Agricultural Science Commons^™

Red Clover Isoflavones And Establishment In The Context Of Tall Fescue Toxicosis Mitigation In The Mid-South, Jonathan L. Stephens

Theses and Dissertations--Plant and Soil Sciences

Low levels of red clover (Trifolium pratense L.) have been shown to mitigate tall fescue (Lolium arundinaceum (Schreb.) toxicosis symptoms. This is because of the presence of plant-produced compounds known as isoflavones. Production of a red clover supplement on a commercial scale would require industrial-level processing of raw plant material into granules or pellets. The first study of this thesis evaluated the impact of drying temperature on bioavailability of isoflavones. Drying temperatures up to 104°C had minimal impact on isoflavone concentrations. Additionally, varietal differences in isoflavone concentrations were documented. The second study of this thesis evaluated optimal establishment …

The Effect Of Cover Crop Management Strategies On Nutrient Availability In No-Till Corn, Emily C. Marsh

Theses and Dissertations--Plant and Soil Sciences

Cover crops are reported to have long-term soil health improvements, one of which is reducing erosion. However, popular cereal cover crops, such as rye (Secale cereale L.), have the potential to cause a yield penalty in the following corn (Zea mays L.) crop due to a reduction in available nitrogen. Legumes, such as Austrian winter pea (Pisum sativum L. var. arvense), are thought to reduce this yield penalty due to their capacity to fix nitrogen. Sulfur is another nutrient of interest, especially as rates of atmospheric deposition of sulfur have declined, leading to more deficiencies being …

Kentucky Bluegrass (Poa Pratensis L.) As A Perennial Groundcover: Establishment And Weed Management In Corn, Kiera S. Searcy

Theses and Dissertations--Plant and Soil Sciences

Perennial groundcover (PGC) systems offer a cost-effective alternative to annual cover crops, by providing continuous soil cover, reducing soil erosion, and contributing to integrated weed management (IWM) in corn (Zea mays L.) production systems. Kentucky bluegrass (Poa pratensis L.) has been proposed as a perennial groundcover for corn due to its low growth habit and seasonal dormancy; however, successful adoption is limited by challenges associated with establishment-phase weed competition and compatibility with weed management programs during corn production. The objectives of this research were to (1) evaluate weed management strategies that support Kentucky bluegrass establishment and (2) assess …

Characterizing Agroecosystem Effects Of Industrial Hemp On A Rotational Row Cropping System And Microbial Communities, Kent D. Pham

Theses and Dissertations--Plant and Soil Sciences

The implementation of crop rotation on a farm can have many benefits for agroecosystem health and production. This practice can potentially reduce nutrient amendments, disrupt pest and disease cycles, and increase crop yields. In Kentucky, one common rotation consists of either corn or soybean grown the first year, followed by the other crop, repeated every two years. Industrial hemp, grown for fiber or grain, is an emerging crop that has shown promise as a rotation alternative, although not much is known about its effects on soil health, agroecosystem functioning, and microbial communities. To better characterize hemp’s role within American agriculture, …

Factors Impacting Germination, Emergence, And Establishment Of Direct Seeded And Transplanted Hemp (Cannabis Sativa L.), Paul Cockson Dr.

Theses and Dissertations--Plant and Soil Sciences

Industrial hemp (IH) establishment has many challenges including: poor emergence, low stand establishment, and variable plant development in direct seeded hemp. In floral hemp production, quality transplant production is a challenge with seedlings often becoming root bound and etiolated. In both direct seeded and transplant hemp, the relationship between root vigor and vegetative growth has not been studied and may prove insightful for managing emergence and establishment challenges. The goals of this study were three-fold: 1) to measure and describe root system architecture (RSA) and root phenotypes observed in selected IH cultivars especially in regard to identifying agronomically important RSA …

Evaluation Of Poaceae Species And Suppression Application Methods For Perennial Groundcover In Corn, Hallie A. Sandeen

