FORAGE PRODUCTION, WEED SEEDBANK AND ALLELOPATHIC POTENTIAL OF SELECTED GRASS AND LEGUME SPECIES NATIVE TO THE GREAT PLAINS REGION OF CANADA
Serajchi, Mostafa 1982-
The forage yield and quality, weed seedbank abundance and allelopathic potential of seven native grass and legume species were evaluated in field and greenhouse experiments conducted at the Agriculture and Agri-Food Canada (AAFC), Swift Current Research and Development Centre (SCRDC), Saskatchewan, Canada. Native perennial forage species were selected from three functional groups (C3, C4 grasses and legumes) and seeded in 2010 and 2014 in monocultures and mixtures, including: western wheatgrass (WWG) (Pascopyrum smithii (Rydb.) Barkworth & D.R. Dewey), bluebunch wheatgrass (BBW) (Pseudoroegneria spicata (Pursh) Á. Löve), nodding brome (NOB) (Bromus porteri (J.M. Coult.) Nash), little blue stem (LBS) (Schizachyrium scoparium (Michx.) Nash), side-oats grama (SOG) (Bouteloua curtipendula (Michx.) Torr.), purple prairie clover (PPC) (Dalea purpurea Vent.) and white prairie clover (WPC) (Dalea candida Willd.). Objectives of this thesis were to: 1) evaluate the long-term forage yield and quality of these forage species in monocultures and mixtures; 2) determine the weed seedbank density and aboveground weed populations in stands of these species; and 3) evaluate the allelopathic effect of these species on three problematic weeds: dandelion (Taraxacum officinale F.H. Wigg.), scentless chamomile (Matricaria perforata Mérat) and foxtail barley (Hordeum jubatum L.). Forage mixtures produced greater dry matter than monocultures at all harvesting times. Mixtures of which WWG was a component produced higher forage yield, and a mixture of WWG, BBW, LBS and legumes can provide sustainable forage yield and quality and can be suitable options for seeded pastures. In this study, the forage stands experienced one of the driest and wettest years in the history of the region. We observed no significant differences in forage production of each species from dry to wet year supporting the idea of high stability and productivity of native species during varying climate conditions. Mixtures of forage species also promoted lower weed densities in the seedbank and in the swards aboveground compared to monocultures. Among mixtures, those containing WWG had a significant lower abundance of weeds in the seedbank and aboveground weed populations compared to other forage species. The weed seedbank varied seasonally with the minimum number of weed seeds in early spring and maximum in late summer. The most abundant weeds in the seedbank were the least abundant weeds in aboveground population and vice versa. WWG showed promising results as a native forage species by demonstrating the potential to suppress weeds and reduce weed seed size when seeded in monocultures and mixtures. In the greenhouse, root leachate from WWG, LBS and SOG reduced the aboveground and belowground growth of weeds up to 90%. These findings suggest that the use of allelopathic species may provide weed control and management benefits in seeded pastures and native prairie restorations. In conclusion, forage mixtures produced greater dry matter and promoted lower weed densities in the seedbank and aboveground populations compared to monocultures. This demonstrates that increasing forage mixture diversity can increase forage yield and be an effective ecological and non-chemical weed control tactic in seeded pastures.
DegreeDoctor of Philosophy (Ph.D.)
CommitteeLamb, Eric G; Schellenberg, Michael P; Coulman, Bruce; Biligetu , Bill; Johnstone, Jill; Warkentin, Tom
Copyright DateAugust 2017