Theses and Dissertations at Montana State University (MSU)
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Item Integration of Puccinia punctiformis into organic management of Cirsium arvense(Montana State University - Bozeman, College of Agriculture, 2023) Chichinsky, Daniel Jacob; Chairperson, Graduate Committee: Fabian D. Menalled; Tim F. Seipel (co-chair)Cirsium arvense is a perennial weed that causes significant economic losses in agriculture. An extensive rhizomatous root system makes C. arvense difficult to manage, particularly in organic cropping systems that use tillage as a primary management tool. To improve organic management of C. arvense, there is a need for the development of alternative and integrated weed management toolsets that include C. arvense biological controls. Puccinia punctiformis is a fungal pathogen that systemically infects C. arvense, with the potential to reduce host vigor. The goal of this research was to assess the impacts of P. punctiformis within organic cropping systems, using a greenhouse and a field study that examined integration of the biocontrol with cultural and mechanical management tools. In the greenhouse, P. punctiformis was integrated with a competitive annual cropping sequence, where C. arvense's biomass production and competitive ability was assessed. Cirsium arvense biomass production was significantly reduced when P. punctiformis was integrated with the cultural management tactic, more than individual use of the biocontrol or cultural management alone. Additionally, P. punctiformis reduced the competitive ability of C. arvense over time. In the field, P. punctiformis was integrated with mechanical management, where reduced and standard tillage treatments were evaluated to determine the effects on P. punctiformis and C. arvense abundance. The reduced tillage treatment caused a greater increase in P. punctiformis infected C. arvense stems compared to standard tillage, however there was no impact to asymptomatic C. arvense stem density from either tillage treatment. In both tillage treatments, there was a reduction in asymptomatic C. arvense stem density in samples where P. punctiformis infection was present. Integration of P. punctiformis with cultural and mechanical tools can be an effective way to reduce C. arvense vigor. However, successful integration of the biocontrol can be dependent on a combination of environmental factors and deliberate cropping system management. While P. punctiformis is not a singular management solution, it has potential to be integrated into reduced disturbance cropping systems for long-term and sustainable C. arvense management.Item Integrated weed management for the suppression of rhizomatous perennial weeds in organic agriculture(Montana State University - Bozeman, College of Agriculture, 2023) Hettinger, Kara Ann; Co-chairs, Graduate Committee: Perry Miller and Tim F. SeipelConvolvulus arvensis (L.) (field bindweed) and Cirsium arvense (L.) Scop. (Canada, creeping, or Californian thistle) are the most problematic weeds for organic grain farmers in semi-arid Montana and the wider Northern Great Plains (NGP) due to their rhizomatous, perennial root systems. Historically, intensive tillage was used to disrupt and control the root systems. An integrated approach, which combines biological, cultural, and mechanical controls, has been recommended to manage difficult perennial weeds while reducing reliance on a singular management strategy like intensive soil cultivation. Two associated studies were conducted to assess C. arvensis and C. arvense responses to different combinations of tillage, grazing, and crop sequences. In both studies, treatments were arranged on a spectrum of crop competition and tillage intensity, which were inversely related. For example, a two-year sequence of perennial alfalfa (Medicago sativa L.) constituted maximum crop competition and minimal tillage intensity, whereas wheat (Triticum spp.) followed by two consecutive years of tilled fallow represented minimal crop competition and maximum tillage intensity. Treatments within this gradient had crop sequences with varied mixtures of annual and biennial monocot and dicot crops and minimal to moderate tillage regimes, sometimes including livestock grazing with sheep (Ovie aries).Tilled fallow and multi-year alfalfa treatments prevented or decreased both C. arvensis and C. arvense populations over three-year periods across the two studies. For C. arvensis, a treatment using a biennial sweet clover crop and livestock grazing for crop and weed termination increased C. arvensis density. Crop sequences with multiple years of annual monocot or dicot crops increased C. arvense density and biomass over time. There were no differences in C. arvense populations due to tillage method (e.g., standard or reduced). Both studies demonstrated that intensive soil cultivation or intensive crop competition in the form of perennial alfalfa were most successful in suppressing perennial weeds. Highly diverse annual or biennial crop rotations, under either standard or reduced tillage methods, did not prevent population perennial C. arvensis or C. arvense from increasing. Incorporating a perennial forage or temporary pasture phase into annual organic grain rotations of the NGP is recommended to reduce perennial weed pressure.Item Precision organic agriculture(Montana State University - Bozeman, College of Agriculture, 2023) Loewen, Royden Alexander Sasha; Chairperson, Graduate Committee: Bruce D. Maxwell; This is a manuscript style paper that includes co-authored chapters.Organic agriculture addresses some of the shortcomings of industrialized conventional agriculture, but is prevented from more mainstream uptake by reduced yields. Organic agriculture relies on knowledge of intricate biological interactions in place of synthetic inputs used in other forms of agriculture, and in this way reflects an older way of practicing agriculture. Precision agriculture (PA) conversely is a technologically driven method of farming and combines guidance and data collection via remote sensing technologies to bring new efficiencies to farm operations. In this dissertation PA tools were used to explore the potential of improving organic production through site-specific management. By conducting on farm precision experiments (OFPE) with PA farmers can learn quickly about spatial variability across fields enabling well defined management templates. In organic systems this experimentation can be conducted with varied seeding rate inputs of both cover and cash crops. Here, we explored the relevancy of PA in organic settings, first broadly laying the philosophical foundation for the paradigm shift from production-oriented agriculture to precision agroecology. Secondly, a greenhouse experiment was used to develop the first-principle relationship between cover crop and cash crop seeding rates to maximize net return, establishing the basis for field experiments. Field scale experiments on five organic grain farms across the northern great plains deployed OFPE to optimize net returns, or suppress weeds, with varied seeding rates of cover and cash crops. Based on OFPE data, simulations across all sites found net returns could be improved on average by $45.82 ha-1 if economically optimum variable seeding rates were used. While seeding rates were found to have variable effects on weeds across fields, an optimized site-specific seeding strategy to balance net return and weed minimization improved net return and weed suppression compared to farmer-chosen seeding rates in every field tested. Overall, these results reveal the relevancy of precision agriculture to be deployed in organic systems to improve management for increased farmer net returns, and as a weed management method. In this way modern tools can be used to augment farmer knowledge about their local spaces to enable greater understanding and improved management of complex agroecosystems.Item Temporal and spatial dynamics of herbicide resistant weeds(Montana State University - Bozeman, College of Agriculture, 1997) Davidson, Robert MayfieldItem Integrating herbicides, fertilizer, and grazing to manage spotted knapweed infested rangeland(Montana State University - Bozeman, College of Agriculture, 1999) Carter, JoElla Ray