Earthworm activities in cassava and egusi melon fields in the transitional zone of Benin: linking farmers' perceptions with field studies

Abstract

Farmers' perceptions of earthworm activities were studied in the transitional zone of Benin and linked to scientific explanations of earthworm casting activities. Earthworm activity was assessed in farmers' fields with three different cassava cultivars and in a field experiment with three different egusi melon species. The experiment included plots with cowpea and maize. The study also comprised group discussions and a survey with 91 individual farmers. All farmers were aware of earthworms, but there were significant gender differences in terms of perception of earthworms. The presence of earthworm casts is used by farmers as an indicator of soil fertility and of good conditions for crop growth. Cast production over a period of two months was highest in fields with maize, followed by cowpea, cassava and egusi melon. Farmers' ranking of earthworm abundance showed a pattern almost the opposite of our assessment, with cassava and egusi melon fields being ranked highest and those with maize and cowpea lowest. We suggest that farmer's criteria are context-dependent, with earthworm casting activity being relevant when judging whether a field can be intensively cropped again. Casts showed significantly higher plant nutrient contents than the topsoil. Nevertheless, the amount of nutrients recycled in casts is relatively low. Farmer involvement in the research activity increased their interest in earthworms.