DOI: 10.36347/sjavs.2019.v06i07.001

Pages: 165-170

A study was conducted in Gagnoa in West-Central of Côte d'Ivoire, in one of the main areas of production of plateau rice, with a view to identifying the physico-chemical constraints of soils that are causing yield declines. The test was carried out at the research station of the National Agronomic Research Center (CNRA) in Gagnoa. Soil samples were collected using the diagonal method and sent to the soil analysis laboratory for the determination of physical and chemical parameters. Soil chemical analyses included particle size, acidity, total organic carbon, organic matter content, total organic nitrogen, total and assimilable phosphorus, exchangeable cations, the capacity of cationic exchange (CEC), the sum of the exchangeable bases and the rate of saturation in bases of the adsorbent complex of the soil. The results showed that the soil horizons are compact with a high level of coarse elements (> 50%), consisting mainly of ferruginous nodules, gravel and quartz fragments in the 0-20 cm horizon. Soils are acidic (pH = 5.2) and poorly humidified with a low organic matter content (2.53%) and a cationic exchange capacity (CEC) of 28.6 cmol.kg-1 very high. The sum of the exchangeable bases (1.53 cmol.kg-1) and the saturation rate of the base adsorbent complex are also very low (5.35%). As a result, high concentrations of certain acidity-generating ions such as iron Fe2+ (177 mg.kg-1) and manganese Mn2+ (205 mg.kg-1) were observed in these soils. Organic amendments would be needed to improve the fertility of these soils and the productivity of the rice in Gagnoa area.