Soil improvement using a post hole auger? Pros and Cons?

So I came across a couple comments in different threads that were similar to something I have been doing, but in a slightly different way.

They were talking about how to plant trees in wet ground. The suggestion was to auger holes into the ground around where you are planting a tree. The purpose being to send the water into these deeper holes and keep it from pooling in the hole for the new tree and drowning the little tree.

I have augered holes in order to fill them with manure, compost, and new soil, then top it with the original soil and the new tree. The hope was to give the tree a place it could get lots of mixed nutrients and easily send its root deep. I have very heavy clay soil just 6-10" below the topsoil so it can be difficult to establish a tree.

I have not done a lot of these holes and actually I screwed up on the first batch. I put in a bunch of "hot" chicken manure that was not composted properly. It killed the trees very quickly. They were dead in 3-4 weeks. I have since learned from that experience. I use mainly compost and a good garden soil that sits on top of the well composted manure in the bottom. That way the tree grows thru the soil first, then compost, and gets to the manure last. No more dead trees. The only problem I have had with this is the mice and ground squirrels digging into the root zone and damaging the tree that way.

On to my actual questions...

What do people think of using an auger to dig several 3' holes around a tree then filling with a manure/compost/straw/wood chip mix?
Then planting deep rooting plants surrounding the whole area?
Could this be a legitimate way of improving the soil quickly?
If I did a whole bunch of these in a larger area and filled them all with the large amount of manure my livestock create would this be worth the effort?
Would this get more nutrients into the ground and help increase the microbial diversity and health of the soil?
I could even inoculate each hole with mycorrhizal fungi.

What would be the problems with this idea?

It almost sounds like you are planning on doing cylindrical in-ground hugelcutlures around your trees. Seems like a great way to improve the soil, although not for those who shy away from hard work.

Also, it takes a surprising amount to actually drown a tree...and even more when the tree is dormant. Here's an image of a young Asian pear tree that was submerged for about a week and is doing just fine. What you can't see are fully submerged apricot trees in the background that were planted shortly before the river flooded and stayed underwater for about 2 weeks. They are also now doing fine (well, except for those that got taken out by the rabbits).

Auger a single hole in clay for a tree and you just made a pot without a drain. It doesn't take long to kill a tree. But more than a week.

You have to be careful the don't go anaerobic, but otherwise it should work.

R Scott pegged my concern, anaerobic decomposition is done by largely pathogenic organisms and produces toxins that can really slam your plants. I would not want to load a hole in a heavy clay soil with straight manure, for fear of anaerobic conditions. Throw some woodchips in along with the manure to provide for air space, or maybe straw? something to help with getting oxygen in there.

The 'plug' approach can definitely work for converting relatively large spaces with relatively small numbers of plants, but I am not as confident about plugs of uncomposted manure.

That anaerobic decomposition is done by nasties that make nasty stuff.

Thank you all for your responses!

John, I hadn't thought of the possible huglekultur similarity but I guess that makes sense. If I put branches in as well it really would be. Thankfully I don't have much standing water problems. Most of my property has specific areas for collecting water. Overall it prevents the drowning of most things.

R Scott, the clay pot with no drain is totally true, and it is a problem. I'm not doing this in low spots. I plant the trees above the level of the top soil in a small mound. Less risk that way. I should have explained a little better. With this other technique I was thinking I would not be augering a hole under the tree. The holes would be 1 or 2 feet away from the tree. I would only loosen the soil under the tree

Peter, you make a very good point about the anaerobic problem. I hadn't thought about it but you are completely right. Can you explain what you mean by "plug"? Do you mean the little seedling plugs that nurseries grow? Most of the trees I have planted were plugs. Or do you mean my filled holes would be the plugs?

The manure I use has been composted for 3 years before it is placed in the garden or used in an auger hole. That is why I said I learned not to use fresh manure. Same thing for both the chicken manure and the sheep manure. Adding a good amount of wood and fresh straw is a really good idea. I wasn't really thinking about how much to use, but I will take your warning to heart and use as much as I can. I'll need to find a landscaper that wants a place to dump his waste.

