TY - JOUR T1 - Effect of Nitrogen Application Timing on N Uptake by <em>Vitis labrusca</em> in a Short-Season Region JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 246 LP - 252 DO - 10.5344/ajev.2004.55.3.246 VL - 55 IS - 3 AU - Randall J. Vos AU - Thomas J. Zabadal AU - Eric J. Hanson Y1 - 2004/01/01 UR - http://www.ajevonline.org/content/55/3/246.abstract N2 - 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. ER -