Silicon application influences the imbalance between nitrogen and potassium fertilization in young olive plants

Nutritional imbalances are frequently observed in many olive orchards from the Mediterranean Basin and are associated with excess nitrogen fertilization and low levels of potassium in leaves. Si application can positively affect uptake, assimilation, and remobilization of nitrogen and alleviates the negative effects of potassium deficiency in many crops. However, the relationship between silicon and olive nutrition is poorly documented. A preliminary experiment was performed with ‘Picual’ growing under shade-house conditions in Córdoba, southern Spain to elucidate whether Si applied through the irrigation water improves vegetative growth and N and K nutrition in young olive plants treated with different N and K doses. Plants received weekly two levels of Si (0 or 20 mg L^‑1) through irrigation water. When differences in silicon leaf content appeared, the treatments resulting from the combination of different levels of nitrogen (0, 100 and 400 ppm N, Ca(NO₃)₂) and potassium (0.05 and 2.5 mM KCl) were started. The experiment was arranged in a completely randomized block design, with five blocks and 12 treatments. The application of Si promoted both vegetative growth and N uptake in those plants under 0 or 100 ppm N levels independently of the KCl treatment. By contrary, K nutrition was negatively affected by Si treatment. A reduction in K accumulation was observed in those plants treated with Si having any effect the dose of N applied to the irrigation water.