Articles
Whole almond orchard recycling and the effect on second generation tree growth, yield, and soil fertility
Article number
1406_33
Pages
217 – 224
Language
English
Abstract
The grinding and incorporating into soil of almond trees during orchard removal has become a sustainable practice that enhances both air and soil quality in California.
The objective of this study was to compare the effect of whole orchard recycling (WOR), on-site tree burning and ash incorporation, and a control of tree removal to a co-generation facility, based on their impact on soil carbon, fertility, tree growth, and yield.
In our 2008 trial an Iron Wolf rock-crusher was used to grind up and incorporate standing trees to a soil depth of 30 cm.
The WOR grinding incorporated an estimated 67,000 kg of woody biomass per hectare (30 t acre-1). For the burn treatment, trees were pushed into a pile, burned, and the ash was spread evenly throughout the plots.
All seven replicate plots were re-planted with bare-root almond trees in 2009. All trees were irrigated and fertilized equally throughout the trial.
Significant increases in tree circumference were observed from trees growing in the WOR treatment when compared to the burn treatement.
Yields were determined from 2011-2022 in the ‘Butte’ cultivar, and the WOR treatment cumulative yield was 2,804 kg ha-1 (2,502 lbs ac-1) greater than the control.
Yields were also determined in the ‘Nonpareil’ cultivar from 2014 to 2022, and the grind treatment cumulative yield was 2,628 kg ha-1 (2,341 lbs ac-1) greater than the burn treatment.
Significantly more total carbon, soil organic matter, nitrate, iron, and magnesium were measured in the soils of the plots receiving the grind treatment.
Soil pH was significantly lower in the grind treatment plots.
In our 2019 trial, a Peterson horizontal grinder was used to grind up old trees, a manure spreader was used to distribute the wood chips, and a Northwest Tiller was used to incorporate the wood chips to a depth of 30 cm.
The tilling incorporated 136,972 kg (61 tons ac-1) of woody biomass per hectare.
Wood chips were not spread in the control plots.
All five replicate plots were re-planted with bare-root almond trees in 2019 and irrigated and fertilized equally.
We fertilized all the trees equally and a total of 142 g N per tree (5.0 oz tree-1) or 52 kg ha-1 (46.6 lbs ac-1) was applied in 2019. In early 2020, the trees growing in the WOR treatment had significantly greater tree circumference when compared to the control trees, even though they received the same amount of fertilizer and water.
WOR has increased carbon sequestration, soil organic matter, improved soil quality, and increased tree growth and yield.
This project demonstrated that whole orchard recycling is a sustainable alternative to burning in the field or in a co-generation facility.
We estimate that over 86,000 ha (214,000 acres) of trees have been recycled in California since 2015.
The objective of this study was to compare the effect of whole orchard recycling (WOR), on-site tree burning and ash incorporation, and a control of tree removal to a co-generation facility, based on their impact on soil carbon, fertility, tree growth, and yield.
In our 2008 trial an Iron Wolf rock-crusher was used to grind up and incorporate standing trees to a soil depth of 30 cm.
The WOR grinding incorporated an estimated 67,000 kg of woody biomass per hectare (30 t acre-1). For the burn treatment, trees were pushed into a pile, burned, and the ash was spread evenly throughout the plots.
All seven replicate plots were re-planted with bare-root almond trees in 2009. All trees were irrigated and fertilized equally throughout the trial.
Significant increases in tree circumference were observed from trees growing in the WOR treatment when compared to the burn treatement.
Yields were determined from 2011-2022 in the ‘Butte’ cultivar, and the WOR treatment cumulative yield was 2,804 kg ha-1 (2,502 lbs ac-1) greater than the control.
Yields were also determined in the ‘Nonpareil’ cultivar from 2014 to 2022, and the grind treatment cumulative yield was 2,628 kg ha-1 (2,341 lbs ac-1) greater than the burn treatment.
Significantly more total carbon, soil organic matter, nitrate, iron, and magnesium were measured in the soils of the plots receiving the grind treatment.
Soil pH was significantly lower in the grind treatment plots.
In our 2019 trial, a Peterson horizontal grinder was used to grind up old trees, a manure spreader was used to distribute the wood chips, and a Northwest Tiller was used to incorporate the wood chips to a depth of 30 cm.
The tilling incorporated 136,972 kg (61 tons ac-1) of woody biomass per hectare.
Wood chips were not spread in the control plots.
All five replicate plots were re-planted with bare-root almond trees in 2019 and irrigated and fertilized equally.
We fertilized all the trees equally and a total of 142 g N per tree (5.0 oz tree-1) or 52 kg ha-1 (46.6 lbs ac-1) was applied in 2019. In early 2020, the trees growing in the WOR treatment had significantly greater tree circumference when compared to the control trees, even though they received the same amount of fertilizer and water.
WOR has increased carbon sequestration, soil organic matter, improved soil quality, and increased tree growth and yield.
This project demonstrated that whole orchard recycling is a sustainable alternative to burning in the field or in a co-generation facility.
We estimate that over 86,000 ha (214,000 acres) of trees have been recycled in California since 2015.
Authors
B. Holtz, M. Culumber, C. Zuber, G.T. Browne, D.A. Doll, E. Jahanzad, M.A. Yaghmour, F. Niederholzer, P. Gordon, A. Poret-Peterson, S. Gao, A. Gaudin
Keywords
carbon sequestration, carbon recycling, soil organic matter
Groups involved
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