It Pays to Watch Water Needs of Young Trees

To avoid stressing young trees and ensuring future productivity and orchard uniformity, a successful start for trees is important. This photo shows different growth based on different levels of SWP for young almonds (photo by Ken Shackel, UC Davis.)

Paying close attention to water needs of young almond trees and delivering the optimum amount of water at the right time has proven to not only improve the health and vigor of young trees, but to improve the bottom line.

Luke Milliron, orchard systems advisor in Butte, Glenn and Tehama counties, demonstrated the effect a good irrigation program has on tree productivity. Studies conducted by UCCE Specialist Bruce Lampinen showed that after eight years at seasonal average midday stem water potential at minus 8 bars, minus 12 bars and minus 16 bars, the cumulative yields differences were significant. At minus 8 bars, trees produced 3,500 pounds per acre or 14,000 pounds over eight years. At minus 12 bars, yields dropped to 2,807 pounds per acre and at minus 16 bars, yields were 1,687 pounds per acre or 6,748 pounds cumulative yield.

The summary of potential revenue loss from tree stress during canopy development phase was (in prices at the time of the research) $173 per acre at one year for each 1 bar of stress. Over eight years, loss per acre for each 1 bar of stress was $1,386.

To avoid stressing young trees and ensuring future productivity and orchard uniformity, a successful start for trees is important. Barriers include initial small rootzone, changing canopy volume and water needs and growing the rootzone. Initial irrigation for potted trees is also trickier, Milliron said.

Using refined ET estimates, basic irrigation can be done using historical ETc for an average orchard. Intermediate level irrigation is receiving weekly ETc reports for UCCE and applying a percentage of ETc based on tree age. Advanced level is receiving weekly ETc reports and applying a percentage ETc based on percentage of canopy shading at midday.

Critical information in developing a detailed irrigation program includes how much water is being applied, how much water is the soil storing, what is being lost from soil and canopy, how long between irrigations and how long to run irrigation. Milliron said looking at soil or plant water status is also important.

Questions include how long to run irrigation sets and how frequently, how quickly is water being lost and what is the soil bank account between irrigations.

As a backup to check plant water status or soil moisture, use a pressure bomb or rootzone soil moisture by feel or with a soil probe.

For those who don’t want to do the math involved in irrigation calculations, ET/irrigation system calculators can be found at Milliron believes that using regular pressure chamber readings is the most effective way to dial in young orchard irrigation management. You can learn more at

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Cecilia Parsons
Cecilia Parsons has spent the past 30 years covering agriculture in California for a variety of newspapers, magazines and organizations. During that time she has been fortunate to witness some of the important events that have shaped this diverse industry and worked hard to examine and explain these events for readers. When Cecilia first moved to the San Joaquin Valley in 1976, her first journalism job was at a small daily newspaper where she covered “farm news.” From there she branched out to writing for a dairy magazine and a regional weekly agriculture publication. Cecilia is part of a farming family from the rural community of Ducor where she also raises purebred sheep and is attempting to master versatility ranch horse riding.