I went to a harvest festival a couple of weeks ago in the Cully neighborhood of NE Portland and it was really interesting. We made cider. I brought some apples for it. I think they were inspired by the Paul Gautschi film "Return to Eden"? with the deep mulching that he used. It was sponsored by a 7th Day Adventist Church and a sustainability organization. As such, it was an interesting mix of groovy environmentalists and mostly Black Evangelicals. Since it is a 7th Day Adventist church, they encourage vegetarianism, and they offered vegetarian foods. It was a really interesting cultural mix. They really have been using the deep mulching for years. The most amazing thing about it was that with their deep mulching, they did not water the garden at all for the whole year. Even with our multi 100 F days and more than a month of no rain. The plants looked very healthy. Also it wasn't really an orchard. It was mostly small garden vegetables, like peas, cabbage, green beans, leafy veg with some tomato plants. Which is even more impressive to me.
I have been bringing in wood chips for years, but I don't leave it a foot or more deep. I just spread it around an inch or so deep. It really got me thinking about bringing in more wood chips. I'm pretty old and I threw out my back last year for a few weeks, trying to hurry up and distribute all of the wood chips quickly. This year, I'm taking my time and just bringing in a few wheelbarrows of chips each day to not throw out my back again. Their garden was very impressive. I'm going to try to go in that direction this year.
In my rural space where I spend alot of time and this past summer I ended up with wild raspberry producing much more than the usual. Like what you witnessed of no need for summer watering this raspberry stand wasn't watered either although it is sprinkled with rain in this location. The big changes to date should be attributed to years of what was a septic leach area that dispersed human effluent for a few years and 10 years ago that were close to the formerly sparsley productive raspberry. The install was my own of long running domes that create a long air chamber 2 feet below the surface. Sometimes by sccident you run into these things and now I'm on track of increasing this method towards other things.
Along another side of the place where I would bring in loads of horse waste and tilled that down also yeilds well to those that rent my garden. I provide river water in a resevoir for them so they water by hand there. I was impressed by a 20 pound cabbage that came out of there by a first time gardener. Not bad for so short of a season for interior Alaska.
The list of those that I personally know who uses wood for an orchard has grown to two people. Your the second one trying this shallow mulch system but I suspect for you the results are kind of trickier to see what has the greatest vantage over the others you use such as the biochar you use. I have used neither yet. The first person I found in this was in Alberta at a newly established upick cherry farm where the orchard had all 5 of the 'romance series' of cherry as they were first selected and released from Saskatchwen. They had been open for picking for at least 2-4 years as I remember and all bushes looked fine but they never recorded any decent crops. Wood chips were brought in and mulched a few inches thick similar to what I found at Paul's web site that I looked at and the way you kind of described it.
There was one individual cherry which produced much more of all the hundreds and to this day it still may not be known why one was.
On the riverfront that belongs to the gardenspace I rent is another cold and challenging land that I would like to compare to the Pete upick operation near Innisfail AB which before it was mine got flooded with trees in the great flood of 1967. About 10 foot of shore was lost that year and at 15 myself my brother and I witnessed this drstruction of trees while our father rented part of the place for beekeeping before he bought it.
...fast forwards ...the trees that were drifted so thickly are now decomposed and encompassed into layers that range 2 feet deep. I found this out through excavations for a septic leach areas. This bend of the river may have the most important trees that will be found in interior Alaska because of the rare alder population on the shore. They are there for two reasons. They are toxic to beaver and secondly (what I am learning recently) they would be what was important for regaining fertility back.
I am now for the first time inspired to collect the seed of alder as it's being shed. All year old saplings of alder have these root nodules that according to at least this one borrowed wordpress article are important agents affixed to roots to restore any kind of previously damaged situations (eg. previous floods).
The upick cherry operation if it has not picked up in production by now (ie. this 10 years since not seeing) should be interested in this as well as the saints you visited recently if too much nitrogen robbing rots are presently decomposing that much mulch. It only takes a year after alder germination to see these big nodules.
Over ten years ago there were farmers in Eugene, Oregon, who told me that they grew tomatoes and other vegetables using this method. They swore that they used no supplemental water, and Eugene tends to be warmer and possibly drier than the Portland area.
I've not been using wood chips around my orchard trees because of voles, since the chips give them protection. However I've never been comfortable with that decision. It seems that the compromise may be to keep the wood chips about a foot from the trunk.
Yes, keeping them away from the trunk is what I've always done, and I've never had a problem with voles. We always told people about that when we were teaching the classes for HOS.
Huh. Interesting. I've also shallow mulched here. We always have the tree trimmers for the electric company empty their truck here if they are around. Maybe I should ok another truck load or two.
Its off topic but deep mulch also works very well for chickens.
This is a little off-topic also, but dry farming most likely applies many of the same principles. This article from the "Columbian", Clark County, Washington's newspaper, is about dry farming apples and other produce in California.
The irony of reading this during a flood watch is not lost on me!
There is both a dry farming institute here in Oregon
And also OSU as part of the small farms program.
We bought some dry farmed vegetables from them and they were super flavorful.
OSU has done research on fruit, but not trees that I am aware. Sunbow produce, here in Philomath , grows everything include fruit trees via dry farming. My wife and I have been to the farm several times, both farmers are great.
Chris in Philomath