Large-scale organic farming enhances soil properties and earthworm communities in relation to conventional farming in the Pampas region of Argentina

Abstract

Organic farming is considered with the potential to reduce the impact on soil and its biological communities, incomparison to conventional agriculture. Organic farming primarily seeks to promote the biodiversity andfunctionality of soil, thereby reducing the reliance on external inputs. Earthworms have a crucial role in nutrientcycling and soil aggregation, and thus their conservation is essential in any strategy to maintain soil health andimprove agricultural sustainability. In this contribution we aim to assess the differential impact of large-scaleorganic and conventional farming on earthworm communities and soil properties, in comparison with naturalgrasslands in the Pampas region of Argentina. A total of twenty-five sites were sampled, including large-scaleorganic (Org) and conventional (Con) non-experimental sites, and natural grasslands (Gra) used as reference.The Gra had the highest content of mineral-associated organic matter, and together with Org, had the highestcontent of particulate organic matter (POM) and the lowest bulk density, in comparison to Con. The highestabundance, biomass and species richness of earthworms were observed in Gra, followed by Org, and in both caseswere higher than in Con. The Gra and Org showed the highest species diversity and the lowest dominance, whileCon showed the opposite pattern. The earthworm communities of Gra and Org exhibited greater similarity toeach other than the Con communities. A strong positive correlation was observed between soil POM and thespecies Microscolex dubius (Fletcher, 1887), Aporrectodea rosea (Savigny, 1826) and A. trapezoides (Dug`es, 1828),which are primarily associated with the Gra and Org sites. The results indicate that organic farming has a positiveimpact on soil health, as evidenced by increases in the abundance, biomass, richness and diversity of earthworms, soil POM content and porosity, as well as preserves earthworm communities that are more similar tothose of grasslands than of conventional farming. The relevance of these findings is further reinforced by the factthat the organic farms under study are large-scale farms surrounded by conventional agriculture landscapes.