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 proc ess in the Sahel, Set little quantitative information is available for that region on soil losses by wind erosion under different land management prac tices. A 3-yr, on-farm experiment was, therefore, set up to assess the effe ct 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 ap proximately perpendicular to the orientation of ridges and residue bands, s ediment mass balances were calculated from the change in horizontal sedimen t mass fluxes measured across the experimental plots with Big Spring Number Eight sand traps. Mass balance calculations for 16 events over 3 yr indica ted 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 i n 1995, 1996, and 1997, respectively, Broadcast and banded residue mulches were not significantly different (P = 0.05) in terms of their sediment trap ping efficiency. During the same time period, ridges reduced soil losses by an average of 57% compared with the control plots, but their efficiency wa s reduced to less than 15% after 100 mm of cumulative rainfall as ridges co llapsed. Linear regression analysis using the incoming sand fluxes as the i ndependent variable was used to estimate potential soil losses for all even ts with sediment fluxes <25 kg m(-1) irrespective of wind direction. The ca lculations 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 singl e gear. For wind erosion control, broadcast millet stover mulching constitu ted the most effective control technique because it effectively protected t he soil against erosion and its trapping efficiency is expected to be indep endent of wind direction.