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Long-term weed dynamics and crop yields under organic and conventional cropping systems in the Canadian prairies

dc.contributor.advisorShirtliffe, Steveen_US
dc.contributor.committeeMemberBlackshaw, Roberten_US
dc.contributor.committeeMemberWillenborg, Chrisen_US
dc.contributor.committeeMemberLamb, Ericen_US
dc.contributor.committeeMemberWalley, Franen_US
dc.contributor.committeeMemberRyan, Matthewen_US
dc.creatorBenaragama, Dilshanen_US
dc.date.accessioned2016-04-21T12:00:17Z
dc.date.available2018-10-16T17:31:20Z
dc.date.created2016-04en_US
dc.date.issued2016-04-20en_US
dc.date.submittedApril 2016en_US
dc.description.abstractDifferences in cropping practices, including tillage, inputs and crop rotations are the driving factors affecting weed dynamics (weed abundance, composition and crop-weed competition), which can ultimately affect crop yields. Several experiments were carried out to assess the impact of long-term organic and conventional cropping systems on weed abundance, weed community composition, crop yield and yield loss using a long-term (18 year) alternative cropping systems study (ACS) at Scott, Saskatchewan, Canada. The ACS study consisted of three input systems, namely high (conventional tillage), reduced (no-till conventional) and organic input systems and three crop rotation diversities (low diversity, diversified annual grains and diversified annual-perennials). A statistical analysis of the 18-year rotation revealed that the organic rotations have four and seven times higher weed density and 32% and 35% lower crop yields than the reduced and the high input systems respectively. Weed community composition was consistently different in organic rotations compared to the two conventional rotations throughout the years, but year to year random variations were more profound. All cropping systems showed an increase in weed density, weed biomass and crop yields over time, probably due to an increase in rainfall over time. Increasing the crop rotation diversity with annual and perennial crops did not reduce weeds, but decreased crop yields in all systems. A two-year micro-plot experiment with four additional weed competition treatments on the ACS study revealed that the wheat yields were lower in the organic rotations even in the absence of weeds, implying that lower crop yields were due to soil fertility related factors. A greenhouse pot experiment from soils obtained from both organic and reduced rotations revealed that wheat yields were still lower in organic compared to the reduced input systems, even after excess mineral N and P were added. Furthermore, no differences in crop yield loss due to weed competition among cropping systems were identified. Overall, this study revealed that eliminating tillage and reducing inputs are possible without long-term changes in weed abundance, weed community composition or affecting crop yields. However, eliminating synthetic inputs as was done in the form of organic crop rotations resulted in increased weed abundance, changed community composition and decreased crop yields.en_US
dc.identifier.urihttp://hdl.handle.net/10388/ETD-2016-04-2510en_US
dc.language.isoengen_US
dc.subjectLong-term, weed abundance, weed competition, crop yields, organic, conventional, crop rotationsen_US
dc.titleLong-term weed dynamics and crop yields under organic and conventional cropping systems in the Canadian prairiesen_US
dc.type.genreThesisen_US
dc.type.materialtexten_US
local.embargo.terms2018-01-24
thesis.degree.departmentAgricultural and Bioresource Engineeringen_US
thesis.degree.disciplinePlant Scienceen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophy (Ph.D.)en_US

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