Yeast Growth in Riesling Juice as Affected by Vineyard Nitrogen Fertilization

Nitrogen (N) fertilizer was applied through drip irrigation to a mature vineyard of Riesling grapes at rates of 0, 56, 112, or 224 kg N/ha/year from 1986 to 1988. Growth in juice of Saccharomyces cerevisiae str. Epernay, as measured by Klett turbidity, increased with increasing N fertilization. Only two of 16 juices from the 0 kg N/ ha vines completed fermentation, while only seven of 16 juices from the 56 kg N/ha vines completed fermentation. Only one of 32 juices from the 112 and 224 kg N/ha vines did not complete fermentation. Assimilable N concentration of about 150 mg/L juice was required for completion of fermentation, a concentration achieved by applying 112 kg N/ha/year to a N-deficient soil. Information obtained in other portions of this study indicated that excessive canopy growth and an unacceptable delay in fruit maturation occurred when more than 56 kg N/ha/year were applied.