Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/17/2005
Publication Date: 9/19/2005
Citation: Hendrickson, J.R., Berdahl, J.D., Liebig, M.A., Karn, J.F. 2005. Tiller persistence of eight intermediate wheatgrass entries grazed at three different morphological stages. Agron. J. 97:1390-1395. Interpretive Summary: Intermediate wheatgrass provides high quality pasture and forage in the Northern Great Plains but does not last long under grazing. We wanted to try to increase the persistence of intermediate wheatgrass by grazing at different stages of growth. We also wanted to see if some entries are more persistence that others. We grazed 8 different entries of intermediate wheatgrass when it was in 1) the 3-5 leaf stage, 2) the stems had 2 nodes you could feel or 3) the plants were starting to head out. We found that regardless of grazing treatment, intermediate wheatgrass was not very persistence. However, grazing before the plants started to head out increased the persistence of intermediate wheatgrass. An experimental entry of intermediate wheatgrass developed at the location performed better than the other entries over the time of the study. Number of new shoots was strongly correlated with persistence. Therefore, breeding for plants with the ability to initiate more new shoots may improve the persistence of intermediate wheatgrass.
Technical Abstract: Intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey subsp. intermedium] provides high quality forage for hay and pasture in the Great Plains of North American, but lacks persistence under grazing. A study near Mandan, ND evaluated whether changing the time of grazing and corresponding stage of plant development could enhance persistence of intermediate wheatgrass. Eight different cultivars and strains of intermediate and pubescent wheatgrass [T. intermedium subsp. barbulatum (Schur) Barkw. & D.R. Dewey] were seeded into nine paddocks in 1997. The study area was hayed in 1998 and 1999 and grazing began in 2000. Grazing treatments were 1) grazed during the early vegetative stage, 2) grazed during mid-culm elongation, and 3) grazed during late boot. Four tillers were marked on one plant plot-1 in May 2000. Recruitment and mortality on these tillers and any newly recruited tillers were recorded at regular intervals. Tiller replacement ratios, which incorporated cumulative recruitment and mortality, were greatest on plots grazed during early vegetative and mid-culm elongation. Plots grazed in the early vegetative stage had significantly greater tiller replacement ratios than did the other two grazing treatments or the controls. There was a grazing treatment by entry interaction in 2001. 'Mandan 1871' had the greatest tiller replacement ratio among entries. During 2001, all of the grazing treatments and the controls had at least one entry whose population was increasing. Tiller recruitment was more strongly correlated with tiller replacement ratio (r = 0.76) than was tiller mortality (r =0.22). Time of grazing can influence rate of stand decline in intermediate wheatgrass and selecting for tiller recruitment may enhance tiller persistence.