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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #209579

Title: Autumn Application of Foliar Urea Alters Winter Storage and Nitrogen Uptake and Growth of Container-Grown Rhododendron and Azalea the Following Spring

item Scagel, Carolyn

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 3/25/2007
Publication Date: 7/1/2007
Citation: Guihong, B., Scagel, C.F., Fuchigami, L., Regan, R. 2007. Autumn application of foliar urea alters winter storage and nitrogen uptake and growth of container-grown rhododendron and azalea the following spring. HortScience. 42(4):939.

Interpretive Summary:

Technical Abstract: One-year-old liners of rhododendron (Rhododendron 'H-1 P.J.M.') and azalea (Rhododendron 'Cannon's Double') grown at different N fertilization rates were used to assess the influence of foliar urea application in the autumn and soil nitrogen (N) applications during the growing season on N storage, N uptake and use for new growth. N uptake efficiency during the first growing season declined with increasing rate of N fertilization. For both cultivars, foliar urea application in the autumn significantly increased plant N content without affecting plant size, regardless of plant N status. Leaves of rhododendron accumulated more N than other plant structures. Plants sprayed with foliar urea in the autumn had more new growth the following spring than plants receiving no urea regardless of whether plants received fertilizer in the spring. For azalea, N uptake in the spring was, in general, not affected by urea applications during the previous year. For rhododendron, urea application in the autumn decreased N uptake the following spring. For both cultivars, increasing N availability during the growing season increased the ratio of aboveground to belowground dry weight. Our results suggest that combining optimum soil N applications during the growing season with foliar urea application in the autumn can improve N uptake efficiency, increase N storage and optimize growth of Rhododendron.