Companion crops and weeds compete with alfalfa (Medicago sativa L.) during establishment and affect forage yield, composition, quality, population density, and net income. We compared four establishment systems seeded in April and again in May. The four systems were (i) oat (Avena sativa L. var. 'Starter') mulch with a postemergence herbicide on oat leaving residue, (ii) oat companion crop harvested at boot stage, (iii) solo seeding with a herbicide, and (iv) solo seeding without a herbicide. Field studies were conducted for 2 yr on a Waukegan silt loam (mixed, mesic Typic Hapludoll). The highest season total forage yields were obtained with solo seeding without herbicide and with oat companion crop systems. The highest season total alfalfa yields and lowest percentage oat or giant foxtail (Setaria faberi Herrm.) composition in forage were obtained when solo seeding with herbicide. Forage usually contained significant levels of oat or giant foxtail when managed without herbicides. Forage relative feed value (RFV) was highest with alfalfa solo seeding with herbicide, and lowest with companion crop or solo seeding without herbicide systems. Use of herbicides to establish alfalfa consistently resulted in forage of highest quality and value, but not always the highest net income after yield and production costs were considered. April plantings resulted in higher net income than May plantings. When soil moisture was adequate and the date of seeding conducive for alfalfa growth, the most profitable method of establishing alfalfa was with oat mulch systems, or when solo seeding with herbicide. If alfalfa planting was delayed or soil moisture limiting, herbicide systems were similar to, or less profitable than the oat companion crop or solo seeding without herbicide systems. Oat companion crop or giant foxtail did not decrease alfalfa population density the year following establishment, and decreased residual alfalfa yield in only one of four seeding dates.
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