Theses and Dissertations--Plant and Soil Sciences

Intensive grain production aims to provide food security but has depleted once-perennialized land. Perennial groundcover (PGC) offers ecosystem services to intensive annual corn (Zea mays L.) production. In past research conducted in the U.S. Midwest, Kentucky bluegrass (Poa pratensis L.) has been the standard PGC species. However, it is slow growing and difficult to suppress. To characterize the PGC system in the midsouth, two separate field trials in Lexington, Kentucky, were conducted to (i) compare the first-year establishment of alternative cool-season species to Kentucky bluegrass, with and without a spring-applied broadleaf herbicide, and their impact on corn grain …

Revolutionizing Grapevine Breeding Programs: A Mobile Genome Editing System For Perennial Crops, Bridget Bolt

Theses and Dissertations--Plant and Soil Sciences

Grapevine (Vitis vinifera) faces unprecedented challenges from climate change, with up to 90% of current growing regions potentially becoming unsuitable for production within decades. Traditional breeding approaches require 25-30 years for variety development, creating a time constraint incompatible with the pace of environmental change. This research establishes the approach for a novel mobile RNA-based gene editing platform that addresses longstanding bottlenecks in grapevine improvement while preserving cultivar identity and reducing breeding timelines.

This research developed a three-component system for transgene-free gene editing in grapevine. First, a mobile CRISPR/Cas9 system was established using Agrobacterium rhizogenes transformation and the cut-and-dip …

Evaluation Of Winter Cereal Cover Crops Across Nitrogen Management Strategies In No-Till Corn Production, Robert Nalley

Theses and Dissertations--Plant and Soil Sciences

Rye (Secale cereale L.) is the most popular winter cereal cover crop utilized before corn, but wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) may provide a comparable value due to their similar fibrous root systems. Despite the benefits associated with winter cereal cover crops, drawbacks are possible for the subsequent corn crop. A field study was conducted with three site-years in Kentucky to measure the impact of the three winter cereals across nitrogen (N) management strategies. Wheat produced the most biomass compared with barley or rye cover crops. Wheat and rye needed approximately 100 more …

Identifying Physiological, Morphological, And Genetic Drivers Of Key Intermediary Phenotypic Traits Associated With Stalk Lodging Resistance Within Genetically Diverse Maize Germplasm And Sorghum, Norbert Bokros

Theses and Dissertations--Plant and Soil Sciences

Maize stalk lodging reduces grain yields due to the permanent breakage or deformation of stalk tissue before grain harvest. To reveal new insights into the complex problem of maize stalk lodging, this dissertation will examine three primary objectives. First, the direct, diurnal influence of turgor pressure will be shown to have only marginal effects on stalk bending strength, a key trait associated with stalk lodging resistance. Up to a dozen individual stalks, grown to physiological maturity within the same field, were tested using a DARLING testing device. In parallel, stalk turgor status as measured by leaf water potential and turgor …

The Effect Of Spring And Winter Killed Cover Crops On Soil Physical Properties And Soil Organic Carbon, Danielle Doering

Theses and Dissertations--Plant and Soil Sciences

Maintaining soil organic carbon (SOC) and healthy soil physical structure in agroecosystems is crucial to sustainable production. To assess medium term impacts of cover crops on soil health in the top 90 cm, we conducted a field experiment in central Kentucky with varying levels of winter cover: spring and winter kill cover crops, weedy and bare winter fallows. After eight years of cover crop use, some soil physical properties improved: 35% greater mean weight aggregate diameter at 0-30 cm with spring kill covers and 5.2% more C held within large aggregates for both cover crop treatments compared to winter fallow. …

Comparison Of Botanical Composition Methods And Change Over Time In Kentucky Pastures, Echo Elizabeth Gotsick

Theses and Dissertations--Plant and Soil Sciences

Botanical composition of pastures has been measured with numerous methods over the last century, but there have been limited direct comparisons between methods. The objective of this study was to compare botanical composition methods, to determine the most accurate and efficient method, and to access pasture composition change over time. Six farms with two pastures each were monitored across the state of Kentucky. Sampling occurred fall 2020 through fall 2022, three times a year using the following methods: step point, visual estimation, occupancy grid, and point quadrat (used as a reference method). The occupancy grid showed the highest similarity to …

