The New Mexico State University Extension recommends the use of glyphosate for the control of all bluestem grasses. The chemical is sold under different trade names.
Products containing glyphosate are systemic, non-selective herbicides that help to control a number of sedges, grasses, woody plants and broad-leaved weeds. The broad-spectrum herbicide is used for weed control on crops and non-crop areas. Glyphosate is often used in combination with other chemicals to increase efficacy.
Target spray shorter KR bluestem with herbicide. You can brush the herbicide on the leaves of the taller growing weeds. This will help to reduce damage to the desired plants or grass around the weed. You will have to repeat the application for proper effect. After the weed is eradicated, reseed the bare land with desired grass.