Do they? I mean minerals of course must come from the soil, but aren't vitamins and the macro-nutrients created in the plant itself? And can heavy farming really drain so much of the mineral content from the soil that future crops grown there will have fewer minerals? I know crops can drain nitrogen and other gases from the soil, but that's what fertilizer and tilling are for.

With Nitrogen what's going on is that there's a tiny bacterium using some seriously advanced chemistry to attach Nitrogen gas (ubiquitous in our air) to Hydrogen (from water which is also ubiquitous) to make ammonia‡, which can then easily be used to make organic molecules. Plants which have a symbiotic relationship with these bacteria are readily available and can be grown to "fix" nitrogen into your soil.

‡ What's advanced here is not spending a ludicrous amount of energy, we can fix nitrogen, but we use a factory with high temperature and pressure to make the conversion work, the bacterium does it happily inside a peanut plant.

That's an emphatic "yes". Standard fertilizer is NPK- Nitrogen, Phosphorous, Potassium. If it was not possible to drain all of the (bioavaliable) P & K, ask yourself, why would anyone ever need to use NPK?

Thanks! I did a little bit more reading on the subject. It seems like P and K are the two main minerals provided by fertilizer, but there's also zinc, copper, iron, manganese, and, oddly, molybdenum. And some plants apparently also deplete other elements, like sugar beets use a lot of boron.

I wonder about the environmental tradeoffs between using crop rotation vs. fertilizer for some of the micronutrients. On the one hand, there's an environmental cost to creating fertilizer, there's dangers of over-fertilizing, runoff, etc. But a crop rotation system means some fields will have to lie barren, or with less valuable crops, and potentially with lower yields, which means you need more farmland to grow the same amount of food, which means clearing more forests. Of course, I'm not even a novice in this subject, I'm sure there's a lot I'm missing.

The rotation/organic/etc argument is that properly managed soil & fields sustain their yields indefinitely with significantly less fertilizer, water, etc input, whereas the traditional industrial ag model achieves higher yields initially but the soil quality & yields decline rapidly & require ever more fertilizer, water, etc input. In short, the first model has lower peak yields but is more sustainable; the second has higher peak yields but "uses up" the land, and within only 1-3 decades at that.

A related example of the consequences of "using up" land can be seen with bananas. In that case, a deadly banana fungus is slowly, inexorably spread through the soil by human activity. Eventually a plot of land becomes unusable for growing bananas due to the spread of the fungus. No matter, the banana company just cuts down more rainforest for new land and abandons the old plot. Later, in perhaps ten years, the new plot will be contaminated & unusable, and the cycle continues.

Soil is not sterile.

The microbes at work synthesizing nutrients from those chemical fertilzers and raw minerals, making them bio-available and aiding uptake are vital.

http://www.pnas.org/content/114/44/11574

I rather wish that subject was approached.

As I understand it (coming from rural Ontario—5th largest agri-region), farms and especially large farms (around there) are required to—or at least make it a habit of best practice—strategically rotate crops every n seasons to allow the soil to replenish.

It's not so simple as that, but I'm no biologist or farmer—just a former country boy. Maybe somebody more knowledgeable could enlighten or expand.

As a farmer (also in rural Ontario, coincidentally) that is definitely something we try to do. It is not required by law, but anytime I've watched someone not rotate their crops, it isn't long before they are out of business. To extent that, on my farm, we consider it well worth growing unprofitable crops through that rotation to ensure that the ground will grow something profitable next year. It has also become quite popular to grow a second cover crop over the winter to improve soil health even further.

But what concerns me most about modern farming is the separation of animal production from plant production. I'm the sixth generation on my family's farm, and I'm the first generation to not also have animals. I do worry about the long-term effects of that. When I get into ground away from the historic family farm, that hasn't seen animals for decades or longer, you really notice a difference in the quality of soil vs. the home farm that has had animals for centuries as part of that crop rotation. Rotation is important, but rotation with animals seems to give the very best results. It is the model that agriculture grew up on and something we have lost (somewhat) recently.

>Rotation is important, but rotation with animals seems to give the very best results. It is the model that agriculture grew up on and something we have lost (somewhat) recently.

Again from a naive standpoint, it sounds like that's an issue that fertilization is supposed to supplant. Are there other observations outside of that you could point to?

I'm asking out of sincere curiosity at this point. Also what part of Ontario, if you don't mind me asking?

What are the animals’ role? Fertilization?

Just so I am clear, my concern comes from observation of the farms I work. All the usual caveats of anecdotes apply. It is not something that I have formally studied.

With that said, I think fertilizer is a big part of it. While we always used some synthetic fertilizer in my lifetime, the needs are greater now. Another thought is a greater opportunity to diversify the crops grown in the rotation. Things that humans can't eat, but animals can. There seems to be a difference in growing food for people for a few years and then growing food for animals for a few years over trying to grow food for people every year, where the choices are much more limited.

But this is speculation on my part.

Exactly this. For instance after sugar beet has been harvested, the land needs 5-10 years to regenerate back to proper nutrient levels and may not yield anything.

You must be describing some unique situation. Sugar beets don't do well if they are planted year after year, but they are included in crop rotations with no fallow years, never mind 5 or 10.

I am describing common knowledge in Balkan agriculture - in Vojvodina, Serbia, it is widely known that after harvesting sugar beets you simply can't have a solid harvest no matter what you plant for the next 5 or more years, and our land is mainly https://en.wikipedia.org/wiki/Chernozem . Usually you plant garlic/onion/phacelia or something similar in the subsequent years to "reset" the land.

Not saying there is a fallow, but that sugar beets take a lot of nutrients from the land, at least in this area.

Sorry for the lack of proper terminology, agriculture is not my primary occupation.