Q. How many gallons should a fruit tree receive for each watering if it’s trunk is 1.5 inches in diameter 24 inches above the ground? A. Watering amounts are usually related more to the size of the canopy or total height than the trunk. Trunk size is sometimes used more for estimating how much fertilizer to apply.             That tree size would require around 10 to 15 gallons for each watering. If you are using drip emitters, you should be using four (4) emitters in a square pattern 12 to 18 inches from the trunk. So running 3 gallon per hour emitters for one hour would equal 12 gallons. Just to remind readers we follow the PET curve developed for here and is below. Months are January=1 to December=12. Numbers on top of the bars represent inches of water per day. We would change irrigation frequencies in months 2, 5, 7, 8, 10 and 12.The amount applied each time stays relatively constant, just the times per week is changed.