Two of the major concepts used to describe sustainability in agriculture are to keep land productive for the long term and to improve our basic resources (Box 1994). One of the primary concerns is to prevent an increase in desertification. The judicious use of herbicides is a principal method to reduce further degradation of, and improve, rangelands in the Chihuahuan Desert. Mesquite, creosote bush, and tarbush (scientific names of plants