Influence of Re-Greening on the Infiltrability of Soils in South-Central Niger

Abstract

In the Sahel, the climate and the agricultural practices are the main factors used to observe regreening process. But the extension of the latter not being uniform in the farming fields, we can suppose that there are other factors that contribute to the re-greening of certain zones and not others. The infiltrability of soils is considered as an important factor for these changes in the last decades. The influence of re-greening on the infiltrability of soils in the southern strip of Niger was studied through a comparison of zones according to the type of sandy soils ( Jigawa/Rerey ), siltyclay ( Guiéza ), silty-sandy ( Hako ) and clay-silty-sandy ( Laka ). The evaluated parameters are the texture, the infiltrability and the ecological characteristics (specific index of regeneration “SIR” and the Importance Value Index “IVI”). The main conclusions were: the soils of Niger South-Central are characterized by a sandy texture for more than 80%. The soils which are very sandy (“ Jigawa ”, “ Rerey ” and “ Guieza ”) are more permeable and have more trees contrary to the soil Hako and Laka . Their encrusting has the tendency to reduce the vegetation cover on the soil. The infiltration measurements indicated that the rate of initial and stationary infiltration diminishes while going down towards the South. In fact, it has been recorded a rate of 123 mm/min of initial infiltration and 87 mm/min stationary in Dan Saga on the sandy soils against 76 mm/min and 65 mm/min in Daré respectively for the initial and stationary rate. Therefore, the infiltration seems to influence the density, the SIR and the IVI of the trees from the North towards the South. Some additional work is necessary in order to determine the contribution of Farmer Managed Natural Regeneration (FMNR) in the improvement of the quality of soils and the movement of water in the superficial zones of the soil.