Combining Ability of Binary Mixtures of Native, Warm-Season Grasses and Legumes

Legumes may also be used to extend the production season in the cooland warm-season grass pastures. Growing complementary plant species is an alternative approach Grazing systems using forage legumes increase animal to enhancing pasture production. Our objective was to estimate combining ability for native, warm-season grasses and legumes grown in production (Fribourg et al., 1979; Jung et al., 1985; Raybinary mixtures in the field using a combining ability analysis of burn et al., 1980; Stricker et al., 1979), and pastures with variance. Six monocultures and 15 binary mixtures of the following legumes have greater crude protein content, digestibilspecies were studied: big bluestem, Andropogon gerardii Vit.; Illinois ity, and mineral composition for livestock diets, rebundleflower, Desmanthus illinoensis (Michx.) MacM.; roundhead sulting in greater forage intake and animal performance lespedeza, Lespedeza capitata Michx.; slender lespedeza, L. virginica (Marten, 1985). Kroth et al. (1982) reported the nitrogen (L.) Britt.; switchgrass, Panicum virgatum L.; and indiangrass, Sorgh(N) benefits from birdsfoot trefoil (Lotus corniculatus astrum nutans (L.) Nash. General combining ability (GCA) effects L.) and alfalfa (Medicago sativa L.), producing 115 and were found for forage dry matter yields (DMY, P # 0.05) of Illinois 200 kg N ha21, respectively, annually. Residual N fixed bundleflower (21240 kg ha21 ), roundhead lespedeza (23460 kg ha21 ), by legumes increased subsequent forage growth of ryeslender lespedeza (23300 kg ha21 ), and switchgrass (8370 kg ha21 ). Specific combining ability (SCA) effects were found for DMY (P # grass (Lolium multiflorum Lam.) and was equivalent to 0.1) of switchgrass-legume mixtures (1360 kg ha21 ) and indiangrassa fertilization with 111 kg N ha21 for arrowleaf clover Illinois bundleflower mixtures (1230 kg ha21 ). General combining (Trifolium vesiculosum Savi) and 121 kg N ha21 for a ability and SCA effects were found for crude protein concentration mixture of arrowleaf and crimson clovers (Trifolium (CPC) of all species and mixtures (P # 0.1), respectively. General incarnatum L.; Lynd et al., 1984). combining ability effects were found for in vitro dry matter digestibility Legumes and grasses grown in mixtures can either be (IVDMD) for switchgrass and the three legume species (P # 0.05). compatible—avoid competition with each other, comThe compatibility of these species could not be predicted solely by petitive—make demands on the same resources, or allelDMYs. Compatible mixtures, however, were identified with greater opathic—interact with each other (Harper, 1977). These confidence when other variables, such as CPC, IVDMD, and visual relationships are difficult to measure in traditional plot observations, were taken into account. On the basis of total forage protein (DMY times CPC), the only compatible grass-legume mixture and grazing experiments because dominant species in was indiangrass-Illinois bundleflower (SCA effect 5 100 kg ha21, mixtures have competitive advantages at the onset of P # 0.05). measuring their compatibility and interactions. Combining abilities for species and for specific species mixtures can be estimated by a combining ability analysis of variM producers use or want to adopt native, warmance. This analysis has typically been used by plant season grasses for pasture. In the southern Great and animal breeders to estimate combining abilities of Plains, native, warm-season grasses begin growth in breeding lines using variance components (Griffing, early to mid-April and provide excellent forage until 1956). We used this approach to estimate combining abilithe end of June. On rangelands consisting primarily of ties of binary mixtures of grasses and legumes (Springer big bluestem, cattle weight gains of 1.0 kg head21 d21 et al., 1996). from April to June are common (Owensby and AnderProducers need information concerning combining son, 1967). As plants form reproductive tillers, generally abilities for cooland warm-season species presently in July or August, forage becomes less palatable and grown or having the potential of being grown for forage. nutritious; consequently, animal gains decline. By OctoIn other regions, laboratory, greenhouse, and field studber, dietary supplements are needed to avoid weight ies have shown allelopathic and competitive effects of loss. One approach to enhance pasture forage productall fescue (Festuca arundinacea Schreb.) and white clotion and maintain quality is to over-seed grass pastures ver (Trifolium repens L.) toward other species (McCloud with one or more forage legume species. Forage legumes and Mott, 1953; Peters, 1968; MacFarlane et al., 1982; provide a renewable source of nitrogen for plant growth Springer et al., 1996; Springer, 1996). Compatibility has and quality forage for grazing livestock (Hoveland, 1989). been shown for tall fescue with either birdsfoot trefoil or white clover (Pederson and Brink, 1988; Beuselinck T.L. Springer, USDA-ARS, Southern Plains Range Research Station, et al., 1992; Springer et al., 1996) and for switchgrass, 2000 18th Street, Woodward, OK 73801; G.E. Aiken, USDA-ARS, indiangrass, or sideoats grama (Bouteloua curtipendula Dale Bumpers Small Farms Research Center, Booneville, AR 72927; Michx.) mixed with either purple prairieclover [PetalosR.W. McNew, Univ. of Arkansas, Dep. of Statistics, Fayetteville, AR 72701. Mention of a trademark or a proprietary product does not temon purpureum (Vent.) Rydb.], roundhead lespedeza, constitute a guarantee or warranty of the product by USDA or the leadplant (Amorpha canescens Pursh), Illinois bunUniv. of Arkansas and does not imply approval to the exclusion of dleflower, catclaw sensitive brier [Schrankia nuttallii other suitable products. All programs and services of the USDA are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap. Received Abbreviations: CPC, crude protein concentration; DM, dry matter; 13 June 2000. *Corresponding author ([email protected]). DMY, dry matter yield; GCA, general combining ability; IVDMD, in vitro dry matter digestibility; SCA, specific combining ability. Published in Crop Sci. 41:818–823 (2001).