Soil application of olive oil residues: a sustainable strategy involving olive pomace and composted olive pomace

Aplicação de resíduos oleícolas ao solo: uma abordagem sustentável com bagaço de azeitona e bagaço de azeitona compostado

Abstract

This study, conducted within the scope of the PRR INOVCIRCOLIVE project, aimed to evaluate the effects of applying olive pomace from a two-phase extraction system, in both composted and raw (no-treated) forms, on soil fertility and the mineral composition and development of ryegrass (Lolium perenne L.). Two pot trials were carried out using five application rates of the two materials (0 to 150 t ha⁻¹), applied to two soils with contrasting characteristics: a Podzol and a Luvisol. The application of composted olive pomace significantly improved soil fertility and plant nutrition without compromising biomass production, particularly in the less fertile soil. In contrast, the raw pomace, while showing some potential as an organic soil amendment, exhibited some adverse effects at higher application rates, especially in soils with low buffering capacity and in sensitive crops, due to its instability and potential phytotoxicity. These results highlight the agronomic value of both composted and no-treated two-phase olive mil pomace, provided their application is technically guided, and emphasize the importance of establishing best practices to ensure the safe and sustainable use of these materials in agriculture.

Key-words – Olive mil waste, composting, agricultural valorization, soil fertility, Lolium perenne