Abstract:
Inland valleys are becoming increasingly important agricultural production areas for rural
households in sub-Saharan Africa due to their relative high and secure water availability and
soil fertility. In addition, inland valleys are important as water buffer and biodiversity hot
spots and they provide local communities with forest, forage, and fishing resources. As different inland-valley ecosystem functions may conflict with agricultural objectives, indiscriminate development should be avoided. This study aims to analyze the diversity of inland
valleys in Sierra Leone and to develop guidelines for more precise interventions. Land use,
biophysical and socio-economic data were analyzed on 257 inland valleys using spatial and
multivariate techniques. Five cluster groups of inland valleys were identified: (i) semi-permanently flooded with high soil organic carbon (4.2%) and moderate available phosphorus
(10.2 ppm), mostly under natural vegetation; (ii) semi-permanently flooded with low soil
organic carbon (1.5%) and very low available phosphorus (3.1 ppm), abandoned by farmers; (iii) seasonally flooded with moderate soil organic carbon (3.1%) and low available
phosphorus (8.3 ppm), used for rainfed rice and off-season vegetables produced without
fertilizer application for household consumption and market; (iv) well drained with moderate
soil organic carbon (3.8%) and moderate available phosphorus (10.0 ppm), used for rainfed
rice and off-season vegetables produced with fertilizer application for household consumption and market; and (v) well drained with moderate soil organic carbon (3.6%) and moderate available phosphorus (11 ppm), used for household consumption without fertilizer
application. Soil organic carbon, available phosphorus, hydrological regime, physical accessibility and market opportunity were the major factors affecting agricultural intensification
of inland valleys. Opening up the areas in which inland valleys occur through improved
roads and markets, and better water control through drainage infrastructures along with an
integrated nutrient management would promote the sustainable agricultural use of inland
valleys.
