Cherry orchards in north Selah, Washington. (TJ Mullinax/Good Fruit Grower file photo)

Cherry orchards in north Selah, Washington. (TJ Mullinax/Good Fruit Grower file photo)

Is irrigating cherry trees during the lead-up to harvest a good or a bad thing?

Dr. Matt Whiting, cherry horticulturist with Washington State University in Prosser, says there are two schools of thought among growers.

Some insist that stopping irrigation two or even three weeks before harvest is the way to produce high quality
cherries. Others claim it’s best to irrigate continuously up to the point of harvest.

Whiting is proposing a two-year research project to resolve the issue and help growers improve cherry quality and, therefore, their profitability. He’ll do trials in an attempt to understand the effects of near-harvest irrigation on key fruit quality traits, such as size and firmness and susceptibility to pitting.

He plans to compare the effects of two irrigation regimes in commercial orchards, one in the southern part of the state and one north of Wenatchee. One irrigation regime will be regular irrigation right up to harvest. The other will not be
irrigated for two to three weeks before harvest.

During the Washington Tree Fruit Research Commission’s cherry research review, Whiting explained that data will be collected on several aspects in each orchard.

Soil texture will be characterized and soil moisture will be monitored using a ­neutron probe at intervals of two to three days, beginning two weeks before the ­irrigation treatments begin.

Tree stress will be assessed by using a pressure bomb to measure stem water potential. Photosynthesis, transpiration, and stomatal conductance will also be monitored. Whiting will measure shoot growth before and during the treatments.

He will also look at how the treatments affect floral bud initiation and the following year’s crop.

Fruit growth will be monitored. Yield efficiency will be calculated and mature fruit will be evaluated for color, weight, soluble solids, firmness, size, stem retention force, and susceptibility to pitting.

Ines Hanrahan, project manager for the Washington Tree Fruit Research Commission, will work with Whiting on the project, along with graduate student Nadia Valverdi, a Fulbright scholar from Argentina. •