Earthworm surface casting activity on slash-and-burn cropped land and in undisturbed Chromolaena odorata and young forest fallow in southern CameroonThe 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Abstract

Summary The effect of slash-and-burn agriculture on earthworm surface cast deposition was assessed in 4–5 year old Chromolaena odorata (CHR) and young forest (YFOR) fallow (12–15 years) in the humid forest zone of southern Cameroon. In the villages Ngoungoumou (56.8% forest cover), Metet (39.5% forest cover), and Nkometou (24.9% forest cover), plots were established in both fallow types and half were slashed, burned, and cropped in 2000, the rest maintained as undisturbed controls. In 2001, cropped plots were split, one half abandoned to fallow, the other cropped a second time as in 2000. Casts were collected weekly from April to December in 2000 and 2001. In 2000, surface cast deposition was different between villages, in both fallow types and land-uses. At Nkometou casting was lowest and no effects of fallow type or land-use were found. At Metet and Ngoungoumou, more casts were deposited in undisturbed fallow (22.5 and 3.0 Mg ha–1, respectively) than in the cropped treatment (7.1 and 0.6 Mg ha–1, respectively). Cropping reduced cast deposition in both fallow types, yet more so in CHR than in YFOR. In 2001, as in 2000, no differences were found at Nkometou. At Metet and Ngoungoumou, more casts were deposited in undisturbed controls than in the other treatments. Cast deposition was higher in plots in the first year of fallow after cropping than in double cropped plots, indicating an immediate recovery after cropping. Cast production was not correlated with soil chemical properties across villages. Earthworm species assemblages were different between villages, with large bodied, endogeic and anecic species most abundant at Metet. Earthworm species assemblage is likely to be the main factor determining surface cast deposition and thus differences between villages.