Evolution of the Mineral Status of Soil Plant Continuums: The Case of Sugarcane Grown on Tropical Ferralsols of Northern Côte d'Ivoire.
Nguessan A. Kouassi Sr., Centre national de recherche agronomique de Côte d'Ivoire, Station de recherche de IRHO-LaMé 13 BP989 Abidjan 13, Km 30 Route d'Alépé, Abidjan, 225, Ivory Coast
Sugarcane is one of the most important cash crops for the populations of northern Côte d'Ivoire. Its plantations cover about 23 000 hectares with a total annual production varying from 150 000 to 180 000 of metric tones. The activities of sugarcane growing and its transformation into sugar by the sugar mills are the main sources of incomes for an important part of the population of northern Côte d'Ivoire. Sugarcane plantations are concentrated at three sites around four sugar mills (Ferké 1, Ferké 2, Borotou-Koro and Zueénoula). Soils of these sites are mainly ferralitic soil varying from moderately to highly dessaturated according to French commission of Pedology and Soil Classification System (CPCS). Such soils correspond mostly to Ferralsols in the World Reference Base for Soil Ressources (WRB) classification system. Like most tropical soils, these soils on which sugarcane is grown in northern Côte d'Ivoire, are naturally poor in nutrient content and delicate to manage. Sugarcane is a nutrient demanding plant; its growth on these soils therefore requires an important application of chemical fertilizers. For efficienct use of these applications, the nutrient status of the soils and the nutrient uptake of the sugarcane cultures are constantly monitored by the farmers in association with the National Agronomic Research Institute of Côte d'Ivoire (CNRA). For this purpose soils and leaf samples of sugarcane are yearly collected following a stratified sampling method adapted to each site. The samples are analyzed by soil and plant laboratories and data are statistically treated using mainly GenStat and SPSS software. Results indicate that, for most of the experimental sites, in general nutrient uptake is increasing. Soil nutrient contents remain low for most elements, especially for the exchangeable ions. While these soils remain low in nutrients, fertilizer utilization policy has proven to be sufficient in fulfilling the nutrient needs of sugarcane cultures. Key words: Soil, nutrients, mineral status, ferralsols, sugarcane, Côte d'Ivoire.