were ground up.
“A lot of growers feared if we added that much carbon to the soil, the microbes breaking down the organic matter would tie up nitrogen and the trees would be stunted,” Holtz said. “But the research results suggest that the trees will do just as well or better in the presence of the additional organic matter.”
One potential barrier to grinding up old trees is the cost. Holtz said the Iron Wolf treatment cost $800 per acre and it is not readily available in the San Joaquin Valley. Burning is nearly cost-free for the farmer, but contributes to air pollution and is highly regulated.
Another option for almond farmers preparing to remove an orchard and replant is employing a large tub grinder, which leaves much finer particles of wood than the Iron Wolf, is more readily available but more expensive. Holtz said he hopes that growers in the future will receive incentives to grind up their orchards and incorporate the wood chips into their soils before they plant a second- or third-generation orchard.
“I'm trying to find growers who would be interested in trying this approach to conduct on-farm research,” Holtz said.
In the video below, the Iron Wolf grinds up whole trees and incorporates the organic matter into the soil:
An initiative to enhance competitive and sustainable food systems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.
David Doll. “You don't notice it until it's too late, and that's when we have a problem,” he said.
Saline accumulation in the orchard soil profile is a recurring headache. But it becomes more acute during droughts, when farmers use more groundwater – which is generally more saline than surface water – or their surface water supply is more saline than normal.
Salinity accumulates in the soil when the tree is growing quickly and almonds are developing throughout spring and summer. When water with dissolved salts is applied, the roots of the tree will exclude the salt, sucking up only water. As salt accumulates from successive irrigations, the tree must work harder to pull up water. The extra stress slows growth and yields drop.
“At this stage, the trees look healthy, but they're not reaching their full potential,” Doll said.
In time, however, salt can accumulate to toxic levels and the tree will no longer exclude the salt.
“The salt toxicity becomes apparent in older leaves, which turn brown along the margins, and eventually fall off the tree,” Doll said. “We saw quite a bit of this in Merced County this year, especially on sandier soils.”
The cure? More water. Winter rain can help leach salt out of the root zone. If California experiences another dry winter, farmers will have to apply groundwater to flush salt away from almond tree roots.
“Seventy-five percent of our almond orchards are OK when there is enough rain,” Doll said, “but some farmers must apply water in the winter even in normal years.”
Doll recommends farmers sample their soils in the fall at various depths to assess salinity in the root zone.
To wash out accumulated salts, enough water must be applied to fill the soil profile, he said. Once the profile is full, smaller quantities of water applied either through rain or irrigation will move salts below the root zone.
An initiative to improve California water quality, quantity and security is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.