Technical Abstract: The use of killed cover crop mulch for weed suppression has been demonstrated in organic no-till or zero-till farming systems in eastern U.S. regions and in Canada. Implements have been developed to make this system possible by terminating cover crops mechanically with little if any soil disturbance. Ongoing research in the U.S. northern Great Plains is being conducted to identify cover crop species and termination methods for use in organic zero-till (OZ) systems that are adapted to the crop rotations and climate of this semiarid region. Several obstacles must be overcome before the use of killed cover crop mulch can be promoted as a weed control alternative to tillage in organic farming systems in the U.S. northern Great Plains. In particular, cover crop termination methods must be improved so that cover crop species are killed consistently and early enough in the growing season so that subsequent cash crops can be grown and harvested successfully. Even when these problems are solved, use of vegetative mulch produced by killed cover crops will not be a panacea for the weed control challenges faced by organic growers. Rather, cover crop mulches must be used along with crop rotation, novel grazing strategies, the judicious use of high-residue cultivation equipment, and perhaps the use of approved herbicides with systemic activity in some instances, to provide organic farmers with new opportunities to practice conservation tillage.