The fields I drive by on my way to work put the lie to the author's premise. A week ago, I saw a road-scrapper type device running around a field that had a spinning laser positioned more or less in the center of the field. The laser provided a level reference that the scrapper responded to moment by moment by lifting or lowering the blade. The machines are designed to build a field with a precise gradient so the farmer can minimize the amount of water needed to irrigate the field as well as to uniformly irrigate the crop. The water may be free but lifting it from the aquifer isn't.
Further down the road, there was a device that was building perfect raised beds covered in plastic. Strawberries need to be grown in well drained soil and the raised beds provide that. The plastic is used to keep a fumigant on the bed until it decays instead of leaking into the atmosphere prior to seeding. Once the soil is fumigated, it's planted by an automated planter that leaves the plastic in place to reduce evaporation - again to save water.
The next field over was being harvested by a machine that requires two people to operate it. Ten years ago, there'd be a crew of 30 doing the same task.
The industrial revolution upended farming from what it was centuries ago and that process hasn't stopped since. The net result is fewer people are needed to grow more food at a lower cost. Downside is calories have become so cheap that most of us are overfed.