Earthworm communities in arable land : effects of crop residue management and field margins

Samenvatting

Earthworms play key roles in cropping systems and thereby contribute to nutrient cycling, soil organic matter formation and decomposition, soil structure formation and water infiltration. Although a considerable amount of research has focussed on earthworm communities of arable fields, many knowledge gaps remain. This thesis investigated how earthworm communities in arable land are affected by the composition of the surrounding landscape and by the management of arable fields, with particular attention to crop residue management at the field level.

The first study consisted of a landscape level field survey focussed on quantifying the relative contribution of three environmental filters, i.e. soil properties, management practices, and composition of the surrounding landscape on earthworm communities of arable fields and adjacent field margins. Furthermore, two experiments were carried out to study the effects of crop residue management on earthworms. One of those took place under controlled conditions in the laboratory, and focussed on the effects of crop residue placement on the performance of earthworm species, each belonging to a different earthworm ecological group, as well as the subsequent effects on soil structure formation. The other experiment consisted of manipulating the placement and amounts of crop residues in arable fields under different tillage intensities, and studying the effects of those manipulations on earthworm communities after introducing an anecic species in those arable fields. The latter ecological group is rarely found in arable fields, and the feasibility for its introductions was also assessed.

Generally, the findings demonstrate the relevance of management practices in shaping earthworm communities of arable fields, while no effects of the surrounding landscape were found for the communities inhabiting the intensively managed arable fields. Regarding crop residue management, the results show that crop residue amounts and placement affect distinct earthworm ecological groups differently, and this effect also depended on tillage intensity. Furthermore, these results are consistent when using different methods regarding the study of communities, i.e., taxonomic and functional approaches. Finally, the work presented on this thesis highlights the need for carefully addressing current arable management practices for improving soil sustainability, which cannot disregard soil fauna.