Understanding The Basis For Increased 2,4-D Tolerance In Red Clover (Trifolium Pratense): Field Evaluations, Metabolism, And Gene Expression, Lucas Pinheiro De Araujo

Theses and Dissertations--Plant and Soil Sciences

Incorporation of red clover (Trifolium pratense L.) into grass pastures offers several benefits. However, red clover cultivars available for Kentucky producers are highly susceptible to synthetic auxin herbicides, such as 2,4-D (2,4-dichlorophenoxy acetic acid), used for pasture broadleaf weed control. To overcome this problem, UK2014 red clover was bred for increased tolerance to 2,4-D. We compared the field performance of UK2014 to Kenland, a standard cultivar grown in the transition zone of the United States. UK2014 and Kenland were seeded in the springs of 2017 and 2018. Single applications of 0, 1.12, or 2.24 kg ae ha^-1 2,4-D …

Remote Sensing For Quantifying C3 And C4 Grass Ratios In Pastures, Jordyn Alyssa Bush

Theses and Dissertations--Plant and Soil Sciences

The following studies investigate the accuracy and practicality of exploiting the color dichotomy present between C₃ and C₄ grass species to estimate their respective proportions from drone or camera captured imagery. Understanding the proportions of C₃ and C₄ grasses in pastures is vital to sound decision making for livestock production. The ability to monitor these proportions remotely will also allow for large scale monitoring as well as detection of changes in botanical composition over time and in response to weather events, management, or climate change. A free green canopy cover (GCC) analyzing software, Canopeo, was used …

The Site Evaluation Of Quercus Alba Metabolites, Zachary Alexander Byrd

Theses and Dissertations--Plant and Soil Sciences

Quercus alba has been the prominent tree species utilized in the spirits industry for decades. Of its many qualities, the ability to impart desirable flavors on spirits combined with its natural abundance makes it the ideal choice for barrels. Creating barrels is a uniform process, but variability still exists in aged spirits even when all other parameters are controlled. In this thesis, I explore how the origin of Quercus alba influences metabolite variability.

Quercus alba is a resilient species that can grow in many climates. This is seen through Quercus alba’s vast growing range, of which barrel quality white oak …

Evaluation Of Corn Agronomic Management Practices Following A Rye Cover Crop, Daniel John Quinn

Theses and Dissertations--Plant and Soil Sciences

Fall implementation of a rye (Secale cereale L.) cover crop (RCC) prior to spring corn (Zea mays L.) planting is a management practice used to improve soil conservation, water quality, and limit herbicide dependence. However, corn growth and yield following a RCC is often reduced due to early-season nitrogen (N) stress and decreased plant emergence, which can limit RCC adoption. The objective(s) of this research were to evaluate corn agronomic management practices (e.g., N and seeding rate management, in-furrow (IF) starter use) following a RCC and determine which management practices can be used to limit corn stress following …

Enhancing Agroecosystem Phosphorus Management: Root Phenotyping And Decomposition For Improved Phosphorus Cycling, Rebecca Kay Mcgrail

Theses and Dissertations--Plant and Soil Sciences

Plant roots are often overlooked when making nutrient management decisions. Evaluating differences in P acquisition strategies and cycling resulting from years of shoot-specific plant breeding will aid in reducing fertilizer inputs, with the ultimate goal of improving economic sustainability of crop production and preservation of ecosystem services. To achieve this goal, this research screened a diverse panel of winter wheat cultivars that included old and modern, dwarfed and wild type varieties for physical and chemical root phenotypes related to P acquisition. Old cultivars had larger root systems with more roots that grew two times faster than intermediate/modern cultivars. Wild type …

Arthropod Resistant Tomatoes: Screening Tools, Yield And Nutritional Quality Of Interspecific Hybrids, Mohammad Hasan Salman Ali Dawood

