Theses and Dissertations at Montana State University (MSU)
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Item Spatial patterns in soil depth and implications for offseason nitrogen dynamics in dryland wheat systems of central Montana(Montana State University - Bozeman, College of Agriculture, 2022) Fordyce, Simon Isaac; Co-chairs, Graduate Committee: Clain Jones and Craig Carr; Pat Carr, Clain Jones, Jed Eberly, Scott Powell, Adam Sigler and Stephanie Ewing were co-authors of the article, 'Exploring relationships between soil depth and multi-temporal spectral reflectance in a semi-arid agroecosystem: effects of spatial and temporal resolution' submitted to the journal 'Remote Sensing of environment' which is contained within this thesis.; Pat Carr, Clain Jones, Jed Eberly, Rob Payn, Adam Sigler and Stephanie Ewing were co-authors of the article, 'Spatiotemporal patterns of nitrogen mineralization in a dryland wheat system' submitted to the journal 'Agriculture, ecosystems, and environment' which is contained within this thesis.Shallow soils (< 50 cm) under dryland wheat (Triticum aestivum L.) production lose large amounts of inorganic nitrogen (N) to leaching. Crops grown in shallow soils may be more responsive to N fertilizer due to lower fertilizer recovery and suppressed mineralization, raising questions as to whether standard practices of N fertilizer rate determination can increase risks of leaching and groundwater contamination in these environments. Mineralized N can be a major nutritional supplement for wheat crops in dryland agroecosystems, so accurate estimates of mineralization inputs can have important economic and environmental implications. To assess the potential for suppressed N mineralization in shallow soils, we used spectral reflectance from up to three sensors (unmanned aerial vehicle, National Agricultural Imagery Program, and Sentinel 2) to spatially characterize soil depth on three fields in Central Montana (Chapter 2) and compared surface (0-20 cm) carbon and N cycling indices across soil depth classes (Chapter 3). Carbon dynamics were stable across depth classes while N mineralization was lower in the shallow class. Results confirm multispectral imagery as a valuable tool for non-destructively characterizing fine-scale spatial patterns in soil depth and corroborate previous findings of lower N mineralization in shallow soil environments. Given the potential for heightened fertilizer responsiveness due to lower mineralization in these environments, decision support systems for site-specific fertility management (e.g., variable rate fertilizer application) should assess the environmental consequences of leaching alongside the economic benefits of applied fertilizer rates which maximize responses of yield, quality and same-year net revenue.Item Water quality response to water and nitrogen movement through a semi-arid dryland agroecosystem in Montana, USA(Montana State University - Bozeman, College of Agriculture, 2020) Sigler, William Adam; Chairperson, Graduate Committee: Stephanie A. Ewing; Stephanie A. Ewing, Clain A. Jones, Robert A. Payn, E.N. Jack Brookshire, Jane K. Klassen, Douglas Jackson-Smith and Gary S. Weissmann were co-authors of the article, 'Connections among soil, ground, and surface water chemistries characterize nitrogen loss from an agricultural landscape in the upper Missouri River Basin' in the journal 'Journal of hydrology' which is contained within this dissertation.; Stephanie A. Ewing, Clain A. Jones, Robert A. Payn, Perry Miller and Marco Maneta were co-authors of the article, 'Water and nitrate loss from dryland agricultural soils is controlled by management, soils, and weather' submitted to the journal 'Agricultural ecosystems & environment' which is contained within this dissertation.; Stephanie A. Ewing, Scott D. Wankel, Clain A. Jones, Sam Leuthold, E.N. Jack Brookshire and Robert A. Payn were co-authors of the article, 'Drivers of denitrification across a semiarid agroecosystem revealed by nitrate isotopic patterns' which is contained within this dissertation.Humans have increased reactive nitrogen (N) on the planet by an order of magnitude over the past 150 years. Most of this reactive N is used for fertilizer to feed a growing population, but loss of N from cultivated soils threatens agricultural and environmental sustainability. Nitrate accumulated in soil from fertilization or decomposition of soil organic N (SON) may be lost via leaching, which can reduce soil fertility and compromise water quality. Nitrate concentrations commonly exceed human drinking standards in groundwater resources around the globe. In the Judith River Watershed (JRW) in central Montana, nitrate has been detected above the standard since the 1960s. This dissertation contributes to a more holistic understanding of the fate and transport of N in the JRW. An interdisciplinary team engaged with farmers in a participatory research project, making observations in soils, groundwater, and streams to characterize water and N movement. At the landform scale, 5 to 9 cm yr -1 of the 38 cm yr -1 mean annual precipitation moves through soil to recharge groundwater and leaches 11 to 18 kg ha -1 yr -1 of nitrate-N from soil. These leaching rates are approximately 20-30% of fertilizer rates but likely reflect inmixing