Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
8 results
Search Results
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 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 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.Item Diversity, spatial patterns, and competition in conventional no-tillage and organically managed spring wheat systems in Montana(Montana State University - Bozeman, College of Agriculture, 2007) Pollnac, Fredric Winslow; Chairperson, Graduate Committee: Bruce D. Maxwell.The long term sustainability of agricultural systems has become a major concern. In light of this, interest in integrated weed management systems has increased. A better understanding of ecological processes occurring within the weed community might yield insights into how to control weeds while reducing chemical inputs. The objectives of this study were to 1) compare weed species richness and diversity between conventional no-till and organic spring wheat systems, 2) compare spatial patterns of the weed community between these two systems, and 3) examine the joint effects of weed species richness and density on spring wheat performance. Objective 1 was carried out on experimental plots and three production farms in Montana. A nested plot sampling design was used to generate species-area curves. The intercept and slope of the species-area curves were then used to estimate relative α and β diversity respectively. Data indicated higher species richness, α and β diversity in organic systems. We concluded that levels of α and β diversity may serve as indicators of underlying processes occurring in these two systems.Item Phosphorus fertility in Northern Great Plains dryland organic cropping systems(Montana State University - Bozeman, College of Agriculture, 2009) Rick, Terry Lynn; Chairperson, Graduate Committee: Clain Jones; Richard E. Engel (co-chair)Maintaining phosphorus (P) fertility in northern Great Plains (NGP) dryland organic cropping systems is a challenge due to high pH, calcareous soils that limit P bioavailability. Organic P fertilizers, including rock phosphate (RP) and bone meal (BM) are sparingly soluble in higher pH soils. Certain crops species have demonstrated an ability to mobilize sparingly soluble P sources. Objectives of this project were to 1) evaluate the effect of green manure (GM) crops and organic P fertilizers on the P nutrition of subsequent crops, and 2) investigate P fertility differences between organic and non-organic cropping systems. A two-year cropping sequence was conducted on an organic farm in north-central Montana (mean pH=6.6; Olsen P=16 mg kg-¹). Spring pea (Pisum sativum L), buckwheat (Fagopyrum esculentum L.), yellow mustard (Sinapis alba L.) and tilled fallow were fertilized with 0, 3.1 and 7.7 kg P ha-¹ as RP, grown to flat pod stage and terminated with tillage. Winter wheat (Triticum aestivum L.) was grown on these plots in year two. Phosphorus uptake of winter wheat was enhanced (P>0.05) by RP following buckwheat only (P=0.02) at 7.7 kg P ha-¹ compared to 0 P. Results indicate buckwheat can enhance P in a subsequent crop. A greenhouse pot experiment in a low P soil (Olsen P=4 mg kg-¹) consisted of four green manures; buckwheat, spring pea, wheat, and a non-crop control fertilized with 7.0 and 17.5 kg available P ha-¹ as RP, 13.0 and 32.5 kg available P ha-¹ as BM and 10 and 25 kg available P ha-¹ as monocalcium phosphate (MCP). Green manures were harvested, dried, analyzed for nutrient content, and returned to pots. Pots were seeded with wheat. Phosphorus uptake in wheat following all crops was enhanced by MCP (P<0.05). Phosphorus uptake of wheat following buckwheat was enhanced by all P sources over the control. Buckwheat demonstrates the capacity to increase the availability of organic P fertilizers. Soil sampling of organic and non-organic no-tillage (NT) cropping systems was conducted in two separate studies to determine differences in P availability between management systems. Soil analysis determined available P tends to be lower in non-fertilized systems.Item Seeking sustainability for organic cropping systems in the northern Great Plains : legume green manure management strategies(Montana State University - Bozeman, College of Agriculture, 2007) Izard, Erica Jean; Chairperson, Graduate Committee: Perry R. Miller.Soil fertility in organic cropping systems of the northern Great Plains (NGP) is most often achieved through inclusion of leguminous green manures. The objectives in this study were to evaluate the efficacy of pea as green manure; and more specifically, measure the effects of pea green manure type, termination timing and method for soil water use and soil N contribution. A study consisting of winter pea, spring pea, mustard, buckwheat and fallow was conducted at Big Sandy Montana. In Bozeman, MT, termination methods of winter and spring pea were compared. Green manures were terminated at one of two timings, first bloom or first pod. Winter pea was the superior annual green manure in this study, optimizing the soil water conservation and N fertility goals of organic dryland growers in the NGP. Winter pea terminated at bloom also provided the greatest soil N at the end of the green fallow period relative to other green manures. However, pod-terminated winter pea may enhance soil N fertility due to greater N fixation over the long-term.