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Building soil quality, enhancing soil microbial function, and alleviating chlorosis in Concord grapes with inter-row cover crops

Leaf yellowing, or chlorosis, occurs on more than 50% of the Concord vineyards in central WA, resulting in significant reductions in vine size, uniformity, and productivity. The yellowing of the leaves resembles classic Fe-deficiency chlorosis, however many studies have attempted without success to determine the precise cause and effective treatment of this type of chlorosis. All work, to date, supports the concept that some aspects of soil quality, specifically soil biogeochemistry, is involved in grape chlorosis in Washington state. We conducted a pilot study in 2014 to assess possible relationships between soil microbial community and Concord chlorosis and discovered a significant correlation between rooting zone bacterial community composition and Concord leaf tissue Fe content. We now propose to expand the study by testing a panel of four cover crops known to enhance soil quality by means of siderophore production, nitrogen fixation, or simply building soil organic matter and enhancing biological activity as a means to manage beneficial soil microbes. Two different orchards will be tested with five replicate plots of each cover crop and a bare-soil control at each orchard.  Measures of chlorosis severity, soil quality, fertility and microbial community composition and function will all be assessed over two years. This research proposal will best fulfill the first BioAg priority area: “Biologically intensive and organic approaches to building soil quality;” but also strongly addresses the second priority area: “Novel approaches to weed, disease, pest and/or fertility management that transcend traditional conventional or organic approaches; and that seek to exploit and integrate biological, chemical and physical processes.” The fundamental goal of this research is to economically enhance Concord grape production through microbial biogeochemistry.

Grant Information

  • Project ID: 163
  • Project Status: No-cost extension granted


  • Principal Investigator(s): Sullivan, T.
  • Investigator(s): Davenport, J.
  • Grant Amount: $39,978