What's the best spring planting to build soil? I plan to only have about 2 months of growth--plant mid May and till under July 4th. Located near the northern tip of Wisconsin.... I was considering Buckwheat or Clover. Which would you choose, or is there something different you think is better than these two? I should add, the main purpose of me doing this is to be able to plant Big and Beasty every year.