Vegetative Growth and Nitrogen/Carbon Partitioning in Blueberry as Influenced by Nitrogen Fertilization

in Journal of the American Society for Horticultural Science
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  • 1 Horticultural Sciences Department, University of Florida, Gainesville, FL 32611

Nitrogen uptake and N and C partitioning were evaluated in `Sharpblue' southern highbush blueberries fertilized with different N forms. Plants were grown in acid-washed silica sand and fertilized with a modified Hoagland's solution supplemented with 5.0 mm N as NH4+ or NO3-. Nutrient solution pH was adjusted to 3.0 and 6.5 for the NO3- and NH4+-treated plants, respectively. After 12 months of growth, plants were dual labeled with 14CO2 and 10% enriched 15N-N as either NaNO3 or (NH4)2SO4 and harvested 12 hours after labeling. Fertilization with NO3--N increased leaf, stem, and root dry weights compared to NH4+ fertilization. Total 15N uptake did not differ between N fertilization treatments, thus whole plant and root 15N concentrations were greater in NH4+-fertilized vs. NO3--fertilized plants. Fertilization with NO3--N increased C partitioning to new shoots compared to NH4+-fertilized plants. However, C partitioning to other plant parts was not affected by N form. Although NO3- uptake in blueberry appears to be restricted relative to NH4+ uptake, this limitation does not inhibit vegetative growth. Additionally, there appears to be adequate available carbohydrate to support concurrent vegetative growth and N assimilation, regardless of N form.

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