Seasonal variation of macro- and micro- nutrients in leaves of fig (Ficus carica L.) under Mediterranean conditions
Agricultural University of Athens, Department of Natural Resources Management and Agricultural Engineering, Laboratory of Soil Science and Agricultural Chemistry, Iera Odos 75, GR11855 Athens, Greece
Leaves of ‘Smyrna’ fig (Ficus carica L.), variety ‘Smyrneiki’, were collected at four stages of the annual growth cycle, namely (1) at flowering, (2) during fruit development, (3) at fruit maturity and (4) after fruit harvest, during two consecutive years (2018 and 2019) and the leaf macro-(N, P, K, Ca, Mg) and micro-(Fe, Zn, Cu, Mn, B) nutrient concentrations were determined. Mean concentrations of N, P, K, Ca and Mg ranged between 14.4–28.6, 0.5–1.7, 2–31.2, 22–80.3 and 2.1–6.7 g kg-1 (on a dry weight basis-d.w.), respectively, while concentrations of Fe, Zn, Cu, Mn, and B, ranged between 84–280, 11–70, 2–86, 40–206, and 18–39 mg kg-1 d.w., respectively. The mean leaf concentration of N decreased significantly at each successive growth stage, whereas those of P, K, Fe and Zn, also decreased progressively, but not always to a statistically significant level between each stage. In contrast, the mean leaf concentration of Ca increased significantly throughout the season, while the concentrations of Mg and Cu also increased, but not to a statistically significant level at each stage. The Mn concentration of fig leaves decreased significantly at fruit maturity, then increased significantly after fruit harvest. Overall, the nutrient concentration of fig leaves varies throughout the period from flowering to fruit harvest, suggesting that trees may need different amounts of nutrients depending on the developmental stage. The seasonal variation of the nutrient concentration in fig leaves confirmed the need for reference values for each phenological stage for leaf analysis interpretation and for developing an efficient fertilization program.