SOILS OF INLAND VALLEYS OF WEST-AFRICA GENERAL FERTILITY PARAMETERS

In an effort to improve the critical food situation in West Africa, we tlands are currently receiving the necessary attention as the environm ent most suitable for rice production. Various scientific studies are required to effectively put these wetlands into sustainable crop produ ction. Between 1983 and 1989 inland valleys (IVs) of West Africa were surveyed with the main objective of characterizing these soils; soil s amples were therefore collected from these IVs throughout the various climatic zones. As inland valleys of West Africa have undergone intens e leaching and weathering, the soil pH is generally low. Mean soil pH values (0-15 cm) are: West Africa, 5.3; Equatorial forest (EF), 5.3; G uinea savanna (GS), 5.3; Sudan savanna (SuS), 5.9; and Sahel savanna ( SS), 6.0. Exchangeable cations for West Africa IVs are ion:; also low for IVs of EF; very low for GS IVs; and moderate for the drier zones ( SuS and SS), Total carbon and nitrogen contents (12.8 g kg(-1) C and 1 .11 g kg(-1) N) of these soils are low for West Africa in general, mod erate for EF (20.4 g kg(-1) C and 1.66 g kg(-1) N), and very low for t he three savanna zones. Mean values of available phosphorus suggest th at the phosphorus status of these soils is low (West Africa and EF) to very low (GS, SuS, and SS) throughout the region. This study revealed that most of the soils of IVs of West Africa are characteristically l ow in plant nutrients. For effective and sustainable crop production, farming systems that are both soil restoring and enriching need to be developed.