If the hole is empty in 24 hours, the soil has good internal drainage. If it requires 48 hours to drain, the internal drainage is poor but adequate. If any water remains after 48 hours do not plant trees. Create a special raised bed or plant in a container if a tree is to be planted in the selected site. In Arizona it is not uncommon to confront a soil condition known as caliche.
Caliche is a chalky type soil, white in color and chemically composed of calcium carbonate.
It can be found in many forms throughout the soil such as solid layers or crumbled pieces. The solid layers will restrict drainage and need to be cracked or drilled to allow water drainage. Another problem with caliche is its high pH which restricts the uptake of micronutrients such as iron and zinc. Be prepared to add these nutrients if trees are planted in caliche based soil. Avoid poorly drained soils at all cost, they invite failure.