Orchardgrass (Dactylis glomerata L.) is a valuable pasture species in much of temperate humid North America. However, profuse and early flowering in spring creates management problems for graziers and reduces intake of livestock in a management‐intensive rotational grazing system. The objectives of this study were to estimate environmental stability, genotypic variability, and frequency of nonflowering and sparse‐flowering plants in two sparse‐flowering orchardgrass populations. Seven cultivars and 299 half‐sib families were evaluated for 2 yr at five locations between 42° and 47°N latitude. Sparse‐flowering populations WO‐SF‐B and WO‐SF‐C were later in maturity, produced fewer panicles per plant, and had higher frequencies of sparse‐flowering and nonflowering plants than the cultivars. Plants had varying levels of expression of the nonflowering trait, ranging from slightly sensitive (sparse flowering in one year) to highly sensitive (stable nonflowering across years), with highly sensitive plants found only within populations WO‐SF‐B and WO‐SF‐C. The nonflowering trait of orchardgrass appears to be controlled by floral‐regulation genes that are turned off by short‐day temperatures below a critical threshold. Such a threshold appears to exist for all orchardgrass plants, but is increased in those plants expressing the nonflowering trait.

Orchardgrass (Dactylis glomerata L.) is a major component of many pastures in temperate North America. Early and profuse flowering in pastures is problematic, because livestock refuse to consume flowering stems, prompting many graziers to simply avoid using this species. The objective of this research was to determine the impact of reduced flowering on the quality of harvested forage under two harvest managements of orchardgrass. Six cultivars, three normal cultivars and three sparse‐flowering cultivars (mean panicle density of 141 vs. 61 panicles m⁻2, respectively), were evaluated in field experiments at 21 locations in North America under a 3‐cut harvest management. These cultivars were also evaluated at seven locations under a 5‐cut harvest management. Sparse‐flowering cultivars averaged 9% greater crude protein (CP), 3% lower neutral detergent fiber (NDF), 2% greater NDF digestibility, and 2% greater in vitro dry matter digestibility (IVDMD) than normal cultivars. For the two digestibility measures, differential panicle density between the cultivar groups explained a significant portion of variability, indicating that the increase in forage quality was proportional to the decrease in panicle density below a threshold of about 50 panicles m⁻2. Lastly, differences in regrowth forage quality between cultivar groups were smaller, less consistent, and of lesser statistical significance than for first harvest. While selection for sparse flowering in orchardgrass resulted in significant cause‐and‐effect increases in first‐harvest forage quality, these effects were too small to offset the reduced forage yield associated with the sparse‐flowering trait.

Orchardgrass (Dactylis glomerata L.) is a major component of many pastures in temperate North America. Early and profuse flowering in pastures is problematic due to livestock refusal to consume flowering stems. The objective of this research was to determine the stability and agronomic impact of recently developed sparse‐flowering orchardgrass populations across temperate North America. Six cultivars, three sparse flowering and three normal flowering, were grown at 21 locations in temperate North America and evaluated for panicle density, heading date, and forage yield. Sparse‐flowering cultivars had 57% fewer panicles than normal‐flowering cultivars, but this effect was highly dependent on mean winter temperature, with normal‐flowering cultivars showing twice as much temperature sensitivity compared to sparse‐flowering cultivars. Forage yield of sparse‐flowering cultivars was reduced by approximately 24 to 32% for first harvest and 2 to 9% for regrowth harvests compared to normal‐flowering cultivars and this reduction in forage yield was independent of mean winter temperature. The forage yield reduction associated with sparse flowering is most likely due to a combination of physiological load (loss of stems) and opportunity cost (lack of selection pressure for yield), suggesting an opportunity to improve forage yield potential of this sparse‐flowering germplasm pool.

. 2002. Nitrogen management of spring milling wheat underseeded with red clover. Can. J. Plant Sci. 82: 653-659. The benefits of underseeding cereals with legumes and grasses have been established. However, research is required to determine the effects of underseeding spring wheat with red clover on yield and milling quality. The objectives of this study were: (1) to determine the rates of supplemental N required to obtain 13.5% or greater grain protein of three spring milling wheat (Triticum aestivum L. em Thell.) cultivars underseeded to red clover (Trifolium pratense L.); (2) to determine the effect of supplemental N on establishment of red clover, and (3) to relate the N status of the soil after harvest to grain protein. Field experiments were conducted from 1998 to 2000 on three sites: Hartland, New Brunswick; Truro, Nova Scotia; and Harrington, Prince Edward Island. Grain yield and protein content increased with increasing amounts of supplemental N. In most years, supplemental N above a base application of 55 kg N ha -1 applied at 52.5 kg N ha -1 at Zadoks GS 30 resulted in 13.5% protein in the grain of Grandin and AC Barrie, but 70 kg N ha -1 was required for AC Walton. Based on the N content of the straw, Grandin was less effective in partitioning N into the grain than AC Barrie and AC Walton. Increasing rates of supplemental N caused a reduction in red clover establishment. Soil pH decreased with increasing rates of supplemental N. Nitrate N in the soil at 0-5 and 0-20 cm depths increased with supplemental N, but there was no effect on ammonium N. Differences in pH or levels of soil N after harvest did not account for differences in grain protein. In the Maritime provinces, to reach a desirable milling protein level in spring wheat of 13.5%, producers will need to add supplemental N at a rate of at least 100 kg N ha -1 over and above background levels; however, this will be at the risk of reducing red clover establishment and increasing levels of soil N available for leaching. La variation du pH ou de la concentration d'azote dans le sol après la récolte n'explique pas la fluctuation de la concentration de protéines dans le grain. Les producteurs des Maritimes devront épandre au moins 100 kg d'azote par hectare en sus du taux de base pour récolter du blé de printemps de qualité acceptable pour les meuneries (13,5 % de protéines). Ils courront néan-moins le risque de voir l'établissement des peuplements de trèfle rouge ralentir et la concentration de N dans le sol augmenter, avec les conséquences qu'on suppose au niveau de la lixiviation.