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Alfalfa Survival and Vigor in Rangeland Grazed by Sheep

1986; University of Arizona; Volume: 39; Issue: 1 Linguagem: Inglês

10.2307/3899688

2162-2728

J. D. Berdahl, A. C. Wilton, Russel J. Lorenz, A. B. Frank,

Rangeland Management and Livestock Ecology

Few detailed comparisons have been made among alfalfa (Me&ago spp.) cultivars and strains grazed in semiarid, rangeland environments.The objective of this study was to determine survival and vigor of alfalfa cultivars and experimental strains that were grown in association with rangeland grasses and grazed by sheep for 3 seasons.Three-month old seedlings of 5 cultivars and 6 experimental strains of winterhardy alfalfa were transplanted in June 1979 into grass sod on 0.9-m centers at a hillside site with a west-facing 16% slope and Amor loam (Typic Haploboroll) soil.Dominant vegetation was western wheatgrass (Poscopynun smithii (Rydb.)L&e.Syn: Agropyron smithii (Rydb.)J,blue grama [Bouteloua gracilis (H.B.K.) Lag.], and smooth bromegrass (Bramus inermis Leyss.).For 3 seasons after the establishment year, each replicate was grazed in sequence for 2 weeks at a stocking rate of 48 yearling ewes/ha during summer and then mowed to a height of 10 cm in September.Only 5 of the 11 entries had greater than 50% survival after the third season.Three germplasm pools derived from local alfalfa plantings that had persisted more than 50 years in association with rangeland grasses were highest in survival, ranging from 72-74%.Drylander and Roamer, 2 cultivars developed primarily for grazing in semiarid regions of western Canada, had 65 and 62% survival, respectively.Phenotypic variability found among surviving plants in this study will permit further genetic improvements in alfalfa for rangeland.Interest in introducing alfalfa (Me&ago spp.) into rangelands in western North America dates back to the early 1900's when N.E.Hansen of the South Dakota Agricultural Experiment Station described alfalfa that he collected from the dry steppes of Siberia (Hansen 1909).Low seed production and seed shattering have been major factors limiting widespread commercial use of these hardy, creeping rooting accessions of yellow-blossomed 'Siberian' alfalfa (M.fulcata L.) collected by Hansen.Oakley and Carver (1917) reported that the greatest value of M. fulcuta lies in its ability to form fertile hybrids [M.sutiva subsp.vuriu (Martyn) Arc.] with common, purple flowered alfalfa Q4. sutivu L. subsp.sutivu).They further state that, "those who fail to see beyond h4.fulcutu's agronomic defects as it exists in the natural state are missing an opportunity in the field of plant breeding."Major sustained efforts to develop alfalfa cultivars for rangeland in the semiarid Northern Plains region of North America did not materialize until breeding programs were initiated by Agriculture Canada at Swift Current, Saskatchewan, in 1938 (Heinrichs 1954) and by the South Dakota Agriculture Experiment Station in the 1940's (Adams 1956).Several winter and drought-hardy cultivars intended primarily for dryland grazing have been developed through these breeding programs.Most of the grazing management research and commercial usage of alfalfa in rangelands has been with seeded mixtures of alfalfa and various grass species (Lorenz 1982).Recent development of interseeding technology (Chisholm et al. 1982) has provided a means of introducing alfalfa into native range or into established stands of seeded grass.This study compared survival and vigor of 11 alfalfa cultivars and experimental strains that were spaced-planted into rangeland and grazed by sheep for 3 seasons.