Soil, Environmental and Atmospheric Sciences electronic theses and dissertations (MU)
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The items in this collection are the theses and dissertations written by students of the Department of Soil, Environmental and Atmospheric Sciences. Some items may be viewed only by members of the University of Missouri System and/or University of Missouri-Columbia. Click on one of the browse buttons above for a complete listing of the works.
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Item Evaluation of corn nitrogen use efficiencies and inherent soil properties on central Missouri claypans(University of Missouri--Columbia, 2025) Raether, Tory Rose; Davis, Morgan P.[EMBARGOED UNTIL 12/01/2026] Nitrogen (N) fertilizer is a central driver of corn (Zea mays L.) productivity, yet efficient use of applied N remains a challenge in modern cropping systems. Missouri corn production occurs across variable claypan landscapes where nutrient requirements, soil properties, and yield potential differ across fields. This thesis examines N fertilizer optimization through two complementary approaches: nitrogen use efficiencies (NUEs) and soil health indicators. Chapter 2 quantifies yield response to six N fertilizer rates (0–235 kg N ha-1) with and without cereal rye (Secale cereale) cover across four Boone County field sites. Yield typically followed quadratic plateau patterns, producing agronomic optimum N rate (AONR) estimates that ranged widely by field, reflecting strong site-specific variability. Increasing fertilizer rate consistently reduced NUEs indicating diminishing return on fertilizer when N supply exceeded plant demand. Despite no yield benefit from cover crops, site-specific interactions suggested context dependent N cycling effects. Chapter 3 evaluates physical, chemical, and biological soil health indicators to understand how inherent soil properties relate to yield across the same claypan region. Biological indicators, soil respiration and protein, and chemical indicator permanganate oxidizable carbon correlated most consistently with yield, while many physical and chemical indicators showed weak or variable (weak ρ < 0.3) associations. Correlations diminished at high N rates, suggesting that soil health to yield linkages weaken when N is not a limiting factor. Collectively, findings demonstrate that both optimal N rate and soil function are site-specific, reinforcing the need for regionally adaptable fertilizer strategies and soil health-based benchmarks rather than uniform statewide recommendations.Item Agronomic management practices for industrial hemp production in Missouri(University of Missouri--Columbia, 2025) Anjeeta; Kaur, Gurpreet[EMBARGOED UNTIL 12/01/2026] Industrial hemp (Cannabis sativa L.) has re-emerged as a multipurpose crop in the United States, for grain, fiber, and biomass production. However, its performance is strongly influenced by interactions among genotype, environment, and management. This thesis integrates results from two field studies conducted in Missouri from 2023-2025 to develop agronomic recommendations for optimizing hemp production through multilocation cultivar evaluation and nitrogen response experiments. The first study was conducted to evaluate thirteen industrial hemp cultivars across five environments (Albany, Novelty, Spickard, Columbia, Portageville, and Fair Grove) using a randomized complete block design replicated four times from 2023-2025. Significant genotypic and environmental effects were detected for all agronomic traits. The AMMI1 (Additive Main Effect and Multiplicative Interaction) biplot explained over 60% of the total variation in biomass and grain yield, indicating strong genotype-by-environment (G x E) interactions. Albany consistently produced the highest biomass yields (up to 20,430 kg ha-1 for ‘MS-77' and ‘Puma'), while the greatest grain yields were observed at Novelty, where ‘Futura 83' and ‘Orion 33' exhibited stable performance. Fiber-type cultivars (‘Puma', ‘Yuma', and ‘Jinma') attained greater height, and total biomass yields but were specifically adapted to favourable environments. Dual-purpose varieties (‘Futura 83', ‘Felina 32', and ‘Orion 33') demonstrated wide adaptability and stability across years. Frequent rainfall events at Spickard, Columbia, and Fair Grove caused waterlogging, which resulted in plant mortality from Pythium and Fusarium damping-off diseases. Forage quality analysis indicated significant varietal differences in crude protein (CP), digestible NDF (dNDF48), and in vitro true digestibility (IVTDMD48) with dual-purpose varieties generally exhibiting superior forage quality. The second study was conducted at Albany and Novelty in 2024-2025 using a split-plot design with four varieties (Futura 83, Orion 33, Puma, and Yuma) as main plots and five nitrogen (N) rates (0, 45, 90, 135, and 180 kg N ha-1) as sub-plots. Nitrogen significantly influenced plant height, stem diameter, biomass yield, and N uptake, but it had limited effects on grain yield and forage quality. Biomass yield increased with N rate up to 135 kg N ha-1, after which marginal declines were observed. The grain yield response was modest with peak yields at 135 kg N ha-1. Agronomic efficiency and partial factor productivity were highest between 45-90 kg N ha-1, indicating diminishing returns at higher rates. Soil N distribution revealed greater ammonium-N accumulation in the surface layer (0-15 cm) and nitrate buildup in deeper layers (15-30 cm) under high N rates. Fiber cultivars (‘Puma' and ‘Yuma') showed higher biomass and N recovery, while dual-purpose cultivars (‘Futura 83' and ‘Orion 33') maintained balanced grain yield and N efficiency. Forage quality parameters such as CP, dNDF48, and IVTDMD48 were not significantly affected by N rate, suggesting that genotype was the dominant factor influencing forage