0000000000562993
AUTHOR
Zibo Garba
Six années de suivi du flux d'érosion éolienne sur un sol sableux cultivé au Sahel : Impacts des résidus de culture et de l'encroûtement
In the Sahel, wind erosion occurs particularly in cultivated fields. This work was leaded at Banizoumbou in Niger where wind erosion fluxes have been measured for six years. The aims of this study was i) to monitor crop residues cover on traditional field and to quantify its influence on wind erosion ii) to characterize the impacts of soils crusting on erosion flux, iii) to characterize the impact of herbaceous strips on wind flux. Results showed that crop residues efficiently prevent cultivated fields from wind erosion during the dry season (January to April) and considerably reduce erosion fluxes at the beginning of the rainy season (May to July). Under a minimal crop residues cover rate …
Evolution des paysages Sahélines au cours des six dernières décennies dans la région de Niamey : de la disparition de la brousse tigrée à l'encroutement de surface des sols
In the Sahel, the rapid increase of the population during the last decades and the climate variation lead to an important environmental degradation. This work aims to measure the impacts of the human pressure on ecosystem during the six last decades. A diachronic cartography of a 100 km² area close to Niamey was done with aerial photographs (1950 and 1975) and GPS measurements (2009). Results showed that the tiger bush vegetation was completely cleared between 1950 and 2009 while the fallow decreases from 7 % to 1 %. In the sandy valley, the increase of cultivated fields from 20,7 % (1950) to 69,4 % (1975) favoured wind and water erosions which allowed surface soil crusting. Between 1975 an…
Classification et chronologie de bas fourneaux de réduction du fer à usage unique au sud-ouest du Niger
In southwestern Niger, near Niamey, several thousand single-use bloomery furnaces have been mapped and identified. The archaeological study of approximately 30 furnaces and their slag reveals the existence of four methods for iron smelting: three types of pit furnace and one slag-tapping type. The slag pit furnaces are clearly differentiated by the form and volume of their pits. All slag-tapping furnaces drain off slag through small openings. The slag is tapped either vertically or laterally. According to radiocarbon dates, the smelting activity developed in the 2 nd century AD and intensified through to the 14 th century. It continued to evolve until the middle of the 20 th century. The lo…
Impact of very low crop residues cover on wind erosion in the Sahel
International audience; In the Sahel, with average annual precipitation in the order of 500 mm yr− 1, wind erosion occurs mainly on cultivated millet fields whose surfaces are only partially covered by crop residues. The impact of these residues on wind erosion was not clearly established. The objective of this study is thus to quantify the actual amount of crop residues in traditional Sahelian fields and to determine their impacts on wind erosion by reference to a bare surface throughout the seasonal cycle over several years. At the beginning of the year during dry season, Sahelian farmers use to "clean" their fields, i.e. cut and lay flat on the soil surface any millet stalks still standi…