of nitrate from SON decomposition. Soil modeling analyses suggested that water and N losses were dominated by intense precipitation periods on wetter soils, such that more than half of simulated deep percolation and leaching occurred in two of 14 model years. Simulations further suggest that thinner soils (<25 cm fine-textured materials) experience water and nitrate loss rates five to 16 times higher than thicker soils (>100 cm). Soil sampling demonstrated that increased soil water during fallow periods facilitates conversion of SON to nitrate. Soils are then primed for water and N loss with subsequent precipitation, resulting in disproportionately high leaching rates during and following fallow periods. Isotopic evidence from fallow periods further suggests that nitrate is lost to the atmosphere via denitrification, a gas phase loss combining with leaching losses to compromise the goal of delivering N to crops. These findings suggest that reduction of fallow increases N use efficiency and reduces nitrate loss to groundwater.Item Impacts of crop rotations and nitrogen fertilizer on soil biological factors in semi-arid Montana(Montana State University - Bozeman, College of Agriculture, 2021) Fouts, Willa Constance; Chairperson, Graduate Committee: Catherine A. ZabinskiEvaluating the effects of cropping and fertilizing techniques is key to informing agricultural best practices. We must continue monitoring how we manipulate soils in order to preserve and cultivate high-quality soil ecosystems that can support us in the face of climate change and widespread soil loss and deterioration. We assessed the effects of common agricultural practices in Montana by measuring biological indicators of soil quality in the 18th year of a field plot experiment with 100% and 50% the recommended rate of synthetic nitrogen (N) fertilizer and crop rotations incorporating wheat, fallow, and legumes. The biological indicators measured were four soil extracellular enzymes, potentially mineralizable N (PMN), and microbial biomass. We sampled once in spring 2020 and subsampled in the fall. We also tested whether enzymes and PMN were correlated to aboveground plant residue, which was represented by the sum of the dried plant mass from past two years left on the plots after harvest. Plant residue was positively correlated with the C, N, and S-cycling enzymes and to PMN. The positive correlation between PMN and residue reflects that increased biomass inputs could increase easily mineralizable N. Soil with the high N-rate had a slightly higher geometric mean enzyme activity. This could be from the resulting increase in plant residue. The high N-rate treatment slightly decreased soil PMN but was not affected by crop rotation treatments. Fallow systems had lower enzyme function overall, indicating a lessened fertility and decomposition rate compared to continuously cropped treatments, which keep the soil covered with a crop for more months out of the year. The positive correlations of plant residue, along with the general lower performance of the fallow systems, especially the tilled fallow rotation, support that aboveground biomass inputs are a driver in soil ecosystem function. Continuous no-till crop rotations have increased aboveground plant organic matter, which could increase nutrient cycling and decomposition, and thereby soil biological quality and fertility.Item Pest management challenges and climate change in water limited winter wheat agroecosystems in southwestern Montana(Montana State University - Bozeman, College of Agriculture, 2020) Nixon, Madison Grace; Chairperson, Graduate Committee: Fabian D. MenalledDryland winter wheat production is influenced by many environmental factors including climate, disease, and resource availability. In Montana, Bromus tectorum (cheatgrass) and Fusarium pseudograminearum (a fungus causing root crown rot) are major winter wheat pests; reducing yield and grain quality. However, little is known how climate change and resource availability impact winter wheat, B. tectorum, and F. pseudograminearum individually as well as their multi-trophic interactions. Thus, this research aimed to 1) Determine the susceptibility of B. tectorum to F. pseudograminearum and assess how CO 2 and nitrogen impact their growth, and 2) Evaluate how elevated temperature, reduced precipitation, and plant competition impact winter wheat and B. tectorum growth and reproduction. Utilizing growth chambers, high and low nitrogen treatments, fungal inoculated and uninoculated treatments, and ambient and elevated CO 2 treatments, Bromus tectorum was found to be a host of F. pseudograminearum, and the fungus significantly reduced root, shoot and total biomass, as well as primary physiological processes of B. tectorum. Fusarium pseudograminearum infection was not impacted by nitrogen or CO 2 level. Low nitrogen increased emergence and root production early on, while high nitrogen increased shoot production at later growth stages. Low nitrogen also improved stomatal conductance and transpiration rate. High CO 2 increased B. tectorum root, shoot, and biomass production, as well as intercellular CO 2. An interaction between ambient CO 2 and low nitrogen resulted in the greatest shoot relative growth rate between the first and second harvest. Field tests, using