Seasonal Variation of Nutritional Status of Olive Plants as Affected by Boron Concentration in Nutrient Solution

Abstract

Ten-year-old olive plants, (Olea europaea L.) cv. ‘Chondrolia Chalkidikis,’ were cultured under ambient conditions in 50 L plastic pots containing inert sand-perlite medium and irrigated for a period of 18 months with 50% Hoagland's nutrient solutions containing 0, 0.5, and 5.0 mg boron (B) L−1. The highest B concentration in the leaves was observed during the period May–June, and declined afterwards. Potassium (K) concentration in the leaves was the lowest in winter, but reached the maximum during the period June–July. Conversely, calcium (Ca) and magnesium (Mg) concentrations increased during the period June–March of the following year. No differences in phosphorus (P), iron (Fe) and zinc (Zn) concentrations were recorded between the treatments. However, P concentration fluctuated from 0.1% to 0.3% D.M. (dry matter) during the year, showing many minima and maxima. Iron and manganese (Mn) concentrations increased gradually from January of the first year to January of the second year and declined afterwards. The highest Fe concentration was about 200 mg kg−1 (D.M.) while leaf Mn varied between 10–50 mg kg−1 (D.M.). Leaf nitrogen (N) concentration was more or less constant during the experiment. The −B and the +5.0 mg B L−1 treatments reduced significantly the percentage of perfect flowers and affected B concentration of inflorescences, as it was 3–4 times greater with 5.0 mg B L−1 in comparison with the control.