Fonctionnement hydrique de différents types de placages sableux dans le sahel burkinabè

The study was performed in the Sahelian part of Burkina Faso. The country is subject to difficult climatic conditions, a strong demographic growth and a continuous decrease in soil fertility. The resulting degradation affects the processes which govern ecological systems and leads, on the long run, to a modification of the ecosystems. This is particularly the case of the eolian formations, the only ecological units susceptible of being useful in the area, since they present good infiltration capacity and support the main part of the vegetation. Field measurements (rainfall, runoff, saturated hydraulic conductivity, bulk density, hydraulic conductivity function, soil water content and pressure head) have been done to asses the impacts of the environmental degradation on the hydrodynamic behavior of these formations. Within this context, an experimental device made of seven measurement sites has been installed in three contrasting zones. The results show significant differences in the hydrodynamic behavior of the soils, according to their surface properties. On one hand, the sites located on an erosion crust as well as on a drying crust in transition towards an erosion crust, are characterized by a low infiltration capacity which favors runoff. The quantity of infiltrated water is very low when compared to total precipitation. Water is stored near the soil surface (in the first 30 cm) favoring evaporation in the days following rainfall events. Thus, little water is available for plants. The resulting water stress causes a weak density, or even complete absence of plants which have difficulties to colonize such surfaces. Surface runoff is favored with runoff coefficients ranging from 50 to 80 %. On the other hand, the sites situated on drying crusts are characterized by good hydraulic conductivity and infiltration capacity. The storage of water in the root zone is more important. Water flows deeper into the soil and, occasionally, drains at the reference depth of 50 cm. The runoff coefficients were found to be lower than in the other sites (30 to 40 %). This differentiated behavior is one of the main factors affecting the formation of different landscapes in the area through the existence of a relationship between soil surface properties, the type of landscape and the ratio runoff/infiltration. The sites located on an erosion crust and those in transition towards an erosion crust behave like impluviums, while those situated on drying crusts are more favorable to infiltration. Observation of the evolution of the hydraulic properties of the soil surface shows a progressive alteration that frequently leads to strongly degraded mediums unfavorable to plants. Control and rehabilitation methods considered in the study, namely "restoration" and "mise en défens" have only partial and time-limited effects; they do not make it possible to stop durably degradation or to favor rehabilitation. Among the other measures assessed on the INERA plots, only the restitution to the soil of the beforehand mown plants causes an improvement of the soil surface properties; the restitution causes the formation of an important macroporal system favoring water infiltration and circulation in the soil. The effects of those different measures occur mainly in the first years after their introduction and concern especially vegetation regeneration, soil protection against degradation factors, improvement of hydrodynamic soil properties, reduction of runoff and erosion. They make it possible to slow down soil degradation, but not to stop it definitively. Within this context, proposals of further studies focussed on other measures to control and rehabilitate degraded areas have been suggested, taking into account the specificity of the sahelian zone, the endogenous knowledge of the agro-pastors, as well as socio-economic and ecological conditions

Clinical and pathological kidney aspects of sickle cell anemia at Dakar: study of 11 cases of renal biopsies

Few studies are devoted to the practice of renal biopsy in sickle cell nephropathy; our objective was to determine the histological and evolutionary patterns of renal lesions in sickle cell patients who underwent renal biopsy in Dakar.Methods:This was a retrospective multicentric study (conducted from December 2009 to August 2011) on renal biopsies performed on sickle cell anaemic patients at the Nephrology Department of Teaching Hospital Aristide Le Dantec and the Albert Royer Childrens Hospital. The histological, therapeutic and evolutionary data were analysed.From the 292 total renal biopsies, 11 (3.80%) were performed on sickle cell patients (6SS, 1SBth + 4 AS) with a mean age of 23.1 [13-51 years]. Nephrotic syndrome was the indication of renal biopsy in all cases. Focal segmental glomerulosclerosis was the most frequent histological finding (five cases), followed by a combination of various specific lesions (hypertrophy of glomerular and peritubular capillaries), minimal glomerular lesions (three cases), membranoproliferative glomerulonephritis (two cases) and extra-membranous glomerulonephritis (one case). Complete remission after treatment was achieved in seven cases and one patient expired. Three patients did not continue with follow-up appointments.Conclusions:Renal biopsy is not very frequent in the course of sickle cell anaemia and in most cases it is performed because of nephrotic syndrome. The histological findings are diverse with a predominance of focal segmental glomerulosclerosis

