Silicon Affects Growth and Nitrogen Uptake of Young Olive Plants

Nitrogen (N) is commonly used in the fertilization plans for Mediterranean olive orchards, often regardless of the nutritional status of the plant. However, improper use of N fertilizers can reduce soil health and crop yields. Silicon (Si), although not essential for plants, could be an environmentally friendly alternative to some chemical fertilizers. The application of Si seems to positively affect many aspects of N nutrition (uptake, assimilation, and remobilization), but that related to olive is unknown. Therefore, the aim of this work was to study the effect of Si application on N nutrition in the olive. To study these effects, an experiment involving young olive plants of ‘Picual’ growing mainly under shade house conditions in Córdoba, Southern Spain, was performed. The experiment was arranged in a completely randomized block design with 9 treatments resulting from the combinations of two Si levels, 0 or 20 mg·L −1 Si [YaraVita ACTISIL ® (YARA, Bio Minerals N.V., Belgium);0.5% Si], applied through the irrigation water or onto leaves, and different levels of N [0, 100, 400 ppm N, Ca(NO 3 ) 2 ]. The results indicated that vegetative shoot growth was significantly affected by Si application, and that this effect was more marked when it was applied through the irrigation water. In addition, these plants showed longer and thinner stems. Additionally, Si fertilization increased the N concentration in plants grown under 0 or 100 ppm N. However, no response was observed in plant treated with the highest doses of N, thus showing the interaction effect. The positive effect of Si on N nutrition suggested the use of Si as a sustainable practice for olive orchards to reduce N fertilizers.