Raphanus sativus var. longipinnatus 

Dual purpose cover crop and food crop! The long tapered white roots can be eaten raw, fermented or pickled. As a cover crop Daikon is used to help break up clay based or compacted soils - like those from a former pasture. Daikon is great when combined with other cover crop plants like buckwheat. In the summer this combination helps build soil structure and to suppress weeds. 

photo attribution: Ctg4Rahat, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons