Soils of inland valleys of West Africa

Abstract

In an effort to improve the critical food situation in West Africa, wetlands are currently receiving the necessary attention as the environment most suitable for rice production. Various scientific studies are required to effectively put these wetlands into sustainable crop production. Between 1983 and 1989 inland valleys (IVs) of West Africa were surveyed with the main objective of characterizing these soils; soil samples were therefore collected from these IVs throughout the various climatic zones. As inland valleys of West Africa have undergone intense 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; Guinea savanna (GS), 5.3; Sudan savanna (SuS), 5.9; and Sahel savanna (SS), 6.0. Exchangeable cations for West Africa IVs are low; 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, moderate for EF (20.4 g kg^-1 C and 1.66 g kg^-1 N), and very low for the three savanna zones. Mean values of available phosphorus suggest that 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 low in plant nutrients. For effective and sustainable crop production, farming systems that are both soil restoring and enriching need to be developed.