Forage yield and quality of six annual Medicago species in the north-central USA

Annual medics (Medicago spp.) have been extensively used as winter annual forage and green manure crops in Mediterranean regions, but their potential use in the north-central USA has not been evaluated. Our objective was to determine the summer and fall forage yield and forage quality of spring- and summer-seeded annual medics. Twelve commercial annual medic cultivars from Australia (representing five species) and 'George' black medic (M. lupulina L.), 'Nitro' alfalfa (M. sativa L.), and 'Arlington' red clover (Trifolium pratense L.) were seeded in spring and summer at Rosemount and Morris, MN, in 1991 and at St. Paul and Becker, MN, in 1992. Forage yields were taken at a single harvest in summer (when most medics were reproductive) from spring-seeded stands and in the fall first frost (0°C) from summer-seeded stands. Forage yields of spring and summer-seeded annual medics ranged from 1.2 to 5.7 and 0.5 to 5.5 Mg ha^-1, respectively, depending on location and species. Barrel medic (M. truncatula Gaertn.), snail medic [M. scutellata (L.) Mill.], and burr medic (M. polymorpha L.) cultivars were among the highest yielding, while Nitro alfalfa, George black medic, and Arlington red clover were consistently among the lowest yielding forage species. George black medic, Harbinger strand medic (M. littoralis Rohde ex Loisel.), and Kelson snail medic were among the highest in forage crude protein (CP) concentration for both summer and fall harvests. Forage fiber concentrations of all annual medics except Sava snail medic were equal to or lower than those in Nitro alfalfa. Our results indicate that annual medics have the potential for producing high yields of quality forage in the north-central USA and might be used as short-season annual crops for harvest in fall and summer when traditional forage supplies are inadequate.