A scientific study in Turkey revealed that two foliar KNO3 sprays at 1% or 2% statistically significantly increased yield and hundred berry weight compared to the control. The trial was designed in randomized blocks with 4 replications in a 10 year old vineyard with two varieties; Colombard and Carignane. Soil analysis results showed a sandy-loam texture, high pH, low organic matter content and 130 mg/kg available K in the soil. Best result was observed with two sprays of 2% KNO3, which increased the yield of Colombard grapes with 24% and Carignane with 43% compared to the control (Figure 1). Furthermore, foliar potassium nitrate sprays both at 1% and 2% increased total soluble solids (TSS) and improved leaf N and K contents, although not statistically significant. It was concluded that the doses of 1% and 2% can be suggested for agricultural practice.
Figure 1. The effect of KNO3 sprays on the yield of Colombard and Carignane grape varieties.
Altındişli, A., M.E. İrget, H. Kalkan, S. Kara and M. Oktay. 1999. Effect of foliar applied KNO3 on yield, quality and leaf nutrients of Carignane and Colombard wine grapes. Springer Netherlands - Improved Crop Quality by Nutrient Management, 103-106.