as a method of "hugelkultur", by putting them in the soil either under or around whatever you are planting, hollow side up. This would create little "buckets" to hold water, and slowly rot away over time, normally by which time the tree will be more able to retrieve its water from deeper in the subsoil. Cheers.
Why is the word "abbreviation" so long? And this ad is so short?
learn permaculture through a little hard work and get an acre of land