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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #220353

Title: Rate of Nitrogen Application during the Growing Season and Spraying Plants with Urea in the Autumn Alters Uptake of other Nutrients by Deciduous and Evergreen Container-Grown Rhododendron

Author
item Scagel, Carolyn
item BI, GUIHONG
item FUCHIGAMI, LES
item REGAN, RICHARD

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2008
Publication Date: 9/21/2008
Citation: Scagel, C.F., Bi, G., Fuchigami, L., Regan, R. 2008. Rate of nitrogen application during the growing season and spraying plants with urea in the autumn alters uptake of other nutrients by deciduous and evergreen container-grown Rhododendron. HortScience. 43:1321-1627.

Interpretive Summary: The influence of nitrogen fertilizer rate during the summer and spraying plants with urea in the autumn on the uptake of nutrients other than N was assessed using one-year-old, container-grown rhododendron (Rhododendron 'H-1 P.J.M') and azalea (Rhododendron 'Cannon’s Double'). Spraying Rhododendron with urea in the autumn alters uptake and allocation of nutrients other than N; however, although spraying may increase uptake of specific nutrients and allocation to storage by some cultivars it may cause losses of nutrients in other cultivars. The influence of urea sprays in the autumn on uptake of nutrients has potentially positive benefits for growth the following spring; however, when using urea sprays in the autumn as an N management technique during nursery production, plant demand for other nutrients in the spring may also be higher. Consequently spring fertilizer practices may also need adjustment to ensure optimal growth. A better understanding of the physiological changes induced by urea sprays is required for predicting plant responses to this practice.

Technical Abstract: The influence of N rate during the growing season and spraying plants with urea in the autumn on the uptake of other nutrients was assessed using container-grown rhododendron (Rhododendron 'H-1 P.J.M') and azalea (Rhododendron 'Cannon’s Double'). Plants were grown with a complete fertilizer containing different N rates from May to September of 2004, sprayed or not with urea in the autumn, and grown with a complete fertilizer containing different N rates in the spring of 2005. Plants fertilized with 10 mM or greater N in 2004 contained similar concentrations and contents of most macronutrients in the winter of 2004. In general, rhododendron stored nutrients primarily in roots and 2004 leaves and azalea primarily stored these nutrients in roots and 2004 stems. Spraying rhododendron with urea increased P, Ca, and Mn uptake and storage. Spraying azalea with urea increased Cu uptake and storage, and decreased K uptake and storage. Urea sprays also caused shifts in Fe, Mn, and Zn allocation by azalea. Spraying plants with urea increased the demand for P, K, and S in the spring of 2005 by both cultivars and increased the demand for Ca by rhododendron and K, Mg and Mn by azalea. Increased P and Ca uptake by rhododendron sprayed with urea in 2004 was correlated with plant growth in 2005. Our results indicate that spraying Rhododendron with urea in the autumn alters uptake and allocation of nutrients other than N; however, although spraying may increase uptake of specific nutrients and allocation to storage by some cultivars it may cause losses of other nutrients. The influence of urea sprays in the autumn on uptake of nutrients has potentially positive benefits for growth the following spring; however, when using urea sprays in the autumn as an N management technique, plant demand for other nutrients in the spring may also be higher. Consequently spring fertilizer practices may also need adjustment to ensure optimal growth. A better understanding of the physiological changes induced by urea sprays is required for predicting plant response to this practice.