29 research outputs found
Architecture racinaire et aptitude au drageonnage de trois espĂšces forestiĂšres
Les systĂšmes racinaires de Balanites aegyptiaca (L.) Del., Sclerocarya birrea (A. Rich.) Hochst. et Diospyros mespiliformis Hochst. ex A. Rich. ont Ă©tĂ© caractĂ©risĂ©s par une analyse dĂ©taillĂ©e de leur architecture dans des sols de texture diffĂ©rente en RĂ©gion Centre-Sud du Burkina Faso. Ils ont Ă©tĂ© Ă©tudiĂ©s Ă partir de plants dâĂąges divers, certains prĂ©levĂ©s en pĂ©piniĂšre et dâautres partiellement excavĂ©s en forĂȘt. Des tests dâinduction de drageonnage par sectionnement complet de racines traçantes ont Ă©galement Ă©tĂ© effectuĂ©s sur ces espĂšces. Les donnĂ©es obtenues indiquent que ces trois espĂšces semblent montrer une certaine plasticitĂ© en fonction des textures de sols et de leur Ăąge. B. aegyptiaca et S. birrea exhibent une tubĂ©risation trĂšs nette de leur pivotante dans le jeune Ăąge. En forĂȘt, des drageons ont Ă©tĂ© observĂ©s sur les racines de B. aegyptiaca et D. mespiliformis. Lâinduction artificielle de drageons en aoĂ»t, presquâen fin de la saison des pluies, a donnĂ© des rĂ©sultats positifs surtout pour S. birrea et dans une moindre mesure pour D. mespiliformis, mais pas pour B. aegyptiaca.Mots clĂ©s : SystĂšme racinaire, multiplication vĂ©gĂ©tative, Burkina Faso
Les formations à Piliostigma en zone sahélo-soudanienne du Burkina Faso: Etat des peuplements, dynamique de la régénération sexuée et pression anthropique
Les formations Ă Piliostigma au Burkina Faso connaissent une forte adoption dans les systĂšmes agrosylvopastoraux. Or, il nâexiste pas dâĂ©tude sur la dynamique et la structure des peuplements de ces ligneux.La prĂ©sente Ă©tude permet une analyse comparĂ©e de la rĂ©activitĂ© des Piliostigma face aux conditions environnementales. Suivant un transect allant du Nord au Sud du pays, des formations Ă Piliostigma (de 20 Ă 30 ans), ont Ă©tĂ© dĂ©terminĂ©es. Dans chaque peuplement, des placettes de 30 m x 30 m ont Ă©tĂ© installĂ©es. Dans la placette de 900 m2, tous les individus de Piliostigma ont Ă©tĂ© inventoriĂ©s. Les paramĂštres mesurĂ©s sont la hauteur du pied, la grosseur du tronc, le diamĂštre du houppier et la pression anthropique. Dans les placettes, deux sous relevĂ©s de 5 m x 5 m ont Ă©tĂ© effectuĂ©s pour lâapprĂ©ciation de la rĂ©gĂ©nĂ©ration. Les jeunes pieds sont dĂ©nombrĂ©s par espĂšce et rangĂ©s selon 03 classes de hauteur. La classe de hauteur] 100- 200 cm] contient la plus forte proportion des Piliostigma quelle que soit la zone phytogĂ©ographique, tandis que la classe ] 200- 300 cm] marque le dĂ©but du dĂ©clin dĂ©mographique. La population de Piliostigma diminue grandement Ă partir de la classe de houppier ] 200-300 cm] Ă d > 400 cm. Piliostigma prĂ©sente une faible rĂ©gĂ©nĂ©ration sexuĂ©e qui varie selon les zones phytogĂ©ographiques. La classe [0-20 cm[ est gĂ©nĂ©ralement la mieux reprĂ©sentĂ©e dans les diffĂ©rentes zones. La pression anthropique est diversifiĂ©e et forte sur les peuplements de Piliostigma.Mots clĂ©s: peuplements, Piliostigma, croissance, pression anthropique, rĂ©gĂ©nĂ©ration
Structure dĂ©mographique de peuplement naturel et rĂ©partition spatiale des plantules de Pterocarpus erinaceus Poir. dans la forĂȘ
Pterocarpus erinaceus de la famille des Fabaceae, est un arbre éminemment utile pour les populations. Câest une espĂšce endĂ©mique multi-usage des zones guinĂ©o-soudaniennes et soudano-sahĂ©liennes. La prĂ©sente Ă©tude analyse les paramĂštres structuraux du peuplement naturel de P. erinaceus, dĂ©termine la distribution spatiale des plantules et leurs relations spatiales avec leurs gĂ©niteurs et les autres espĂšces. Des mesures dendromĂ©triques et la cartographie des peuplements naturels de Pterocarpus erinaceus ont Ă©tĂ© effectuĂ©es dans la forĂȘt de Tiogo en zone soudanienne du Burkina Faso. Lâanalyse des structures en diamĂštre et en hauteur montre que le peuplement est dominĂ© par des individus ĂągĂ©s, les individus jeunes Ă©tant absents. La distribution spatiale des jeunes plantules de lâespĂšce montre quâelles ont une distribution grĂ©gaire et ont besoin des milieux plus ou moins ouverts pour germer. Lâanalyse de la fonction L12 (r) montre que ces plantules sont en compĂ©tition avec la plupart des espĂšces en prĂ©sence hormis Acacia macrostachya et Vittelaria paradoxa. Cette germination prĂ©fĂ©rentielle des milieux ouverts expose ces plantules Ă la sĂ©cheresse pendant la saison sĂšche, aux feux de vĂ©gĂ©tation et Ă la dent des herbivores qui parcourent chaque jour les forĂȘts en zone soudanienne.Mots clĂ©s : Structure, distribution spatiale, rĂ©gĂ©nĂ©ration, Pterocarpus erinaceus, Tiogo, Burkina Faso
Carbon storage in soils of Southeastern Nigeria under different management practices
