Ken plants many green manures. These are crops that add organic matter to the soil, some add nitrogen, some have roots that break up hard soil. Out in the field he has peas and oats planted where he will plant crops in a few weeks. These peas add nitrogen.
And by the mobile high tunnel he also has oats and peas. The roots will remain in the soil and add organic matter.
He will probably pasture the hens here later and they will eat the oats and peas.