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La dégradation des sols cultivés constitue l'une des contraintes majeures limitant la productivité de l'agriculture en Afrique sub-saharienne. Cependant, dans une même zone climatique, ce sont surtout les pratiques agricoles qui vont déterminer le niveau de fertilité d'un sol donné. La présente étude, conduite en zone cotonnière à l'Ouest du Burkina Faso, avait pour objectif d'évaluer les effets des pratiques de fertilisation sur les caractéristiques chimiques d'un sol ferrugineux lessivé. Un échantillon de 22 champs a permis de caractériser les pratiques de fertilisation à l'aide d'enquêtes et de prélever l'horizon 0-20 cm du sol pour des analyses de laboratoire. Les principales pratiques de fertilisation identifiées sont les apports de fumier sur des portions des champs, les apports d'engrais sur les cultures de cotonnier et de maïs et la jachère. Les résultats ont montré que seules les apports organiques ont permis une amélioration significative au seuil de 5 % des teneurs en matières organiques, de la capacité d'échange cationique (CEC), de la somme de bases échangeables et du pH du sol. Il apparait donc que l'utilisation durable des sols dans la zone nécessite le renforcement de la fumure organique à travers le développement de nouveaux modèles de restitutions organiques.

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In Burkina Faso, about 100,000 ha of Jatropha were planted during the past 10 years. Despite this enthusiasm, few results exist on the impact of the plant on soil properties. This study contributes to better knowledge of Jatropha farming and was carried out in 2013 with Jatropha farmers in Torokoro and Tin villages in the south Sudanian zone of Burkina Faso (rainfall 900-1200 mm). Data collection plots of 400 m 2 repeated 3 times were installed in 3 farmers' fields in each village. Soil samples were collected at 3 distances (D0= under the crown, D1= 1m and D2= 2m) from the Jatropha trees lines and in a fallow as a control sample for each field. The results showed significant differences between distances for soil pH. Soil nutrients increase with distance from the crown (from 9.33% to 12.20%) for available phosphorus in Torokoro-6 years and decrease from 22.45% to 23.71% in Torokoro-2 years). Soil respiration and microbial biomass decreases also with distance. The density of spores of mycorrhizal fungi is higher for the control soils (14.64%) and it decreases from crown to 2m (from 2.22% to 9.53% in Tin-2 years). The study showed the contribution of Jatropha trees on soil fertility improvement.

Saturated soil irrigation (SSI) has been reported as a great technique that increases water productivity in fully irrigated rice cultivation. However, this technique should be employed in a dry prone area where rainfalls fail to fulfill rice water requirements and fill up reservoirs for sufficient irrigation. Therefore, an experiment was conducted to identify the most effective complementary irrigation that restores soil moisture to saturation and increases water productivity with fewer yield expenses. The study used a complete randomized blocks design with four replications and four soil saturation treatments: Sat200% (farmer practice), Sat160%, Sat120%, and Sat80%. In Sat160%, Sat120%, and Sat80% irrigation was applied once a week in the absence of rainfall. In Sat200%, water was daily applied except the day of rain. The results showed that reductions in soil saturation decreased plant height, tillers, and leaves number by 10%, 18%, and 14%, respectively. Yield and components were reduced between 26.09% and 4.8%. Weekly soil saturation at 120% exhibited greater irrigation productivity (0.69 kg/m3), rainwater productivity (1.02 kg/m3), and water-saving (90.53%) with less production penalty (5 × 10−3 kg/m3). We advocate that saturated soil irrigation should be recommended in the rainfed rice system as a drought mitigation measure in semi-arid conditions.