WIND EROSION CONTROL WITH CROP RESIDUES IN THE SAHEL

Mulching for wind erosion control in Sahelian farming systems is limit ed by low biomass production and use of crop residues for other purpos es. The aim of this study was to test the effectiveness in soil protec tion created by two low amounts of crop residues. A field experiment w as conducted in southwest Niger, on a Psammentic Paleustalf (sandy, si liceous, isohyperthermic) during the early rainy seasons of 1994 and 1 995. 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 mu lch cover. Afterward, one plot was covered with nat pearl millet [Penn isetum glaucum (L.) R. Pr.] stalks. The application rates were 1500 an d 1000 kg ha(-1) during the first and second seasons, respectively. To quantify the mulch effect, mass transport rate differences between th e two bare plots were quantified with a multiple linear regression mod el (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 reduc ed 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 spee d. Linear regression indicated that the reduction in mass transport be comes zero at wind speeds of 11.1 and 16.0 m s(-1) for the 1000 and 15 00 kg ha(-1) covers, respectively, The 1000 kg ha(-1) cover even enhan ced sediment transport by 6.5% during one storm with a nind speed of 1 1.3 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 applica tion rate for wind erosion control in the Sahel.