You can add additional emitters or microtubes as needed. Newly planted trees require 5 to 8 gallons of water per week in summer, usually split between two applications, especially on sandy soils. The amount depends on heat, wind, and the soil's water-holding capacity. Drip irrigation should begin in each growing season while good, but not excessive, soil moisture exists. If you wait until soils are excessively dry, drip irrigation will penetrate vertically but have little horizontal spread.
More roots are satisfied with maximum lateral spread of moisture.
Each year, increase the amount of weekly irrigation about 50 percent. Adjust rates and frequency accordingly. Irrigation volume is changed principally by size or number of emitters, frequency of applica- tion, and hours per application. The least change is by pressure, which is specified by the manufacturer. Mature trees, depending on vigor and planting density, may use 24 to 50 gallons of water per week or about 26 acre-inches per season.