A Comparative Study of Earthworm Density and Diversity in Grasslands and Arable Lands

Grasslands and arable lands differ in their use – grasslands are primarily used as grazing areas or sources of forage while arable lands are designated for intensive crop production, often requiring cultivation practices and fertilization. Earthworms have a crucial role in both ecosystems by influencing soil structure, enhancing aeration processes, and contributing to the decomposition of organic matter.

This study aims to compare the density and species diversity of earthworms in arable soils and grasslands and evaluate the stability of soil aggregates in these environments. It also seeks to explore the relationship between land use, soil structure, and earthworms, emphasizing their influence on soil quality.

The research was carried out in eight areas, comprising four grasslands and four arable lands, situated in the Wieliczka Foothills, Nowy Wiśnicz Foothills, Rożnów Foothills, Ciężkowice Foothills, and the Low Beskids in southern Poland. Five soil blocks measuring 20 × 20 cm and 25 cm deep in each study area were collected, and earthworms from these samples were extracted using the hand-sorting method. The collected earthworms were washed and classified using an identification key according to their maturity stage, ecological categories, and species. Soil samples (100 g from each block) were combined, mixed, dried, and analyzed for properties such as pH, carbon and nitrogen content, texture, and aggregate stability.

The lowest earthworm density was recorded on arable land, at 10 individuals per square meter (ind. m^-2). The tillage treatment that was carried out on the arable land 18 days before the study included soil loosening methods (ploughing, tillage, ridge-making or deep ploughing). The tillage treatment carried out on the arable land 18 days before the study involved soil loosening methods such as ploughing, tillage, ridge-making, or deep ploughing. These processes, including soil inversion by ploughing, can disturb the natural habitat of earthworms, leading to their migration to other areas or a reduction in their numbers within the field. In contrast, the highest density was observed in grasslands (480 ind.m^-2), which were characterized by rare trampling or its absence and no use of fertilizers. The earthworm density in grasslands (349 ind. m^-2) was more than twice that of arable lands (133 ind. m^-2), highlighting the more favourable environmental conditions in grassland ecosystems.

This research was funded through the 2022-2023 Biodiversa+ COFUND call, under the European Biodiversity Partnership programme, and with the funding organisations: National Science Centre 2023/05/Y/ST10/00098.