Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 11, 2004
Publication Date: July 31, 2004
Citation: Berdahl, J.D., Karn, J.F., Hendrickson, J.R. 2004. Nutritive quality of cool-season grass monocultures and binary grass-alfalfa mixtures at late harvest. Agronomy Journal. 96:951-955. Interpretive Summary: Haying operations in the Northern Great Plains often destroy nests, eggs, and incubating hens of waterfowl, pheasants, and other upland nesting birds. Nesting success would be greatly improved if haying could be deferred until mid-July, but forage quality is known to decline with advancing stages of plant development. This study was conducted to determine nutritive quality of four commonly used grass cultivars in pure stands and in simple two-species mixtures with alfalfa at a single mid-June or mid-July cutting under two levels of nitrogen fertility. Nitrogen fertilizer applied at 45 lb N per acre was needed to maintain forage yield and protein concentration of grass grown in pure stands and cut in mid- June. Protein concentrations of pure stands of grass at the mid-July cutting would not be adequate for lactating cows, even when nitrogen fertilizer was applied. Grass-alfalfa mixtures containing crested wheatgrass or smooth bromegrass provided adequate digestibility and protei at the mid-July cutting, but mixtures with intermediate wheatgrass had low protein for some classes of beef cattle. Feasibility of deferring hay harvest until mid-July would be dependent on use of either a legume in pure stands or on maintenance of alfalfa or another legume with high forage quality in a grass-legume mixture. These data will help producers make informed decisions on options to defer hay harvest to facilitate successful reproduction of upland nesting birds that are recognized to have increasing economic and aesthetic value.
Technical Abstract: Often only a single cutting of hay is possible in semiarid portions of the Northern Great Plains, and reproduction of waterfowl, pheasants (Phasianus colchicum), and other upland nesting birds would be improved if haying operations were deferred until mid-July or later. This study was conducted to compare nutritive quality of four cool-season grass monocultures and their respective binary grass-alfalfa (Medicago sativa L.) mixtures receiving annual applications of 0 and 50 kg N ha-1 and cut in mid-June when alfalfa was at early-bloom or in mid-July at late-bloom to early-pod stage of plant development. 'Reliant' and 'Manska' intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. and Dewey], 'Lincoln' smooth bromegrass (Bromus inermis Leyss.), and 'Nordan' crested wheatgrass [Agropyron desertorum (Fisch.) Schult] were seeded in monoculture and in binary mixtures with 'Rangelander' alfalfa [M. sativa subsp. x varia (Martyn) Arcang.] on a Parshall fine sandy loam (coarse-loamy, mixed, superactive, frigid, Pachic Haplustolls) near Mandan, ND. Nitrogen fertility level did not affect IVDMD, which was adequate for grass monocultures and grass-alfalfa mixtures at both the mid-June and mid-July cutting dates. Feasibility of deferring hay harvest of grass-legume mixtures until mid-July in the Northern Great Plains is dependent on maintaining the legume component in the mixture, which increased CP from 71 g kg-1 for grass monocultures to 109 g kg-1 for grass-alfalfa mixtures when no supplemental nitrogen fertilizer was used.