EVALUATION OF GRAZING TOLERANCE IN ALFALFA
ACROSS THE DIVERSE ENVIRONMENTS OF THE NORTHERN GREAT PLAINS
A. Singh1,2, W. P. McCaughey2, S. R. Smith1, Jr., S. Acharya3, J. D. Berdahl4, B.Berg5, A. D. Iwaasa and P. G. Jefferson6
1University of Manitoba, Winnipeg, MB, R3T-2N2, 2Agriculture and Agri-Food Canada, Brandon Research Centre, Brandon, MB, R7A-5Y3, 3Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB, T1J-4B1, 4United States Department of Agriculture, Northern Great Plains Research Laboratory, Mandan, ND, 58554, 5Alberta Agriculture, Food and Rural Development, Lethbridge, AB, T1J-4C7, 6Agriculture and Agri-Food Canada, Semiarid Prairie Agricultural Centre, Swift Current, SK, S9H-3X2.
Beef and dairy producers have long recognized the feed value of alfalfa-rich pastures. But two problems have historically stood in their way — bloat and a lack of persistence under grazing. The introduction of "bloat-reduced" and/or "grazing tolerant" alfalfa cultivars may open the door for more profitable beef production. Many of the experimental genotypes being developed are "dual-purpose" varieties (hay or graze) featuring high quality, multiple disease resistance, high yield, and grazing tolerance. The big question remains is that under the climatic conditions of the northern Great Plains, will grazing stress lead to poor plant persistence.
A comprehensive grazing trial was initiated in 1996 at Lethbridge, AB; Swift Current, SK; Brandon, MB; and in 1997 at Mandan, ND. A collection of 23 alfalfa cultivars and experimental lines was evaluated in a 3 year grazing experiment assessing persistence in pure stands and in mixture with meadow bromegrass under both continuous and rotational stocking. Different soil types and extremes in moisture and temperature provided adequate data to compare genotypes across the diverse environments.
Separation among persistent cultivars was initially observed in the spring of 1999 in Swift Current, SK and Brandon, MB, while the other two sites showed moderate losses under continuous stocking only. Severe losses under both rotational and continuous stocking systems in Brandon, MB, and Swift Current, SK strongly suggested that persistence under grazing in the northern Great Plains is inextricably linked to winterhardiness. As expected, the grazing intolerant check, Apollo (according to the standard protocol of the North American Alfalfa Improvement Conference) has not persisted well at all sites after two grazing seasons. However, unexpectedly, the grazing tolerant check, Alfagraze, suffered widespread losses in Brandon, MB and Swift Current, SK. In general, alfalfa varieties and experimental lines well adapted to grazing stress in central and southern US (e.g. Alfagraze) have failed to demonstrate a superior advantage over well adapted hay-type cultivars of western Canada (e.g. Beaver, Anchor, Barrier). In contrast, alfalfa varieties of the subspecies falcata (e.g. SCMF 3713) or containing high falcata parentage (e.g. Rangelander, Spredor II, Rambler) have persisted extremely well at all sites.