Every tree is an individual, with its own unique environmental, soil and underground conditions. Even a few feet can make a substantial difference in overall requirements. Some adjustment of these guidelines may be necessary for each tree. .
Your new tree's root zone is small, so it will dry out quickly. This is why new trees need more frequent watering until the roots grow outward and can soak up more of the ground water. If proper watering is performed in the first year, the tree should be well established and able to thrive mostly on its own going forward.