Pinegrass (Calamagrostis rubescens) was clipped at several frequencies and intensities at three sites in the Douglasfir (Pseudotsuga menziesii) zone of British Columbia. The effect of herbage removal on pinegrass vigor could be assessed by measuring tiller height, tiller number/mz, or yield/m2 the year following clipping. Variability in pinegrass cover at a site necessitated measuring initial plot cover so than an analysis of covariance could be done to statistically isolate its effect. Initial pinegrass cover did not affect the tiller height measurement however. Plant vigor decrease due to herbage removal depended upon the degree and time of herbage removal and either the environmental conditions during the year of clipping or plant history before herbage removal or both. Pinegrass vigor was most sensitive to clipping during the last half of July and early in August. This is the time when pinegrass growth is slowing down and summer dormancy is setting in. It is recommended that pinegrass be grazed for a short time while it is actively growing (early in June) and then later when midsummer dormancy is well established (August) to maintain its vigor. If pinegrass must be grazed during July, then it should be rested during July the following year. Further work is required to establish grazing schemes that will maximize animal production and maintain adequate pinegrass vigor.

. Effect of stage of growth of alfalfa on the incidence of bloat in cattle. Can. J. Anim. Sci. 80: 725-727. Alfalfa of different maturities was produced simultaneously by varying the timing of the first cut. Groups of fistulated steers were confined and simultaneously fed alfalfa herbage at three stages of growth once a day. More bloat occurred during the vegetative stage of growth, it declined during bud development, and it was absent during bloom. This pattern occurred with both the number of cases of bloat and with the severity of bloat, which was much greater during the vegetative stage. Feed quality components also varied significantly between stages as did the leaf:stem ratio. Nous avons obtenu simultanément, de l'herbage de luzerne de différents stades de croissance en manipulant les dates de la première récolte. Des groupes de bouvillons fistulisés élevés en claustration recevaient en même temps une fois par jour de l'herbe de luzerne coupée à trois stades de pré-cocité. Les cas de météorisme les plus fréquents correspondaient à la consommation de luzerne au stade végétatif, ils diminuaient quand la récolte était au stade du bouton et disparaissaient complètement avec le stade de floraison. Ce comportement s'appliquait aussi bien au nombre de cas de météorisme qu'à leur degré de gravité, lequel était beaucoup plus élevé au stade végétatif de la culture. Les composantes nutritionnelles du fourrage, ainsi que le rapport feuille : tige, manifestaient également des variations significatives selon le stade de croissance.

storage effects on germination and hard seed content of alfalfa. Can. J. Plant Sci. 79: [201][202][203][204][205][206][207][208]. The impermeable coat of alfalfa (Medicago sativa L.) seed can reduce germination to an extent unacceptable for commercial use. The usual method of increasing germination of lots with high proportion of impermeable or hard seeds, mechanical scarification, can damage seeds. Experiments were conducted to determine the effect of cultivar, year of production and storage conditions on germination and hard seed content in alfalfa. Experiments with four Canadian cultivars indicated a significant effect of cultivar on seed weight, germination and hard seed content in freshly harvested seed. Year of production had a greater influence on these seed traits than cultivar. Under uncontrolled storage conditions, germination of 35 alfalfa synthetics increased and hard seed content decreased with time, although not at the same rate for all synthetics. Storage at 20°C for up to 64 mo did not significantly decrease hard seed content. At 35°C, hard seed content decreased continuously for all cultivars (for one cultivar to <5%) after 64 mo. Over 80.5 mo storage at room temperature (22 ± 2°C), germination increased in a nonlinear fashion. Storing seed in sealed plastic bags at 35°C delayed seed dehydration and the loss of hard seeds. Levels of nonviable seed were low (<10%), even after storage at 35°C for 64 mo. Brief (1 min) exposure to liquid nitrogen increased germination of freshly harvested alfalfa seed to >90%. The results indicate that the germination percent of alfalfa can be increased and hard seed content reduced by short exposure to liquid nitrogen or storage at nonlethal high temperatures (35°C) such that mechanical scarification may be unnecessary. Key words:Medicago sativa, hard seed, stored seed, seed dehydration, high temperature treatment, liquid nitrogen treatment Acharya, S. N., Stout, D. G., Brooke, B. et Thompson, D. 1999. Effets du cultivar et des conditions de conservation sur le contenu en semence dure chez la luzerne. Can. J. Plant Sci. 79: 201-208. Le tégument imperméable qui enveloppe la graine de la luzerne (Medicago sativa L.) peut en réduire le pouvoir germinatif au point de la rendre inacceptable pour le commerce. La srarification mécanique, la méthode ordinaire d'accroître la germinabilité de lots à forte proportion de semences dures ou imperméables, risque d'endommager les graines. Nous avons réalisé des expériences pour déterminer l'effet du cultivar, de l'année de production et des conditions de stockage sur le pouvoir germinatif et sur la proportion de graines dures. Les essais effectués sur quatre cultivars canadiens ont mis en évidence un effet cultivar significatif sur le poids des graines, sur le pouvoir germinatif et sur la proportion de graines dures dans des lots de graines frais récoltées. L'année de production avait un effet plus prononcé sur ces caractères que le cultivar. En conditions de conservation non contrôlées, le pouvoir germinatif des graines de 35 var...

Grass

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