Intercropping Annual Medic with Conventional Height and Semidwarf Barley Grown for Grain

Interseeding annual legumes with grain crops has been proposed as a cropping strategy to enhance ground cover, thereby reducing weed competition, suppressing soil erosion, and providing N for use by subsequent crops. The potential of annual medics ( Medicago spp.) for intercropping in small‐grain cropping systems has not been adequately assessed for the north‐central United States. Our objective was to evaluate a spring barley ( Hordeum vulgare L.)‐annual medic intercrop system for barley grain yield, fall biomass production, suppression of fall weeds, and quantity of N available for incorporation into the soil. Field experiments were conducted in four Minnesota environments (Becker, Morris, Rosemount, and St. Paul). Conventional height ‘Robust’ and semidwarf ‘Royal’ barley were intercropped with each of three medic species [‘George’ black medic ( M. lupulina L.), ‘Mogul’ barrel medic ( M. truncatula Gaertn.) and ‘Santiago’ burr medic ( M. polymorpha L.)]. Intercropping with medics reduced barley yields by an average of 6% at Rosemount, 30% at St. Paul, and 76% at Becker, compared with monoculture barley fertilized with N. Medics increased yields by 9% at Morris. Intercropping with medic reduced fall weed mass by an average of 65% across environments, compared with the fertilized Royal monoculture. Nitrogen available for incorporation from the barley‐medic intercrops ranged from 66 to 140 kg ha −1 over the environments, whereas N available for incorporation from fertilized barley monoculture ranged from 22 to 80 kg ha −1 . We conclude that the prospects for successfully intercropping with annual medic in a barley grain production system are mixed and depend in part on the medic species used and barley stature. A wider array of medic types should be evaluated for their suitability in intercropping with small grains.