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clay orchard

Posted by Laura Sieger 
clay orchard
May 31, 2022 06:35PM
Hi all,

We're working on improving the heavy clay soil that is part of the Maine Heritage Orchard, which we have already planted trees into. Looking for some advise and to hear about anyones experience working in clay soils in regards to cover cropping, cultivation and intercropping. Our two year plan is for subterranean disturbance/ intensive intervention, with a long term goal for an orchard understory of native plants.

Our soil tests revealed that we have a pH of 5.6, low levels of boron, zinc, copper and organic matter (1.3%); medium levels of phosphorus, calcium, sulphur, iron & manganese; optimum levels of potassium and magnesium. Because of the low fertility, we will add more compost or manure and calcitic lime to the site, and amend around the trees with boron, feather meal, blood meal and azomite.

Wondering if anyone here has experience working with dense clay soils. Could you provide insight on the following:
1. success/ failure with certain cover crops
2. cultivation implements (specifically a seedbed cultivator)

Laura & crew

Maine Heritage Orchard
Unity, ME zone 5a
Re: clay orchard
June 01, 2022 03:16PM
Get ready to work! I began a similar process of improving my heavy clay soil about 5 years ago, and while the apple tree "beds" have improved, it's been an arduous process.

My first effort was to double dig (by hand) a row for future tree planting and amending with compost as I went. After a day of back-breaking work I finished an area 6' wide by 72' long. So I rented an excavator for the next bed, which in addition to heavy clay had a layer of shale about a foot down. This was definitely easier, but still plenty of exercise as I jumped in and out of the cab. Two people working together would go much quicker, but mine is a one person operation. Anyway, my point is it takes a lot of effort to prepare beds for trees, but now that it's done, I think it was worth it. Dig down at least 2'. Even deeper if you can. Amend with compost and the inputs your soil test indicated, then "raise" the beds by edging and piling the soil in the center.

Once I had beds constructed, I began sowing covers. But since I was eager to get the tree growing process started, I've had to manage doing so around stems in the ground. This too has presented ample opportunity to sweat! Since I'm unable to maneuver my tractor with cultivator attachment around the trees, I tried a small battery-powered garden cultivator to prepare a seed bed and beat down the jungle of weeds that grew seemingly overnight after the excavation work. It worked okay, but while waiting for the battery to recharge I switched to a 7" stirrup hoe and that went about as well. Both afforded me hours of time to ponder the long history of humanity's battle with plants trying to grow in places they are unwanted.

That first year was tough because I tried to establish a stand of bell beans which I'd read do wonders for fruit trees. But of course, they're a pain to plant and they don't crowd out weed competition! So the next year I switched to buckwheat. I can get in 2 plantings a season. The things I love about it are how easy it is to sow. Just scatter the seeds before yanking out handfuls of the previous stand and you've both planted and harvested with one action. And how well it out-competes weeds. It's still tough prepping the seed bed for the first planting in spring, but I'm confident the soil will loosen over time.

For winter covers, I'm rotating rye, oilseed radish, and oats. I plan to do this for at least the first five years after each bed's construction, and longer if the soil remains heavily bound in clumps. Still a few years away before I'll know how well my cover rotation worked. But eventually, my plan is to let the rows naturalize and establish a bio-diverse microhabitat under the shade of the trees above, as Michael suggested in his books on orcharding.

In the next field I'm developing for orchard space, I plan to give myself a couple years of soil building time before putting trees in the ground. I'll excavate/double-dig as before, then use my tractor with cultivator attachment to more easily sow a series of covers over two seasons. This way, I can even mix in some clover and vetch without having to worry about fighting it by hand to sow something else.

So this has been my experience with previously untouched clay. Hope it helps spark some ideas for your own situation!

Craig Bickle
Hap Woods
Zone 6a
East-Central Ohio

Edited 1 time(s). Last edit at 06/22/2022 01:39PM by Craig Bickle.
Re: clay orchard
June 01, 2022 03:22PM
Laura, I just re-read your post and noticed you mentioned you're improving beds you already have trees in. I think much of my previous post is still relevant, but obviously you're past the point of constructing new beds using deep excavation.

Still, hope my cover crop rotation notes are useful. And if you come up with a better way of cultivating around trees for seed bed prep, by all means, let me know! smiling smiley
Re: clay orchard
June 01, 2022 06:55PM
Hey Laura,

I've had to do this in a mediterranean climate and note: this was the height of my permaculture bent and I was on a salary to do what every I felt like. I don't know the outcome because I wasn't there to see it, but "The Permaculture Orchard" went out there about 7 years later to do a workshop on this site and he said it looked great, lol. The basics is just get that clay exposed to air, water, and positively charged elements.

I did the following:
-Cut the grass VERY short so I could see the surface of the soil
-Aerated around and within each drip-line using broadfork tines (I didn't "broadfork" because that's far too much work...just stuck it in the ground and pulled it out )
-Created a liquid slurry of biochar, compost, some gypsum, and I don't remember what else and poured it over the holes I created. You could probably do this without making it into a liquid, but it was a drought out there and I wanted to try and adhere to the clay as much as possible.
-Seeded daikon radish and then covered with a light mulch consisting of fermented wood chips

One thing about the diakon: I wouldn't use them in heavy clay soils again. The problem is that they don't go down into the soil and instead they grew 3"+ into the air. This created a huge rodent problem for me and hurt a lot more than help. When I pulled them up, they were only maybe 1-2" inches into the soil. If I were to do this again, I'd try to find a chop-and-drop type crop that has some amazing vigor and more of a fine root system to just cut back a couple times a year until you want them gone.

