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 Biodegradable composite hydromulches for sustainable organic horticulture(Montana State University - Bozeman, College of Engineering, 2023) Durado, Andrew Dalton; Chairperson, Graduate Committee: Dilpreet S. BajwaIn agriculture, mulch helps retain soil moisture and temperature while preventing weed growth. The most common material used for commercial mulching is low-density polyethylene (LDPE). At the end of the growing season, this plastic is typically buried or burned, causing a negative impact on the environment. This project aims to develop an alternative to LDPE mulch that is acceptable for organic farming and biodegradable. The tested hydromulch (HM) treatments contain a mixture of paper pulp, wood fiber, or hemp hurds combined with a tackifier and water. The tackifiers evaluated were guar gum, psyllium husk, and camelina meal, at various concentrations. These treatments were tested for tensile strength, puncture resistance, rain fastness, density, soil adhesion, porosity, and C:N ratio. The results have shown that samples containing tackifiers outperformed the control that contained no tackifier in the strength tests but not in the rain fastness or soil adhesion tests. Paper was the best fibrous material and guar gum was the top performing tackifier. When tackifier blends were considered, an interaction between two tackifiers occurred resulting in a decrease in strength. Blends containing wood fiber and hemp hurds did not show promising results. The puncture resistance of all mulches significantly decreased at 50% moisture level regardless of tackifier type. Some formulations performed well and could be promising in future field trials. The next step will be to examine these formulations outdoors in large-scale field studies.Item Does temporary land retirement promote organic adoption? Evidence from expiring conservation reserve program contracts(Montana State University - Bozeman, College of Agriculture, 2022) Wing, Hannah Rose; Co-chairs, Graduate Committee: Kate Fuller and Daniel P. BigelowThe Conservation Reserve Program (CRP) is a temporary land retirement program that allows producers to remove environmentally sensitive farmland from agricultural production in exchange for a yearly rental payment. While enrolled in the CRP, land is, by definition, not being used for production and therefore typically complies with standards for organic certification. In order for an operation to become certified organic, producers must comply with organic practices for 36 months prior to when production can be labeled organic. Among other requirements, operators transitioning to organic production cannot apply synthetic pesticides or fertilizers to the land. However, some of the costly three-year transition period can be avoided through participation in the CRP as land enrolled in the program may be eligible to become certified organic in the year that it exits the program. In this paper, we study the extent to which CRP enrollment promotes organic certification. We find that CRP contract expiration leads to increases in organic adoption, and estimate a 0.157 percent increase in new organic operations in response to a 10 percent increase in expiring CRP contracts.Item Impacts of dryland farming systems on biodiversity, plant-insect interactions, and ecosystem services(Montana State University - Bozeman, College of Agriculture, 2018) Adhikari, Subodh; Chairperson, Graduate Committee: Fabian D. Menalled; Laura Burkle (co-chair)Farming system impacts the structure and functioning of associated biodiversity and plant-insect interactions. However, the extent of these impacts is largely unknown in drylands of the Northern Great Plains, an important region for cereal, pulse, oilseed, and forage production. Using three complementary studies, I compared the impacts of conventional and organic systems on associated biodiversity (weeds, bees, insect pests, and parasitoids), bee-flower networks, and bumblebee colony success. First, I assessed stem cuts by and parasitism on Cephus cinctus (wheat stem sawfly) in spring and winter wheat cultivars grown in conventional and organic fields. I found that organic fields had less C. cinctus infestation and more braconid parasitoids of C. cinctus, indicating an increased pest regulation in organic system. I compared C. cinctus preference and survival on Kamut with Gunnison and Reeder wheat cultivars and found the lowest C. cinctus oviposition and survival in Kamut, suggesting that Kamut is a potential genetic source for this pest. Second, I assessed the impacts of conventional and organic systems on forb and bee communities. I found greater forb diversity and more connected bee-flower networks in organic fields, but bee communities did not differ between systems. Comprising only 12% of the landscape, natural habitat did not affect small-bodied bees in either system but had a positive effect on large-bodied bees at the scale of 2000 m radius. These results indicate that an increased forb diversity and bee-flower interaction in organic fields is not enough to offset the negative effects of landscape homogeneity on bees. Third, I compared Bombus impatiens colony success, worker condition, and colony-collected pollen between farming systems. I found greater growth rate, brood cells, and pollen species richness in B. impatiens colonies as well as lower wing wear and greater body lipid mass in workers from organic fields, than in conventional fields. The greater colony success and better worker conditions could be a proxy for better ecosystem services provided by organic fields. Overall, my studies show that organic farming supports greater associated biodiversity, more complex bee-flower networks, and better biodiversity-based ecosystem services in the Northern Great Plains.Item An assessment of influences on organic agricultural producers' attitudes, behaviors, and decisions related to sustainable best management practices(Montana State University - Bozeman, College of Agriculture, 2018) Kurnick, Rebecca Anita; Chairperson, Graduate Committee: Shannon ArnoldA definition for sustainable agriculture that spans competing