In response to the continuing decline in the fertility of tropical agricultural soils, the use of grain legumes has been developed as an alternative form of organic fertilization, as it integrates the conservation and sustainable management of biodiversity. The present study, conducted in the Karamokola area in central-western Côte d’Ivoire, falls within this framework and aims to compare the effect of two legume crops (soybean: Glycine max and bean: Phaseolus vulgaris) on soil macroinvertebrates. To this end, an experimental design consisting of four randomized blocks comparing four treatments (beans, soybeans, beans and soybeans, and a control) was set up on two fallow plots that were more than five years old. The results showed that the plots with a previous monoculture of beans and a previous mixed crop (beans and soybeans) harbored 15 taxonomic groups, compared to 10 groups for the control. In addition, there was a greater abundance of macroinvertebrates, with 675.75 individuals per m2 (previous bean monoculture) and 653.25 individuals per m2 (previous bean-soybean intercropping). Furthermore, soybean monoculture hosted an intermediate abundance of macroinvertebrates of 156.12 individuals per square meter.In addition, bean monoculture significantly improved (p˂0.05) the organic matter content (OM = 1.82%), carbon (C = 1.06%), and nitrogen (N = 0.09%) content of the soil compared to the other treatments (soybean monoculture and bean-soybean combination), which recorded statistically identical values (OM = 1.00% soybean and 1.17% bean-soybean); C = 0.58% soybean and 0.68% bean-soybean: N = 0.05% soybean and 0.06% bean-soybean). The positive correlations (r ≥ 0.85) between soil organic status and macroinvertebrate density, taxonomic richness, and Shannon diversity index suggest a synergistic relationship between these two compartments (soil organic status and density). The mechanisms governing the increases in abundance and diversity under the bean and bean-soybean treatments are discussed, and we recommend that farmers grow beans or bean-soybeans before planting any other crops in the Karamokola area of Béré in Côte d’Ivoire.

Chromolaena odorata is a fast-spreading invasive plant species that poses a serious threat to agricultural ecosystems, particularly in sub-Saharan Africa. Despite its reputation as a harmful weed, there has recently been an increase in interest in its potential use as an organic soil improver. This study evaluates the impact of C. odorata biomass on soil physicochemical properties, specifically pH and moisture content, as well as on the agronomic performance of maize (Zea mays). The experiment was conducted in Zépréguhé, in the Haut Sassandra region of central-western Côte d’Ivoire, using a randomised complete block design. Four treatments were tested: C. odorata biomass alone; C. odorata combined with a 170 kg/ha mineral fertiliser (NPK 15-15-15); mineral fertiliser alone; and an untreated control. A single maize variety (LG-501) was used to ensure consistency across the treatments. The agronomic parameters measured included plant height, the number of leaves, the stem base diameter and the yields of ears and grain. Soil pH and moisture were also assessed. The results showed that the treatments involving C. odorata significantly enhanced plant growth and increased soil moisture, while slightly neutralising soil acidity. Applying C. odorata alone produced the highest yields (10.74 t/ha for ears and 7.62 t/ha for grain), outperforming the mineral fertiliser treatment and the control. The combination treatment also yielded good results, albeit slightly lower. These results suggest that C. odorata biomass could be used as an effective, inexpensive alternative to or addition to synthetic fertilisers, thereby promoting soil health and sustainable maize production in tropical agroecosystems.

In the department of Daloa, one of the main agricultural areas of Côte d’Ivoire, the change in land use is so enormous that it threatens the ecosystems and, with them, the services provided, in particular the stabilization of the climate via carbon storage in vegetation and soils. Thus, one of the major environmental challenges to be met in this department is to determine, among the crops grown, those that have a significant potential for reducing CO2 emissions into the atmosphere by conserving existing carbon reservoirs in the soil. This is the objective that was targeted in the present study. It consisted in choosing in three different villages, three same crops (cocoa tree, hevea and oil palm) among the most practiced. The physico-chemical properties of the soils were determined from three soil pits located on a useful plot of 10000 m2, by land use. The carbon stocks contained in the first 100 to 120 cm of the soils were calculated. It emerged that soils under cocoa trees store carbon better than soils under hevea. The latter have greater potential than soils under oil palms. However, the stocks measured remain low overall, which shows that the farming practices assessed should be improved.