Dry farming is entirely new to me David but from what I understand, a
deep planting hole with lose soil forces the roots to go deep in search
of ground moisture. This is said to give a better root system for the
plant to absorb nutrients. I have also read that a clay or clay loam
soil lends itself better to dry farming than does a sandy soil. The
clay simply retains more moisture for a longer period of time. There
are some areas where chefs seek out dry farmed tomatoes because of the
taste. They also sell for a much higher price which in part is due to
the lower yield I would suspect.

Rich