Wind erosion control with crop residues in the Sahel

Mulching for wind erosion control in Sahelian farming systems is limited by low biomass production and use of crop residues for other purposes. The aim of this study was to test the effectiveness in soil protection created by two low amounts of crop residues. A field experiment was conducted in southwest Niger, on a Psammentic Paleustalf (sandy, siliceous, isohyperthermic) during the early rainy seasons of 1994 and 1995. Particle mass transport was quantified in two plots of 55 by 70 m. During the first storms of both seasons, the plots were without a mulch cover. Afterward, one plot was covered with nat pearl millet [Pennisetum glaucum (L.) R. Pr.] stalks. The application rates were 1500 and 1000 kg ha(-1) during the first and second seasons, respectively. To quantify the mulch effect, mass transport rate differences between the two bare plots were quantified with a multiple linear regression model (R-2 = 0.89), using wind speed (7.4-12.3 m s(-1)), wind direction, and storm duration (464-3835 s). Total mass transport rates were reduced from 365.2 to 132.9 g m(-1) s(-1) (63.6%) with 1500 kg ha(-1), and from 325.1 to 188.0 g m(-1) s(-1) (42.2%) with 1000 kg ha(-1) of crop residues. Soil protection tended to decrease with increasing wind speed. Linear regression indicated that the reduction in mass transport becomes zero at wind speeds of 11.1 and 16.0 m s(-1) for the 1000 and 1500 kg ha(-1) covers, respectively, The 1000 kg ha(-1) cover even enhanced sediment transport by 6.5% during one storm with a nind speed of 11.3 m s(-1). The 1500 kg ha(-1) mulch cover reduced sediment transport from 49.7 to 80.2% during five storms with wind speeds varying from 8.3 to 10.6 m s(-1), and is therefore recommended as the better application rate for wind erosion control in the Sahel.