Date of Award

Spring 5-17-2020

Document Type

Honors Thesis


Environmental Science

First Advisor

Maggie Douglas




Forage radish (Raphanus sativus var. Longipinnatus), a member of the brassicacea family, is becoming increasingly popular in conservation tillage practices. Brassica cover crops have been observed to have allelopathic effects on soil organisms due to the glucosinolates in their tissues. A pilot study examining the effects of different tillage methods on earthworm populations found a significant lack of earthworms in forage radish roll-down tillage when sampling with mustard solution compared to roll-down tillage without forage radish. This study seeks to explain these results by exploring two alternative hypotheses. The first hypothesis is that the lack of earthworms observed in the pilot study was due to negative response of earthworms to brassica cover crops. The second hypothesis is that the results were a sampling artifact because of an interaction between the brassica-derived, mustard sampling solution and the brassica cover crops.

Field trials and habitat choice chambers were used to assess earthworm preference for different cover crops, including forage radish. Fall and spring field trial sampling was conducted with mustard and onion solutions to identify any interaction between brassica cover crops and the sampling method. Results of field trials and choice chamber trials suggested no significant earthworm avoidance of forage radish. Results of the field trials also suggested that cover crop habitats did not significantly influence the effectiveness of mustard sampling solution. This study can assist farmers deciding whether to use forage radish in their agricultural systems.