On-farm evaluation of ridging and residue management practices to reduce wind erosion in Niger

Wind erosion is regarded as a major contributor to the desertification process in the Sahel, Set little quantitative information is available for that region on soil losses by wind erosion under different land management practices. A 3-yr, on-farm experiment was, therefore, set up to assess the effect of ridging and either banded or broadcast millet stover mulches (2000 kg ha(-1)) on soil loss in a millet-coo,pea intercrop, For wind directions approximately perpendicular to the orientation of ridges and residue bands, sediment mass balances were calculated from the change in horizontal sediment mass fluxes measured across the experimental plots with Big Spring Number Eight sand traps. Mass balance calculations for 16 events over 3 yr indicated an average soil loss of 17.5, 15,4, and 18.0 Mg ha(-1) On control plots, and deposition of 15,5, 15,3, and 7.4 Mg ha(-1) on banded residue plots in 1995, 1996, and 1997, respectively, Broadcast and banded residue mulches were not significantly different (P = 0.05) in terms of their sediment trapping efficiency. During the same time period, ridges reduced soil losses by an average of 57% compared with the control plots, but their efficiency was reduced to less than 15% after 100 mm of cumulative rainfall as ridges collapsed. Linear regression analysis using the incoming sand fluxes as the independent variable was used to estimate potential soil losses for all events with sediment fluxes <25 kg m(-1) irrespective of wind direction. The calculations indicated potential soil losses of up to 79 Mg ha(-1) on control plots and deposition of 41 Mg ha(-1) on broadcast residue plots in a single gear. For wind erosion control, broadcast millet stover mulching constituted the most effective control technique because it effectively protected the soil against erosion and its trapping efficiency is expected to be independent of wind direction.