These questions are based on surveys of 192 almond professionals who attended one of two UC ANR field days in 10/2018, attended the Almond Conference in 12/2018, or responded to an email from West Coast Nut Magazine in 12/2018. Similar questions have been aggregated, with the most common questions at the top.
FAQs about whole orchard recycling
- Q: Will whole-orchard recycling perpetuate diseases in the orchard? Should I still recycle my orchard if I have disease problems?
- A: Research on this topic is in its infancy, so very little data is available yet. However, there is good reason to believe that most almond diseases will not be transmitted by recycled wood. Most diseases (whether the pathogens are fungi, bacteria, viruses, or oomycetes) can only survive in living tissue, and only above-ground. There are several important exceptions: Armillaria root rot (also called oak root fungus) and Ganoderma butt rott can thrive in dead wood as well as invading living wood. Crown gall (Agrobacterium tumifasciens) can survive in soil. Therefore, we do not currently recommend recycling orchards that are infested with Armillaria, Ganoderma, or crown gall. See our Tree Health page for more information.
- Q: Do I need to apply extra nitrogen in the first year after replanting? If so, how much and for how long?
- A: Yes, extra nitrogen is essential to avoid stunting of the replant orchard. Based on our field trials so far, we recommend doubling N applications in the first year after replanting, from 3-4 ounces of N per tree (50-70 lbs N per acre) to 6-8 ounces of N per tree (100-140 lbs N per acre). This extra N should be started early and applied gradually. Our data so far suggests that extra N application in the second year is generally not necessary unless problems arise.
- Q: How quickly do the chips break down? Will they still be there at the first harvest, and if so, will they cause any problems?
- A: The longevity of wood chips in the orchard depends on the chip size, the total amount of chips, whether they were pre-treated to speed decomposition, and the depth to which they were incorporated. Some recycled orchards have almost no chips visible at planting time a few months later, while others still have visible chips on the soil surface several years later. Fortunately, very few growers and hullers/shellers have reported problems with wood chips contaminating the nuts in the first few harvests. Wood chips are much less apparent after three years, especially if tillage, irrigation, and/or vegetative cover are used in row middles. Those remaining chips that do get swept up with the nuts are usually easily removed with the rest of the orchard trash by standard hulling / shelling equipment.
- Q: What are the long-term benefits of whole-orchard recycling? Will it improve yields in the long run?
- A: Based on the Kearney trial, started in 2008, we are optimistic that WOR will confer long-term improvements in kernel pounds per acre and water use efficiency. (You can read more on the Orchard Productivity page.) However, we note that these data are from only one trial at one location that was performed under significantly different conditions than what most growers are using now. We hope to collect long-term yield data from several additional field sites to help put firmer numbers on these potentially substantial benefits.
- Q: How much extra does it cost?
- A: Whole-orchard recycling has a higher upfront cost than the alternatives. The cost difference depends on what alternative it is being compared to. Because wood chips are now in higher supply, and there is lower demand due to biomass power plant closures, the low value of the chips no longer covers the cost of orchard removal. The most common option for getting rid of the trees (not including the subsequent costs of land preparation) is to push and burn the whole trees (generally around $600-$800 per acre, including cost of fees or permits). Also common is to grind the orchard and having the chips removed for a fee (generally a total of around $700-$1000 per acre). Spreading the chips instead of removing them adds about $150-$300 per acre, sometimes more, depending on the volume of chips. Additional short-term costs may accrue from incorporating the chips and applying extra N fertilizer. However, research to date suggests that WOR will have long-term payoffs in terms of water savings and higher yields. See the Grower’s Guide and Cost Guide for more detailed cost information.
- Q: Are there any incentives (such as carbon credits) to help offset the cost?
- A: Statewide carbon credits for orchard recycling are not yet available, though they may become so in the future. In the meantime, the San Joaquin Valley Air Pollution Control District offers an incentive of $600 per acre for biomass chipping with soil incorporation (up to 100 acres per applicant per year).
- Q: Does this work in all soil types? How might the process and the benefits be different for my particular soil type?
- A: Most experience with whole-orchard recycling comes from the northern to central San Joaquin Valley in sandy loam soils. Less information is available on how well the practice works in the Sacramento Valley and in the southern San Joaquin Valley. None of the current WOR research sites have heavy clay soils; it is likely that heavier soils would experience greater difficulty with wood chip incorporation and perhaps more modest benefits in terms of water-holding capacity. More work is needed on how WOR affects salinity, boron toxicity, and soils prone to waterlogging.
