Yes, the initial till "lightens" the soil by introducing a lot of air into the soil profile. But it's an unnatural way of pushing that air into the soil, and it quickly compresses back to an even more compacted state because there is nothing present that holds the soil structure open. Further, all that extra oxygen artificially pumps up the microbial activity, which in turn eats up the soil carbon. Within a couple of months, you've burned through the soil carbon, leaving just mineral soil --- and that compresses like a punctured basketball.
Soil aggregation and aggregate stability are not a result of mechanical processes (running a plow through the soil) but chemical and biological processes. Well-aggregated soils are crumbly and “open”, allowing water to easily infiltrate rather than run off during heavy rain events. They will have the texture of cottage cheese. The exudates produced by plant roots are the glue that binds soil into the crumbly texture. Root surface fungi also produce aggregate glues, further enhancing aggregate stability. Without these glues, no amount of tillage will permanently "lighten" the soil because it all goes back to an even tighter formation.
The name of these fungal glues is glomalin—a chemical produced by Mycorrhizal fungi that increases microporosity (creating empty space within soil for water and air to flow through). Glomalin hangs around for about six months after the root dies and the fungi are no longer present. But it eventually breaks down, and the soil aggregates turn to powder. Every time you till, you rip those fungi to pieces, and thus hinder the production of glomalin. If you want your soil to remain aggregated, you've got to have a continual supply of glomalin being pumped into the soil ---- a living root with attached fungi, preferably, 12 months a year.
So I'd argue that its best to never till --- even the first time. If you can establish a cover crop without tilling, you'll be much better in the long run. If you can innoculate your cover crop seed with a fungal starter, all the better. But even if you don't, there are enough fungal spores floating around out there (and already present in your soil), fungi will eventually colonize your soil.
Best of luck.
Here's a link that talks about soil aggregation.
Tom Turner wrote:
But that doesn't also mean that the small sustainable farmer should not choose instead to promote soil porosity and stability through organic material in the soil. And for the simple-minded small sustainable farmer (like myself) it seems like common sense to put the organic material IN the soil, not ON the soil.
Marco Banks wrote:Adding so much wonderful organic matter to your soil clearly has made it healthy and full of life. It takes a bit more work on your part, but it makes the soil very healthy. I certainly have experienced that myself. But the volume of compost needed to continue to feed such a system on any kind of scale quickly out paces the available supply. Even with a healthy composting system, I don't have enough compost to go around, and that's even after I've dumped hundreds of yards of wood chips all throughout my system.
So as you mention Gabe Brown -- he farms hundreds and hundreds of acres but uses no such inputs as you or I do. He's not making compost on that level --- and even his cows aren't doing it to the scale that we are. He leans heavily on naturally occurring fungi to make his soil fertile and friable. You and I can bring in these amendments (chips, compost, etc.) but you could never do that on a large-scale commercial operation like Gabe runs. That's why he's 100% no-till.
I'm getting older, and with that, I'm certainly getting lazier. I hope I'm also getting wiser. Could I increase my production if I were able to find a way to significantly increase the volume of compost I were able to add to my soil? Absolutely. But I don't have the time or energy to do that. It stands to reason (in my humble opinion) that if tillage exponentially "blooms" the microbial life of the soil to burn through all the wonderful soil organic matter (SOM) that gets added, it's a vicious cycle to work so hard to make compost, only to till it in to feed an artificially stimulated microbial herd. I'd rather take the slow route of creating a virtuous cycle (as you would find in a forest) where the soil food web self feeds, but never over-feeds. That seems to me to be much more sustainable (certainly for my back and for the fossil fuels I will not be burning to gather up all those extra compost ingredients).
Permaculture is a design system predicated on mimicking natural systems. Forests or savanna systems don't till, yet the soil is fertile and self-sustaining. That's what I'm shooting for.
Tom Turner wrote:
The other example is the South American rain forests which, blessed with sunshine and moisture has (or had) a massive abundance of biomass yet has proven to have extremely shallow soil depth.
The popular myth is that woodlands create topsoil at the rate of 1 inch per century (?).
Can anyone explain that seeming conundrum?
Erwin Decoene wrote:... Nutrients leach out and mostly end up in the ocean. In some climates the leaching process is fast. In tropical soils humic acids, dissolved CO2 break down rocks extra fast and leach out lots of it. ...
Marco Banks wrote:
There are a couple of variables at play.
1. Warm, wet ecosystems provide an ideal climate for ... (above ground) active bacterial community ...
2. ... S L O W decomposition ... underground ...
3. ... In grass-lands ... Ruminants eat the top of the plant ... causing the grass to sluff-off roots. We call this maintaining the "root to shoot ratio". Prairie grasses have roots that go 4, 5, 6 feet deep or more. Buffalo or elk eat grass. Grass sluffs-off roots. Bio-mass is integrated deeply into the soil. Top-soil is built.
Erwin Decoene wrote:Some people here have argued here that tillage does not automatically mean erosion. Perhaps under some circumstances it does not but here in Europe there is lotst of scientific proof for the (historical) correlation.
Tom Turner wrote:
I do not understand why this is not the agricultural standard around the world.
Tom Turner wrote:There is a limit to the economic factor of the-economy-of-scale. The agribusiness large enough to buy two of the largest tractors available has no scale advantage over two businesses half the size with one super tractor each.
Gilbert Fritz wrote:I think the main goal of soil disturbance is to prevent succession.
Gilbert Fritz wrote: Besides, have you ever wondered why humans put so much work into annuals compared to perennials?
Post Today 8:37:47 AM MDT Subject: To Till, or Not to Till, and WHY
Gilbert Fritz wrote:
Besides, have you ever wondered why humans put so much work into annuals compared to perennials?
Ben Zumeta wrote: It helps to start with asking, "why are you tilling?" It seems largely to increase the immediate availability of nutrients and air by reducing particle size and increasing surface area. This works in the short term to increase the mass of bacterial life if organic matter is continuously added. But in both respects the benefits are short lived and require continuous maintenance.