St-Pierre-Lepage, S et al. "Use of six annual companion crops to establish alfalfa–timothy mixtures at different seeding dates" Agronomy Journal. 2023

Oat (Avena sativa L.) is the main species used as a companion crop when establishing perennial forages in eastern Canada, and, although other annual species are used, they have not been systematically evaluated. A field study was conducted across five environments to contrast the use of six annual species (berseem clover, Trifolium alexandrinum L.; forage peas, Pisum sativum L.; annual ryegrass, Lolium multiflorum Lamarck; oat; Japanese millet, Echinochloa esculenta [A. Braun] H. Scholz; sudangrass, Sorghum × drummondii [Nees ex. Steud.] Millsp. & Chase) as companion crops for the establishment of alfalfa (Medicago sativa L.)-timothy (Phleum pratense L.) mixtures. The control treatment consisted of the perennial species seeded without companion crop. Treatments were seeded at three dates and evaluated during the seeding and post-seeding years. The performance of the six companion crops evaluated herein varied depending on the seeding date and the environment. For a mid-May to early June seeding total seeding year forage mass was greatest with use of oat, Japanese millet, or sudangrass as companion crops; for a mid-June to late June seeding with Japanese millet or sudangrass; and for a late July to early August seeding with oat or Japanese millet. These species, however, reduced in some environments seeding year alfalfa or timothy mass compared to a control seeded without a companion crop. Such reduction was also observed in some environments in the first post-seeding year. Companion crop choice to establish alfalfa–timothy mixtures needs to take into consideration seeding date and forage needs on the short term versus the long term.