The Effect of Municipal Wastewater Irrigation and Rate of N Fertilization on Petiole Composition, Yield and Quality of Okanagan Riesling Grapes

Okanagan Riesling (Vitis sp.) vines, planted on a sandy soil in 1983, were trickle irrigated with municipal wastewater or well water and with each source of water there were 3 rates of N fertilization (0, 17 and 34 g N as NH4NO3 vine−1 y−1), 1984–1987. The zero-N treatment was increased to 8.5 g N vine−1 in 1986–1987. Wastewater-irrigated vines had increased petiole P, K and Ca but decreased Mg and in 2 of 3 yr decreased N in August. Increased rate of N fertilization increased petiole N at bloomtime but not in August, had minor effects on petiole P, K, Ca and Mg, and increased petiole Mn at highest N rates, especially (2 of 4 yr) in association with wastewater irrigation. Yield increased both for vines irrigated with wastewater and linearly with rate of applied N in 2 of the 3 fruiting years. Increased yield was not associated with increased petiole N concentration in August. Minor increases in soluble solids and juice pH of grapes at harvest were measured for wastewater-irrigated grapes in 2 yr. No horticultural limitations to the use of this wastewater to irrigate Okanagan Riesling grapes were observed over the 4-yr period.