Infiltration and Sediment Rates Following Creosotebush Control With Tebuthiuron

Abstract

The effects of chemical creosotebush (Larrea tridentata [D.C.] Cov.) control on infiltration rates, wetting-front depth, and sediment production were examined in the Chihuahuan Desert of southern New Mexico. Study sites were treated with aerial applications of tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N’-dimethylurea) as part of a brush control program administered by the US Bureau of Land Management. Study sites were equally distributed among 3 geographic regions and included 6 sites treated 5-9 years ago, 6 sites treated 15-18 years ago, and 12 contiguous nontreated sites. Paired 1-m2 rainfall simulation plots encompassed the creosotebush canopy zone and adjacent interspace area with runs made using simulated rainfall at 9.1 cm hr-1 for 30 minutes. Runoff and sediment were collected every 5 minutes, and wetting-front depths were measured at the end of rainfall simulations. Infiltration rates were significantly higher in the canopy zone than in interspace areas and were highest in 5-9-year-old sites, intermediate in nontreated sites, and lowest in 15-18-year-old sites. Regression equations showed that infiltration rates within the canopy zone were positively correlated with litter mass, and cover of litter, shrubs, and grasses. Within interspace areas, infiltration rates were most correlated with aggregate stability and cover of litter, rocks, and grasses. Wetting-front depths were significantly deeper in the canopy zone than in interspace areas for all treatments. Sediment concentration (kg L-1) was higher in the canopy zone than interspace, but total sediment yield was not significantly different between these areas or affected by any treatments.