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Item Pulse crop management to enhance biological nitrogen fixation in the northern Great Plains(Montana State University - Bozeman, College of Agriculture, 2022) Baber, Kaleb Wade; Chairperson, Graduate Committee: Clain Jones; Clain Jones, Perry Miller, Sydney Atencio, Samuel Koeshall and Peggy Lamb were co-authors of the article, 'Lentil nitrogen fixation response to fertilizer and inoculant in the northern Great Plains' submitted to the journal 'Agronomy journal' which is contained within this thesis.; Clain Jones, Kevin McPhee, Perry Miller and Peggy Lamb were co-authors of the article, 'Assessment of nitrogen fixation among pea and lentil varieties in the semiarid northern Great Plains' submitted to the journal 'Agronomy journal' which is contained within this thesis.Pulse crop production has increased dramatically in Montana and the surrounding northern Great Plains over the past few decades. Through N fixation, pulse crops, including pea and lentil, can reduce N fertilizer requirements, both by replacing non N-fixing crops and positively contributing to soil N pools for subsequent crop uptake. Three studies were conducted in Montana over three years to investigate pulse crop management practices that enhance N fixation of pea and lentil. The first study investigated lentil N fixation response to fertilizers and inoculant types. Inoculant and S fertilizer each increased N fixed by lentil in 40% of site-years, but response was not well correlated with cropping history or soil sulfate-S levels. In one site-year, N fixation appeared to continue increasing at the highest tissue S concentration while seed yield plateaued below that highest level, indicating that S fertilizer could increase the soil N benefit of lentil even if a yield response is not expected. Potassium fertilizer nor inoculant type influenced N fixed. The second study assessed differences in N fixation among lentil and pea varieties. Amounts of N fixed varied in 75% and 50% of site-years for lentil and pea, respectively. Differences among varieties were sometimes large, up to 45 kg N ha-1. Two lentil varieties, CDC Richlea and Riveland, were frequently among the top N-fixers, while no pea varieties consistently fixed more N than others. Correlations between N fixed and seed yield ranged from weak to moderate, and pea more frequently had positive relationships than lentil. The third study evaluated N fixation response of two pea varieties to inoculant formulations. Inoculant formulation did not impact N fixed by either variety, and the uninoculated treatment performed as well as the inoculated treatments. This suggests producers may not need to inoculate pulse crops to achieve sufficient N fixation when effective rhizobia populations exist in their fields. These results contribute to the researchers' understanding of N fixation by pulse crops in the region. Together, these studies can help producers in the northern Great Plains better manage pea and lentil, improving both economic and environmental sustainability of the region's cropping systems.Item Long term multispecies cover crops in semi-arid Montana: soil response and aboveground biomass(Montana State University - Bozeman, College of Agriculture, 2020) D'Agati, Kristen Mary; Chairperson, Graduate Committee: Catherine A. Zabinski; Perry Miller (co-chair); Perry R. Miller, Clain A. Jones and Catherine Zabinski were co-authors of the article, 'Soil biological effects of herbicide-terminated multi-species cover crop mixes, in semi-arid Montana' which is contained within this thesis.; Catherine Zabinski, Clain A. Jones and Perry R. Miller were co-authors of the article, 'Aboveground biomass quality and quantity of long-term multispecies cover crop mixes, in the semi-arid Montana' which is contained within this thesis.; Maryse Bourgault, Perry R. Miller, Clain A. Jones and Catherine Zabinski were co-authors of the article, 'Soil biological response to spraying, grazing, or haying of long-term multispecies cover crops in semi-arid Montana' which is contained within this thesis.Low and variable annual precipitation (250-350 mm) make management strategies that conserve soil moisture imperative for wheat producers in semi-arid Montana. A wheat-fallow rotation was historically the most common dryland cropping system in semi-arid Montana, due to its ability to conserve soil water; however, summer fallow has negative environmental impacts (Campbell et al., 1991). There is interest to incorporate cover crops into a rotation as a partial replacement for summer fallow to enhance soil quality. An eight-yr study explored the effect of cover crops on biological soil properties through aboveground biomass inputs of four plant functional groups: brassica (BC), fibrous root (FR), tap root (TR), and nitrogen fixers (NF) grown as two-species mixes, six-species mixes (three functional groups), a full eight-species mix, and two controls--chemical fallow and sole pea. Cover crops grew for about 60 days, were terminated with glyphosate, then soil samples were taken nine months after termination at wheat seeding. The only difference in biological parameters based on functional group was that mycorrhizal colonization in wheat was higher following FR than BC at one site. Potentially mineralizable nitrogen (PMN) was 1.6-1.7 times higher and microbial biomass was 1.4 times higher in soils from cover crop treatments relative to fallow at one of two sites. PMN was 1.2-1.3 times higher in soils from six-species mixes than two-species mixes at both sites, and six-species mixes produced 1.4 times more biomass at one site. Nitrogen fixers had the lowest C:N ratio of the functional groups at both sites, while FR had the highest at one site. In a second study of cover crop termination, cover crops were grown about 90 days and terminated with one of three strategies: chemically, grazing, or haying. Soils were sampled nine months after termination at the time of wheat seeding. Few enzyme differences and no PMN differences or meaningful patterns were discovered among termination strategies. Minimal differences in biological parameters, even when shoot biomass was removed, may mean grazing or haying could improve net revenue without detracting from soil health. In semi-arid annual systems, water limitations may be the main concern with growing cover crops.Item Role of the P-cluster and FeMo-cofactors in nitrogenase catalysis(Montana State University - Bozeman, College of Letters & Science, 2017) Keable, Stephen Michael Keable; Chairperson, Graduate Committee: John W. Peters; Andrew J. Rasmussen, Karamatullah Danyal, Brian J. Eilers, Gregory A. Prussia, Axl X. LeVan, Lance C. Seefeldt and John W. Peters were co-authors of the article, 'Three structural states of the nitrogenase P-cluster revealed in MOFE protein structures at poised potentials' submitted to the journal 'Biochemistry' which is contained within this thesis.; Jacopo Vertemara, Karamatullah Danyal, Andrew J. Rasmussen, Brian J. Eilers, Oleg A. Zadvornyy, Luca De Gioia, Giuseppe Zampella, Lance C. Seefeldt and John W. Peters were co-authors of the article, 'Acetylene interaction with the nitrogenase femo-cofactor investigated by structural and computational analysis' submitted to the journal 'Biochemistry' which is contained within this thesis.; Dissertation contains two articles of which Stephen Michael Keable is not the main author.Biological nitrogen fixation has been extensively researched for over four decades, yet due to the complex nature of this process, numerous questions still remain regarding the catalytic mechanism, and investigation of this system has relevance across a number of disciplines. Nitrogen is a fundamental element to all biological systems, primarily occurring in proteins and nucleic acids. However, most nitrogen on Earth is found in the form of nitrogen gas, a form that is biologically unavailable to most organisms owing to the strength of the triple bond between the two nitrogen atoms. The limited abundance of biologically accessible (or fixed) nitrogen has driven an anthropomorphic thrust to supplement the nitrogen cycle with nitrogenous fertilizers, thereby boosting agricultural output. The primary industrial method to produce these fertilizers, derived from the Haber-Bosch synthesis, is an energy intensive process that consumes approximately 1- 2% of the world's energy portfolio. This process utilizes metal iron catalysis, high temperatures and high pressures, along with hydrogen usually obtained from reformed fossil fuels, to reduce atmospheric nitrogen gas to ammonia. Aside from the environmental consequences that arise from the production of nitrogenous fertilizers, long-term agricultural application may also have disastrous ecological ramifications, such as eutrophication. Additionally, biological nitrogen fixation supports more than half the human population, and having a more complete understanding of this complex process has the potential to displace some of the demand for fertilizer production. The aforementioned reasons are clearly enough to warrant serious investigation into biological nitrogen fixation, however, the fascinating intricacies and comparative relevance to other biochemical systems further motivates the study of this system. The enzyme committed to this task, nitrogenase, orchestrates an elegant unidirectional multiple electron reduction and activation of the nitrogen triple bond. Historically, mechanistic characterization of this enzyme has been difficult for a number of reasons; however, studies to date have revealed many aspects of the process as biochemical techniques have improved. Nitrogenase is an oxygen sensitive, complex two-component enzyme that is mechanistically pertinent to many other biochemical processes. Presented here are studies revealing insight into substrate binding and the unique gated electron transfer mechanism of this fascinating enzyme.Item Management of nitrogen symbiosis and plant nitrogen nutrition of field pea (Pisum sativum) and chickpea (Cicer arietinum) with spectral reflectance(Montana State University - Bozeman, College of Agriculture, 2001) McConnell, Jody ToddItem Effects of chemical seed treatment upon seed germination and stand establishment of forage crops and also upon nodulation of leguminous plants(Montana State University - Bozeman, College of Agriculture, 1957) Niffenegger, Daniel A.Item Nitrate uptake and water use of Centaurea maculosa (spotted knapweed) and native grasses(Montana State University - Bozeman, College of Agriculture, 2000) Blicker, Pamela SueItem An evaluation of factors influenced by nitrogen fixation in sainfoin (Onobrychis viciifolia Scop.)(Montana State University - Bozeman, College of Agriculture, 1980) Hill, Nicholas ScottItem The effects of soil salinity on growth of and dinitrogen fixation in Phaseolus vulgaris L. and Vicia faba L.(Montana State University - Bozeman, College of Agriculture, 1983) Kisha, Theodore JamesItem Variability for traits associated with N 2 fixation of juvenile sainfoin (Onobrychis viciifolia Scop.)(Montana State University - Bozeman, College of Agriculture, 1982) Cash, Steven DennisItem Symbiotic nitrogen fixation and establishment of six Montana native legumes species(Montana State University - Bozeman, College of Agriculture, 2005) Metcalf, Sarah Jean; Chairperson, Graduate Committee: Jeff Jacobsen.Legume species have been known to increase soil N content and are incorporated into land restoration seed mixes in hopes of improving degraded soils and plant communities. The goals of this project were to determine effects of soil type, soil moisture, inocula and fungicide treatments on legume establishment, N2 fixation capacity and plant biomass for six individual native legume species. In potted greenhouse studies, legumes were grown in five field soils to verify nodulation without inocula. In a second phase, plant biomass was measured in two soils at two moisture contents (60 and 80% of field capacity). The efficacies of Rhizobia inocula and fungicide treatments were also tested. The greenhouse studies were used to supplement data gathered at three field sites around Montana. Native soils contained Rhizobia that were specific to many of the plant species tested and induced nodulation. Soil moisture content, inoculation and fungicide treatments had less effect on nodulation and biomass than the soil characteristics. Fungicide treatments benefited establishment of Lupinus argenteus, and had mixed effects on Astragalus canadensis and Dalea candida. Benefits were dependent on soil nutrient content, microbial biota and other characteristics. Shoot biomass at each field site also varied significantly; in general A. canadensis had the highest nodulation and biomass, while Dalea purpurea and D. candida typically had the lowest biomasses and nodulation. This research should assist land managers in selecting species to suit a wide variety of ecological conditions and land restoration scenarios.