1992. Growth characteristics of rough fescue (Festuca scabrella var. carnpestris) after three years of repeated harvesting at scheduled frequencies and heights. Can. J. Bot. 70: 2125-2129. A study was made in the rough fescue grasslands of southwestern Alberta to determine the growth response of rough fescue (Festuca scabrella var. catrzpestris Rydb.) to five cutting frequencies and three cutting heights after 3 years of repeated treatments. The same plants were cut either 1, 2, 4, 8, or 16 times over a 16-week period beginning in mid-May, at 16-, 8-, 4-, 2-, or 1-week intervals, respectively, and at heights of either 5, 10, or 15 cm above ground level. After 3 years of repeated treatment, dry matter yields, etiolated growth, tiller height, tiller number, and growth rate decreased with increased cutting frequency and decreased cutting height. A single harvest at the end of August, cut at a height of 15 cm, produced yields that were similar to previously undisturbed plants. This treatment also produced the maximum sustainable forage yields. The study confirms the high susceptibility of rough fescue to grazing during the growing season and indicates that optimum management should include dormant-season grazing.
Two ecotypes and three varieties of white clover (Trifolium repens) of contrasting morphology were established in monoculture field plots in Truro, Nova Scotia (45° N) in July 1985. Destructive measurements were taken at monthly intervals from August to November 1985 and April to August 1986. The seasonal distribution of number of active stolons/m 2 , number of leaves, number of leaves per stolon, and lamina weight together with dry weights of leaves-I-petioles, stolons and flowers + peduncles were recorded. Number of leaves was inversely proportional to leaf weight, smaller-leaved varieties and ecotypes having higher leaf densities than large-leaved white clovers. Leaf and petiole dry-matter yields were related to leaf and number of active stolons in 1985 and to leaf weight increments in 1986. The two naturalized ecotypes exhibited considerably less leaf loss than the three varieties in a winter where mean minimum air temperatures drop to as low as -13°C. There were considerable differences between ecotypes and between varieties in the seasonal distribution of leaves and petioles, stolon and flower dry weights over the limited time period of this study.
(Fraser 1989) and is more persis-perlite on 3 May 1985. The seedlings were tent in the long-term compared with recom-allowed to establish in a cool greenhouse mended cultivars (Fraser 1986). The seasonal under natural daylight for 10 wk. On 12 July, distribution of growth and dry matter of two 20 healthy seedlings of comparable size and native populations and three white clover cul-growth stage were selected from each flat and tivars has been documented in Nova Scotia transplanted into the field at Plumdale Farm, (Fraser 1988). In this study, dry matter yields Nova Scotia (42"22'N,63'20'N 40 Population from a native pasture (Fraser 1989).Population from a native pasture (Fraser 1989).Population from a native pasture (Fraser 1989 Higher yielding than Sacramento in monoculture and in mixtures with orchardgrass and timothy (Fraser, unpubl.).Higher yielding than Sacramento/orchardgrass mixtures in first and second production years, but lower yields in the fourth production year (Fraser, unpubl.
S U M M A R YThe influence of four seeding times on herbage dry matter (DM) yields and clover content of white clover (Trifolium repens L.)/orchardgrass (Dactylis glomerata L.) mixtures was evaluated at Truro, Nova Scotia and Charlottetown, Prince Edward Island from 1985 to 1988. Sacramento, Sonja and Milkanova white clover/orchardgrass mixtures were assessed under simulated grazing (four or five harvests per year) over two production years at each location.Delaying seeding from May to August reduced total herbage DM yields significantly in the first production year, from 81 to 33 t/ha in Truro and from 110 to 7-2 t/ha in Charlottetown. Late seeding significantly reduced clover content in the herbage of the first two harvests in the first production year but, by the mid to late-season harvests, white clover content had increased to levels similar to those of the May seeding. Estimated white clover DM yields were highest in June, and dropped in the second production year at both locations. Sonja and Milkanova white clovers consistently outyielded Sacramento in herbage DM yields and clover content in both locations irrespective of seeding dates.
FRASER, J. 1989. Characteristics of naturalized populations of white clover (Trifolirrm repens) in Atlantic Canada. Can. J.Bot. 67: 2297 -2301. Some characteristics of seven populations of naturalized white clover (Trifolium repens L.) from native pastures in Nova Scotia, Prince Edward Island, and New Brunswick were investigated. Nine vegetative characters were measured on 16-to 18-week-old plants, and within and between population differences determined for cyanogenesis. Variation was observed between and within populations for all measured characteristics. Leaf marks were predominately the central V-shaped chevron; one population had plants without the chevron. Relative leaf size (length X width) ranged from 145 to 784 mmz. Hydrogen cyanide concentrations in leaf laminae were lower in cyanogenic (AcLi) and glucosidic (Acli) genotypes than enzymatic (acLi) genotypes. HCN concentrations in genotypes varied between and within populations. A population from Charlottetown, Prince Edward Island, had several desirable agronomic features, e.g., larger leaves, longer petioles, and thicker stolons than other populations, and could be used in a breeding programme for improved winter-hardy white clover varieties suited for rotational grazing and silage in Atlantic Canada. FRASER, J. 1989. Characteristics of naturalized populations of white clover (Trifolium repens) in Atlantic Canada. Can. J. Bot. 67 : 2297 -2301. L'auteur a CtudiC certaines caractCristiques chez sept populations de trbfle blanc (Trifolium repens L.) provenant de paturages indigbnes en Nouvelle-Ecosse, au Nouveau-Brunswick et 2 l'ile du Prince Edouard. I1 a mesurt neuf caractbres vtgCtatifs sur des plants agCs de 16 i 18 semaines ainsi que les diffkrences de cyanogtnbse dans les populations et entre les populations. I1 existe des variations dans et entre les populations pour tous les caractbres mesurCs. Les caractkres foliairCs sont liCs surtout i la coloration centrale en forme de chevron; dans une des populations on ne retrouve pas cette marque en forme de chevron. La dimension foliaire relative (longueur x largeur) est de 145 i 784 mm2. Les concentrations de cyanure d'hydrogbne dans la lame foliaire sont plus faibles dans les genotypes cyanogCniques (AcLi) et glucosidiques (Acli) que dans les gCnotypes enzymatiques (acLi). Les concentrations en HCN dans les genotypes varient entre et dans les populations. Une population provenant de Charlottetown, l'ile de Prince Edouard, montre des propriCtCs agronomiques intCressantes par example des feuilles plus grandes, des pCtioles plus longs ainsi que des stolons plus forts que les autres populations; cette population pourrait servir de base pour un programme d'amtlioration gCnCtique visant i amCliorer la rusticitt i l'hiver de variCtCs de trbfle blanc adaptCes au paturage en rotation et i l'ensilage, pour la rtgion Atlantique du Canada. [Traduit par la revue]
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