Yield and grape must composition in 'Cabernet Sauvignon' grape vine subjected to potassium fertilization in high altitude soil

Potassium (K) increase in the soil can affect grape must yield and quality; and consequently, the quality of wine; however, studies in this field approaching altitude soil in Southern Brazil (used for viniculture) are scarce. The aim of the present study is to evaluate yield, critical K level in the leaves and their association with grape must composition in 'Cabernet Sauvignon' vines subjected to K application in high altitude soil in Southern Brazil. The experiment was performed in a 'Cabernet Sauvignon' vineyard subjected to the application of different K doses (0, 30 and 60 kg K2O ha(-1)) in three seasons. Potassium (K) availability in soil and leaves, as well as total soluble solids (TSS), pH, total titratable acidity (TA) content in grape must were evaluated. Potassium fertilizer applications increased K availability in the soil, but its concentration only increased in leaves collected at full bloom in the 2013/2014 season. Potassium applications in the soil did not affect yield, but K concentration increase in the leaves led to increased TSS and pH values in grape must, as well as to TA and tartaric acid decrease, a factor that can impair the quality of wine.