On-farm evaluation of field-scale soil losses by wind erosion under traditional management in the Sahel

In the West African Sahel, few direct estimates are currently available on the extent of Soil losses by wind erosion in traditionally managed farmers fields. Field scale sediment balances in western Niger were derived from airborne sediment fluxes measured using BSNE sand traps. Results from a first study in 1997 indicated that sediment fluxes in a cultivated field increased linearly over distances :5 80 m, irrespective of wind power. Sediment deposition in an adjacent fallow was well described by an exponential decay function with a near constant trapping efficiency coefficient of 0.1 m(-1) for incoming sediment fluxes greater than or equal to 10 kg m(-1), Mass balances up to -17.5 and +10.5 Mg ha(-1) Acre measured in a single storm in the Field and fallow, respectively. Starting in 1998, a second study was setup in a newly cleared, 8 ha farmer's field equipped at 87 locations with BSNE sand traps Whereas a net sediment balance of +5.4 Mg ha(-1) was measured in 1998, the experimental field was subject to a net soil loss of -5.0 Mg ha(-1) in 1999. This was attributed to changes in ground cover and difrerences in sediment influx from adjacent fields.