Whole Orchard Soil Re-incorporation: an Alternative Orchard Removal Strategy
Written by Brent Holtz (UCCE San Joaquin) and David Doll (UCCE Merced) You may have heard the news—co-generation plants are limiting the amount of chipped biomass they are accepting. This is reducing the rate in which old orchards are removed, impacting the orchard redevelopment process. The soil incorporation of chipped or ground almond, peach, plum, or cherry trees during orchard removal could provide an alternative to co-generation plant or burning and could add valuable organic matter to our San Joaquin Valley soils. Traditionally, many growers feared that wood chips or grindings would stunt tree growth by either allelopathic compounds or reduced nitrogen availability due to the high carbon to nitrogen ratio. Interestingly enough, recent research has found this not to be true if the ground material is spread across and incorporated into the soil In 2008, University of California Farm Advisors and a USDA Plant Pathologist undertook a project at the UC Kearney Research and Extension center to compare the grinding of whole trees with burning as a means of orchard removal. Twenty-two rows of an experimental orchard on nemaguard rootstock were used in a randomized blocked experiment with two main treatments, whole tree grinding and incorporation into the soil with ‘The Iron Wolf,’ a 50-ton rototiller, versus tree pushing and burning. We examined second-generation orchard growth and hypothesized that soils amended with woody debris will sequester carbon at a higher rate, have higher levels of soil organic matter, increased soil fertility, and increased water retention. Second generation almond trees (Nonpareil, Carmel, Butte) were planted in January/February 2009. The whole tree grinding did not stunt replanted tree growth. In 2015, Greater yields were ultimately observed in the grind treatment, when compared to the burn (previous year’s yields were similar). In 2013, 2014, and 2015, soil analysis revealed significantly more calcium,
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