Drip irrigation for application of potassium to tart cherry1

Abstract

Abstract Fertilization of fruit crops through drip irrigation is an efficient method of meeting the crop's nutritional needs, though cumulative effects or interactions with native minerals may be pronounced in the restricted zone of application. Sources of potassium (K) for tart cherries have not been previously compared for their effects on tree performance and possible interaction with other nutrients under conditions of drip application in an orchard. Our objective was to evaluate these factors by drip application of four rates (0, 0.35, 0.7, and 1.4 kg K2O per tree) of three sources (KCl, KNO3, and K2SO4) of K to tart cherry trees during three consecutive growing seasons. Application of non‐Cl sources of K by this method maintained foliar K within the sufficiency range and increased fruit yield in one year of the study, but had no effect on fruit size or quality. Maximum fruit yield was obtained at 1.5–2.0% foliar K. Application of non‐Cl sources suppressed uptake of calcium (Ca) and magnesium (Mg) in relation to the amount of added K. High rates of KCl resulted in chloride (Cl) toxicity, suppression of phosphorus (P) uptake, and increased manganese (Mn) uptake during the third year of the study. Drip application of K is a satisfactory method of providing K nutrition for cherries if Cl sources are avoided and foliar K, Ca, and Mg are monitored to avoid excess K rates and related, undesirable interactions.