Improving hardpan/caliche - best way to do this?

I live in the Sonoran desert in Southern Arizona. About half of my yard is either caliche or hard pan(clay originally) that is probably 2-3 feet thick.

I am trying to improve the soil in the entire yard, not just specific gardening areas, and I was hoping I might be able to run by what my plans were, to see if anyone more knowledgeable (so, pretty much everyone) has some advice.

What I don't have: a lot of compost or money to buy compost, an animal making manure, manure or money to buy manure, a lot of soil amendments or money to buy amendments, a lot of extra water. My area also does not have worms breaking down the soil, nor much in the way of mushrooms or rot - it's too hard and dry (things above ground often desiccate rather than decay).

What I do have: a teen to do labor with me, hardpan that is shallow enough I can dig through it, a lot of brown and green plant matter that I have let grow wild for a few years that I can chop down, chop up, and add as plant matter to the soil, and an annual season of heavy rain (like 4-5 inches in two months, in a good year). Termites, ground squirrels, and packrats are the main critters that break down the soil and plant matter underground, so we've got those, too.


I was thinking of simply digging into most areas that don't have roots from existing trees, through the caliche/hardpan, breaking the clods up into finer pieces, mixing in green and brown plant matter in small pieces, and simply putting it right back into the ground like that to slowly break down over the next few years.

Anyone know if this might work? Any ideas for improving it, huge flaws I'm missing?

I would honestly be just as happy to try and build up good soil without digging at all, but I don't think I'd see results in my lifetime. I've encouraged one area to grow, with native trees, shrubs, vines, supporting plants, etc...  It's been growing like this for ten years now. And while the soil is significantly better than elsewhere, it's only about 1 inch thick, and the caliche and hardpan underneath is essentially unchanged, barring a few spots where roots dug down deep.

I'd like to try and speed up the process a bit more than that, you know?

Any and all advice would be welcome!

I would call all the tree services in the area.  Tell them they can dump every bit of their tree trimmings onto your driveway or any convenient place on your property.  Have that teen help you get it into your yard.  When you have a giant pile of tree trimmings, go to Home Depot and rent a wood chipper.  Fill a trash can or whatever you have with water and soak the wood chips before spreading them around.  Put down 6 inches or so of soaked wood chips down and then add as many more chips as you can on top of it.  Cover every bit of your property as deep as you can.  A foot deep would be good, and two feet would be better.  

I would plant as many trees as possible wherever you can.  Open a hole in the wood chips and plant them in the soil.  I would make depressions a foot or so deep and a couple feet across around the trees to catch more water.  Pull the wood chips back around them after planting.  Water as often as you are able.  The wood chips and the shade from the trees will help hold moisture in.  Monsoon season in particular will help if you can catch all that rain in wood chips and with trees.  As the trees grow, the will drop leaves and add even more.  Keep chipping wood and adding it as often as possible.

Plant any other plants that will grow.  Natives will be best until you can get more soil built and more plants going.  As soil is built and you get more and more plants growing, you can sacrifice some natives for chop and drop.  In a few years, you should have improved your soil greatly and have enough plants growing to have lowered the soil temperature a large amount.  Things will snowball after that.

Thank you so much for your response, Trace. I love your idea, but unfortunately I don't think I have the water to make it work.

Rainfall here is 5-12 inches a year, and humidity is exceedingly low. Large amounts of wood chips are something a lot of folks use here for gardening, but only if one can irrigate a LOT in that area so it breaks down, you know?  Otherwise, you end up with a bunch of wood chips that sit there, dry and not breaking down at all, for years (there used to be a good video on the channel 'the vegan athlete,' on youtube, who lived in a similar environment and you could see the beautiful breakdown of wood chips where it was watered frequently, and the absolute lack of breakdown of wood chips where he didn't). I know of a log that was partially chopped up by the side of a hiking trail, and ten years later, it was still there, as well as most of the wood chips, mostly unchanged.

Also, even 6 inches of wood chips and the water during many of our rain events won't penetrate enough to get to the ground, unfortunately.

On the good side, I do have a lot of trees already - native - so I've got a lot more shade in my yard and cooler soil than most of the surrounding area. They drop leaves annually, they've allowed a lot of bushes and herbaceous growth around the trees as well that are covering the soil in many areas.  But the soil underneath is still very poor, past that top inch of better soil that has taken years to build up.  And many of these plants are not ones I necessarily want to grow, but precursors to what I hope to grow, but require better soil for.  

Any other ideas, for low water, high evaporation areas?

I lived in a desert area that averaged 9 inches of rain a year, and I did it the way I described.  I did use drip irrigation to get most of my trees going, so that probably made the difference. I'm familiar with the area you're in, so I've seen the desiccated cactus carcasses that have been lying on the desert floor for years without decay.   Anything exposed to the sun and dry air there does just dry up and stay there.  The only way i know to deal with it is to get organic matter down as deep as possible and add any water you can.  If you can get tree trimmings deep enough, and with the fronds and leaves mixed in, or anything other greens you can get your hands on, you may be surprised.  If you truly can't get any water on it, it's going to be an uphill battle.

Shauna,

Whenever I complain about my hard clay soil I need to remind myself that I don’t have caliche.  My grandmother retired from Minnesota to Arizona and wanted a tree planted in her property.  My uncle tried to dig it for her and gave up.  I tried it in scorching heat and I could barely make a dent.

Caliche is some tough stuff.

You mentioned that the Caliche has a bottom perhaps 2-3 feet down?  You also mentioned that you have free labor (a teenager?).  If you really felt ambitious I would consider digging down past the caliche and filling the hole with organic matter of some kind.  *I* would use woodchips and grass clippings, but that’s probably not an option for you.  So instead I would find whatever organic matter I could possibly find—including food scraps and especially coffee grounds—and fill up the hole.  I would then top off with some water, just enough to moisten and have a small reserve to account for evaporation.  Finally I would cover with straw (if available) or perhaps a couple sheets of cardboard.

Now you hurry up and wait.

This is not going to be a quick process.  I am assuming that there must be some level of decomposers on the organic matter.  I would want to really want to get those going and at least make some compost in the hole.  If you can find something—almost anything—that either likes caliche or likes the ground beneath, maybe you could get something growing that would try to penetrate the Caliche.  I know this is a long shot and I know how hard Caliche is, but my goal would be to get some type of life growing in that hole and see if it cannot at least partially penetrate the Caliche layer.

Please take or leave as much of this suggestion as you like.  I would love to hear what your ultimate solution is.  Please keep us updated.

Eric

Wood chips are probably your only hope. How you are gonna get enough and keep them moist underneath is problematic. Drip line underneath should work, maybe doing a small area at a time. WHat you are saying will work but it has to be kept protected or the results will be real slow. I'd plant some soil building crop in the spots where you mix in the plant matter. Then when they inevitably die in the heat the roots will have added to your efforts. I dunno, man.... good luck.