Potential Soil N Mineralization in Upland and Lowland Soils of Inland Valleys of Cote d’Ivoire, West-Africa

Abstract

This article studied soil samples from the various rice-based environments of the inland valleys of Cote d’Ivoire to evaluate their native capacity of mineralization of N. Soil N, is subject to intense chemical and microbiological transformation processes (hydrolysis, oxidations, reduction). All these transformation processes are subject to water availability and therefore show a strong variability related to soil grains size and vegetative cover. In order to applied appropriate technical strategies aiming at conserving soil N or using it for food crop, it is important to evaluate its mineralization potential in the concerned soils. In this paper, the nitrogen supplying potential of soils from the ten major rice-based production systems of Côte d’Ivoire was determined by incubation experiments in 1997. The net N mineralization potential (N supplying capacity during 6 weeks of anaerobic incubation) from soils of the various rice-based systems of Côte d’Ivoire varied between 4 and 16 mg N kg-1 of soil. It was generally less in the savanna than in forest upland soils and intensified land use reduced soil N supplying capacity more in savanna than in forest ecosystems. It may be concluded that N mineralization from soils of the various rice-based systems of Côte d’Ivoire strongly varied. Soil N supply was generally less in the sandy than in clay soils. Land use intensification affected N release more in the savanna than in the forest and tended to reduce the N supplying capacity more in lowland than in upland soils. As soil nutrient mineralization rates are also controlled by the specific character of the vegetation occupying a site, plant-soil-plant feedback loops in agricultural systems will influence the N dynamics over time.