Gerald H. Neilsen

Late-Season Foliar Urea Applications Can Increase Berry Yeast-Assimilable Nitrogen in Winegrapes (Vitis vinifera L.)

In the Okanagan Valley of British Columbia, low rates of nitrogen fertilizer are typically applied early in the growing season to prevent excessive vine growth, disease, and adverse changes in grape juice composition. As a consequence, grape juice yeast assimilable nitrogen (YAN) concentrations at harvest are often below the level considered sufficient to complete fermentation during winemaking and require augmentation with additional nitrogen. Over a three-year period at seven study sites planted to five winegrape varieties, late-season foliar applications of urea-N were investigated as a method for enhancing grape juice YAN. Foliar-applied solutions of urea at rates equivalent to 14–18 kg N/ha/yr (1% w/v, applied in one year only) or 28–36 kg N/ha/yr (2% w/v) caused significant improvements in grape juice YAN concentrations in six out of seven of the study sites each year, but there was no consistent pattern among years as to which study sites were most amenable to treatment. Little of the N applied in the foliar spray treatments appeared to be retained by the vines, and there were only few, small negative effects of treatment application on vine performance and juice quality. Thus, urea sprays applied to the foliage around the time of veraison show considerable promise as a supplement to more traditional soil fertilization programs on these and similar sites.

EFFECT OF TYPE, RATE AND INCORPORATION OF LIME AND OF NITROGEN FERTILIZER AND GYPSUM ON MOVEMENT OF LIME IN SOIL COLUMNS

Soil columns were used to study downward movement of calcite and dolomite applied at two rates on the soil surface or incorporated 0–5 cm deep in combinations with gypsum and surface-applied N fertilizer. The columns were irrigated with 800 mm of deionized water applied over 3 wk. Incorporation of the liming materials greatly accelerated their downward movement in soil. Calcite and dolomite were equally effective in raising soil pH at the lower depths. Neither gypsum nor fertilizer nor doubling the liming rate had much effect on lime movement. Key words: Lime movement, calcite, dolomite, gypsum