Modern farming techniques consider sustainability, the larger problem is countries using traditional methods that are extremely harmful like burning forests.
The industrial farming of corn in the US requires using hybrid corn strains to reach the yields it has, which in turn requires the use of fertilizers because the natural soils is incapable of sustaining the density of corn plants that hybrid varieties achive.
Those fertilizers in turn are mainly made from Oil, which is a non-renewable resource, making the whole thing unsustainable. It's is possible to make the fertilizers sustainably, it's just much more expensive so that's not done.
The US is so deeply involved (including outright military invasions) in the Middle East from where most of the oil comes because in the US oil it's not just a critical resource for Transportation and Energy, it's also a critical resource for Food because it's so incredibly dependent on corn (which is estimated to add up directly and indirectly to more than 70% of the human food chain there)
PS: There is a book called The Omnivore’s Dilemma which is a great read on this.
Fertilizers are made from Amonia which in turn is made using the Haber-Bosch process which requires fossil fuels to provide the necessary energy and as reactants (see this related article).
There is also "natural" fertilizer made from organic mass left over from other activities which would otherwise go to waste, but that's insufficient for large scale intensive farming (composting is fine for your community garden or even for supplementing low intensity agriculture, but not for the intensive industrial farming growing things like hybrid corn).
Finally, the use of techniques like crop rotation which lets letting fields lie fallow so that natural nitrate fixation occurs and the soil recovers do not make the soil rich enough in nitrates to support hybrid corn growing because, as I mentioned, the plant density is too high to be supported by natural soil alone without further addition of fertilizers.
Fertilizers are made from Amonia which in turn is made using the Haber-Bosch process which requires fossil fuels to provide the necessary energy and as reactants
That's exactly what I said! Fertilizer is not made from oil. The factory is powered by oil. Just like your home where you garden is powered by oil.
Natural Gas - which is not renewable - is a reactant and Oil is still involved indirectly as a means to generate the power needed for the process. This can be replaced but is more expensive.
That said, it's unclear to me if Oil is somehow used at the chemical plant to generate said energy (for example, to reach the necessary temperatures) or if it's even more indirect than that and it's just fuelling Power Generation plants which in turn provide electricity used in the heating, pressure generation and subsequent cooling for that process, in which case it could be replaced by something renewable.
If it is the latter case I have to agree that it's not quite as bad in the renewable sense as I thought.
Yeah sure. They consider sustainability in that the current generation of poisons they use haven't been proven unsustainable YET. When they are proven unsustainable, they'll move to the next generation, that hasn't been proven YET...
Also systemically annihilating everything except that one crop you want to grow makes your farmland an ecological desert, that doesn't sound very sustainable either.
Unless you're of the conviction that farmland shouldn't be in any way part of nature, and we should concentrate on just growing crops there and every other kind of life there should be discouraged, and by doing that as dense as possible we keep more space for actual nature.
Though i think farming that leaves meaningful room for (some) nature to coexist with it doesn't do that much worse in yield to make the modern 'kill everything' approach worth it. But we'll see what the future brings i guess.
But just being like 'modern farming techniques consider sustainability' seems pretty naive to me...