- Q: Do I need to add anything to the chips to help them break down faster?
- A: Some growers add extra fertilizer, manure, biological soil amendments, and/or irrigation water on top of the chips for several months before incorporation in late winter / early spring. However, others have had good results without any additives.
- Q: What is the optimal size of wood chips in a recycled orchard?
- A: Practices vary. Grinding smaller chips consumes more time and fuel, so there is a tradeoff between cost and chip size. A 2” screen produces fine chips that will break down more quickly, but it can make the grinding process take twice as long and cost almost twice as much as a 4” screen, which is what most growers use (results pictured here).
- Q: What is the optimal incorporation depth for wood chips?
- A: Optimum incorporation depth is generally “the deeper, the better” – deep chips are less likely to tie up nutrients needed by tree roots and are more likely to store carbon for a long time. But the achievable depth is limited by available equipment. In practice, most growers end up with >90% of the chips in the top 6” of soil and still have acceptable results. The importance of deep incorporation partly depends on the amount of wood chips: a 1” layer of chips can be well-dispersed in the top 6” of soil, whereas a 4” layer of chips cannot.
- Q: What special equipment is needed? Is it difficult to obtain? If I don’t already have the equipment, where can I find someone who can do this process for me?
- A: A spreader (usually a modified manure spreader) is the one piece of equipment needed in whole-orchard recycling that is not generally needed for other orchard preparation practices. It may also be necessary to use deeper ripping, larger discs, and/or plows to incorporate the chips sufficiently. Most orchard removal companies now also offer wood chip spreading, and many land preparation companies have equipment and techniques that are fine-tuned for wood chip incorporation. We list some of these companies on our Resources page.
- Q: Should I incorporate all the chips or only some of them? Can I still sell some of the wood or chips for other uses?
- A: Most growers incorporate all their chips and are happy to have done so. However, many growers choose to return only some of the chips to the orchard, and orchard removal companies can generally accommodate this. For example, Carl Kruppa sells his almond trunks for firewood (40% of the total biomass) and recycles the other 60%. Christine Gemperle tried spreading 20% of her wood chips on roads and parking lots. If the pulled trees are unusually large, it is possible to have too many chips – some growers have reported frustrating and unsatisfactory experiences when trying to incorporate more than 4” of chips.
- Q: Does the land need to be fallowed for a year or two after orchard recycling and before replanting?
A: Either fallowing or non-fallowing can be successful. Some growers cannot, or choose not to, bear the short-term costs of taking the land out of production. Same-year replanting can work well if all necessary contracts have been secured well in advance and if close scrutiny is given to tree N status during the first year. Those who have chosen to use fallows (including Norma Stretch and Steve Thorley) have generally been happy they did so. It takes time pressure away from land preparation, reduces pest and disease pressure, makes fumigation less necessary, and helps the chips break down. A compromise is to do a six- to nine-month fallow followed by a fall planting with potted trees.
- Q: How do the costs and benefits of WOR compare to other organic matter amendments (e.g., compost addition; cover cropping)?
A: This is a good question, but no comparisons have been done yet. A comprehensive long-term cost-benefit analysis of WOR is not yet possible, because in all but one trial so far, the recycled orchard is not yet of bearing age. We are not claiming at this time that WOR is necessarily superior to all other organic matter additions to almond orchards, but we believe there is ample evidence of net benefits, especially when there are few other alternatives for wood chip disposal. The Research Findings and Impacts page has more details.
- Q: Can fumigation and land leveling still be done effectively after whole-orchard recycling?
A: Yes, both fumigation and land leveling can proceed as normal and should be fully effective. None of the growers in our sample who had done whole-orchard recycling reported any problems with either practice.
- Q: Does whole-orchard recycling affect populations of plant-parasitic nematodes?
A: This is unknown. None of the whole-orchard recycling research plots in the UC ANR field trials have experienced nematode problems, but none of these orchard blocks had high parasitic nematode populations to begin with. It is not clear how the nematode population in a heavily infested field might respond to WOR. At the moment, there is no evidence or theory to suggest that WOR would exacerbate nematode problems.
- Q: Where can I see whole-orchard recycling demonstrated in the field?
A: Please check our Outreach page for the latest information on whole-orchard recycling field days and other educational events.
- Q: What if I have more questions that weren’t answered here?
A: Please get in touch with us via the Contact Us page. Thank you for your interest!