Relationship between soil water content and crop yield under sahelian climate conditions: case study of Tougou experimental site in Burkina Faso

This study aims at assessing the relationship between soil water stock and the yield of agricultural practices in Tougou catchment located in northern Burkina Faso. It is a region that has experienced a significant and continuous degradation of its natural resources, especially soils, due to the climate variability and the rapid increase of the population. Areas allocated to subsistence agriculture are increasing at the expense of pastoral land. This degradation causes a change in processes and mechanisms that control ecological systems. In order to provide solutions to this issue, some agricultural practices have been implemented to improve crop yield. This is particularly the case of traditional techniques:za, stony line and half-moon, which can significantly improve the soil infiltration capacity and yield. Daily monitoring of soil moisture and pressure in experimental plots based on these agricultural practices show that half-moon and Za¯ provided good yield with 2180kg / ha and 1070 kg / ha respectively compared to that of the control plot with about 480 kg/ha. These important yields are due in large part to the improvement of the retention capacity of these soils, thus giving to crops the necessary water need for their development even in drought period

Local contextual factors of child stunting found via shared values of stakeholder groups: an exploratory case study in Kaffrine, Senegal

Abstract Objective: This work aims to demonstrate an original approach to identify links between locally-situated shared values and contextual factors of stunting. Stunting results from multi-factorial and multi-sectoral determinants, but interventions typically neglect locally-situated lived experiences, which contributes to problematic designs that are not meaningful for those concerned, and/or relatively ineffective. Design: This case study investigates relevant contextual factors in two steps: by first facilitating local stakeholder groups (n=11) to crystallize their shared-values-in-action using a specialised method from sustainability studies (WeValue_InSitu). Secondly, participants (n=44) have focus group discussions about everyday practices around child feeding/food systems, education, and/or family life. Because the first step strongly grounds participants in local shared values, the FGDs can reveal deep links between contextual factors and potential influences on stunting. Setting: Kaffrine, Senegal, an “Action Against Stunting Hub” site. December 2020. Participants: Eleven stakeholder groups of mothers, fathers, grandmothers, pre-school teachers, community health-workers, farmers, market traders, public administrators. Results: Local contextual factors of stunting were identified, including traditional beliefs concerning eating and growing practices; fathers as decision-makers; health worker trust; financial non-autonomy for women; insufficient water for preferred crops; merchants’ non-access to quality produce; religious teachings; and social structures affecting children’s food environment. Conclusions: Local contextual factors were identified. Pre-knowledge of these could significantly improve effectiveness of intervention designs locally, with possible applicability at other sites. The WeValue_InSitu approach proved efficient and useful for making tangible contextual factors and their potential links to stunting, via a lens of local shared values, showing general promise for intervention research

How Non-Governmental-Organization-Built Small-Scale Irrigation Systems Are a Failure in Africa

Every year, millions of dollars are invested in irrigation development in Sahelian African countries. After shifting from governmental organizations to non-governmental organizations (NGOs), the vulnerability of local populations has not changed much over the last 60 years in Africa. In this study, ten 1 ha small-scale irrigation systems—spread over the two driest climatic zones—were investigated in Burkina Faso. The soils and subsoils were characterized using double-ring infiltration measurements and two soil databases. The irrigation systems’ operability was assessed by sampling 10–12 farmers per system. A total of eight pumping tests were performed on a sample of wells. To assess the yield of cultivated onion, 5 to 7 squares were followed up in each of the 10 systems. Results indicated that water availability was ensured nowhere. The 32 wells were dug in clayey subsoils. Six of them yielded available water Ve flows ranging from 0.0 to 6.1 m3/day, far below the 80 m3/(ha·day) required by onion. To solve this issue, the NGOs shifted to a low-pressure drip irrigation solution, but the too-low pressure of 0.1 bar led to clogging. Ultimately, all 10 systems (except Louda) broke down a few months after the project’s end