Theses and Dissertations--Plant and Soil Sciences

Tomato (Solanum lycopersicum) is one of the most economically important vegetable crops grown around globe but is a host for numerous pests and pathogens. In the future, tomato breeders will have to focus on increasing fruit quantity and on enhancing pest resistance. Many accessions of the wild relative of tomato, S. habrochaites display high levels of resistance towards arthropods such as spider mites. The presence of the sesquiterpene hydrocarbon, 7-epi-zingiberene, found in S. habrochaites type IV trichomes has been associated with arthropod resistance. However, the presence of other compounds in its trichome secretions may also be related …

Soil Carbon Dynamics And Greenhouse Gas Emissions In Conservation Tillage Systems At Multiple Scales, Yawen Huang

Theses and Dissertations--Plant and Soil Sciences

Conservation tillage practices like no-tillage and reduced tillage have been widely implemented worldwide, with expectations they would provide multiple benefits (e.g., yield enhancement and soil carbon sequestration) for food security and climate adaptation and mitigation. However, the adoption of conservation tillage faces both opportunities and challenges. A knowledge gap still exists regarding the effects of conservation tillage on the carbon cycle in agroecosystems. This dissertation reflects a comprehensive evaluation of conservation tillage at multiple scales using an integrated systems approach, a combination of data synthesis, the agriculture ecosystem model, and field observations and measurements. I first conducted a meta-analysis to …

Cover Crops And Cover Crop Mixes: Stratification Of Biological Effects, Landon M. Gibbs

Theses and Dissertations--Plant and Soil Sciences

The potential nutrient cycling benefits from legumes (e.g. N₂-fixation) and the high biomass potential of cereal rye are well known. Further studies are warranted to evaluate bi-culture mixtures and their effects on soil nutrient stratification and microbial enzyme activity because these two properties may be differently expressed (enhanced) by legume/grass mixes. The objectives of this study were: (1) show different cover crops and cover crop mixes containing grasses and legumes differentially stratify carbon and N; (2) show the change in microbial enzyme activity in soils planted with individual cover crops relative to cover crop mixes; 3) determine the …

The Balancing Act Of Cytokinin In Environmental Stress Tolerance, Sumudu Sandeepani Karunadasa

Theses and Dissertations--Plant and Soil Sciences

Cytokinin, long known as a phytohormone that regulates plant growth and development, has been recently recognized as an important regulator of stress responses. However, our current knowledge about the mechanisms by which cytokinin regulates stress responses is fragmentary, as many of the studies in this field yielded conflicting results. Most of the work described here has focused on analyses of the molecular mechanisms of cytokinin-dependent regulation of growth and development under stress conditions, with an emphasis on the role of cytokinin-dependent regulation of protein synthesis in development and stress tolerance.

One of the important contributions of this study is the …

Long-Term Land Management Practices And Their Effect On Soil Health And Crop Productivity, Thomas Joseph Muratore Jr.

Theses and Dissertations--Plant and Soil Sciences

Agricultural intensification reliant on monocrops could change soil health in a way that does not support maximum crop productivity. Twenty-nine-year-old no-till field plots at the University of Kentucky Spindletop research farm showed a significant reduction in corn yields from continuous corn plots compared to those from plots in various types of rotation. The objective of this study was to determine what role soil microbes might play in yield reduction and how management and time effects microbial community structure. Samples were collected from the following treatments: continuous corn (CC), continuous soybean (SS), a 2-year corn/soybean rotation (CCSS), Corn in rotation with …

Optimizing Cover Crop Rotations For Water, Nitrogen And Weed Management, Cintia Soledad Sciarresi

Theses and Dissertations--Plant and Soil Sciences

Winter cover crops grown in rotation with grain crops can be an efficient integrated pest management tool (IPM). However, cover crop biomass production and thus successful provisioning of ecosystem services depend on a timely planting and cover crop establishment after harvest of a cash crop in the fall. One potential management adaptation is the use of short-season soybeans to advance cover crop planting date in the fall. Cover crops planted earlier in the fall may provide a greater percentage of ground cover early in the season because of higher biomass accumulation that may improve weed suppression. However, adapting to short-season …

