Effect of nitrogen application timing on N uptake by Vitis labrusca in a short-season region.

摘要

N fertilizer was applied during 2001 and 2002 to V. labrusca cultivars Niagara and Concord in Michigan, USA, at various times to determine its effect on soil N levels and N fertilizer recovery in vine tissues. Labelled ammonium nitrate (15NH415NO3) was applied to the soil beneath the vines at 68 kg/ha at various times between bud break and 6 weeks after bloom. Soil was sampled at one- to two-week intervals after fertilizer application to follow the inorganic soil N dynamics. Vines were excavated during commercial grape harvest to quantify fertilizer N recovery. All times of fertilizer application resulted in less than 20% uptake of the N applied. Vines treated at bud break generally contained less N fertilizer and allocated a greater fraction of the N fertilizer to fruits and leaves than those treated at later dates. Vines supplied with N fertilizer later in the season absorbed more N fertilizer and allocated more of the fertilizer and total N to the roots than those supplied with N fertilizer earlier. Later applications resulted in more N fertilizer remaining in the top 90 cm of the 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 6 weeks after bloom than at bud break.