Phosphorous and Potassium Nutrient Management for Tart Cherry Productivity and Quality

Recent work with apples has shown that supplemental phosphorus (P) and potassium (K) improve fruit quality under high crop load conditions when conventional soil tests would indicate sufficiency.  Fruit producers in Utah are interested in whether or not a similar positive response could be obtained for tart cherries (Prunus cerasus ‘Montmorency’).  Different rates and formulations of P and K were applied to replicated single-tree plots of mature tart cherries in 2009.  Formulations included Steric Potassium (SK), Steric Phosphorus and Potassium (SPK), Potassium Sulfate (SOP), and 16:16:16.  Fruit and leaf tissue samples from the treatments were compared for P and K content, and fruit quality was evaluated on the basis of soluble solids, titratable acidity and color.  The 16:16:16 formulation applied twice during the early growing season showed the most significant increase in fruit quality and the highest tissue P and K concentrations.  These early results indicate that growers can improve tart cherry fruit quality with a relatively low-cost source of P and K fertilizer.