Dynamique des compartiments du carbone et de l'azote dans le sol cultivé en niébé et sorgho dans le système zaï en zone Nord soudanienne du Burkina Faso

La gestion appropriée des sols cultivés peut permettre un stockage de carbone, en plus de l’avantage supplémentaire du maintien du niveau de fertilité qui en résulte. L’objectif de cette étude est d’appréhender l’influence réelle de pratiques culturales sous niébé ou sorgho dans le système zaï, sur l’évolution et  l’organisation des teneurs de carbone (C) et d’azote (N) du sol à l’échelle de la parcelle. Un dispositif factoriel en blocs de Fisher a été utilisé. Les traitements comprenant des apports de fumier seul ou associé au burkina phosphate avec exportation des résidus de cultures ont été testés. Le fractionnement  granulométrique de la matière organique du sol a été utilisé, séparant trois fractions. Les résultats révèlent que la répartition de C et N dans les fractions  granulométriques n’a pas été affectée par les espèces cultivées. Quelle que soit la culture, le carbone et l’azote se trouvent  essentiellement sous forme de  matière organique stable dans la fraction 0-20 μm, soit respectivement 64% et 73% pour C et N. L’apport du fumier seul ou combiné au phosphate, entraîne une  augmentation de la matière organique labile ; 38% de C et 31% de N sont stockés dans la fraction 50-2000 μm. La dynamique de la matière organique du sol à  l’échelle de la parcelle est plus influencée par les amendements que par les espèces cultivées.Mot clés : Matière organique, sols dégradés, légumineuse, céréale, fumier, burkina phosphate

Valorisation de substrats organiques divers dans l'agriculture péri-urbaine de Ouagadougou (Burkina Faso) pour l'amendement et la fertilisation des sols : acteurs et pratiques

Organic substrates recycling in the sub-urban agriculture of Ouagadougou (Burkina Faso) for soils fertilization: description of the different actors and their practices. This study aimed to establish an overview of the main actors of the sub-urban agriculture of Ouagadougou, their practices and expectations, and to characterize the used organic substrates (OS). For that, a farm survey was carried out on the most representative sites with 64 persons (cereal farmers, truckers and nurserymen) randomly chosen. OS were sampled with each actor, when available. Thus, 27 samples were taken and characterized through chemical analyses and laboratory incubations to follow organic carbon mineralization. The results highlighted that 35% of cereal farmers, 69% of truckers and 95% of nurserymen were 20 to 40 years old, that a large proportion of cereal farmers and truckers were not sent to school while 70% of nurserymen had at least primary education. Sub-urban agriculture was the only activity for 43% of farmers, 83% of truckers and 91% of nurserymen. Moreover, 71% of cereal farmers and 73% of nurserymen used municipal wastes as source of organic matter against only 17% of truckers, the majority of them using animal manures. The main criterion of choice of OS was their availability without any other consideration. Even if a large majority of the actors think that composts of OS were better than brut OS, a minority of them used currently composts. The best ways for an adoption and utilization of OS composts were to facilitate their accessibility and to promote these composts, composting techniques and their interests through advertising in mass media. Chemical analyses and laboratory incubations showed a great variability of the SUW, both in the same group and actors' groups. However, in case of total organic carbon, total nitrogen and total phosphorous contents, the following tendencies were observed: Contenttruckers > Contentfarmers > Contentnurserymen. For the sum of major elements Ca, K, Mg, Na (SME), it was observed that SMEtruckers ≈ SMEfarmers > SMEnurserymen. In addition, except a few atypical substrates, OS used by nurserymen were largely stabilized compared to those of cereal farmers and truckers

Morphological Abnormalities in Vitamin B6 Deficient Tarsometatarsal Chick Cartilage

The aim of this study was to test the hypothesis that deficiency of vitamin B6 would produce morphological characteristics of osteochondral lathyrism. To accomplish this goal, morphological characteristics of chick cartilage in which lathyrism was produced by two separate dietary regimens was compared to morphological changes encountered in vitamin B6 deficiency. Vitamin B6 deficiency should reduce activity of lysyloxidase needed for producing intermolecular cross-links. The question to be addressed was: would this latter deficiency impair collagen morphological features and secondarily other structures indirectly by reducing collagen molecular assembly? Failure of cross-linking of collagen in the positive controls was related to a lack of functional aldehyde cross-link intermediates which are blocked by homocysteine and aminoacetonitrile. Day-old-male Lohmann chicks were fed adequate (6 mg/kg) or vitamin B6-deficient diets. Cross-link defects were induced by homocysteine-rich diets (0.6% w/w) or a diet containing aminoacetonitrile (0.1% w/w). Animals were sacrificed at 6 weeks of age and Ossa tarsalia articular cartilage specimens, as well as the proximal end of tarsometatarsus were dissected from the tibial metatarsal joint, a major weight-bearing site. Light microscopic observations revealed reduction of subarticular trabecular bone formation, concurrent with overexpansion of the hypertrophic cell zone. Ultrastructural electron microscopy observations of articular fibro-cartilage indicated significant thickening of collagen fibers in vitamin B6 deficient birds, as well as the positive controls in comparison to that of cage-matched control birds. It was concluded that vitamin B6 deficient cross-linking may be responsible for the observed delay in bone development and aforementioned cartilage histological alterations

Linking green militarization and critical military studies

The precipitous increase in commercial poaching across parts of Africa has been met by progressively more militarized responses. Amounting to green militarization, we now see national armies, increasingly paramilitarized rangers, military tactics, and even sophisticated military technology used to address the problem. Scholarly investigations on the topic have largely been approached from a political ecology perspective and hence have not made connections with the equally relevant field of critical military studies (CMS). We see this as a missed opportunity. This paper is thus an early attempt to begin forging these connections. At the most general level, we introduce green militarization – as a practice and realm of scholarly debate – into CMS. By bringing in environmental conservation and non-human nature, this offers a broader view into the vast areas of nominally civilian life that are increasingly militarized, a defining interest of CMS. Second, we draw from core CMS insights – especially regarding the link between development and security – to grasp changing practices and trends in green militarization. In particular, we illustrate how the recent shift towards softer militarized approaches amounts to poaching-related soft counter-insurgency, which we capture in the concept of the conservation–security–development nexus. Here, communities become the object of development interventions to ‘win hearts and minds’ and prevent their involvement in poaching, thereby neutralizing the security threats poaching might pose. We close by suggesting future areas of intersection between CMS and the political-ecological work on green militarization in hopes of inciting a deeper engagement