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Does Water Stress Reduce Shaker Injury?

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Tests show shaker injury unaffected by irrigation.

Everyone knows that you have to cut off the water well before harvest in order to minimize shaker injury to almond trees. Right? Well, maybe not, says Ken Shackel, pomologist at UC Davis. He's been testing that thesis for years and in his latest experiment, the results of which were released last year, all indications are that irrigation is not a factor.

Shackel irrigated 408 almond trees in three plots in the Bakersfield area with different treatments: wet, medium and dry. The wet plot got full irrigation to within two days of harvest. The medium plot had its irrigation cut off at the normal time - nine days before harvest. The dry plot had its water removed 21 days before harvest.

All three plots had some water stress in mid-August because of irrigation system problems. The experiment included 296 25-year-old trees and 112 replant trees in the four- to seven-year-old range.

All but 36 of the trees were shaker-harvested according to normal practice. The 36 (14 older trees and 22 replant trees) were shaken at high pressure (2000 psi) for a long period (15 seconds) in an attempt to cause damage.

Surprisingly, no shaker damage could be observed in any tree regardless of tree age, irrigation treatment or severity of shaking. These results agreed with those found in 1997.

Shackel concludes that his experiments refute the commonly held belief that irrigation cut off is necessary to strengthen almond bark and to reduce tree susceptibility to shaker injury.