Q. My fig tree is receiving 12 gallons of water a week in the middle of the summer. I water it for 40 minutes, three times a week right now while it is hot. Some of the leaves are brown on the edges. The fruit did not mature and they dropped off.
A. 12 gallons of water a week is not enough. Trees at the University Orchard in North Las Vegas that are 6 to 7 feet tall and about just as wide should get 30 gallons of water, three times per week or a total of 90 gallons.
Fruit trees are moderate water users but the soil cannot become dry when they are producing fruit. If it does, it affects the fruit size and quality and it's possible it may not develop at all.
When figs are not given enough water (either the quantity is not enough or they are not receiving water often enough) the fruit becomes small, hard and often times drops from the tree.
I don't know how much of this water is actually getting to the roots. When watering, enough water should be applied in a single application to water roots to a depth of 18 inches, minimum, 24 inches is better.
The water should be applied under the canopy so that at least half of the area under the canopy is wet.
Take a piece of 3/8 inch rebar and push it into a wet area under the trees canopy. You should be able to push it easily to this depth. Pushing it into the soil easily means the soil is wet. It pushes with a lot of difficulty if the soil is dry.
Applying a 4 inch layer of surface mulch helps keep the soil moist, reduces fruit drop and improves fruit quality. Both rock and wood surface mulch works but wood is better for fruit trees.
I am guessing a tree that is 4 feet tall might require 15 to 20 gallons, three times per week right now.