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ARS Home » Plains Area » Mandan, North Dakota » Northern Great Plains Research Laboratory » Research » Publications at this Location » Publication #309055

Title: Can targeted grazing reduce abundance of an invasive perennial grass (Kentucky bluegrass) on native mixed grass prairie?

item Hendrickson, John
item Kronberg, Scott
item SCHOLLJEGERDES, ERIC - New Mexico State University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2020
Publication Date: 7/1/2020
Citation: Hendrickson, J.R., Kronberg, S.L., Scholljegerdes, E.J. 2020. Can targeted grazing reduce abundance of an invasive perennial grass (Kentucky bluegrass) on native mixed grass prairie? Rangeland Ecology and Management. 73:547-551.

Interpretive Summary: Kentucky bluegrass has increased on native rangelands in the northern Great Plains over the past 30 years and has negatively impacted ecological services. Previous grazing management recommendations have emphasized not starting grazing until native plants are in the 3 ½ leaf stage which is usually late May to early June. However, since Kentucky bluegrass starts growth relatively early, this delay may give it an advantage. We evaluated cattle grazing in the early spring with a more traditional start to the grazing season. Grazing early increased native grass abundance by 26% over a five year period. However, the impacts on Kentucky bluegrass depended on year. Early spring grazing by cattle has potential, but should be incorporated into a management program that is adaptable enough to take advantage of differences between years.

Technical Abstract: The rapid increase of Poa pratensis L. (Kentucky bluegrass) on North Dakota grasslands during the past 30 years has negatively impacted ecological services. Kentucky bluegrass grows earlier in the spring than many native grasses which provides an opportunity to use targeted grazing to reduce Kentucky bluegrass and increase native grasses. A five year replicated study used 10 cow-calf pairs or pregnant cows to graze 3-ha paddocks in early spring (EARLY) until 30% of the native species were grazed. After June 1st, five cow-calf pairs were grazed on 3-ha paddocks (LATE) for twice as long as the EARLY treatment. Biomass was clipped inside and outside of cages after each grazing event and outside cages in the fall. In each paddock, 100 10-point frames were taken to determine percent native grass, Kentucky bluegrass, Bromus inermis Leyss. (smooth bromegrass), native forbs and introduced forbs. After five years, native grass abundance in the EARLY paddocks was 26% greater than in the LATE paddocks. Kentucky bluegrass abundance only differed in 2010 when the EARLY paddocks had 32% less Kentucky bluegrass than the LATE paddocks. Total biomass was greater in the EARLY paddocks than LATE paddocks in 2010 (886 ±74 g m-2 vs. 608 ± 28 g m-2 for EARLY and LATE respectively). Targeted grazing by cattle in early spring can increase native grass abundance and depending on the year, decrease abundance of Kentucky bluegrass. Early spring targeted grazing should be used as a tool in adaptive management programs focusing on reduction of Kentucky bluegrass.