Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/30/2007
Publication Date: 12/7/2007
Citation: Springer, T.L., Gillen, R.L., McNew, R.W. 2007. Combining ability of binary mixtures of introduced, cool- and warm-season grasses and legumes. Crop Science. 47:2540-2546. Interpretive Summary: Agricultural producers need information about the ability of cool- and warm-season species to coexist and thrive together. Determining the combining abilities for species presently grown or having the potential to be grown together for forage is important. The combining ability effect of growing introduced, cool- and warm-season grasses and legumes in binary mixtures using a combining ability analysis of variance was investigated. Given the conditions of this experiment, ‘Morpa’ weeping lovegrass is highly adapted to the sub-humid environment of NW Oklahoma and should probably be grown in a monoculture. It grows well with limited moisture giving it a competitive advantage. In contrast, ‘Luna’ intermediate wheatgrass and ‘Max Q’ novel endophyte-‘Jesup’ tall fescue are not adapted to this environment and should not be grown. Prolonged drought often reduces the stands of perennial, cool-season grasses to a point that they have to be reseeded. Some alfalfa cultivars, rhizomatous birdsfoot trefoil, and yellow bluestem are also well adapted to this environment, but both legume species compete directly with yellow bluestem. Yellow bluestem-legume mixtures averaged 59% yellow bluestem: 41% legume dry-matter forage across harvests. Thus, yellow bluestem-legume mixtures may be a sustainable forage production system.
Technical Abstract: When two forage species are grown together they can be compatible, compete, or interact with each other. We estimated the combining ability effects for introduced, cool- and warm-season grasses and legumes grown in binary mixtures in NW Oklahoma. Six pure stands and 15 mixtures were transplanted into field plots in a replicated randomized block design. Mixtures were planted at a 1:1 ratio. Plots were harvested three times a year over a two year period. Each harvest was analyzed as a mixed model combining ability analysis. The dependent variables were forage dry-matter (DM) and crude protein (CP) yield. The specific combining ability (SCA) effects for DM yield were either zero or negative for mixtures of cool-season grasses or mixtures of warm-season grasses. The SCA effects for CP yield for all harvests were either zero or positive for cool- and warm-season grass mixtures. For DM yield, cool-season grass-legume mixtures had either zero or positive SCA effects while warm-season grass-legume mixtures had either zero or negative SCA effects. Although a few grass-grass and grass-legume mixtures produced positive SCA effects, their species compositions were highly skewed toward one species. Over time the primary species would likely replace the secondary species. When SCA effects are zero, a competition between species exists. This was the case for yellow bluestem [Bothriochloa ischaemum (L.) Keng. var. ischaemum (Hack.) Celarier and Harlan]-legume mixtures. Yellow bluestem-legume mixtures averaged 59% yellow bluestem: 41% legume DM forage across harvests. Thus, yellow bluestem-legume mixtures may be a sustainable grass-legume forage production system.