Effects of cultivation and DDT on earthworm activity in a forest soil in the sub-humid tropics.
The effects of bush clearing, cultivation and crop protection with DDT on surface casting activity and populations of earthworms were monitored over a 4-year period in southern Nigeria. Surface casting activity by Eudrilus spp. was low in uncleared bush plots but increased progressively from year to year in cultivated plots, untreated with DDT. Casting activity in DDT-treated plots remained low. Hyperiodrilus sp. surface casting activity was reduced in cultivated treatments with or without DDT to 3% of that in bush plots. Despite reduced casting activity in DDT-treated plots, population studies revealed no significant effects on total earthworm populations, in terms of numbers and biomass per unit area, of DDT treatments. However DDT residues were greater in earthworms from DDT-treated plots.