Effect of Nitrogen Application Timing on N Uptake by Vitis labrusca in a Short-Season Region

¹ Department of Horticulture, Michigan State University, East Lansing, MI 48824

Email: zabadal{at}msu.edu

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.

Note:
Acknowledgments: The authors wish to thank the Michigan Agricultural Experiment Station and Project GREEEN for support of this work.

Key words: nitrogen isotopes, fertilization, ammonium, nitrate

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