The Effect of Source and Rate of Potassium on the Performance of ‘Concord’ Grape Vines Grown on Clay Loam Soils1

Abstract

Abstract The responses of ‘Concord’ grape vines (Vitis labrusca L.) to 3 potassium fertilizer sources (KCl, K2SO4, and KNO3) used at 2 rates were compared. Fertilizers were applied for 10 years to vines on a poorly drained Jeddo clay loam soil. Performance on a moderately well-drained Oneida clay loam as influenced by KCl and K2SO4 levels was also studied. There was no reduction in yield, fruit quality, or vine vigor with high rates of KCl. KCl and K2SO4 were equally effective in increasing petiole K but the response was slow under Jeddo clay loam conditions. Yield, vigor, and petiole K levels were less with vines receiving KNO3 than with those receiving other sources of K, or with the non-treated control vines. KNO3 was undesirable as a source of K. Petiole K was higher in grape vines growing on Onedia clay loam than on Jeddo clay loam; in addition, they responded more quickly to applied K irrespective of source. There was an indication of a yield response one year to high levels of KCl but no such response occurred with K2SO4. No toxic response to high rates of KCl was detected at either location.