Seasonal variation of nutrient concentration in two olive (Olea europaea L.) cultivars irrigated with high boron water

The aim of this research was to study the effect of high boron (B) irrigation water on the appearance of B toxicity symptoms and on the seasonal variation of nutrients in leaves and fruits of two table cultivars of olive (Olea europaea L.). The cultivars 'Chondrolia Chalkidikis' and 'Amfissis' located in the same orchard and irrigated with water having an average B concentration of 3.6 mg 1(-1) were studied. Leaf samples from the current and the previous year non-bearing shoots were collected at 15 or 30 d intervals for a period of 15 months (24 months for B samples). All the leaf and fruit samples were analysed for N, P, K, Ca, Mg, B, Fe, Mn, and Zn. Inflorescence samples were collected at full bloom, while fruit samples were collected 30, 60, 90 and 120 d after full bloom. Also, samples of irrigation water and soil were collected during the experiment and analysed. The results indicated that olive is a species relatively tolerant to excess soil B and no visual symptoms of B toxicity were observed on leaves. Furthermore, B concentration of leaves was at an adequate level, or slightly above it. The two cultivars followed a similar pattern of the fluctuation of B concentration during summer. The maximum B concentration in leaves was 175 mg kg(-1) dry matter in 'Chondrolia Chalkidikis' leaves and about 70 mg kg(-1) dry matter in 'Amfissis' leaves. The nutritional status of trees for K, Ca, Mg and Fe was found to be sufficient, while Mn was deficient. Nitrogen and P were at the sufficiency level in 'Chondrolia Chalkidikis'. but at the marginal level in 'Amfissis'. Generally, B concentration of flowers was higher than that in the leaves, for the same sampling time. 'Chondrolia Chalkidikis' presented significantly higher B concentration in fruit than 'Amfissis', during the harvesting period.