Responses of the earthworms Lumbricus terrestris and Aporrectodea caliginosa to wheat straw provision across a range of residue sizes

Bentley, Peter and Butt, Kevin R. (2026) Responses of the earthworms Lumbricus terrestris and Aporrectodea caliginosa to wheat straw provision across a range of residue sizes. European Journal of Soil Biology, 128: 103799. ISSN 1164-5563

Abstract

Earthworm mediated incorporation of soil surface applied crop residues could provide benefits to belowground ecosystem services, such as an increased rate of soil formation and carbon sequestration. In addition, increased soil organic matter within the upper soil profile can increase food availability for other soil fauna and microorganisms, with potential benefits for soil structure and health. Previous research has assessed the potential mass of surface applied organic matter that can be assimilated by earthworms; however, particle size of material may limit the rate of bioturbation and influence earthworm function and behaviour. The aims of the present study were to investigate the preference and utilisation of wheat (Triticum aestivum) straw residues at different particle sizes by two common, temperate earthworm species, Lumbricus terrestris and Aporrectodea caliginosa. These were addressed within controlled laboratory experiments, where two different scales were tested: Expt 1; with 3 modal straw lengths, as determined from the field post-harvest (40, 20 and 1 cm); and Expt 2; micro particle sizes (1 cm and 1 mm). The effect of straw length on earthworm utilisation was tested by earthworm incubation experiments in plastic bags, where removal from the soil surface was measured over a period of 8 weeks in monocultures and mixed species treatments. Litter removal was investigated by mass depletion over time and depth of incorporation. Choice chambers were used to quantify straw selection and removal at micro particle size. Expt 1 showed straw removal (63 ± 6 %) was significantly higher with a L. terrestris monoculture and 1 cm length. The largest masses of straw were incorporated at 0–60 mm depth of soil. There was no evidence to support a facilitation effect of L. terrestris on A. caliginosa, and increased earthworm mortality was detected in mixed species treatments. The choice chambers of Expt 2 indicated a preference for 1 mm particle size by both earthworm species with a more rapid use by L. terrestris than A. caliginosa. These experiments highlight how retention of straw residues on the field, linked with tillage practices and further straw management post-harvest could have significant implications for plant protection and earthworm populations.