We water our olives too and use kaolin. Why don’t you use a jute cloth around the trees? Instead of tilling this leaves the soil untouched, alway better with microbes and mycorrhiza etc, avoids weeds, preserves moisture and is less work. Jute will eventually be composted. Just lift it to put in your fertilizers. And mulch on top would also be a good idea.
If you would put jute around the trunk alone, this would leave that part untouched. We are going to do that. For the rest around the tree we use wood chips as mulch and top the jute off too. If any weeds grow, we just cut them off. No tilling as olives have a lot of superficial roots like many trees btw.