Effects of Chromolaena odorata Biomass Combined with Mineral Fertiliser on Soil Macrofauna Density and Maize (Zea mays L.) Growth in Central-Western Côte d’Ivoire

Abstract

This study evaluated the effects of Chromolaena odorata L. biomass, applied alone or in combination with mineral fertiliser, on soil macrofauna density and maize (Zea mays L.) growth in the Daloa region of central-western Côte d’Ivoire. The experiment was conducted on fallow land dominated by C. odorata using a randomised complete block design with four replicates and four treatments: C. odorata biomass alone (Co), C. odorata biomass combined with NPK (Co+NPK), NPK alone (T1) and an untreated control (T0). Soil macrofauna were collected using monolith sampling and were identified and counted. Maize growth was assessed from 34 to 62 days after sowing using plant height, number of leaves and stem collar diameter. The recorded macrofauna comprised three principal groups: Clitellata, Insecta and Diplopoda. A total of nine species and 1,200 individuals were recorded across treatments. The Co treatment produced the highest macrofauna density (464 individuals m⁻²), whereas Co+NPK showed the greatest species richness, with six species and 400 individuals m⁻². The control recorded 272 individuals m⁻², while NPK alone had the lowest density and diversity, with 64 individuals m⁻² and three species. Maize height increased over time and reached its maximum at 62 days after sowing. The tallest plants were observed under NPK-based treatments, with T1 reaching an average height of 144 cm. Stem collar diameter showed treatment-related variation during intermediate growth, but values converged at approximately 30 mm at 62 days after sowing. Leaf number varied only slightly, from 10.48 to 10.83 leaves per plant, with no significant treatment effect. Overall, C. odorata biomass supported soil macrofauna, while its combination with NPK maintained biological activity and supported maize growth.