If you have all the information concerning the individual plant site, the following pieces of this puzzle fall into place. We find out our tree needs 12 gallons of water per day. Now we need to determine the number of drippers needed to apply 12 gpd to the 10' tree. Different plant species can vary considerably in their rates of evapotranspiration.
Some plants transpire large amounts of water, while others use relatively little.
Values for plant factor or crop coefficients are sometime available through local sources such as Agricultural Extension Services and local newspapers. Check in your area. When available, this data tends to be more accurate and can save time.