Farmers' perception of the effects of earthworms on soil fertility and crop performance in southern Cameroon

The knowledge and perception of the effects of earthworms on soil fertility and crop growth was surveyed in a humid forest zone of southern Cameroon. A total of 215 farmers were interviewed in seven villages: two villages were near the capital Yaounde, severely deforested with a high land-use intensity, three villages were 60-100 km south of Yaounde,,moderately deforested with a medium land-use intensity and two villages were 130 200 kit south of Yaounde, mainly forested with a low land-use intensity. To assess if the fallow phase had attained sufficiently high levels of fertility the status of the soil macrofauna was used by 42% of farmers as an indicator. The presence of earthworm casts was used by 35% of farmers to determine if the land was ready for cropping. Earthworms were not believed to have any effect on soil fertility (98.6%) and only 0.7% of farmers believed that earthworms either increased or decreased soil fertility. Across all crops, 71.6% of farmers reported that earthworms had no effect on crop yields. Any positive effects on yields were regarded as crop specific: 30.1% of farmers believed that groundnut (Arachis hypogaea) and cassava (Manihot esculentus) yields increased if earthworms were present. For maize (Zea mays), plantain.(Musa spp.), cocoyam (Xanthosoma sagittifolium) and cacao (Theobroma cacao), between 27.7 and 19.2% of farmers believed that earthworms created yield increases. Few respondents (mean across crops 1.8%) believed that earthworms decreased crop yields, with the greatest proportion of these relating to plantain (3.8%). The farmers' perception of earthworms; effects on cassava and groundnut yields was very dependent on the location and related to the levels of surface casting.