The central problem with modern agriculture is hinted at by the Economist's reference to "food prices". The commoditisation of most food staples has meant that most people consider a banana to be a banana, a carrot to be a carrot, and so on, without any understanding of how the item was grown and treated, and as a result, what it actually contains. So one banana should cost the same as the rest of them, and there should be a central "banana price" which we can all fret over, and measures of "banana yield" as well. This is different to how we think of most products, including some foods (e.g. wine, and increasingly coffee and chocolate).

The fact is that the food we see is just a package for what we actually need (or desire) - tiny invisible nutrients, many of which we are yet to identify. One banana can be markedly different from another on many dimensions, but until recently we have only optimised for one dimension: price.

I highly recommend Michael Pollan's books, particularly the first third of The Omnivore's Dilemma, where he describes this process with respect to corn.