I was pretty amused by the idea of grocery shopping as a literary experience, featuring the classical modernist "untrustworthy narrator".
Another interesting theme in this chapter -- and I think it's one that some people at BookTalk are likely to balk at -- is that of scientific reductionism. The reduction of soil fertility to NPK -- nitrogen, phosphorus, and potassium -- makes for a pretty classical example of the tendency of scientific researchers to look for a way of atomizing all brands of knowledge. Sir Albert Howard (another author I'd like to look into) makes the case for a more holistic view of things, and I think there's a certain amount of wisdom in that view -- the practical utility of which Howard and his agricultural descendants seem to have demonstrated quite aptly. The question that occurs to me is, if reductionistic science led to problems in agriculture, couldn't it be the root of problems in other domains as well?
I was also appalled to read about the tendency of the Cornish Cross breed of chicken to leg failure. Technically, this is natural selection at work (or is it artificial selection?). They're selected, by their relationship to us, for meat yield, at cost of their general fitness. Outside the confines of domestication, it's doubtful that the Cornish Cross could ever survive, unless it could evolve a stronger, more reliable form of locomotion. And beyond their genetic fitness, leg failure sounds as though it must be at least moderately painful. I imagine bones breaking, or, at the least, muscles collapsing.