Mechanical Tillage Diversely Affects Glomalin Content, Water Stable Aggregates and AM Fungal Community in the Soil Profiles of Two Differently Managed Olive Orchards

This work was designed to investigate the effect of mechanical tillage on glomalin content, arbuscular mycorrhizal fungi (AMF) abundance and diversity, and the concentration of water stable aggregates (WSA), in two adjacent olive groves located in Basilicata (Italy) that were managed over the course of 11 years in accordance with different horticultural models (conventional and sustainable). Soil sampling was performed at four depths between the trees within a row and between rows. In the end, WSA was found to be a highly sensitive indicator (especially in the “macro” fraction) of the effect of management on soil structure, showing the highest statistically significant values within the sustainable system. In the same regard, the diversity of the AM fungal community was negatively affected by conventional practices; on the other hand, a higher concentration of glomalin in the first 20 cm layer of the conventional system is here reported for the first time, as a likely result of disruption of the mycelium provoked by the mechanical tillage.