I have about 2-3,000 lbs of waste hay each year that gets composted or spread around the pasture and sheep pens. I try to feed in the areas that look like they need more fertilizing or organic material in the soil (which is the whole property). That way the sheep do the work after I break open the bales. The hay disappears very quickly each spring. I read a great article a few years ago that talked about feeding cattle this way. The rancher would place big round bales in the pastures where the pasture wasn't doing as well. He then fenced them off from the cattle. As the cattle finished a bale he would remove the fencing from another one. This way the cattle moved around the pasture all winter and slowly fertilized exactly where it was needed. I thought it was a great idea that I could use with the sheep. I hate having to shovel out the chicken coops and haul it around.

I have about 4 cubic yards that is almost 4 years old, 8 yards that is 2 years old, and maybe 4 yards of just started hay with very little manure in it. There are a couple yards in the chicken coops as well. It has been composting in the coops for almost three years. The chickens and I mix it a couple times a year.

Question: what if I were to use mainly just leaves and wood chips? Would that be a better way to go? Kind of like ramming branches into the ground...? I would definitely inoculate these.

Your ideas and method are good except for the cover the holes after filled part. Drill lots of holes in an area and fill those with your compost materials, leave these open to the air. I would try to wait a year before planting trees in an area I used this method on.

Composted manure is always a good addition when combined with straw, wood chips, leaves etc. Since it has already been composted the likelihood of it heating up again is minimal, especially if you don't put a cap on the filled holes.

By taking an area and giving it the filled hole treatment, then waiting a year to plant the trees, you will be giving them a better chance at survival. The compost filling the holes should disperse into the clay soil somewhat and that will help condition the clay soil. As the compost goes away, refill the holes.

The comments the others have made are very good observations and cautions, heed their words and concerns. You will want to check the condition of your plug holes frequently to make sure they are not going sour (anaerobic), if they are, just turn the plug filling or find a way to pump some air into them.

Bryant, you make a good point about leaving the holes open after filling. I wasn't really thinking about sealing them but by planting and moving the soil around them it is very likely the I would cover them.

I like your suggestion of doing the holes one year then planting the next. I could combine the holes with deep rooting plants this year, and plant to plant trees next year. My thought being that the holes would start to do their thing while the deep roots could work on the ground between the holes and start pulling nutrients into the ground where the trees would be planted. I would do a few rows of daikon and sweet clover since that is what I have on order.

Any suggestion on how I might check on my plugs?

I have used this method for orchard grounds in the past, it works. I use a length of 3/4" EMT conduit to poke into the filled holes, this cores the filling and with a piece of solid rod that is 1/2" diameter and about 8" longer than the EMT I can poke out the core for examination, this lets you see, layer by layer, exactly what is going on in the hole. It also adds air passages if you take more than one core sample per hole.

Bryant, that is great idea. Of course that would work. I have a 3' length of black iron pipe that would be perfect. I can even sharpen the end so that it cuts thru nicely.

I've had post holes bored to a depth of 4 feet just to fill them with wood chips. I think the texture of your soil is a big factor. I have fine sand with a little light clay, beautiful stuff, but no organics, and some compaction from construction. The wood chips allow for deep er penetration of water and air,( I live int he desert, water penetration is good for my situation with the sandy soil, it lets me deep water, and as we know, the best place to store water is in the soil!)

I bored these holes in a ring, then planted hops in the ring, but not necessarily in the same holes. The hops are very healthy.

If you have clay soil, and a little bit of slope, you could prevent the holes from filling up with water by making the opposite of a swale, and eyebrow shaped little berm on the up hill side. I think you'll do fine, since you've already understand the danger of an inground pot with polished walls. (I grew up with adobe soil, so I have "unpolished" many a plant hole.

Thekla