WSU--Tree Fruit Research & Extension Center

Research Summaries


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Orchard soil management and deciduous fruit tree nutrition

Frank J. Peryea, Associate Soil Scientist and Associate Horticulturist, WSU

Micronutrient nutrition

Deficiencies of micronutrients frequently occur in Washington orchards. Zinc and boron deficiencies are the most common and are controlled by regular use of zinc and boron fertilizers. Iron and copper deficiencies occur occasionally in certain fruit growing areas. Research at the WSU-TFREC focuses on improving methods to diagnose the micronutrient status of trees and on developing or refining fertilizer application practices to optimize micronutrient nutrition. Specific studies include determining the physicochemistry of micronutrients in orchard soils and in foliar nutritional sprays; comparing the various forms, rates and timings of zinc and boron fertilizers on tree growth and fruit quality; testing of management practices to reduce iron chlorosis; and evaluation of copper fertilization practices and their influence on apple fruit set and quality.

Predicting bitter pit development

Many orchardists spray calcium fertilizers on apple trees during the growing season to reduce the incidence of a physiological disorder called bitter pit. Although the calcium sprays often are effective, the quantitative relationship between fruit calcium and bitter pit development is poor. A collaborative project has been established between the WSU-TFREC and the Swiss Federal Research Station for Fruit-Growing, Viticulture and Horticulture in Wädenswil, Switzerland, to develop the mathematical framework for a stochastic prediction model relating the likelihood of bitter pit development to one or more independent predictor variables, such as calcium spray rate or fruit calcium content. The objective is to devise a means of predicting the probability that a population of fruit will develop a bitter pit incidence that exceeds the maximum amount acceptable to a destination market. This predictive tool will help fruit growers to make informed decisions regarding calcium fertilizer programs and will help fruit shippers to determine how to best allocate different lots of fruit to various markets.

Management of old orchard soils

Soil used for tree fruit production before 1947 in Washington and later in other states and countries often contains residues of lead arsenate pesticides. Growth of fruit trees may be impaired when soil arsenic levels are high enough. Research at the WSU-TFREC is examining the geochemistry and bioavailability of lead and arsenic in these soils. Recent studies have confirmed that fruit accumulates very little lead and arsenic and that tree stunting is the principal concern in orchards. Current research is focusing on management practices to reduce soil arsenic phytoavailability and improve tree growth.

Washington State University
Tree Fruit Research and Extension Center
1100 N. Western Ave.
Wenatchee WA 98801

phone: 509-663-8181
fax: 509-662-8714

Wenatchee WA
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