three climate treatments (ambient, increased temperature, reduced precipitation with increased temperature) and three plant competition levels (monoculture winter wheat, monoculture B. tectorum, and biculture of the two), found that for both winter wheat and B. tectorum monocultures, ambient and warmer climates produced similar yields and biomass, respectively, whereas the drier with warmer treatment reduced these factors. Additionally, B. tectorum presence increased winter wheat grain protein. A quadratic interaction model of winter wheat yield as a function of B. tectorum biomass by climate treatment suggests that at low to moderate B. tectorum biomass levels, winter wheat yield was negatively impacted by the warmer and drier treatment, whereas ambient and warmer treatment results were similar.Item Cycling and storage of reactive soil carbon and nitrogen pools: management implications for semiarid crop production(Montana State University - Bozeman, College of Agriculture, 2017) Romero, Carlos Matias; Chairperson, Graduate Committee: Richard E. Engel; Richard Engel, Chengci Chen and Roseann Wallander were co-authors of the article, 'Microbial immobilization of nitrogen-15 labelled ammonium and nitrate in an agricultural soil' in the journal 'Soil Science Society of America journal' which is contained within this thesis.; Richard E. Engel, Chengci Chen, Roseann Wallander and Clain A. Jones were co-authors of the article, 'Late-Fall, Winter, and Spring broadcast applications of urea to no-till Winter wheat II. Fertilizer N recovery, yield, and protein as affected by NBPT' in the journal 'Soil Science Society of America journal' which is contained within this thesis.; Richard E. Engel, Juliana D'Andrilli, Chengci Chen, Catherine Zabinski, Perry Miller and Roseann Wallander were co-authors of the article, 'Bulk optical characterization of dissolved organic matter from semiarid wheat-based cropping systems' in the journal 'Geoderma' which is contained within this thesis.; Richard E. Engel, Juliana D'Andrilli, Chengci Chen, Catherine Zabinski, Perry Miller and Roseann Wallander were co-authors of the article, 'The oxidizable fraction of organic matter by potassium permanganate in semiarid drylands: from soils to spectra' submitted to the journal 'Ecological Indicators' which is contained within this thesis.Changes in the size and distribution of soil organic carbon (C) and nitrogen (N) pools affect the biogeochemical properties of terrestrial ecosystems; particularly in semiarid drylands where environmental constraints limit crop production. Agriculture in the northern Great Plains (NGP) of North America has undergone a tillage reduction revolution over the past 20 years; it is therefore imperative to elucidate how organic matter (OM) and fertilizer-N cycle under no-till (NT) management given its potential for providing more sustainable cropping systems and mitigating environmental losses. The objective of this dissertation was to characterize the cycling of labile, reactive pools of soil organic C and N among NT wheat (Triticum aestivum L.)-based cropping systems subjected to differing cropping intensity and fertilizer-N management. We conducted both laboratory and field experiments following the fate of 15 N-labelled fertilizer as affected by N management principles. In surface soil, microbial uptake of NH 4+ was greater than for NO 3- forms. Lower immobilization of NO 3- might therefore increase fertilizer-N availability to winter wheat relative to NH 4+ or urea-based sources. In plant tissue, fertilizer-N recovery (FNR) by winter wheat was affected by application timing of urea to the soil surface; FNR was greater for spring than late-fall and winter applications. The addition of urease inhibitor N-(n-butyl) thiophosphoric triamide improved FNR of all urea timings, but the response was greater for late-fall and winter compared with spring applications. We also examined the cycling of labile, reactive OM as affected by differing land management. Specifically, we characterized dissolved organic matter (DOM) and permanganate oxidizable carbon (POXC) concentration and composition from soil samples collected from three long-term (>10 yr) cropping field sites. Annual NT cropping increased the concentration and compositional diversity of DOM and POXC pools; higher inputs of biomass-C promoted the accumulation of fresh, plant derived DOM relative to conventional fallow-wheat management. Such enrichment translated into higher OM accretion rates within the uppermost 0-50 cm layer, likely benefiting FNR by winter wheat. Our experimental approach provided a comprehensive tool for agroecosystem evaluation at the farm level, identifying NT scenarios that can be used for sustainable management frameworks within the NGP.Item Scaling nitrogen retention from trees to forests through succession(Montana State University - Bozeman, College of Agriculture, 2016) Scott-Klingborg, Aaron James; Chairperson, Graduate Committee: Jack Brookshire; Jack Brookshire was an author of the article, 'Large trees dominate nitrogen retention across forest succession' submitted to the journal 'Ecology letters' which is contained within this thesis.; Jack Brookshire was an author of the article, 'Expression of sink-driven and transactional nitrogen limitation following