As most responses agree, rye. Where I disagree is the amount needed. We have been broadcasting 20-25 pounds of rye for the past 8 years. We always get a thick enough stand to suppress weeds the next spring. We have played with decreasing the amount to 10 pounds and still can't see a noticeable difference. Some times we work in the seed with a VT but others we just leave it on top. Have seen little difference in those practices as well.