Nutritive Quality of Cool‐Season Grass Monocultures and Binary Grass–Alfalfa Mixtures at Late Harvest

Nutritive quality of hay is compromised when harvest is delayed, but reproduction of upland nesting birds in the northern Great Plains would be improved if haying operations could be deferred until mid‐July or later to allow completion of nesting. This study was conducted to determine nutritive quality of hay at a single mid‐July cutting from three cool‐season grass species that were grown in monoculture and in binary mixtures with alfalfa [ Medicago sativa subsp. × varia (Martyn) Arcang.] near Mandan, ND. Grasses were intermediate wheatgrass [ Thinopyrum intermedium (Host) Barkw. & Dewey], smooth bromegrass ( Bromus inermis Leyss.), and crested wheatgrass [ Agropyron desertorum (Fisch. ex Link) Schult.]. Annual applications of 0 and 50 kg N ha −1 had no effect on in vitro dry matter digestibility (IVDMD) or neutral detergent fiber (NDF) levels of grass or alfalfa. Grass monocultures and alfalfa averaged 612 and 624 g kg −1 , respectively, for IVDMD and 651 and 567 g kg −1 , respectively, for NDF. At 0 kg N ha −1 , crude protein (CP) ranged from 71 to 78 g kg −1 in grass monocultures and from 92 to 131 g kg −1 in grass–alfalfa mixtures. At 50 kg N ha −1 , CP ranged from 83 to 97 g kg −1 in grass monocultures and from 99 to 133 g kg −1 in mixtures. Feasibility of deferring hay harvest to allow reproduction of upland nesting birds in the northern Great Plains depends on maintaining alfalfa or other legumes with high nutritive quality in grass mixtures to reduce NDF and increase CP levels.