April 20, 2016
The Iron Wolf is a monster rototiller that chews up whole almond trees much as a person devours a single nut, crunches rocks along the way, and in a single pass through an orchard leaves behind material that has significant benefits for the next orchard planted there.
A demonstration of the 50-ton machine at work in a Chowchilla, Calif. orchard left almond growers in awe, said Brent Holtz, director of the University of California Cooperative Extension and farm advisor in San Joaquin County.
Holtz has been looking at the challenge of re-incorporating material from orchards as they are removed, and has found significant benefits that run counter to initial concerns that wood chips or grinding would stunt tree growth.
He said the machine, sold by Iron Wolf Manufacturing of Oklahoma for $1.3 million, moves slowly through the orchard. To be economically viable, it would work best if it were purchased and depreciated over time.
Holtz estimated the cost of removal and re-incorporation with the machine at about $1,600 an acre, compared with the means commonly used to remove and dispose of trees in an orchard, the use of a tub grinder, and other steps to incorporate chips into the soil - a total of $1,000 to $1,200 an acre.
He said that nearly a million acres of almonds are being grown in California, and 50,000-60,000 acre are pushed out each year due to tree age and lost productivity.
Challenges have emerged with the closure of biomass power plants, which formerly paid growers $40 per ton for chips.
Around the state, Holtz said, tub grinders are already in place. And they produce chips that are smaller than those produced by the Iron Wolf. But it’s a five-step process to incorporate those chips into the soil.
There’s an excavator that takes out the trees and a loader that takes trees to a tub grinder. They must then be ground, and the chips are then spread on the orchard floor.
Holtz said that process spreads the chips more evenly than the Iron Wolf approach does. He said some varieties – including the Carmel – are ground up more quickly by the Iron Wolf than others.
Holtz, along with David Doll, a UC farm advisor in Merced County, and Greg Browne, a U.S. Department of Agriculture plant pathologist, have researched the incorporation of orchard material into the soil and found it adds valuable organic matter and has other benefits.
In 2008 research conducted at the UC Kearney Research and Extension Center, 22 rows of fruit trees were ground and incorporated into the soil with an earlier version of the Iron Wolf. Benefits they found from the study include:
The incorporation of chips is an alternative to burning, something that is important given air quality concerns in the central San Joaquin Valley. The study compared grinding whole trees with burning as a means of orchard removal.
Soils with wood debris sequestered carbon at a higher rate.
Such soils have higher levels of organic matter, increased fertility, and increased water retention.
The whole tree grinding did not stunt the growth of Nonpareil, Carmel, and Butte trees that were planted.
Greater yields were ultimately observed in the grind treatment, compared to yield after burning.
From 2013-2015, soil analyses revealed significantly more calcium, manganese, iron, magnesium, boron, nitrate copper, electrical conductivity, organic matter, total carbon, and organic carbon.
Soil pH was significantly reduced in tree grind treatment plots.
Annual leaf petiole analysis showed significantly greater levels of nitrogen, potassium, phosphorous, manganese, and iron from trees growing in the grind treatment, while magnesium and sodium levels were significantly less.
Field observations found less salt burn in ground plots and less wilting when water was cut off for harvest, suggesting an increase in cation exchange and water holding capacity.
Populations of fungal and bacterial feeding nematodes were higher in the ground plot. “They feed on bacteria, algae, and fungi, not the tree’s roots,” Holtz said.
Growers over time could be compensated for adding carbon to the soil, he said, something that is being discussed during international conferences on climate change.
The Iron Wolf can take out 3-4 acres of trees in an eight hour day. Iron Wolf Construction president Todd Howe said the Iron Wolf Slasher 700B is self-contained. The company also makes a machine that can be mounted on a dozer.
The company does site development and excavation for construction sites and oil fields, plus renting machines. Its machines have been used across the U.S. and as far away as Siberia.
The Iron Wolf rents for $52,000 per month. It uses 22-25 gallons of diesel per hour and travels at a top speed of 2.8 miles per hour. It has a 700 horsepower engine. The head alone, which masticates trees, weighs 30,000 pounds.
“It takes three minutes to devour a large almond tree,” Howe said. “Our biggest trees are 30 years old and are 27 inches in diameter. The bigger the trees then the more expensive it is to remove them.”
He said that factor – tree size – could prompt growers to remove trees earlier, as their productive days wane. But Holtz said newer orchards have higher density, meaning trees are not as likely to reach the size they were in past years.
Commenting on the prospect of orchard removal in California, Howe said, “We’re very excited, and will work to get the cost down per acre. We’re committed to working with the industry and finding the perfect machine to make that happen.”
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