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.
In the period 1960–1980, Chinese and Taiwanese cooperations developed irrigated rice schemes throughout West Africa with variable success. In Benin for instance, schemes in Zonmon and Bamè (Ouémé Valley) were abandoned upon withdrawal of the project developers and have been sub‐optimally used ever since, while the neighbouring scheme of Koussin‐Lélé (Zou Valley) is still functional (double rice cropping) and well operated and maintained by the farmers. The factors for success and failure were investigated by comparing the two abandoned schemes with the successful one, using field observations and stakeholder surveys. We observed that (i) operation and maintenance costs associated with irrigation were presumably lower in the successful scheme––where irrigation was driven by gravity––compared to the failed ones––where part of the schemes were designed for motor‐pump driven irrigation. Moreover, contrary to the situation in the unsuccessful schemes, farmers in the successful scheme of Koussin‐Lélé benefit from (ii) external technical support, (iii) a favourable land tenure policy, entailing seasonal redistribution of plots favouring active and motivated producers, (iv) reliable access to credit, and (v) an effective farmer organization. These observations underscore the importance of addressing the longer‐term technical and financial needs of the beneficiaries for the successful development of irrigation schemes advancing smallholder farmers in sub‐Saharan Africa. Copyright © 2013 John Wiley & Sons, Ltd.
To meet food demand after the failure of irrigation system developments, agricultural intensification is occurring in inland valley agro-ecosystems in sub-Saharan Africa. Agricultural enhancement in inland valleys, which undermines environmental sustainability, was assessed using 'Driving Force-Pressure-State-Impact-Response' approach in four agro-ecological zones of Benin. The survey revealed that inland valleys are largely devoid of ligneous species. Crop residues are mainly transferred from inland valley fields to feed cattle, burnt in situ by the farmers themselves or abandoned to wildfires or to pasture-not mulched. Crop diversification is not universal and is limited to rice and vegetables crops. Monocropping of rice, practised by 83.3% of inland valley farmers, requires large chemical fertilizer application despite their impacts on environment including land degradation and water contamination. A major challenge is to determine means of characterizing entire agro-ecosystems of inland valleys in a way that is simple enough to be effectively and efficiently monitored. Inland valley agricultural development projects might include backstopping activities and policies that enable monitoring of chemical inputs and farming practices in inland valleys to reduce negative impacts on the environment and human health.
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