Earlier quoted context omitted.
This is for good reason though. You want to overproduce significantly in ordinary times so that if there is a big negative shock you will still be able to produce enough to feed everyone merely by not destroying the excess anymore.
But in a pure market that would mean that during overproduction times, prices should be low. Which they artificially aren't through industry price fixing.
The result that free markets are Prato optimal, though, requires conditions like low barriers to entry, perfect information, and low cost transactions… none of which seem very well met in the case of agriculture.