Thesis (Ph. D.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Jan. 14, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Plant Science, [Department of] Agriculture, Food and Nutritional Sciences, University of Alberta. Includes bibliographical references.

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Phenotypic characterizations demonstrated that diversity among 19 naturalized North American and 5 commercial Kura clover ( Trifolium ambiguum M.B.) rhizobial strains was limited. Growth chamber and field evaluations indicated the superiority of North American isolates, increasing foliage accumulation by 30% when compared to commercial inoculant strains. Nitrogen fertilization, however, produced greater accumulations in all evaluations. Genetic diversity among 128 isolates from the lower Caucasus was significant. Nodulation specificity of rhizobia from the lower Caucasus was demonstrated to be more complex than what was reported in the literature, as plants of different ploidy levels and even of different species were, in some cases, nodulated by the same isolate. Specificity of a given rhizobial strain varied depending on the isolate. This study identified naturalized North American rhizobial isolates that are more efficient than currently used commercial strains and increased the genetic diversity of Kura clover rhizobia currently available.

Kura clover (Trifolium ambiguum) is a perennial legume species that has been found to have exceptional persistence in the United States, Australia and New Zealand. There are two challenges that impede the incorporation of Kura clover into pasture mixtures in Alberta. The first is the lack of available seed, and the second is poor establishment success in mixtures with highly competitive grass species. A series of experiments were conducted to (i) address the potential for seed production in a central Alberta environment and (ii) to determine alternative strategies for establishment in mixtures. Kura clover successfully flowered and produced seed under central Alberta growing conditions. Seed production was greater from the cultivar Endura than Cossack. Kura clover seed production was not affected by row spacing however, yield was greater when clover was planted at 3 or 6 kg/ha versus 9 or 12 kg/ha. Seed yield ranged from 80 kg/ha to 350 kg/ha. Establishing Kura clover with a cover crop reduced flowering and seed production. Corn (Zea mays) was the least competitive cover crop, followed by faba bean (Vicia faba L.). Canola (Brassica napus), peas (Pisum sativum L.), barley (Hordeum vulgare) and triticale (X Tritosecale) reduced Kura clover seed yield and are not recommended as cover crops. Comparison of above and below ground competition between Kura clover and meadow bromegrass (Bromus biebersteinii), indicated that below ground competition has the greatest impact on Kura clover seedling growth. Altering seeding rate and delaying introduction of the grass species by up to two months significantly improved Kura clover establishment in mixtures. Kura clover survival in established pastures was higher with physical than chemical sod suppression of the standing forage. Dry matter yield of Kura clover was greatest when defoliated at 6 week intervals. Challenges still remain regarding seed production and establishment of Kura clover. However, we successfully addressed the major concerns regarding the potential of Kura clover in Alberta. / Plant Science

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Kura clover was successfully established via sod-seeding in different environments. Its establishment and yields were initially inferior to that of red clover and white clover. But, its presence slowly increased in the sward and, by the first harvest of the second post seeding season, it was yielding significantly more than the legume species presently recommended for pastures. Clover establishment increased with increasing intensity of herbicide suppression. Best overall results were obtained with glyphosate at low rate (0.8 kg a.i. ha-1). Paraquat (0.9 kg a.i. ha -1) did not suppress sufficiently the grass population for clovers to establish while glyphosate applied at high rates (3.3 kg a.i. ha -1) led to excessive grass suppression, excessive legume content and temporary weed encroachment. N fertilization at seeding did not consistently increase establishment of sod-seeded Kura clover. Forage quality was positively correlated with clover content.

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Increasing food, feed, fiber, biofuel production on decreasing amounts of arable land while simultaneously enhancing ecosystem services is challenging. Strategic inclusion of winter rye (<i>Secale cereale</i>) for biomass, silage, grain and Kura clover (<i>Trifolium ambiguum</i>) living mulch into existing Midwestern cropping systems may offer alternative economic income for farmers without displacing or reducing yields of primary crops. Research was conducted at the Purdue Water Quality Field Station (WQFS) where net balances of water, carbon, nitrogen, and radiation can be measured, and greenhouse gas (GHG) emissions are monitored. The agronomic performance of a corn-soybean rotation and continuous corn (controls) were compared to novel systems that included the use of rye cover cropping and Kura clover co-cropping. Rye was harvested for biomass/silage at heading immediately followed by corn or soybean planting. Continuous corn receiving 69 kg N ha^-1was planted into an establishment of Kura clover sod. Controls included these same systems without the rye or clover. GHG samples were taken via the static chamber method and tile-drained water sub-samples were collected, analyzed for nitrate, and load losses calculated. Biomass composition was determined and used to calculate herbage theoretical ethanol (EtOH) yields. Cereal rye did not significantly decrease corn or soybean grain yield. Averaged across years, Kura clover significantly depressed corn grain yields by nearly 70%. Kura clover significantly reduced flow-weighted tile drainage nitrate (NO₃^-) concentrations, however cereal rye did not. Reductions in flow-weighted tile drainage nitrate (NO₃^-) concentrations were found to largely occur during Quarter two (April, May, June). Cover crops did not significantly reduce annual tile drained NO₃^- load losses in most cases, however, they did significantly reduce annual N₂O emissions. Cumulative annual CH₄ emissions were not significantly altered. Annual CO₂emissions were higher after the introduction of Kura clover and not significantly altered following the introduction of cereal rye. Averaged across years, theoretical ethanol yields in the Kura clover system produced 2,752 L EtOH ha^-1, whereas EtOH production in cereal rye systems ranged from 3,245 to 4,210 L EtOH ha^-1. Theoretical ethanol yields of continuous corn and rotational controls ranged from 2,982 to 3505 L EtOH ha^-1 for these same systems without the cereal rye of Kura clover. These data suggest that a multipurpose approach to cover crop inclusion can provide both environmental and economic advantages worthy of consideration.