If it's like most other farm ground it has probably had the stew farmed out of it. Sounds like he may be trying to incorporate some organic matter back into the soil profile. Carbon, an esential plant nutrient, takes a while to become plant available.....my prediction is he'll plant a cropnext spring, after some of the OM breaks down to a labile source of C. People out west let their field sit fallow (in grass) for this very reason, plus prevents salt build up from evapotranspiration. That or he's working for PETA. Sounds like the deer will be bedding in the woods your hunting instead of the grass field. Good luck.