Assessment of soil feeding activity using different bait materials for the bait-lamina test: A small-scale study in Eucalyptus blocks

Abstract

A standard bait material (consisting of cellulose powder, wheat bran and activated charcoal) has been proposed for the bait-lamina test, however, several studies have deviated from using this. It is unclear whether different bait materials deliver similar, comparable results. In a small-scale, field-based study, we compared three baits namely oat bran, nettle (Urtica dioica) and jelly (i.e. Jell-O) to the standard wheat bran bait. Sites, with high environmental variation between them, were selected in mature, cleared and naturally recovering Eucalyptus grandis blocks located in the Western Cape, South Africa. Contrary to previous research, we found soil feeding activity fluctuated across the soil profile instead of progressively decreasing with soil depth, which can potentially be attributed to the soil’s dry and hot summer conditions. Our results indicate that wheat bran remains the most effective bait with the bait-lamina test. Compared to the standard wheat bran bait, the nettle bait presented the lowest estimates of feeding activity across all sites, while the jelly bait showed similar levels of soil feeding activity within each block. Therefore, the nettle bait cannot be recommended as a bait material, while the jelly bait could serve as an adequate proxy for the wheat bran bait. These results are particularly important for small-scale studies, such as the present study, to obtain snapshots of potential bait preferences. However, more research on bait preference is required by conducting larger-scale studies across different systems, climatic regions and environmental conditions in order to understand the relationship between soil organisms and their feeding activity when offered different bait materials.