ABSTRACT:The aim of this research was to study the effects of application of 'hydrocomplex' (H) and 'Norway nitrate' (NN) fertilizers on leaf and fruit nutrient concentrations and some fruit quality parameters in the following apple (Malus domestica Borkh) cultivars (cvs. Black Ben Davis were 10 years old and grafted on MM 106 rootstock. The orchard was well managed and yield was approximately 60 kg/tree.)The experimental trees were central-leader trained and planted at a spacing of 4 × 5 m. Control plants were not fertilized. At the end of March, hydrocomplex (H) (12-11-18, MgO: 2.65%, S: 19.9%, B: 0.015%, Fe: 0.35%, Mn: 0.02%, Zn: 0.02%) and Norway nitrate (NN) (15.5% N, 19% Ca) fertilizers were applied at 0-75 kg per 0.1 hectare, in the following combinations: control, 25NN, 50NN, 75NN, 25H, 50H, 75H, 25NN + 75H, 50NN + 50H and 75NN + 25H. The previous year's fertilization per 0.1 hectare consisted of 35 kg N, 12 kg P and 20 kg K. The soil properties of the experimental orchard are given in Table 1. The soil samples were air dried, crushed to pass a 2-mm screen and analysed for pH at a 1:1 soil to water ratio, electrical conductivity in a 1:5 soil to water extract, texture (hydrometer method), CaCO 3 with a volumetric calcimeter and organic matter content after wet oxidation (PAGE et al. 1982).Leaf samples were collected on July 15 (mid-summer). Leaves were collected from the middle of moderately vigorous shoots from each tree around the canopy periphery, at shoulder height. Fruit samples were collected on September 15 (harvest period). All samples were initially washed once with tap water and twice with distilled water. Leaf samples were dried in a forced draft oven at 68 o C for 72h and ground in a mill to pass a 30 mesh screen. Fruit samples were freeze dried. Nitrogen was determined by Kjeldahl's procedure, B by the azomethine-H method (WOLF 1971), P by the ammonium phosphovanadomolybdate method (JACKSON 1970) and K, Ca, Mg, Fe, Mn and Zn by atomic absorption spectrophotometry. Flesh firmness was measured by an Effegi penetrometer (11 mm tip). Soluble solids analysis was performed with an Atago PR-1 electronic refractometer.The experiment was conducted and repeated for two years and the reported data are the means of the two years. The adopted experimental design was a randomized block with 10 replications of 10 treatments (fertilizer combinations) per cultivar. Diffe- 11 rences between means of nutrient concentrations of leaves and fruits were evaluated using L.S.D. at P < 0.05.
RESULTS AND DISCUSSIONApplication of 50 kg NN, 75 kg NN, 50 kg NN plus 50 kg H and 75 kg NN plus 25 kg H per 0.1 hectare significantly increased leaf Ca concentration of the cvs. Golden Delicious and Black Ben Davis (data shown for the cv. Golden Delicious) in comparison with the control on July 15 (Fig. 1). The role of Ca in postharvest physiology has been extensively studied. Calcium affects fruit quality and senescence by altering intracellular processes and the rate of fruit softening depends on Ca status. Calcium also plays...
