RT Journal Article SR Electronic T1 Effect of Nitrogen Application Timing on N Uptake by Vitis labrusca in a Short-Season Region JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 246 OP 252 DO 10.5344/ajev.2004.55.3.246 VO 55 IS 3 A1 Randall J. Vos A1 Thomas J. Zabadal A1 Eric J. Hanson YR 2004 UL http://www.ajevonline.org/content/55/3/246.abstract AB Fertilizer nitrogen (N) was applied to Vitis labrusca L. cvs. Niagara and Concord grapevines in Michigan at various times to determine its effect on soil N levels and fertilizer N recovery in vine tissues. Labeled ammonium nitrate (15NH415NO3) was applied to the soil beneath vines at a rate of 68 kg N/ha at different times between budbreak and six weeks after bloom. Soil was sampled at one-to two-week intervals after the fertilizer applications to follow the inorganic soil N dynamics. Vines were excavated at the time of commercial grape harvest to quantify fertilizer N recovery. All times of fertilizer application resulted in less than 20% uptake of the N applied. Vines fertilized at budbreak generally contained less fertilizer N and allocated a greater fraction of the fertilizer N to fruit and leaves than later times of application. Vines fertilized later in the season absorbed more fertilizer N and allocated more of it and total N to the roots than earlier times of application. Later applications resulted in more fertilizer N remaining in the top 90 cm of soil at the end of the season. Based on these findings, N application to vineyards in this short-season region was more efficient between bloom and six weeks after bloom than at budbreak.Acknowledgments: The authors wish to thank the Michigan Agricultural Experiment Station and Project GREEEN for support of this work.