agriculturalists' philosophies is ambiguous. Organic agriculture is a transformative approach that balances the goals of sustainable agriculture. Understanding how producers identify themselves may give insight as to what drives their decision to explore innovative practices. The purpose of this study was to assess influences on organic agricultural producers' attitudes, behaviors, and decisions related to sustainable best management practices. The objectives of this research were to: 1.) Describe organic agricultural producers' attitudes surrounding sustainable best management practices, 2.) Describe organic agricultural producers' behaviors surrounding sustainable best management practices, and 3.) Describe other influential factors on organic agricultural producers' decisions to adopt sustainable best management practices. Rogers' Diffusions of Innovations and the Theory of Planned Behavior (TPB) were used to analyze organic producers' attitudes, behaviors, and decisions related to sustainable best management practices (BMP). This descriptive study utilized a survey research design of producer members of the Montana Organic Association. Data analysis was conducted utilizing Confirmatory Factor Analysis to assess the relationships between questions and constructs of the TPB. The strongest pairwise relationships indicated that respondents with a positive attitude to implement sustainable practices likely intend to implement them, and that respondents with a high intention to implement BMP likely will participate in the behavior. Respondents considered themselves risk takers, leaders, and deliberators who use an integrated whole farm approach. Influences of peers and social groups had a significant effect on producers' decisions to implement sustainable BMPs. Results suggest these theories are valuable to study agricultural producers' decisions. Future research should include a much larger population of organic and conventional agricultural producers to allow for the model to draw conclusions about broader populations. Sustainability can be a divisive topic. Future work utilizing the theories should include researching agriculturalists from all backgrounds on their feelings about non-production specific agricultural concepts and terminology. There is unlimited potential for uniting divided groups to solve common problems related to environmental resources, policy, and markets. Future research should include a larger sample of organic and conventional producers to draw conclusions about broader populations.Item The effect of organic certification on farmland value(Montana State University - Bozeman, College of Agriculture, 2017) Boldbaatar, Munkhnasan; Chairperson, Graduate Committee: Joseph JanzenThis research considers the relationship between organic certification and farmland values. We employ the ARMS survey data from 2003 to 2011. We construct three models with different organic status classifications. We control for differences in farm type, NASS crop district, urbanization, and year fixed effects. We find that organic certification has a significant (statistically and economically) effect on farmland value. Our model suggests that a 1 percentage point increase in a farm's organic land would result a 0.23 percentage point increase in the farmland rental rate.Item The harmony seekers : ecologically cultivating land and learning(Montana State University - Bozeman, College of Education, Health & Human Development, 1999) Boyle, Janet AmundsenItem Toward ecologically-based management : biodiversity and ecosystem functions in intensively managed agroecosystems(Montana State University - Bozeman, College of Agriculture, 2014) McKenzie, Sean Cummings; Co-chairs, Graduate Committee: Fabian D. Menalled and Kevin O'NeillConcerns about intensive, chemically-based agriculture have precipitated a call for ecologically-based practices. We investigated the ramifications of two such practices. First, we investigated targeted sheep grazing for cover-crop termination. Second, we compared the community dynamics of carabid beetles (Coleoptera:Carabidae), a group of beneficial insects in agroecosystems, among three vegetation systems in alfalfa (Medicago sativa L.) production. Cover-crops are grown to improve soil quality and reduce erosion. While cover-crops do not provide a direct source of revenue, integrating livestock grazing to terminate them could provide alternative revenue. We conducted a two year study of the impacts terminating cover-crops with sheep grazing on soil quality, weed and carabid communities, and crop yield in a diversified vegetable market garden. In 2012 and 2013, we seeded a four species cover-crop that was terminated by either tractor mowing or sheep grazing following a completely randomized design. In 2013, we planted spinach, kohlrabi, and lettuce into previously grazed or mowed plots following a split-plot design. The cover-crop provided forage worth $24.00 - $44.00 ha -1 as a grazing lease. There were no differences in soil chemistry, compaction, temperature or moisture between grazed and mowed plots. Despite temporal shifts in weed and carabid community structure, we found no differences in those communities between termination methods. Finally, cash crop yields did not differ between strategies. Our results suggest that this practice can provide an economic benefit for producers without detrimental agronomic or ecological consequences. Alfalfa is the third biggest crop in Montana by gross revenue. As a perennial crop, it can allow for high populations of pest and beneficial insects. Practices that favor predatory insects could enhance biological control of pests. We conducted a two year study investigating carabid community dynamics and habitat preferences of common carabid species under three habitat management strategies: monoculture alfalfa, barely nurse-cropped alfalfa and uncultivated refugia. Our results indicate that carabid communities vary among the three systems. Barley nurse-crop systems had greater total carabid activity-density than either of the other two system, which suggests that nurse-cropping may be an effective habitat management strategy to enhance carabid populations.