The effect of NK fertilization on growth patterns and leaf nutrient concentration of carob-trees (Ceratonia siliqua L.)

Abstract

The purpose of this experiment was to analyse soil nutrient availability as factors controlling vegetative and reproductive growth in carob (Ceratonia siliqua) trees. The orchard with 10 year-old trees, was established on a calcareous soil (total calcium carbonate: 65.2 %; active lime: 17.5 %). Four fertilization levels were tested: no fertilizer (C); 0.8 kg N.tree−1 (N treatment); 1 kg K2O.tree−1 (K treatment) and 0.8 kg N.tree−1 plus 1 kg K2O.tree−1 (NK treatment). No irrigation was applied during the experimental period. Branch length increment, inflorescence number, leaf area index, fruit and leaf mineral content were registered. Correlations between growth patterns and climatic variables were evaluated in order to discriminate between fertilization effects and abiotic stress, typical of Mediterranean climate, such as drought. The preliminary results of a NK fertilization trial are here presented and tree responses to N and K application were disc ussed in terms of source-sink effects, namely vegetative versus reproductive growth. The knowledge of these growth patterns could be important for making decisions related to fertilization. Thus, modifying orchard fertilization regimes may be a helpful strategy to improve yield on these particular droughty sites.