Impact of nitrogen fertilization on vine performance and juice and wine composition of 'Riesling' grapes (Vitis vinifera L.) in Washington State

Nitrogen fertilizer was applied through the drip irrigation system to a mature vineyard of 'Riesling' grapes at rates of 0, 56, 112 or 224 kg N(.)ha(-1.)year(-1) from 1986 to 1988. Petiole nutrient levels, yield, vine size, fruit composition, date of harvest at 21% soluble solids, wine composition, and rate of yeast growth in the juice were all influenced by level of nitrogen fertilization, In 1991, wines were analyzed for free and bound monoterpene, higher alcohol, and eater content. Depending on the compound and the vintage, the concentrations of some foe or bound monoterpenes were affected by vineyard N fertilization rate. Application of at least 112 kg N(.)ha(-1.)year(-1) was required to attain juice N concentrations sufficient for "healthy" yeast fermentation. However, this level of fertilization resulted in excessive vine growth, fruit shading, and delayed fruit ripening. Therefore, application of no more than 56 kg N(.)ha(-1.)year(-1) was recommended for 'Riesling' vines grown in N deficient soils.