<p>Abstract</p> <p>Background</p> <p>Changes in agricultural practices-notably changes in crop varieties, application of fertilizer and manure, rotation and tillage practices-influence how much and at what rate carbon is stored in, or released from, soils. Quantification of the impacts of land use on carbon stocks in sub-Saharan Africa is challenging because of the spatial heterogeneity of soil, climate, management conditions, and due to the lack of data on soil carbon pools of most common agroecosystems. This paper provides data on soil carbon stocks that were collected at 10 sites in southeastern Nigeria to characterize the impact of soil management practices.</p> <p>Results</p> <p>The highest carbon stocks, 7906-9510 gC m<sup>-2</sup>, were found at the sites representing natural forest, artificial forest and artificial grassland ecosystems. Continuously cropped and conventionally tilled soils had about 70% lower carbon stock (1978-2822 gC m<sup>-2</sup>). Thus, the soil carbon stock in a 45-year old <it>Gmelina </it>forest was 8987 gC m<sup>-2</sup>, whereas the parts of this forest, that were cleared and continuously cultivated for 15 years, had 75% lower carbon stock (1978 gC m<sup>-2</sup>). The carbon stock of continuously cropped and conventionally tilled soils was also 25% lower than the carbon stock of the soil cultivated by use of conservation tillage.</p> <p>Conclusion</p> <p>Introducing conservation tillage practices may reduce the loss of soil carbon stocks associated with land conversion. However, the positive effect of conservation tillage is not comparable to the negative effect of land conversion, and may not result in significant accumulation of carbon in southeastern Nigeria soils.</p
Efficacy of a cry1Ab Gene for Control of Maruca vitrata (Lepidoptera: Crambidae) in Cowpea (Fabales: Fabaceae)
Cowpea [Vigna unguiculata (L) Walp.] is an important staple legume in the diet of many households in
sub-Saharan Africa. Its production, however, is negatively impacted by many insect pests including bean pod
borer, Maruca vitrata F., which can cause 20â80% yield loss. Several genetically engineered cowpea events
that contain a cry1Ab gene from Bacillus thuringiensis (Bt) for resistance against M. vitrata were evaluated in
Nigeria, Burkina Faso, and Ghana (West Africa), where cowpea is commonly grown. As part of the regulatory
safety package, these efficacy data were developed and evaluated by in-country scientists. The Bt-cowpea lines
were planted in confined field trials under Insect-proof netting and artificially infested with up to 500 M. vitrata
larvae per plant during bud formation and flowering periods. Bt-cowpea lines provided nearly complete pod
and seed protection and in most cases resulted in significantly increased seed yield over non-Bt control lines.
An integrated pest management strategy that includes use of Bt-cowpea augmented with minimal insecticide
treatment for protection against other insects is recommended to control pod borer to enhance cowpea
production. The insect resistance management plan is based on the high-dose refuge strategy where non-Btcowpea
and natural refuges are expected to provide M. vitrata susceptible to Cry1Ab protein. In addition, there
will be a limited release of this product until a two-toxin cowpea pyramid is released. Other than South African
genetically engineered crops, Bt-cowpea is the first genetically engineered food crop developed by the public
sector and approved for release in sub-Saharan Africa
Enhancing Nutrient Use Efficiencies in Rainfed Systems
Successful and sustained crop production to feed burgeoning population in rainfed areas, facing soil fertility-related degradation through low and imbalanced amounts of nutrients, requires regular nutrient inputs through biological, organic or inorganic sources of fertilizers. Intensification of fertilizer (all forms) use has given rise to concerns about efficiency of nutrient use, primarily driven by economic and environmental considerations. Inefficient nutrient use is a key factor pushing up the cost of cultivation and pulling down the profitability in farming while putting at stake the sustainability of rainfed farming systems. Nutrient use efficiency implies more produce per unit of nutrient applied; therefore, any soil-water-crop management practices that promote crop productivity at same level of fertilizer use are expected to enhance nutrient use efficiency. Pervasive nutrient depletion and imbalances in rainfed soils are primarily responsible for decreasing yields and declining response to applied macronutrient fertilizers. Studies have indicated soil test-based balanced fertilization an important driver for enhancing yields and improving nutrient use efficiency in terms of uptake, utilization and use efficiency for grain yield and harvest index indicating improved grain nutritional quality. Recycling of on-farm wastes is a big opportunity to cut use and cost of chemical fertilizers while getting higher yield levels at same macronutrient levels. Best management practices like adoption of high-yielding and nutrient-efficient cultivars, landform management for soil structure and health, checking pathways of nutrient losses or reversing nutrient losses through management at watershed scale and other holistic crop management practices have great scope to result in enhancing nutrient and resource use efficiency through higher yields. The best practices have been found to promote soil organic carbon storage that is critical for optimum soil processes and improve soil health and enhance nutrient use efficiency for sustainable intensification in the rainfed systems