Technical Abstract: Warm-season annual grasses may be suitable as herbicide-free forage crops. A two-year field study was conducted to determine whether tillage system and nitrogen (N) fertilizer application method influenced crop and weed biomass, water use, water use efficiency (WUE), and forage quality of three warm-season grasses, and seed production by associated weeds. Tillage systems were preplant- or zero tillage (ZT). The N fertilization methods were urea broadcast or banded at planting. Warm-season grasses were foxtail (Setaria italica L.) and proso (Panicum mileaceum L.) millets, and sorghum-sudangrass (Sorghum bicolor (L.) Moench X S. sudenense Stapf. cv. Piper). Density of early emerging weeds was similar among treatments, averaging 51 m-2. At harvest, sorghum-sudangrass produced significantly greater biomass and N accumulation than either millet. Millets exhibited higher weed density and weed biomass than sorghum-sudangrass. Water use and WUE did not vary among treatments or grasses and respectively averaged 157 mm and 25.1 kg mm ha-1. Weed seed production by redroot pigweed and green foxtail was respectively 93 and 73% less in sorghum-sudangrass than proso millet. Warm-season grasses offer an excellent fit in semiarid cropping systems, however, improved management systems are needed to reduce seed production by associated weeds in the absence of in-crop herbicide use.