Mark Shepard likes to brag about how he gets less half a harvest of six+ different species in the same field. He's still getting 2-3x as much food out of the space. Most importantly, I believe (and he agrees), when you monocrop you go for broke. If something goes wrong, you have very little to sell at the end of the year. If it's a bumper crop year, prices will be depressed if it's a good year for everybody. In either scenario, the dealer (bank) always wins.

With six crops, the standard deviation between good years and bad years is reduced, which makes farming less of a trip to Vegas. That he gets more out of the same land brings up his average expected income. It's more work, yes, but he points out that many farmers have to take a side job to make ends meet, and he theoretically doesn't (he speaks and consults), so he can invest that time into increasing his farm's productivity.