Chromolaena odorata fallow in food cropping systems : an agronomic assessment in South-West Ivory Coast

In tropical Africa, traditional shifting cultivation can no longer provide sufficient food for the rapidly increasing population, whereas it threatens the remaining forests. An alternative is a fallow system based on the shrub Chromolaena odorata. Food crop cultivation in rotation with this fallow type in Ivory Coast was analysed and options for efficient and sustainable land use were identified. Farmers obtained 1.8 t ha ^-1maize without external inputs in a three-year fallow-cropping cycle. After crop harvest the C.odorata fallow vegetation established rapidly and effectively smothered herbaceous weeds. Experiments showed that the poor nutrient availability in this fallow system limited maize yields. During the cropping period C . odorata in maize was controlled by one weeding in the first month, whereas radical weeding practices set back its re-establishment after cropping. Shorter fallow periods and particularly extended cropping periods impaired both maize yield and C. odorata reestablishment. The C . odorata fallow system will be important for future food production because of the easy establishment and control of the species. To sustain intensive land use, farmers' cultivation practices can be improved by increasing nutrient availability, introducing suitable additional crops and developing practices that hardly check C . odorata re-establishment.