Are old methods of agriculture nearing the peak of their productive potential? They almost certainly are. Will this leave people without enough food?

Yes, if we only look at the current agricultural methods, but not necessarily. Those methods are not conceived and practiced to maximize yield per acre, only yield per unit of labor. Their rule is not “do more”, or at least “do enough”, but “do with as little people as possible”.

Starting from there, C. Eisenstein states that If we had 10% of the population engaged in agriculture rather than the current 1%, we could easily feed the country without petrochemicals or pesticides.

How? With the technique known as permaculture, that he says “can easily feed the peak world population of perhaps 10 or 11 billion we’ll see by mid-century.” Full article here.