Another idea is to plant your trees as you normally would (just slightly higher than the normal soil level so that there is a bit of slope for drainage) and then pile the wood/bio-mass on the south side or the downhill side of your tree.
This does a couple of good things.
1. It uses that bio-mass and keeps it in your soil-system/eco-system. You don't have to bury it in order for it to do all the good things wood does. Just laying it on the soil will still help retain moisture and
boost healthy microbial and fungal life.
2. Trees like their heads in the sun and their feet in the shade. Baby trees don't cast much of a shadow, so the soil around their roots tends to get baked by the sun. Sunlight irradiates soil life—it kills all the best things you want to flourish in your soil: bacteria, fungi, and little soil biota. Piling-up bio-mass on the south side of your tree in a little mulch pile captures that sunlight before it can cook your soil.
3. The soil stays moist and cool under a brush/mulch pile. It doesn't hold as much water as a hugelculture, but it does hold some. As it breaks down, however, it'll hold more and more moisture with each passing year. The worms and beetles will carry rotting vegetation down into the soil. They'll integrate it into the soil profile.
4. You don't have to worry about a blow-out like you might have in a hugel-swale. Water will pass through it and not build up pressure. Brush piles slow the flow of water and capture a percentage of it before releasing it to flow down further.
5. Such piles become a haven for lizards and other reptiles (who, in turn, eat bugs/slugs/snails). Earthworms will grow fat and happy under brush piles. Brush-piles become a kind of "reef" that attracts other life. Having all that life right above the root zone of your fruit tree is a very good thing.
6. Brush piles are an easy way to slowly compost the big brushy stuff. Things like woody herbaceous plants (mature pepper plants, corn stover, okra plants), tomatoes or other vining crops (pumpkins, cucumbers, watermelon, sweet potatoes, jasmine vines, grape vines, etc.) are a pain in the ass to try to compost. They become a tangled mess in a normal compost pile or compost bin. I don't want to take the time to chop them up. So just roll them up and pile them on the downhill side of your fruit trees (or the south/sunny side). There they will slowly break down without you having to try to stick a fork into them and turn them. Pile it up and forget it.
One word of moderate caution: don't pile it directly against the tree. Leave a bit of space for air-flow. Soil and mulch should be at the level of first roots that make their way from the base of the tree. I start my brush piles at the drip-line, or slightly under the
canopy as the trees grow older. I'll pile up BIG chunks of wood and just leave it there—big rounds of
firewood from felled-trees. Within 5 years, they are well on their way to breaking down. If you flip those logs over, they'll see that they are covered with white fungal mycelium. That means the fungal network has found the wood and is feeding on it, and more than likely, is transferring those nutrients directly to your tree roots.
Just one more word of encouragement: you don't have to improve all your soil equally at the same time. Once you get your trees in the ground, concentrate first on just improving those immediate areas around the trees. Cover crops are good, particularly if you use nitrogen fixing legumes and other beneficial companion plants. Mulch piles (as I've written about above) and swales all help improve the immediate area around the tree. As the trees grow and your land produces more and more bio-mass, you'll find the improvement of the soil grows exponentially. Just because you can't have it all perfect at once doesn't mean you can't start doing little things. Be patient. Small trees become big healthy trees, soon
enough. That first year, they'l need a lot of attention. By the third year, they'll be virtually care free.
Best of luck.
2
