Posts Tagged: Brent Holtz
Almond farmers will remember a UCCE demonstration last February when the 50,000-pound Iron Wolf rolled like a tank through an almond orchard in Chowchilla, ripping whole trees into shreds and incorporating the wood into the soil.
Researchers are now considering a less dramatic approach to removing an old orchard and incorporating the wood chips into the soil onsite. Combining a traditional horizontal chipper with a wood chip spreader modified for this purpose can be a viable alternative to the now-mostly banned burning of old orchards or transport of almond tree residue to co-generation facilities that convert biomass to energy.
“It's still cheaper for the farmer if he or she can sell the wood chips for co-generation,” said Brent Holtz, UC Cooperative Extension advisor in San Joaquin County and the research leader. “But co-generation plants are closing and our research is showing that incorporating the biomass into the soil has many benefits.”
When the wood breaks down, it returns nutrients to the soil. Organic matter increases, resulting in carbon sequestration, important for moderating the release of greenhouse gases into the atmosphere that may contribute to climate change.
The chipper and spreader combination pencils out at about $1,000 per acre, while the Iron Wolf costs about $1,500 per acre.
“The Iron Wolf turned out much more expensive and slower than we anticipated,” Holtz said. “It could only grind up and incorporate about two acres of trees per day, while the horizontal chipper can chip 15 acres per day. With the chipper and spreader combination, the chips do have to be disked in, which most growers can easily do.”
The whole orchard recycling project was funded by the Accelerated Innovation Management program of the Almond Board of California.
Whole Orchard Recycling Demonstration
11630 S. Airport Way (near Roth Road), Manteca, Calif.
Thursday, Oct. 13, 2016
Whole almond orchard recycling and the effect on second generation tree growth, organic matter and soil fertility presentation
Brent Holtz, Ph.D., UC Cooperative Extension advisor
Kuhn & Knight Wood Chip Spreading Demonstration
Randy Fondse, G & F Ag Services, Ripon, Calif.
Morbark Horizontal Chipper Demonstration
Randy Fondse, G & F Ag Services, Ripon, Calif.
When an orchard is removed for replanting, the trees are usually uprooted, chipped and hauled to a biomass plant. However, burning the wood in a cogeneration plant removes carbon from the orchard and biomass plants are becoming fewer and farther from farms.
One alternative is grinding up the trees and incorporating the wood into the soil in the orchard. UC Agriculture and Natural Resources (UC ANR) scientists have been studying the effects of incorporating the wood chips into the soil since 2008.
“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,” said Brent Holtz, UC ANR Cooperative Extension advisor. “But the research results suggest that the trees will do just as well or better in the presence of the additional organic matter.”
For the 2008 study, an IronWolf machine was used to grind up whole stone fruit trees and bury the organic matter in the soil in some plots. For comparison, the researchers burned trees and spread the ashes in the soil of other plots. Holtz compared the nutrient availability in the soil and health of trees planted in the research plots.
In a new study, Holtz hopes to compare the effects of using the IronWolf to recycle an almond orchard to using a large tub grinder, which leaves much finer particles of wood.
Holtz invites growers and other interested people to watch the IronWolf 700B, a newer version of the machine used in 2008, grind up almond trees in Chowchilla on Feb. 16 at 10 a.m.
“There has been increased interest in the project because of the closure of many of the biomass plants statewide. They used to take the debris of removed orchards,” said Holtz. “The purpose of this demonstration is to see if this method of orchard removal will be competitive with the tub grinding process, and become an economically viable alternative that improves soil organic matter and fertility.”
WHO: UC ANR Cooperative Extension advisors, growers, IronWolf equipment representatives.
WHAT: Watch a 100,000-pound machine push, grind and incorporate whole almond trees into the soil.
WHEN: 10 a.m., Tuesday, Feb. 16, 2016
WHERE: AgriLand Farming, 20875 Avenue24, Chowchilla, CA 93610
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.
The newly named county director for San Joaquin County UC Cooperative Extension, Brent Holtz, was profiled in the Stockton Record today by the paper's longtime ag reporter, Reed Fujii. Holtz begins his new job Jan. 4, but was already able to share a goal.
"One of the crucial things I'm going to be working with is to try to get a Delta specialist position," Holtz was quoted in the story.
The Delta advisor would focus on issues concerning the unique soil and growing conditions of the inland estuary as well as the need to protect the quality of the Delta's waterways, the story said.
Fujii's article noted that Holtz earned his doctorate in plant pathology from UC Berkeley in 1993, and was a post-doc at the UC Kearney Research and Extension Center before beginning a 15-year stint as the plant pathology farm advisor in Madera County.
Ironically, the new job brings Holtz closer to home. He lives in Modesto with his wife and two sons, the story said.
"I'm actually going to be able to live in my house," Holtz told Fujii.
Holtz grew up in the San Joaquin County community of Escalon and his best friend's father, Robert J. Cabral, is the namesake of the new agricultural center where UC Cooperative Extension is housed.
Brent Holtz in the laboratory.