In some of my smaller orchards that I manage by hand, I use Egyptian Walking Onions as they spread very quickly, smoother weeds and can work as a chop and drop (not to mention green onions to eat). My initial reason for planting them under apple trees was to encourage robust Sulphur cycling. I have since heard from Fedco Trees in Maine (US) that they plant garlic under the fruit trees to discourage Plum Curculio from finding trunks in Spring time. I will also be trying out Garlic Chives as they naturalize well. Do you have any thoughts on the Sulphur idea?