Effect of potassium, magnesium and nitrogen supply on grape juice composition of Riesling, Chardonnay and Cabernet Sauvignon vines

Abstract

The effect of nitrogen (0 and 60 kg/ha), potassium (0 and 60 kg/ha) and magnesium (0 and 60 kg/ha) supply on grape juice composition was studied in a factorial block design on 3 varieties (Chardonnay, Cabernet Sauvignon and Riesling) grown in the Sunraysia (Karadoc, Nangiloc) (warm, irrigated), Coonawarra (moderately cool) and Mornington Peninsula (Dromana) (cool) districts of Victoria. Increased nitrogen supply appeared to be the most important nutritional factor, significantly increasing grape juice pH and malate concentration in all 3 varieties, citrate in 2 and tartrate and potassium concentrations in 1. Increased potassium supply increased juice pH significantly in only 1 variety, but malate and potassium concentrations in 2. Magnesium was the only fertiliser whose application led, at least in 1 variety, to a significant reduction of grape juice pH. Most treatment effects on grape juice composition were quite small, but nevertheless significant, indicating that particular fertiliser applications could be used as a management tool for the production of quality winegrapes.