INFLUENCE OF FOLIAR NUTRIENT SPRAY CONCENTRATION ON LEAF ABSORPTION AND PHYTOTOXICITY ON APPLE

In order to assess the effects of different carrier water volumes (1500 L/ha, 300 L/ha and 150 L/ha) of foliar sprays of MnSO₄·H₂O (750 g/ha), Mg(NO₃)₂·6H₂O (7500 g/ha), CaCl₂·2H₂O (3750 g/ha) and urea (6000 g/ha) on nutrient absorption, field trials were carried out for two years (1999-2000) in ‘Golden Delicious’ apple orchards. In addition, the incidence of phytotoxic side effects was investigated. The experiments were designed as randomized blocks with four replications. Two treatments per trial were applied between May and June, leaf damage was assessed after each application, leaf samples were taken for chemical analysis 3-4 weeks after treatment and fruit samples were assessed at harvest for incidence of russetting. Leaf analysis revealed a significantly increased foliar nutrient content with decreasing spray volume in the case of Mn and Mg. None of the treatments lead to leaf scorch or increased fruit russetting. These results indicate that low volume sprays of foliar fertilizers can improve nutrient absorption without increasing negative side effects such as leaf scorch or fruit russetting.