[labawi]

Pretty much all organic carbon in the soil ultimately comes from the air.

Yes, atmospheric nitrogen is fixed by bacteria, but it's not just on legumes, they are simply the most known and prominent.

If your comment was true, fertile soil would never have developed in the first place. Read posts where people are gaining about an inch of topsoil per year (in good conditions). They are not trucking it in. Even on depleted soil there is a natural succession that slowly develops fertile soil (not in all conditions, but again, not trucked in, just needs moisture, wind not blowing it off etc).

> If you're not losing carbon in your soils, it's because you're bringing it in from somewhere else, and it's lost there.

Heralding imported soil as soil regeneration is flawed, but so is your premise.

[cmrdporcupine]

The premise is not flawed. I don't disagree it's possible to build topsoil and add carbon and use nitrogen fixers and cover crops to accumulate soil organic matter and nutrition. It's just not possible to do that and grow an annual crop of any sufficient size.

Carbon consumption happens through soil disturbance but also by natural oxidation and microbial processes in the soil. And some of the carbon in the plant matter is from the soil, as well.

The permaculturists are right that natural spaces are mostly self-regenerative systems. The problem is they don't feed people. At least not beyond hunter gatherer type densities.

Then add on top of that that most market garden type places are consuming quantities of unrenewable peat (potting mixes for transplant or nursery growing) and plastic (silage tarps and landscape fabric for occlusion, nursery pots, greenhouse poly, etc.) and fossil fuels... And large scale cash crop farms have their own rather drastic inputs as well.

Growing crops is extractive. We can fiddle with the parameters of how extractive, but farming needs inputs. So we need to think about where those inputs come from.

[labawi]

Please try to be more specific and accurate, as you're essentially making sweeping generalizations, while moving goalposts. It's hard to know what is hyperbole, and what do you actually mean and believe. One cannot finitely argue against a changing topic.

> Every bit of plant matter we ship off our farms in the form of food is carbon and nitrogen that is no longer in our soils.

Do you concede this¹ is false?

To be clear, I completely agree the vast majority of agriculture is extractive. What I think we're discussing is whether (or how much) growing crops must necessarily be extractive.

As I think I've said, I agree it's dishonest accounting to include imported plant matter in regenerative farming². Either way, it only reflects on current practices, as do comments about peat. Your experiences and failures, or those of your neighbors only speak of the inadequacies of specific methods. Comments about oil and plastic bear no sway in the topic at hand.

I specifically take issue with the claim that carbon is a soil resource that must be depleted when growing substantial amounts of food. Yes, when taking away crops, we (necessarily) remove nutrients, and some may necessarily require replenishing, but they are not carbon (or even nitrogen).

Carbon it is in fact one of few resources that comes from thin air, and plants can absorb (fix) it by themselves. Forests show that plants can fix CO₂, in substantial quantities. Conversely, forest mining shows carbon is released when you destroy the soil.

When farming, carbon is the one resource that is not industrially added to the soil³. Most of the carbon is in fact burned, either biologically or physically and cannot be returned.

As specific counter-example, in a discussion of soil regeneration, I've read claims of an inch of topsoil growth per year. Whatever they were doing or supplementing, I don't think they⁴ trucked in an inch of carbon/topsoil per year. Are you claiming it's impossible?

¹ As in, it was not present in soil, as your original claim seems to be.

² Imported matter does seem a good and legitimate way to quicken the process of soil regeneration, if it then becomes net-producing.

³ Carbon is only added in small, non-replenishing quantities, or small areas, not materially changing the carbon balance by itself.

⁴ I'm aware there are those that do repeatedly truck-in an inch of topsoil.