Diatomaceous earth (DE) is composed mainly of fossilized diatoms; its use is generally limited as an insecticide due to its abrasive nature. DE is rich in silica dioxide, so it is also considered a bioavailable source of soluble silicon (Si), known to enhance plant defense mechanisms. This has been most extensively investigated in crops such as wheat or rice, however there is not much information on the response in fruit trees. The study investigated the effects of DE application on hazelnut trees, analyzing its impact on morphological, chemical and antioxidant characteristics of the plants, as well as on the reduction of oxidative stress in roots, leaves and nuts. Two experiments in La Araucan & iacute;a during season 2021/2022 were carried out, Experiment 1, under controlled conditions (Campo Experimental Maquehue, Freire) and Experiment 2 in the field (GADI Orchard, Perquenco), both using Tonda di Giffoni and Barcelona cultivars, the most common planted in Chile. DE application improved plant growth, leaf silicon concentration, antioxidant activity and lipid peroxidation. These findings suggest that DE could be a sustainable tool to improve hazelnut production and quality, with important implications for nutritional management and sustainable nut production. The research addressed key aspects such as nut yield, tree growth, silicon concentration, antioxidant properties and oxidative stress, providing information relevant to the agronomic management and quality of hazelnut crops.