how does subsoil tillage build soil?

I thought tillage in general did the exact opposite: introduces too much oxygen thus depleting OM and disrupts soil fauna. I have seen many people prescribing subsoil tillage for "creating topsoil" but very little explanation as to how it accomplishes this. They mostly talk about the advantage to the farmer.

Is something being tilled in, or is it just tilling? Either way, I think nature can handle the necessary tilling itself.

The reason tilling gave short-term benefits but hurts in the long-run, if I remember correctly from Gaia's Garden's analysis of this, was because it quickly added a lot of organic matter and air back into the soil which kinda kicks starts all the soil microbes- like putting them on hyperdrive. This increased surge in activity uses up the available resources within the soil, like sprinting early compared to steady jogging, and leaves little leftover for maintaining daily functions. Over time, this short series of "bursts" consumes the organic matter and -vitally important- humus within the soil until there is little left. Then, it is down hill from there.....

I am confused, too, as how tilling would create soil???

I think that you are both correct. Tillage doesn't build soil. It depletes it. It kills mycorrhizal fungi by chopping it up and also by moving microorganisms to different parts of the soil levels, kills them because that's not where they can live.
John S
PDX OR

John Saltveit wrote:I think that you are both correct. Tillage doesn't build soil. It depletes it. It kills mycorrhizal fungi by chopping it up and also by moving microorganisms to different parts of the soil levels, kills them because that's not where they can live.
John S
PDX OR

You dont happen to have any idea as to how sub soil tillage advocates believe this practice build soil, do you?

I think they till to kill weeds, make planting more comfortable and build short term bursts of available energy, not for long term soil building. I have never heard of doing it to build the soil.
JohN S
PDX OR

Perhaps tilling organic matter into compacted subsoil can make the amount/depth of soil available for roots and the microherd of soil life to inhabit. One really great episode of double or even triple digging can really change the soil life.

Sub-soil tillage is not the same as tilling in soil or plowing. People in the permies world should be familiar with the concept of sub-soil tillage because of Yeoman's keyline plowing. The Yeoman's plow is essentially a cross between a chisel plow and a sub-soiler. In sub-soil tilling, you are trying to open up compacted areas below the top soil ("sub") level. By having a narrow shank there is very little disruption to the biology at the soil level.

Just running a piece of steel through the sub-soil level isn't going to help create soil on its own. That will open up areas for roots to extend, but one needs to also comine it with grazing or mowing. Grasses tend to grow roots when the tops are cut. That is how so much carbon is getting added to the soil and new soil is created.

Subsoiling without grazing does help by breaking the hardpan that prevents root and water penetration and allowing oxygen in. And it severs roots to build a little mass, but it is grazing (or mowing) that causes the most root die back and soil carbon pathway development.

Organic matter content alone is not a sign of soil health. I have seen farm fields with double digit OM% that were still dead dirt. You CAN'T get high OM content in good soil because the life expands to consume it.

That's right. I have seen really compacted clay that never gets oxygen, organic material or water to it. In hot areas, it's true that it's really hard to get high OM because it will be eaten by the microbial life, but in cold areas you can have good soil with high oM. Most of the time I've seen deep digging recommended, however, it wasn't every year but once in total, or every few years, to let the microbiology and deep roots grow and heal, especially in a perennial growing area/food forest.
JohN S
PDX OR

Justin, please may you explain more about the subsoil tillage. I am having trouble visualizing what is happening in this situation. On Google, these images were what I found:




Is it really just that simple? Would the subsoil plows be analogous to slicing cake with a knife? The cake is still there, just split into sections with a little breathing room inside.

Dave Burton wrote:
Is it really just that simple? Would the subsoil plows be analogous to slicing cake with a knife? The cake is still there, just split into sections with a little breathing room inside.

Pretty much; however, different sub-soilers provide different action at the point. The replacement tip on the Yeoman's plow I know is designed to cut at an angle such that the soil is fractured horizontally away from the tip. So the whole soil above is sort of lifted and dropped slightly (as far as I have seen) yet doesn't turn the soil of destroy the biology.

And as John pointed out above, the idea isn't to subsoil on a regular basis. Instead, you find where your top soil ends or where you have compaction and break at that depth. Maybe next time you go a little deeper. I've subsoiled anywhere from as shallow as I could get it to as deep as I could go. I hope this helps.

