Main content area

Changes in soil quality after subsequent establishment of Chromolaena odorata fallows in humid savannahs, Ivory Coast

Tondoh, Jérôme Ebagnerin, Koné, Armand Wowo, N'Dri, Julien Kouadio, Tamene, Lulseged, Brunet, Didier
Catena 2013 v.101 pp. 99-107
Chromolaena odorata, biomass, calcium, earthworms, ecological invasion, ecosystems, fallow, farmers, food production, forests, infiltration (hydrology), invasive species, macroinvertebrates, magnesium, nitrogen content, phosphorus, savannas, shrubs, soil, soil fertility, soil organic carbon, soil quality, sustainable agriculture, Cote d'Ivoire
In the buffer zone of the Lamto Reserve, a protected area located in the forest-savannah transitional zone in central Ivory Coast, the exotic shrub Chromolaena odorata has invaded abandoned fields and degraded forests. As a result, they have turned into thickets that are used by local farmers as natural fallows to enhance soil fertility for food production. However, information about their impact on soil is scanty and investigations focusing exclusively on baseline data on C. odorata fallows in humid savannahs are still lacking. This study was designed to assess changes in soil physical, chemical and biological properties after the establishment of C. odorata fallows in humid savannahs of Ivory Coast. Sampling sites were selected such that a portion of C. odorata fallow was located next to the shrub savannah, the most common natural ecosystem in the area. Results revealed a rise of soil organic carbon (+27.9%), total nitrogen (+36.7%), total phosphorus (+56.8%), extractable calcium (+68.3) and magnesium (+140.3%) in the first 10cm of soil beneath the C. odorata fallow relative to the savannah. Furthermore, the fallow was associated with high N-mineral pool as N-NO3− and N-NH4+ content increased at +72.5% and +71.5%, respectively. The infiltration capacity of water under C. odorata-based fallow was markedly high and soil macroinvertebrates, mainly earthworms, showed significant increases in density and biomass. The large quantity of good quality standing biomass produced by C. odorata is likely the main factor controlling the improvement of soil quality. The results suggest that there are merits for the integration of C. odorata fallow in a cropping system for sustainable food production in the buffer zone of Lamto Reserve. This can also help to reduce pressure on forest islands.