It is a good idea, once the basin has stabilized, to cover the bottom with straw, sawdust or some other mulching medium. As the roots extend further outward and downward, you will want to add more emitters and move them further away from the trunk of the tree. Under normal circumstances, water the young tree every 5 to 10 days for a period of 6 to 10 weeks. Two to five gallons of water per irrigation will be sufficient provided the ball itself receives water each time and remains damp inside. If you plan to plant these trees in areas where root rot has occurred, or if the area has become secondarily contaminated with Phytophthora cinnamomi, chemical control of this pathogen is recommended to assist the establishment of the trees.
Avocados are native to areas which, unlike California, have almost daily rains during the summer.
Their favored soils under these conditions are often acid, sandy and weak, characterized by good internal drainage which doesn't allow them to remain soggy. Therefore, once your tree has begun to establish a root system, keep the soil damp but not soggy. Apply water according to the needs of the tree. The tree may be watered by basin for a full year. However, the basin should be broken down during the wet season if water has any tendency to stand in it.