Question About Organic Matter in Dry Land Situation

I have a somewhat technical soil question I'm going to ask you guys.

Bear with me while I think out loud.

First, does syntropic farming work for dry land situations?

And in dry land situations, should organic matter ever be left on the surface?

The obvious answer seems to be yes, but I have seen posts about organic matter oxidizing straight into the air on this forum, and I've sort of witnessed something like that in real life.

My grandparents had a conventional farm in Western Kansas that I visited often as a kid. I still remember a giant pile of brush that never broke down over decades and slowly just bleached in the sun. It seemed like it probably never even helped the soil under it. Everything just seemed dead.

So I guess my question is, would it have worked as a Hugelculture if it had been well watered when it was established? Or would it have still dried out and sat there for ages, just with a little bit of dirt on top of it?

And the question that directly applies to my site is: will chopped and dropped plants have the same fate as that old brush pile? I do live farther east.  We do get higher rainfall. I think it can vary dramatically between 15 and 35 inches of rainfall a year.  It's usually on the lower end of that.

I don't want to pile a bunch of grass on the soil that will just sit there for all time. Or go straight back into the atmosphere. But at the same time mulch does seem like it makes the soil nicer underneath.  So even if it's going back into the atmosphere at least the plants around it are benefiting? I guess I'm just wondering if I'm only speeding up CO2 release or if chop and drop will do something to build soil. I just can't imagine that I will see the amazing soil buildup that syntropic farming promises.

Does syntropic farming and chop and drop come down to having the roots die in the soil and leaving their carbon behind? That would make some kind of sense to me.

I'm hoping that's the case because having to make everything into a Hugelculture sounds burdensome, to say the least.  

I lived out in Oakley for a good chunk.  My hugels did amazing without much additional watering.  I dug into them a couple years in and it was some of the best smells I have encountered.

I also did a lot of mulching with cut grass from the school fields, which looking back had a lot of chemical herbicides in them, but seemed to not bother my veggies much.  Those spots retained moisture well, and contributed to reduced watering.  I had to replace the grass mulch frequently as it was rapid in its decomposition.

I am now back in central Kansas, I have grown a lot in my methods but still use hugels, or at least wood in every one of my projects.  If nothing else, those brush piles contribute to the fauna around them.  Where there is fauna there is guano, which is a win for me!

I do heavily incorporate chop and drop comfrey into my routine now, and divide it yearly to get more.  My fruit trees are noticeably better than surround ones, and weed competition is down.  The soil does get better down below the surface as worms and critters eat and burrow, and the top layer is constantly improving through the breakdown alone. From my understanding chop and drop is mostly beneficial because the deep taproots draw the nutrients from those depths to its foliage, which then decomposition does its thing to make it bioavailable to the shallower rooter plants.  Root decomposition is more important to me in my nitrogen fixing plants, as I want that fixed nitrogen to reach the rest of my plants.

I would suggest that dry situations, the more organic matter the better.

Though it might be hard to get the green/brown ratios.

A load of wood chips would put folks ahead of the game, though.  Just leave it in big pile to do its thing.

The oxidation thing is probably more of an issue with fine materials like bare compost sitting exposed in windy spots. A thicker mulch layer tends to insulate itself. Matthew's hugel results in Oakley back that up, if it was oxidizing away quickly he wouldn't have had the moisture retention he did.

You certainly are asking complex questions... I'm in the opposite of drylands, so take my answer as you will.
My understanding is that organic mulch in dry areas can be an issue when rain is light, as it can actually reduce the amount of water soaking in. The moisture just evaporates back off the mulch again. However if the soil underneath does become moist, then the mulch can protect the soil underneath from drying out quite so quickly.

Anna Hutchins wrote:Does syntropic farming and chop and drop come down to having the roots die in the soil and leaving their carbon behind? That would make some kind of sense to me.

I think that the way syntropic farming is supposed to work is that as well as the chop and drop directly feedlng the soil with organic materal, the effect on the plants is supposed to stimulate growth, so increasing root exudates that also stimulate growth in the neighbouring plants that have not been chopped. The polyculture aims at having plants atall stages of growth - young plants though to ultimately mature trees.

There's a fair amount of information on Syntropic agriculture on this thread here.

