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; Tél : +221 77 402 09 18 RESUME Tamra est une vallée très sollicitée pour la culture du riz par les populations des quatre villages implantés dans l'île de Mar. L'étude pédologique a été menée suivant trois toposéquences transversales le long de la vallée. Les différents types de sols rencontrés dans ce milieu fluvio-marin sont disposés d'une manière quasi-concentrique autour de la vallée. Les sols sont affectés par le processus de salinisation et d'acidification. Les causes principales de l'avancée de ce biseau salé le long de la vallée seraient liées à l'environnement climatique peu favorable qui sévit depuis plusieurs années et qui s'exprime par des sécheresses récurrentes. La texture sableuse de ces sols, à dominance de sables fins, et leur niveau topographique font que certains d'entre eux sont exceptionnellement inondés. Ainsi, la réalisation d'une carte d'aptitude culturale des sols s'impose pour une meilleure utilisation des terres de la vallée de Tamra.

Seye et al., J. Appl. Biosci. 2018 Effet d'un dispositif biomécanique sur la récupération de sols salés et la culture du riz dans le bassin fluvio-marin du Sine-Saloum à Ndoff (Sénégal). Seye et al., J. Appl. Biosci. 2018 Effet d'un dispositif biomécanique sur la récupération de sols salés et la culture du riz dans le bassin fluvio-marin du Sine-Saloum à Ndoff (Sénégal). 13163ABSTRACT Objective: The main factors of chemical soil degradation in Senegal is salinization (Sadio 1991). The saline lands of the Sine Saloum area are constantly increasing and represent about 33% of the land surface, according to Chauvin (2013). To address this constraint, the present study exposes the effects of biomechanical design on saline soils and rice cultivation in the Sine-Saloum fluviomarine basin. Methodology and results: The experimental design is a split plot with the species factor of small bunds fixation with three variants (main factor) and the variety factor with three variants (secondary factor). The three rice varieties used are: Diayi (local variety), the War 77 and Rock5 (new varieties). The three plant species for fixing the bunds are: Gossypium hirsutum L. (GH), Andropogon gayanus. Kunt (AG) and Vetiveria zizanioides L. (VZ). The number of repetitions is 3. The results of the experimental site soil characterization revealed that the ground on which the test was conducted is a mineral, salty, acid, sulfated hydro-morph soil, on sandy alluvial-colluvial material. A significant decrease in the electrical conductivity (EC) and an increase in pH show that the established biomechanical device has greatly improved the physical and chemical soil characteristics. Local rice variety (Diayi) in the presence of a plantation of G. hirsutum L. (GH) on the bunds, received the largest average for the total number of productive suckers, the number of plants with ears and the length of the ears. The grain yield of the first season was zero because of a rainfall deficit but that of the biomass was encouraging (10, 96 t.ha-1) Thus, soil biomechanical design, accompanied by a good organo-mineral fertilizers and good agricultural practices is an effective method for the reclamation and valorization of saline lands. However, this experience deserves to be experienced with other short cycle improved rice varieties.

Influence des caractéristiques physico-chimiques des sols sur la flore et la végétation ligneuse de trois stations du tracé de la grande muraille verte du Tchad 8937 Influence des caractéristiques physico-chimiques des sols sur la flore et la végétation ligneuse de trois stations du tracé de la grande muraille verte du Tchad Minda et al. J. Appl. Biosci. 2015 Influence des caractéristiques physico-chimiques des sols sur la flore et la végétation ligneuse de trois stations du tracé de la grande muraille verte du Tchad 8938Effect of soil physico-chemical characteristics on the flora and timber vegetation at three sites of Chad's great green wall line ABSTRACT Description of the subject: Chad, located in a dry to semi-dry zone, is characterized by lot of environmental constraints including severe droughts, soil degradation due to insufficient rainfall and strong wind erosion. Objectives: This study was carried to evaluate the influence of soil's physico-characteristics (texture, salinity and alkalinity) on the flora and timber vegetation at three sites (Lac, Kanem and Bahr El Ghazal) of Chad's Great Green Wall. Methodology and Results: Ten pedologic profiles were described with 3 to 4 profiles per site. Physico-chemical analyses (granulometry, pH, electric conductivity) were carried out using the soil samples of the different profiles. The floral composition and the structure of timber populations around the environment of ten pedologic profiles were determined. The principal component analysis (PCA) of the matrix of the ten described pedologic profiles, the five analyzed soil's physico-chemical parameters and the heighten species recorded in the three sites have evidenced the existence of three groups of soil in relation to the physico-chemical parameters and three groups of species alongside the line. Conclusions and application of results: From this study, it appears that the salinity, the alkalinity and the high content in sand of soils are the major constraints of vegetal production in this Sahelian zone.

From systematic inventories of plant species, this article analyses the floristic composition, and biological and chorological spectra of taxa identified in Lake Guiers following the building of major dams on the Senegal River in the late 1980s; they have improved storage of fresh water and the maintenance of limnimetric height level throughout the year. We have listed 101 species belonging to 64 genera and 30 families. The dicotyledons are more than twice as numerous as the monocotyledons, and the pteridophytes make up 10%. The most diverse families are, in order of size: Poaceae, Cyperaceae, Fabaceae, Amaranthaceae, Convolvulaceae and Oenothoraceae. Half of the families are represented by at least two species. The helogeophytes and therophytes represent half of the biological forms while supernatant hydrophytes constitute only 7% of the flora. The vast majority of species have broad geographical, pantropical and palaeotropical distributions. Cosmopolitan and Sudano-Guinean-Zambezian taxa occur in the same proportions (15%). Better management of the water is essential to control aquatic macrophytes and protect or improve the lake's biodiversity.

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