On-Farm Evaluation of Alfalfa/Grass Mixtures in Minnesota.

Binary mixtures of alfalfa (Medicago sativa L.) with perennial cool-season grasses offer whole-system (soil, crop, and livestock) advantages over alfalfa monocultures.  We are assessing forage yield, quality, and species compatibility of alfalfa/grass mixtures vs. alfalfa monocultures on Minnesota farms.  Replicated 5.6-m² plots of binary mixtures of three alfalfa varieties with two varieties of each of nine grass species were seeded on west-central (WC) and south-central (SC) MN farms in August 2008, and on a central (C) MN farm in May 2009.  Perennial grasses and their seeding rates in binary mixtures were: meadow fescue [Schedonorus pratensis (Huds.) P. Beauv., 9 kg/ha], tall fescue [Lolium arundinaceum (Schreb.) Darbysh., 9 kg/ha], perennial ryegrass (Lolium perenne L., 9 kg/ha), smooth bromegrass (Bromus inermis Leyss., 11 kg/ha), meadow bromegrass (Bromus biebersteinii Roem. & Schult., 11 kg/ha), reed canarygrass (Phalaris arundinacea L., 7 kg/ha), timothy (Phleum pratense L., 4 kg/ha), festulolium (9 kg/ha), and orchardgrass (Dactylis glomerata L., 7 kg/ha).  Data were collected in 2009 and 2010 at WC- and SC-MN, but only in 2010 at C-MN.  Four and three harvests to a 10-cm residual were obtained in 2009 (first production year) at WC- and SC-MN, respectively.  At WC-MN, mixture total-season DM yields in 2009 ranged from 4.2 Mg/ha for alfalfa/timothy to 5.6 Mg/ha for alfalfa mixed with meadow bromegrass, reed canarygrass, or perennial ryegrass; alfalfa alone yielded 5.8 Mg/ha.  Season-average grass percentage at WC-MN ranged from 20% for alfalfa/perennial ryegrass to 54% for alfalfa/timothy.  At SC-MN, total-season DM yields in 2009 ranged from 5.5 Mg/ha for alfalfa/festulolium to 6.4 Mg/ha for alfalfa/smooth bromegrass; alfalfa alone yielded 6.4 Mg/ha.  Season-average grass percentage at SC-MN ranged from 5% for alfalfa/reed canarygrass and alfalfa/tall fescue to 11% for alfalfa/orchardgrass and alfalfa/festulolium.  Through three of four harvests planned for 2010 at WC-MN, mixture DM yields range from 8.1 Mg/ha for alfalfa/timothy to 10.8 Mg/ha for alfalfa/tall fescue, while alfalfa alone has yielded 10.5 Mg/ha; grass percentages range from 10% for alfalfa/perennial ryegrass to 52% for alfalfa/timothy.  Through two of four harvests planned for 2010 at SC-MN, mixture DM yields range from 5.3 Mg/ha for alfalfa/timothy to 6.6 Mg/ha for alfalfa/orchardgrass, while alfalfa alone has yielded 5.4 Mg/ha; grass percentages range from 6% for alfalfa/smooth bromegrass and alfalfa/reed canarygrass to 36% for alfalfa/orchardgrass.  Through two of four harvests planned for 2010 at C-MN, mixture DM yields range from 2.8 Mg/ha for alfalfa/reed canarygrass to 5.6 Mg/ha for alfalfa/orchardgrass, while alfalfa alone has yielded 1.8 Mg/ha; grass percentages range from 30% for alfalfa/reed canarygrass to 87% for alfalfa/orchardgrass.  To date, several mixtures are consistently yielding as much or more than alfalfa alone, with alfalfa/orchardgrass being the top yielder at 2 of 3 locations.