Submitted to: Soil Erosion for 21st Century Symposium
Publication Type: Proceedings
Publication Acceptance Date: 1/3/2001
Publication Date: 1/3/2001
Citation: In: J.C. Ascough and D.C. Flanagan (eds.) Soil Erosion Research for the 21st Century - An International Symposium, ASAE; 2001 Jan 3-2001; St. Joseph, MI. Interpretive Summary: Few direct estimates are currently available on the extent of soil losses by wind erosion in traditionally managed farmers fields. European scientists collaborated with an ARS scientist to evaluate on-farm field-scale soil loss by wind erosion in the West Africa Sahel. We found in this study that sediment fluxes in a cultivated field increased linearly over a distance of 250 feet from the edge of the field. Most of the air-borne sediments from the eroding field were deposited within 100 feet of an adjacent non-eroding fallow field. Except for the fraction of fine sediment that goes into suspension most of the eroded material is subject to local redistribution within fields or between adjacent land units.
Technical Abstract: 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 Big Spring Number Eight (BSNE) sand traps. Results from a first study in 1997 indicated that sediment fluxes in na cultivated field increased linearly over distances 80m, 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 10 kg m-1. Mass balances as great as -17.5 and + 10.5 Mg ha-1 were measured in a single storm in the field and fallow, respectively. Starting in 1998, a second study was set up 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 soi loss of -5.0 Mg ha-1 in 1999. This was attributed to changes in ground cover and differences in sediment influx from adjacent fields. Keywords: Sahel, wind erosion, on-farm, land degradation, sand trap