stand-replacing disturbance in an inland pacific northwest coniferous forest' submitted to the journal 'Ecosystems' which is contained within this thesis.We seek to understand how the ability of trees to acquire and retain nitrogen (N) changes throughout their lifetimes. This capacity enables trees to act as carbon (C) sinks individually and collectively in forest ecosystems over successional time scales. We evaluate how properties that govern nutrient retention change with tree size and forest age, and how allometric relationships scale up to influence ecosystem-level patterns of N cycling and retention. Most generally, we hypothesized that changes in N uptake and recycling efficiency with increasing tree size would vary with forest age and N availability. Additionally, we evaluated changes in ecosystem-level C and N accumulation throughout secondary forest succession following clear-cut logging disturbances in an effort to understand how N limitation may become expressed over time and interact with forest successional dynamics. Our findings highlight the importance of large trees in ecosystem N cycling and growth. We find that increasing mass growth rates are matched by an increasing capacity to acquire and retain N without necessitating increases in growth efficiency. Research findings indicate that mortality of single trees may hold profound consequences for stand-level N retention in addition to C storage. At the ecosystem scale, we find N accumulation and limitation are dynamic processes that fluctuate in strength and source over forest succession, and that ecosystem accumulation of N was driven predominately by increasing N in plant biomass rather than in soil pools.Item Chromatographic, spectroscopic and microscopic analyses reveal the impact of iron oxides and electron shuttles on the degradation pathway of 2,4,6- trinitrotoluene (TNT) by a fermenting bacterium(Montana State University - Bozeman, College of Agriculture, 2003) Borch, Thomas; Chairperson, Graduate Committee: William P. Inskeep and Robin Gerlach (co-chair)Contamination of surface and subsurface environments with explosives such as 2,4,6-trinitrotoluene (TNT) is a worldwide problem. The fate and analysis of TNT were investigated in numerous artificially contaminated model systems. We developed a unique high performance liquid chromatography gradient elution method for the analysis of commonly observed TNT metabolites and EPA explosives. Column temperature was identified as the key parameter for optimal separation. Iron (hydr)oxides play an important role in the reduction, sorption and fate of TNT in soil and sediment. Consequently, characterization of the nature and properties of natural and synthetic Fe (hydr)oxides is important for determining reaction mechanisms and surface-associated chemical processes. This work thus summarizes the potential applicability of imaging and spectroscopic techniques for eliciting chemical and physical properties of iron (hydr)oxides. TNT is persistent in soils due to its low redox potential and sorption. Batch and column studies revealed some of the first results on TNT desorption behavior in two well-defined model soil systems. Biosurfactants were found to be the most promising technique for enhanced TNT desorption. Batch studies with a Cellulomonas sp. in the presence of ferrihydrite and the electron shuttle anthraquinone-2,6-disulfonate (AQDS) were conducted to reveal biotic and abiotic mechanisms contributing to the degradation of TNT. Strain ES6 was found to reduce TNT and ferrihydrite with enhanced reduction in the presence of AQDS. Ferrihydrite stimulated the formation of more reduced TNT metabolites such as 2,4-diamino-6-nitrotoluene. Interestingly, a completely different degradation pathway was observed in AQDS-amended iron-free cell suspensions, showing a rapid transformation of TNT to 2,4-dihydroxylamino-6-nitrotoluene, which transformed into unidentified polar products. The influence of iron phases (i.e. hematite, magnetite, and ferrihydrite) and secondary Fe mineral formation on the degradation of TNT was also evaluated. The initial reduction of TNT was fastest in the presence of hematite; however, the further reduction of hydroxylamino-dinitrotoluenes was fastest, in the presence of magnetite and ferrihydrite (no AQDS). The impact of AQDS was predominant in the presence of hematite resulting in the formation of 2,4,6-triaminotoluene. Ferrihydrite underwent reductive dissolution with the formation of secondary hematite. The enhanced TNT reduction in ferfihydrite-amended systems was therefore most likely due to redox-active Fe(II) rather than secondary Fe phases.Item The use of composted municipal waste to revegetate a high elevation mine site(Montana State University - Bozeman, College of Agriculture, 1993) Vodehnal, Gary LynnItem Development of chemical tests for soil nitrate content as a factor for correlating soil and climatic properties with winter wheat (Triticum aestivum L.) yield(Montana State University - Bozeman, College of Agriculture, 1970) Jackson, Grant D.Item Encapsulated mixed-bed ion-exchange resins : practical uses monitoring nitrate movement and nitrogen soil fertility(Montana State University - Bozeman, College of Agriculture, 1997) Miller, John Howard
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