value. Collectively, these findings demonstrate that moderate N rates (90-135 kg N ha-1) combined with efficient cultivars like ‘Puma' and ‘Futura 83' optimized growth, biomass and grain yield, and N-use efficiency while minimizing nitrate losses and environmental risks. The multi-environment results provided critical insights for developing site and cultivar-specific management guidelines while contributing to the advancement of sustainable industrial hemp production systems in Missouri.Item Integrated drought assessment and susceptibility mapping in Missouri : a multimethod approach using atmospheric, observational, and machine learning techniques(University of Missouri--Columbia, 2025) Weaver, Sarah Elizabeth; Lupo, AnthonyDrought is a complex hazard that affects agriculture, ecosystems, water resources, and rural and urban communities. Accurate assessment remains difficult because most methods fail to connect atmospheric patterns, ground observations, and spatial modeling. This dissertation develops an integrated framework for drought assessment and susceptibility mapping in Missouri (2012–2024). Chapter 2 analyzes the 2022 summer drought and other years using reanalysis data, atmospheric blocking, Integrated Enstrophy (IE), and major teleconnections (Pacific North American, Arctic Oscillation, North Atlantic Oscillation) (PNA, AO, NAO). Results show that specific circulation patterns and weakened storm tracks strongly influence drought onset and persistence. Chapter 3 refines drought evaluation using Condition Monitoring Observer Reports (CMORs) from 2018–2024. Reports were categorized by drought type and linked with U.S. Drought Monitor severity through a New Drought Index (NDI), revealing strong spatial and seasonal clustering. Chapter 4 applies Analytical Hierarchy Process (AHP) and Random Forest (RF) models to key indicators--precipitation, temperature, slope, and topographic wetness index (TWI)--validated with Condition Monitoring Observer Reports (CMOR) data. Together, these studies create a unified framework linking atmospheric dynamics, community observations, and spatial modeling to improve early warning and resilience across Missouri and the Midwest.Item Cover crops on nitrogen dynamics, soil carbon storage, and soil microbes(University of Missouri--Columbia, 2025) Rambadagalla, Rambadagalle Tharindu; Davis, Morgan P.; Udawatta, Ranjith P.[EMBARGOED UNTIL 08/01/2026] Global agriculture is facing more unprecedented challenges than ever before. The world's food production should be increased by 70 percent--100 percent from 2007 to 2050 to feed the entire 9.1 billion population by 2050 (FAO, 2009). Meeting rising global demands for food, fiber, and fuel often comes with increased inputs into agricultural systems that can lead to adverse environmental and human health effects (Davidson et al., 2012). To fulfill these demands, agricultural activities have significantly altered the nitrogen (N) and carbon (C) cycles in ecosystems (Davidson et al., 2012; Harindintwali et al., 2021). More than half of the world population (40 to 60 percent) depends on crops grown with synthetic N fertilizer (Zhang et al., 2015). Synthetic fertilizer application is considered as vital management practice in agriculture, essential for optimizing crop productivity. The annual production of food and bio energy from agriculture, along with industrial energy consumption, has increased more than two folds reactive N on lands globally. However, most of the reactive N in terrestrial ecosystems is not taken up by plants or remains in soils, and finally ends up in water bodies (Davidson et al., 2012). Nitrogen is also highly susceptible to losses from agroecosystems, including processes such as ammonia (NH3) volatilization, nitrate (NO3--) leaching, and emissions of nitrous oxide (N2O) (Mahmud et al., 2021a). Since large amounts of fertilizer used in agricultural lands often ends up in the environment, significant ecosystem pollution has occurred such as ground water pollution, eutrophication, and greenhouse gas emissions (Davidson et al., 2012; Harindintwali et al., 2021). -- page 1Item Altering land use categories using the WRF model to analyze the impact of latent heat flux on the strength of a mesoscale convective system in the corn belt region(University of Missouri--Columbia, 2025) Peine, Cole; Fox, NeilMesoscale convective systems (MCSs) account for much of the warm-season precipitation that falls in parts of the U.S. known for agriculture and high levels of evapotranspiration (ET), such as the U.S. Corn Belt. In this study, we assess the sensitivity of MCS strength and structure to surface latent heat flux (LHF), an energy-based proxy for ET. The Weather Research and Forecast (WRF) model was implemented five times for an MCS event that occurred July 15--16, 2024, with 1-km grid resolution in the innermost domain. The land cover within the innermost domain was modified to achieve different LHF scenarios (cropland (higher LHF), wetlands (higher LHF), grasslands (lower LHF), urban (lower LHF), and a control run (no modified land use)). Statistical and qualitative analyses indicated that consistent and stronger 10-meter wind speeds, low-level vertical velocity, and reflectivity occurred with high LHF (cropland and control) scenarios; thus, leading to a stronger MCS. The strongest and most consistent correlations were observed between LHF and 10-meter horizontal wind speed, with Pearson correlation coefficients of r = 0.7627 (control), r = 0.7174 (cropland), and r = 0.5782 (urban). The findings indicate that surface LHF is a key modulator of MCS strength and structure, which is determined by land use and ET. Changes in land cover can therefore influence convective outcomes in numerical weather prediction, which is important for forecasting intense weather events across regions with high agricultural use during the growing season.