. 2000. Development and evaluation of grazing-tolerant alfalfa cultivars: A review. Can. J. Plant Sci. 80: 503-512. Plant breeders have long sought to improve grazing tolerance of alfalfa without sacrificing the beneficial yield and quality attributes of this species. Most efforts have focussed on selecting for traits (e.g., creeping rootedness) related to grazing tolerance and/or simulated grazing, but these efforts failed to account for the multiple stresses caused by grazing animals. Trait selection often led to sacrifices in yield and other desirable characteristics resulting in cultivars that were not robust across grazing management systems and environments. An innovative selection procedure was recently developed at the University of Georgia which incorporated intensive grazing with continuous stocking by beef cattle. The development of "Alfagraze" using this procedure showed that grazing tolerance and high yields can be incorporated into the same cultivar, along with consistent performance across grazing management systems and environments. Subsequent research has shown that grazing tolerance can be improved within elite, high-yielding, multiple-pest-resistant cultivars and breeding populations. Selection using intensive grazing with continuous stocking has been summarised in a "Standard Test Protocol" that is now being successfully used by public and private alfalfa breeders and in cultivar evaluation programs in the USA, Canada, and other countries. Les sélectionneurs cherchent depuis longtemps à améliorer la tolérance de la luzerne au pâturage, sans compromettre le rendement quantitatif et qualitatif de l'espèce. On s'est essentiellement attaché jusqu'ici à la recherche de caractères particuliers, p. ex. l'enracinement traçant, liés à la tolérance au pâturage ou à la paissance simulée, mais cela n'a pas été suffisant pour contrer les multiples stress causés par les animaux à l'herbe. La sélection axée sur un caractère particulier s'est souvent faite aux dépens des autres caractères désirables, notamment le rendement, ce qui a produit des cultivars ne pouvant persister que dans certains systèmes pastoraux et dans certains milieux de culture. Une technique de sélection originale a été mise au point dernièrement à l'Université de Géorgie (E.U), qui incorpore le pâturage intensif sous à chargement animal continu par des bovins à viande. L'obtention du cultivar Alfagraze par cette méthode démontre que tolérance au pâturage et rendement élevé peuvent être réunis dans un même cultivar, lui assurant ainsi des performances stables, indépendamment du système pastoral utilisé ou des conditions du milieu. Des recherches subséquentes ont montré qu'il est possible d'améliorer la tolérance à la pâture dans des cultivars ou des populations de sélection à haut rendement et à large spectre de résistance aux maladies. La nouvelle méthode, normalisée dans un protocole expérimental standard, est aujourd'hui utilisé avec succès par les sélectionneurs de luzerne, tant privés que ceux du secteur public, ainsi que dans les pr...

alfalfa (Medicago spp.) under continuous and rotational stocking systems in pure stands and in mixture with meadow bromegrass (Bromus riparius Rehm. syn. B. biebersteinii Roem & Schult). Can. J. Plant Sci. 82: 337-347. The continuing development of adapted alfalfa (Medicago sativa L.) cultivars that combine high yield, disease resistance, winterhardiness, and grazing tolerance is of great value to the beef cattle industry in western Canada. This study evaluated alternative management strategies and plant measurements for assessing the grazing tolerance of alfalfa cultivars over 3 yr. Seven hay-type, four pasture-type, and one dual-purpose (hay or graze) cultivars were established in pure stands and in mixture with meadow bromegrass (Bromus riparius Rehm. syn. B. biebersteinii Roem & Schult). Stands were defoliated under continuous or rotational stocking with beef cattle (Bos taurus). Plants were assessed for winterhardiness, percent alfalfa within row, percent alfalfa cover, basal area and species composition. Continuous stocking resulted in consistent and significant differences between cultivars, whether persistence was measured as percent alfalfa within row, percent cover and basal area, in both pure and mixed stands (P < 0.05). High correlations between measurement techniques (r = 0.74 to 0.99; P < 0.05) confirmed the value of alfalfa within row and alfalfa cover as time and labour efficient methods to evaluate grazing persistence. Competition between alfalfa and meadow bromegrass resulted in a significant confounding effect under rotational stocking (P < 0.05). Winter injury was identified as an important criteria to evaluate for grazing persistence. The most grazing-tolerant genotypes were selected for subsequent breeding efforts to combine winterhardiness, grazing tolerance, and high productivity. This research showed that grazing method, grass competition, and severe winter conditions strongly influence differential survival of alfalfa cultivars under grazing in western Canada.Key words: Alfalfa, grazing tolerance, grazing systems, Medicago sativa L., Medicago falcata L. Arcang, persistence Katepa-Mupondwa, F., Singh, A., Smith, S. R., Jr. et McCaughey, W. P. 2002. Tolérance de la luzerne (Medicago sp.) à la paissance dans les régimes de paissance continue et en rotation sur peuplements purs ou mixtes avec le brome des prés (Bromus riparius Rehm. syn. B. biebersteinii Roem & Schult). Can. J. Plant Sci. 82: 337-347. La création continuelle de cultivars de luzerne (Medicago sativa L.) de mieux en mieux adaptés, se caractérisant par un rendement élevé, la résistance aux maladies, la rusticité et la tolérance à la paissance, apporte beaucoup à l'élevage des bovins de boucherie dans l'ouest du Canada. L'étude devait établir l'utilité de divers systèmes de gestion et paramètres végétaux dans l'évaluation de la tolérance des cultivars à la paissance sur une période de trois ans. Les auteurs ont cultivé sept variétés de type fourrager, quatre de type à pâturer et une de type double (foin ou pâturage) en peupleme...

Combining the benefits of legume N2fixation and N fertilization may increase the productivity and profitability of pasture systems. Our objectives were to study the effects of N fertilization on productivity and persistence of legumes in mixtures with cool‐season grasses under rotational stocking with short grazing periods. Twelve N fertilization regimes ranging from 0 to 336 kg of N per ha were applied annually to smooth bromegrass and reed canarygrass in monoculture and mixture with alfalfa, birdsfoot trefoil, and kura clover. Alfalfa was the dominant legume in mixtures with cool season grasses in 1999. As kura clover developed, it became the dominant legume species and by the trials end stands averaged over 70% in mixtures with both smooth bromegrass and reed canarygrass and across N treatments. Nitrogen fertilization did not affect alfalfa stands, but reduced kura clover stands by 17%. Smooth bromegrass‐legume mixtures with no N fertilization produced more forage (10.5 Mg DM/ha) than any smooth bromegrass monoculture with N treatment (336 kg of N per ha produced 8.0 Mg DM/ha). Cost of forage mass in smooth bromegrass‐legume mixtures was less than 50% of smooth brome monocultures. While N fertilization did not increase forage production in treatments with legumes, legumes were able to maintain vigorous stands with up to 336 kg of N per ha.