.. yes? modern agriculture is much less destructive of soil, and uses vastly less land per calorie yielded than any alternative, both of which is getting more true over time, not less. No-till, genetically engineered crops, soil databases linked to computerized and GPS/gallieo enabled farm machinery - all of this increases yield, reduces pesticide and nitrogen runoff (by making dosage tailored to each individual square meter of field) and it all relies on knowhow, data and electronics, not oil.  Desertification is a symptom of low tech farming, not first world practice. The green revolution was a good thing for both mankind and the planet, and it is nowhere near done.
I am not saying economic dislocations will not happen, they will, especially as the third world gets its shit together and adopts best practice and schemes like the solarpowered seawater distilling greenhouses currently being built in north africa and australia.

.. and as for the actual machinery.. even if it proves impossible to build a battery sufficiently powerful to power a tractor - well, post peak oil does not mean no oil, and what is available or synthesized is going to get allocated to critical applications like heavy machinery first, and the car loving public can putter around in electric minis and like it.