Prevent the root zone from becoming too dry or too wet. Water use in winter is low but continues-light, shallow rains are misleading, so use a rain gauge.  On shallow soils don’t limit roots by limited water distribution.  Use a wider water pattern and less volume.  Don’t over irrigate above hardpans.  Short frequent irrigation may be necessary.  One inch of rain equals one watering cycle.  Excess moisture will cause the feeder roots to rot and the tree will wilt or die.

Dry soils tend to result in tip-burn and sunburn both on foliage and fruit and will cause dieback the following season.  Dryness also reduces fruit growth and increases fruit drop.  Avocado trees can be permanently damaged by sunburn when the soil is too dry.

Trees need about 4 to 5 acre feet of water (about 1,304,000 gallons per acre) per year, including rain.  Determine timing by using tensiometers (12 and 24-inch instruments, with results plotted on a graph) , and constant observation.  Apply enough water periodically during summer and fall to leach salts to lower levels and prevent salt buildup in root zones.  Leaf tip-burn, from salt excess, is usually a sign of inadequate irrigation or too much salt in the water or both.

Normal irrigation intervals for avocados are about once every 7-10 days from 8-12 hours depending on your sprinkler volume and time of year.  Hot weather require closer intervals and longer duration.  The avocado cannot tolerate drought.  Excessive moisture is also bad because it restricts the root activity and favors foot diseases.  Let the root zone dry out a little between watering.

The soil serves as a moisture reservoir.  Water is stored in the spaces surrounding soil particles.  Clay soils store more water per unit volume than sandy soils.  Weather conditions and amounts of leaf surface determine how fast your trees use water.  Two factors thus determine irrigation needs:  How much water the soil holds and how much water is being used.  It is just as important to know when to turn the water off as to when to turn it on.