an acre is a nice size food plot for a 40 acre parcel of land--especially since you don't have a high number of deer in your area. The buckwheat will help choke out weeds during the summer and your fall planting of clover should do well. However--if it was me I'd skip the spring planting of buckwheat and concentrate on killing off all the vegetation in your future plot with the use of glyphosate. That way you will have a clean seed bed in the fall. One option is instead of planting buckwheat (which does do a good job on choking out weeds) is to plant roundup ready soybeans. This way you will still provide a great forage for the deer during the antler/fawning months but you can also spray with roundup (glyphosate) during the summer and keep the weeds and grasses under control.
best of luck
todd