Response of Zweigelt Grapevine to Foliar Application of Potassium Fertilizer: Effects on Gas Exchange, Leaf Potassium Content, and Incidence of Traubenwelke

ABSTRACT

Zweigelt grapes have recently become susceptible to infestation with Traubenwelke (grape wilting) and the susceptibility has been assumed to be related to potassium (K) deficiency. The aim of the studies was to determine the effects of foliar application of K on leaf K content, leaf gas exchange, and on infestation of grapes with Traubenwelke. Three foliar fertilizers of K (Agripotash, 27.4% K; Nutrileaf, 33.2% K; and KNO₃, 38.7% K) and one of magnesium (Mg) (Agrovit Mg, 4.8% Mg) were tested on grapevines (Vitis vinifera, L. cv. ‘Zweigelt’) in field studies in 2003 and 2004. Foliar analysis showed that the tested foliar fertilizers had no effect on leaf K content in either year. Furthermore, the frequency of infestation with grape wilting was not reduced by K fertilizers. Measurements of leaf gas exchange in 2004 showed that all fertilizer treatments reduced photosynthesis (A) and stomatal conductance (gs) compared with the untreated control.

Keywords:

• potassium
• foliar fertilizer
• Zweigelt
• Traubenwelke
• grape wilting
• photosynthesis

ACKNOWLEDGMENTS

The authors are indebted to the Federal State Burgenland and the Vereinte Winzer Pannonien, Andau, Burgenland, for financial support of the study.

Notes

¹Samples at bloom 2004 were taken from the vines treated in 2003.