When I lived ten years in relatively dry California, one of my first counterintuitive lessons was not to use mulch as a rule.  It's a fire hazard (this is a big deal in these areas!), and for some reason it ended up being a habitat for large numbers of pests like slugs, snails, earwigs, millipedes etc....way more than I've seen in other climates.  And coarse mulch never broke down....I could read print on cardboard pieces after two or three years.  Allan Savory talks about this in the holistic management stuff....in brittle climates (basically dry climates where annual evaporation exceeds precipitation) organic matter has two main routes to decomposition: 1. in the guts of ruminant animals, and 2. in a fire.  Otherwise it just sits around.  Eventually I learned to put my organic matter IN, rather than ON, the soil as a matter of course....and this went well with converting the most intensive parts of the garden to permanent raised beds with hard edging and mesh underneath because of the gophers.  One or more beds would be dug out every year and filled up with layers of organic matter, animal bedding, and soil. I would use some fine mulch in the wetter seasons, partly to avoid soil splash onto low growing veggies, but most of the summer gardesn were bare soil and drip irrigation.

The techniques are highly dependent on your local climate and conditions.

For us, in a sand/silt soil, the winning strategy in a long line of drought-ish years has been tons of 2/3 composted organic matter in the soil, and a dressing of semi-composted straw mulch on the surface.

The goal is to keep the soil around the plant feeder roots moist and active, with the mulch above holding moisture and preventing that crucial growing layer from drying out.

We have had historicaly hot, dry conditions in England this summer. We will need 120% of recent average winter rainfall to get our of drought by Spring 2027.  So, not "dryland" but a hint of what that's like. Despite rain since late August, our soils are still very dry to a spit deep.

Observations:  cardboard sheet mulch turned to papier-mâché keeping rain & dew out of the soil. I've had to manually remove it.

Living roots in the soil keeping the worm population alive. Probably due to both shading & cooling the soil, and conserving moisture because plants can regulate transpiration for a long time when bare soil cannot.

By far the best tomatoes grown where I trenched part-rotted compost for runner beans, compared to the adjacent bed where I top-mulched.

So next year, I plan to plant into green manures, not to top mulch until the soil is properly rehydrated, and to experiment with more buried compostables, for a start.

I'm composting my comfrey in bins, just to moderate the PAs: https://permies.com/t/286439/Pyrrolizidine-Alkaloids-Comfrey-Boraginaceae-Family

I'm going to ponder how chop-and-drop of other plants might fit into all this.

It's preserving fall/winter/early spring snow and rain that is benefited by top mulch in dry climates. It has time to soak in during cold weather. Summer rains may just cover the surface and be lost to evaporation in the hot sunshine.
Dig under that old brush pile that appears to be doing nothing. I suspect you will find the soil under it has more deep moisture than a bare area nearby.
This year we had a very cool and dry May. My bare earth was bone dry, but mulched areas were still wet.

We were planning to burn some of our grassland this spring, it is mainly tallgrass prairie and has not been burned for 3 years, helps keep some areas of copious willow in check. We did not burn, it was too dry and fire burn restrictions were in place all spring. This turned out to be for the best as the summer continued on very dry. The grassland did quite well because the mulch (duff) layer held in the moisture and the warm season grass was very prolific even with just .7" of rain in a hot July. Had we burned, the soil surface would have been exposed to the heat of the sun and the moisture reserve we had going into the summer would have more quickly been used up. I am rethinking my burn frequency and what is accomplished by it. All of the surface dry matter is consumed by the fire and no litter is left on the surface for the soil life below. My initial soil testing on grassland says a burn occasionally raises the soil organic matter percentage but this needs more research. The soil surface litter was our friend this season and our future grassland management will take this into account. We rotationally grazed some of our grassland this summer and even after grazing a lot of the duff layer remained, protecting the soil surface.

Thank you for your informative replies everyone!  I might have to start trenching organic matter more.  I bet shallow trenches on contour would really help retain water.  And they're easier than a massive Hugelculture!  I live in town so I don't want anything like that. Also it's a lot of work and I have young kids.

I will add that my local extension office does recommend under four inches of mulch for soil moisture retention.  I bet that amount will still let spotty rain through.  So maybe chop and drop is okay in the spring and fall when we get more moisture and cooler temps?  That would be a win because chop and drop is easy, and I don't have to dig out anything.  I'm lazy, and once again, kids.

(Also we usually get very little moisture in the winter so there's not much point trying to build a lot of infrastructure to catch snow. Now that I've said that we're probably going to have incredibly snowy winter.)

Oh and I compost just to keep stuff out of the landfill, but I end up with so little material at the end it almost feels futile. I'm sure that that organic matter is going straight back into the atmosphere. I would be interested in trenching it instead to see if that helps more with soil building and with the plants actually getting some of the nutrients.