Subsoiling is a treatment--if it is done right you have recovered the land and you don't need to do it anymore. In fact, doing it too much will hurt the soil as it does cut microhyphae (?) pathways.

Farmers need to do it over and over because they keep re-compacting their land.

This is pretty interesting! What types of land is subsoil tillage usually performed on? What is their typical soil profile?

Loosening up the soil underground helps roots, fungi, and other microorganisms get farther into the soil, and they can maintain its aeration and levels.

On the other hand, tractors and other heavy machinery would regularly re-compact the soil. Would there be any other reasons why subsoil tillage might be necessary to perform again?

From what I've learned about the Yeoman's plow in particular, it requires less horsepower than a typical subsoiler. So, in theory you could pull more shanks and thus have fewer passes over the soil to cause compaction.

The only two reasons I can think of making repeated sub-soiling are:
- as R Scott said, because the farmer caused compaction
- you may want to increase your depth of sub-soiling over time

I'm on heavy soil with thick clay just below soil. I could see something happening where over time the fine clay settles in to any area sub-soiled, so it's possible it might need a fresh pass. I don't really know for sure.

The Arkansas rice belt is an example of land that does benefit from cycles of subsoil breaking. The land is all Buckshot clay, a very fine, heavy clay that will suck a boot right off your foot, it is also very slippery when wet. Running a breaker (subsoil till) every four years does seem to be of benefit to the rice crop. Most of the farmers also rotate soybeans and soft red winter wheat in these fields. they disc in the left overs after the harvest. every fourth year they let that field lay fallow or plant a cover crop to disc in. There is one farmer outside of Stuttgart that spent three years building the soil on a set of fields his father toasted by using "modern" tillage techniques for years.

He turned their farm into a no-till management system, the only time a field now sees a disc is when the buckwheat and clover cover crops are turned into the soil. After his three year recovery the fields produced bumper crops of soft red winter wheat followed by bumper crops of long grain brown rice. His no-till lands (over 2 thousand acres) are far more productive than two of his neighbors farms, who still hold on to the land destroying multiple tillage methods.

What types of attachments/ends can be added to a subsoil tiller and what do they do?

There are several different brands of subsoil tillers out there, the main differences are the tines and attachments available from the manufacturer. There are different shaped tines, usually anywhere from 1" square to 3" square, 1" X3" and 1" x 4" and 2"x4" and 2" x 6".
These are for different types of soils and/or so that things like coulters, wings, rollers can be attached. The carriage (frame) can be the attachment point for some or all of the goodies, except the wings which are always a part of the tine since these are down in the soil but above the chisel.

Adjustable coulters are an awesome addition, these are like mini disc that slice through the surface just behind the tine, they keep the track line of the tine from closing back up after the pass. I've also seen adjustable double chisel ends which look like little flattened out plough blades, split down the middle and attached to the tine with two bolts, these are more expensive but allow more lifting of the deep soil. The norm for Arkansas farmers, is a set of tines that have a chisel end, this is easy to replace when it becomes worn since it is pretty much just a piece of 3/8" steel strap metal two inches wide and new ones can be welded on fast. These look like a wood chisel laying on the tine end, the tines on most of the big rig farms are 2" wide and 2" thick so their chisel ends are made from 3/8" thick 3" wide strap (flat steel) material, after welding on they are usually quenched to give the metal some hardening for longer wear.

Once you have a subsoil tiller, you can; customize the tine ends, add weight via plates or concrete blocks laid on the carriage, lengthen or make longer tines. I know a fellow that has quit farming because he had welded up several custom parts for his subsoil tiller and his discs and harrows and other farmers wanted them so much he created a business out of the demand. His brothers took over the farming and his new shop is right next to their barn. One of his modifications was to add a pair of "wings" 10" up the tine from the chisel end, these are just slightly tilted and add a second lift to the soil from their position up to the surface.

Dave Burton wrote:What types of attachments/ends can be added to a subsoil tiller and what do they do?

The Australians lead in this. They have a zillion different points available. They have different shaped points for different soil conditions and intended results. Some work better in clay, some work better in loam, some shatter mostly up, some work mostly sideways. Some have wings to slice roots just under the surface like a colinear garden hoe. Some add fertilizer or compost tea injectors. You are only limited by your imagination and budget.

Can I get more information about those wings that are added to the tunes please?