Statistics, Department of


Date of this Version



Published in Agron. J. 108:141–150 (2016)


Copyright © 2016 by the American Society of Agronomy


Crested wheatgrass [Agropyron cristatum (L.) Gaertn., A. desertorum

(Fisch. ex Link) Schult., and related taxa] often exists

in near monoculture stands in the northern Great Plains.

Introducing locally adapted yellow-flowered alfalfa [Medicago

sativa L. subsp. falcata (L.) Arcang.] would complement crested

wheatgrass. Our objective was to evaluate effects of seeding

date, clethodim {(E) -2-[1-[[(3-chloro-2-propenyl)oxy]imino]


sod suppression, and seeding rate on initial establishment and

stand persistence of Falcata, a predominantly yellow-flowered

alfalfa, no-till interseeded into crested wheatgrass. Research was

initiated in August 2008 at Newcastle, WY; Hettinger, ND;

Fruitdale, SD; and Buffalo, SD. Effects of treatment factors on

plant frequency during initial establishment were influenced by

site environments. Late summer and spring were suitable seeding

dates. Clethodim sod suppression increased seedling frequency

in most cases. Seedling frequency increased as seeding

rate increased from 0.56 to 7.84 kg pure live seed (PLS) ha–1.

Specific seeding dates, clethodim sod suppression, and high

seeding rates did not greatly improve initial establishment when

site environments were poor. Residual effects of seeding date

and sod suppression post establishment were not significant

at most locations, but seeding rate effects were evident. Initial

establishment and persistence of Falcata alfalfa was successful at

Newcastle, indicating that interseeding in late summer or spring

using low seeding rates (≤3.36 kg PLS ha–1) without clethodim

can be effective. Assessing grass canopy cover, soil texture, and

management (e.g., haying) is necessary to determine the suitability

of crested wheatgrass sites for interseeding.