Ecotoxicological assessment of basil essential oil on soil nematode communities

Intensive agriculture has over-exploited natural resources and altered the functioning of soil systems, mainly because of the abuse of synthetic products to increase yields. To improve sustainability, the European Commission has adopted the New Green Deal program, which aims to reduce the use of synthetic products by 50% and restore biodiversity by limiting human impact. Essential oils (EOs) can be sustainable alternatives to synthetic pesticides for crops and agricultural products protection against pests and diseases and, therefore, are attracting increasing interest from the scientific community. However, while most studies have focused on in vitro effects on target organisms (i.e., soil borne-phytopathogens, insects, phytoparasitic nematodes), the impact of EOs on natural soil communities remains unexplored. This study employed a field experiment using the Before-After-Control-Impact (BACI) approach to investigate the potential effects of basil EO on nematode communities. Chickpea seeds were coated with a high concentration (25% v/v) of Ocimum basilicum EO in different formulations, with the basil EO and chitosan combination standing out for its potential applicability as a seed-coating treatment for future crop use. The results demonstrated that the basil EO and chitosan seed coating had no significant negative impact on nematode taxonomic diversity or functional indices. Furthermore, the taxonomic community structure-recognized as the most sensitive detection metric-revealed that the observed effects were primarily influenced by temporal changes, likely reflecting the natural progression of the crop system rather than the EO treatment itself. These findings are particularly promising, as they suggest that EO-based coatings can be compatible with maintaining soil health.