The Application of Foliar Sprays Containing Nitrogen, Magnesium, Zinc and Boron to Apple Trees. I. Effects on Fruit Set and Cropping

Abstract

SummaryIn field experiments on cvs Discovery and Cox’s Orange Pippin urea sprays sometimes increased fruit set even on trees judged to be of high N status. ‘Solubor’, supplying B, was inconsistent in effect, sometimes reducing set, and “sprays of MgSO4 and ZnSO4 were both ineffective. The ZnSO4 sprays increased the number of fruit buds, but set was reduced so that yield was unaffected. A multiple treatment in which the nutrients were sprayed separately damaged the leaves and reduced fruit set and yield; this was due to spraying with Solubor in addition to urea and MgSO4. A proprietary foliar spray, contributing only small amounts of nutrients, was ineffective.