As you can see from the responses, there are many ways to go about this that may work. But you’ll need to assess your situation may have some unique elements you need to determine such as drainage, existing soil fertility, etc.
To share a bit of my experience in northern Virginia, here is a patch of pawpaw seedlings I planted near my garage 3 years ago. There are 10 seedlings here, planted much too close together, but I bought them as a package of seedlings and planned to graft them and then pick the 2 or 3 that were growing the best to decide which to keep and then grow them as a clump. I tried grafting them last year (2021) and the grafts failed - the grafts started okay but I grafted too late and it got really hot before they fully healed. If I hadn’t had the failed graft attempt last year and they continued straight up they’d probably be at least 7 feet tall by now. Even with the graft fail, they’re still almost 6 feet tall.
I just planted them directly into my Virginia clay soil and put a little composted manure on the top of the soil and some wood chips on top of that. Worms came in and improved the soil some, but it is still mostly native clay soil. I’ve never fertilized these trees, although I’m sure it wouldn’t hurt to push them a bit. I’m going to regraft them this spring. You’ll definitely need to plan for irrigating your trees during dry spells, since at least for the first year.
I show this example just to note you probably don’t have to dig down and till in if you’ve got some fertility in the soil, get some life going in the soil and have reasonable drainage. My clay soil isn’t great for drainage, but the water will drain out of a hole in 6 to 12 hours, which is okay for pawpaws. They are okay with moist soil, but won’t thrive if they are sitting in water most of the growing season. That’s why I suggested testing the drainage.
Your wood chips will keep breaking down, which is good, but you could also push them aside in the rows where you plan to put the trees and grow some cover crops to build the soil. I personally wouldn’t till, but would just grow a winter crop, chop and drop it in the Spring, grow a spring summer crop, chop it in the Fall, etc. until you are ready to put in your trees.
There are many ways to go about this and there is certainly nothing wrong with working in a bunch of manure and leaf compost that will break down by the time you plant, but cover crops can push their roots deeper and can also bring up some of the nutrients from lower down. Plus growing legumes will build up your nitrogen in the soil. This assumes your current soil isn’t truly horrible and can actually support cover crops now without augmenting it. They don’t need to thrive when your first start, but at least survive and build up the soil to start. They’ll improve as you go along. I have seen someone try to improve their soil with cover crops, but the soil was so compacted that they never really got their first planting growing adequately, so the soil needs to be adequate to support germination and some growth to start with.
And actually, a cover crop’s performance will give you a sense of the overall soil quality, so you’d have a better idea of what you’re working with. If the cover crop fails, then obviously more drastic measures are needed.
I’ve posted this before, but here is a sample of how I improved my clay soil with cover crops and wood chips. I’ve got a persimmon growing in this area now that is growing like a weed!
