Combining ability of binary mixtures of native, warm-season grasses and legumes

Growing complementary plant species is an alternative approach to enhancing pasture production. Our objective was to estimate combining ability for na tive, warm-season grasses and legumes grown in binary mixtures in the field using a combining ability analysis of variance. Six monocultures and 15 bi nary mixtures of the following species were studied: big bluestem, Andropog on gerardii Vit.; Illinois bundleflower, Desmanthus illinoensis (Michx.) Ma cM.; roundhead lespedeza, Lespedeza capitata Michx.; slender lespedeza, L. virginica (L.) Britt.; switchgrass, Panicum virgatum L.; and indiangrass, S orghastrum nutans (L.) Nash. General combining ability (GCA) effects were f ound for forage dry matter yields (DMY, P less than or equal to 0.05) of Il linois bundleflower (-1240 kg ha(-1)), roundhead lespedeza (-3460 kg ha(-1) ) slender lespedeza (-3300 kg ha(-1)), and switchgrass (8370 kg ha(1)), Spe cific combining ability (SCA) effects were found for DMY (P less than or eq ual to 0.1) of switchgrass-legume mixtures (1360 kg ha(-1)) and indiangrass -Illinois bundleflower mixtures (1230 kg ha(-1)). General combining ability and SCA effects were found for crude protein concentration (CPC) of all sp ecies and mixtures (P less than or equal to 0.1). respectively. General com bining ability effects were found for in vitro dry matter digestibility (IV DMD) for switchgrass and the three legume species (P less than or equal to 0.05). The compatibility of these species could not be predicted solely by DMYs. Compatible mixtures, however, were identified with greater confidence when other variables, such as CPC, IVDMD, and visual observations, were ta ken into account. On the basis of total forage protein (DMY times CPC), the only compatible grass-legume mixture was indiangrass-Illinois bundleflower (SCA effect = 100 kg ha(1), P less than or equal to 0.05).