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Fate of 15N-Labeled Urea Applied to Mature Highbush Blueberries


To study the efficiency of fertilizer use by highbush blueberry (Vaccinium corymbosum L.), four mature ‘Bluecrop’ plants were treated before budbreak (21 Apr.) with soil applications of 15N-enriched urea at a rate equivalent to 40 kg N/ha. Leaf samples were collected at 1- to 4-week intervals during the season and whole plants were harvested at the end of the growing season (22 Sept.). Different plant components were separated, dried, weighed, and analyzed by mass spectrometry. Fertilizer-derived N was observed in leaves 2 weeks after application. The percentage of N from the fertilizer peaked 3 weeks after application (16.5%) and declined to ≈11% shortly thereafter. Plants recovered 32% of applied N by the end of the growing season. Leaves accounted for 32% of this total. Shoot tissue also accounted for 32% of fertilizer-derived N in the plant, with the highest percentage accumulating in young shoots. Less than 15% of fertilizer N remained in the soil at the end of the season.