Must composition and nitrogen uptake in a long-term trial as affected by timing of nitrogen fertilization in a cool-climate riesling vineyard

摘要

A long-term, 15-year nitrogen (N) fertilization trial was carried out in Rheingau, Germany. While the control received no N, the fertilized treatments received 30, 60, or 90 kg N/ha. Treatments used in this investigation were 0/0, 30/0, 0/30, 60/0, 30/30, 0/60, 90/0, 60/30, and 30/60 (application of N/ha at budbreak/application of N/ha at fruit set). Fertilization at budbreak resulted in a peak of NO3 in the soil at fruit set; when N was applied at fruit set, the highest amounts of NO3 were found at veraison. Average NO3 concentration in the soil also increased with budbreak fertilization compared with fruit-set fertilization. Leaf analysis showed an increased N uptake with budbreak fertilization of 90 kg N/ha. Grape yield showed a reverse timing effect: earlier fertilization at budbreak resulted in lower yield. The same observation was made for total soluble solids when grapes were fertilized with 60 or 90 kg N/ha. The storage of Mg and Ca in grapes was increased by fruit-set fertilization compared with budbreak fertilization; in the highly fertilized treatment that was also true for N in must.