Alfalfa–Grass Mixtures in Comparison to Grass and Alfalfa Monocultures

Abstract

Core Ideas Alfalfa–grass mixtures are good alternative to alfalfa and grass monocultures. In the establishment year, alfalfa dominated the mixture, whereas as stands got older, grasses increased their contribution to the biomass. Alfalfa had higher crude protein, whereas grasses had higher fiber digestibility. Alfalfa–grass mixtures improved forage seasonal distribution. The most common binary mixture in the northern Great Plains is smooth bromegrass (Bromus inermis L.) (SBG) with alfalfa (Medicago sativa L.). However, other mixtures might have advantages over SBG–alfalfa. The objective was to compare forage yield, nutritive value, seasonal distribution, and persistence of grasses in monoculture or binary mixtures with alfalfa. A field experiment was established in 2010 in Fargo, Prosper, and Carrington, ND, and results were evaluated until 2013. Several wheatgrass species not commonly used in alfalfa–grass mixtures were tested. All grass species produced higher forage yield in binary mixtures with alfalfa than in monoculture. Binary mixtures had higher persistence in normal rainfall conditions and improved forage nutritive value. Alfalfa contributed with higher crude protein, whereas grasses had higher digestibility of the fiber. Intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey], not commonly included in mixtures with alfalfa, had greater biomass yield than many of the grasses in mixture with alfalfa, although not significantly different from SBG–alfalfa mixture. In the establishment year, alfalfa dominated the mixture (77–99% of total biomass), whereas as stands got older, grasses increased their contribution to the harvested biomass. In the third production year, grass in the mixtures was, on average, 50% of the total biomass. Alfalfa–grass mixtures with grasses other than SBG had similar or greater yield than SBG–alfalfa, increasing the number of potential grass choices that can be used in mixtures. In general, alfalfa–grass mixtures had greater forage yield and nutritive value than grass monocultures.