Wish I had more to share!


Edited 1 time(s). Last edit at 06/01/2022 07:04PM by Eliza Greenman.
Re: clay orchard
June 02, 2022 02:49PM
Hi Laura,

We have both brown and blue clay on our orchard in Mid-Coast Maine. Some of our trees are poorly rooted, I'm not as strong as I look and I can shake a twelve-inch diameter tree back and forth. We're just getting started on improving the soil and starting with the youngest trees first. Cornell has a long time study on trees planted in urban settings where large trees are planted in small boxes, between roads and sidewalks or buildings or whatever. They found that adding soil to the gravel under the sidewalks allowed the roots to grow under the concrete. We're reverse-engineering that lesson and pick-axing baby trenches away from those tree rings and adding gravel as a way to encourage the roots to branch out a bit in the less dense gravel and build a stronger platform. Can't report yet on how well that's working because the cosmos decided that the tractor with the loader bucket should break right after the dump truck deposited the gravel. We use a cordless drill with a bulb planting bit attached and drill aeration holes inside the tree ring to allow moisture to drain into the clay. I did the trees that sat in standing water after small rainfalls first and we noticed an immediate positive change. Though tedious, the job isn't too bad if you take the drill on that first coffee cup walk in the morning and drill a few trees a day.

I wonder, Eliza, do you remember what time of year you planted the daikon radish? I have been told that it works quite well to taproot into clay soil but that you must wait until after summer has peaked (when the yellow rocket blooms per Michael Phillips) to plant it otherwise it will bolt instead of sending energy down into the ground.

Shane Patrick
Pleasant Pond Orchard
Richmond, ME 5b
Re: clay orchard
June 02, 2022 04:40PM
I've enjoyed reading everyone's responses and they echo a lot of my own thoughts. A few things to add (in some cases to reiterate), but first ...... my own orchard was planted into a site where the clay predominated (also it was part old vineyard and part scrubby pine forest) and I didn't have enough time to adequately prepare the soil before I planted the trees, so everything was ex post facto.

- First, all the scrub pine was removed.

- Then I subsoiled twice to 12" on a 48" grid to break up the hardpan (it was compacted).

- Then I laid out the rows and rototilled to level and break up the sod brought up by the subsoiler. Normally, I wouldn't do this since the bottom of the tines can create a shallow hardpan (just as moldboard plough can do).

- The intention was always to breakup the hardpan and create vertical channels in the soil. But first I needed to deflocculate the soil to make it easier to plant the trees.

- The trees were planted using an auger (I broke up the sides of a hole with a shovel so they didn't glaze over) and this also helped to open up and aerate the soil esp right around the trees.

- I subsoiled again on either side of the planted row and rototilled again before planting cover crop in the fall (rye/austrian pea/forage radish). While there were some radishes that def didn't go deep, the the preparation and the seasonal loosening/warming of the soil all season meant that most were able to go at least 9-12" deep into the soil.

- I also planted other desirable plants like comfrey, valerian, echinacea, etc.

- Amendment-wise I have added lime, gypsum, compost, wood chips, some nitrogen, and few other things. The biggest nutritional issue was low pH and that has been largely corrected now. The lime and gypsum help to lift and loosen the soil naturally as well as all the other work.

- In retrospect, I would have liked at least one year prior to planting to work the soil. It has taken a few years to "fix" things but feel we're on good footing now. The work is ongoing, but by limiting the equipment traffic, increasing deep-rooted plant diversity, monitoring and "fixing" fertility, subsoiling every year or so.

- I'd like to use a Yeoman's plough eventually and broadfork more regularly as well as add Gypsum/lime regularly, as well as compost, biochar, microbes, rock dust, and wood chips esp in the tree row. But realizing that the tree's roots grow out into the row middle, we can't forget that part of the orchard as well.

- Lastly, testing is important, esp soil food web testing. This gives us insights into the soil biological status of the soil and what we need to do improve the soil biology. Fundamentally, the health of the soil food web will create lasting resiliency (and changes) in the soils themselves.

Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: clay orchard
June 03, 2022 10:14AM
I haven’t tried to do this under existing trees, but in establishing our orchard, which has heavy clay UNDER a loam top soil of varying depth I can offer the following.

“Tillage” radish seemed to work better for us in our second plantings than in our first, (both on bare ground,) though I can’t explain why. It has reseeded itself and I still see quite a few radishes coming up now in its second year, I would definitely do it again.

Prairie Moon nursery has a guide on over seeding prairie plants that might be helpful depending on the native species you are hoping to establish, and your understory management plan. I am a believer in those deep rooted natives as an aid in breaking up clay soils, (those biennial and perennial prairie roots go way deeper than any cover crop you can find,) as well as the anthills that come with machine free prairie ground, (they’ll cultivate deeper than my sub soiler can reach.)

Good luck
Re: clay orchard
August 12, 2022 01:09AM
Here's a question for you clay orchard people: any tips on getting proper depth on soil samples? Our clay is so dense, and often dry this time of year, it is hard to get below 4-6". Even with a step on probe. The only next step I can see is using the auger on the tractor, which both feels ridiculously overpowered for the task, and isn't gonna happen since we try not to swap our PTO implements willy nilly during the season (filed under Laziness, Extreme).

Zone 7a in West-Central MD
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