In an agricultural society, the farm makes sense as the focus of Chol HaMoed activity... Including uprooting kilayim - but did they really do that? Isn't that already done in Adar? Of course, the Gemara resolves it, but raises the question why the kilayim were specifically relevant to Chol HaMoed... On the side of cheap labor. But then how much do you have to uproot to rid yourself of kilayim? Plus, 2 mishnayot - one on watering trees and plants, according to the Chol HaMoed schedule. And one on trapping moles and mice that populate one's field, even on Chol HaMoed. [With apologies for my sneezing - the mic is sometimes a little too sensitive! - AG]