Field Evaluation Of Tobacco Engineered For High Leaf-Oil Accumulation, James Perry

Theses and Dissertations--Plant and Soil Sciences

The biofuel market is dominated by ethanol and biodiesel derived from cellulosic and lipid-based biomass crops. This is largely due to the relatively low costs and reliability of production. At present, production of non-food plant-derived oils for biofuel production in the U.S. is minimal. A research team from the Commonwealth Scientific and Industrial Research Organization (CSIRO), an independent Australian federal government research institution, has developed an efficient transgenic system to engineer oil production in tobacco leaves. This novel system is comprised of multiple transgenes that direct the endogenous metabolic flux of oil precursors towards triacylglycerol (TAG) production. Additional genes were …

Corn Grain Yield Components And Nutrient Accumulation In Response To Nitrogen, Plant Density And Hybrid, Maria Julia Santoro

Theses and Dissertations--Plant and Soil Sciences

Modern maize hybrids exhibit higher yields, increased biomass production, stress tolerance and greater nitrogen (N) use efficiency. Increased biomass accumulation can influence nutrient uptake and lead to increased nutrient removal. Hybrids were tested at seeding rates (SR) of 74000 (low) and 148000 (supraoptimal) plants ha^-1 and at N rates of 0 (deficient) and 390 (non-limiting) kg N ha^-1. Plants were sampled at V7, V14, R3, R5 and R6 and separated into vegetative and reproductive fractions for determination of dry matter and N accumulation. Grain yield was harvested at R6.

The high SR and high N treatment combination …

Measured Soil Hydraulic Properties As Rzwqm2 Input To Simulate Soil Water Dynamics And Crop Evapotranspiration, Saadi Sattar Shahadha

Theses and Dissertations--Plant and Soil Sciences

Agricultural system models integrate many different processes that cannot all be measured in field experiments and help quantify soil water dynamics, crop evapotranspiration, and crop growth with high temporal resolution. Understanding soil water dynamics and crop evapotranspiration is essential to improve agricultural management of field crops. For example, the interaction between nitrogen application rate and water dynamics is not sufficiently understood. In most cases, model simulations deviate from field measurements, especially when model input parameters are indirectly and unspecifically derived. The extent to which measured soil hydraulic property inputs decrease the discrepancy between measured and simulated soil water status is …

Exploring Spatial And Temporal Variability Of Soil And Crop Processes For Irrigation Management, Javier Reyes

Theses and Dissertations--Plant and Soil Sciences

Irrigation needs to be applied to soils in relatively humid regions such as western Kentucky to supply water for crop uptake to optimize and stabilize yields. Characterization of soil and crop variability at the field scale is needed to apply site specific management and to optimize water application. The objective of this work is to propose a characterization and modeling of soil and crop processes to improve irrigation management. Through an analysis of spatial and temporal behavior of soil and crop variables the variability in the field was identified. Integrative analysis of soil, crop, proximal and remote sensing data was …

Impact Of A High Oil And Protein On Agronomic Traits And Overall Seed Composition In Soybean, Maythem Al-Amery

Theses and Dissertations--Plant and Soil Sciences

New soybean lines have been developed with significantly higher oil, protein + oil and higher meal protein. These soybeans contain a VgD1 gene (highly active acyl-CoA:diacylglycerol acyltransferase, DGAT from Vernonia galamensis (VgDGAT1A) produces much higher oil synthesis and accumulation activity in soybean. Soybean with active DGAT from Vernonia galamensis (VgDGAT1A) has active TAG biosynthesis relative to other DGATs including from soybeans and Arabidopsis. DGATs catalyze the final step of TAG synthesis: DAG (diacylglycerol) + acyl-CoA → TAG + CoASH (Coenzyme A is notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in …

Evaluating Soil Physical And Chemical Properties Following Addition Of Non-Composted Spent Coffee And Tea For Athletic Fields, Shuang Zhou

Theses and Dissertations--Plant and Soil Sciences

Physical and chemical properties of non-composted spent coffee (CF) and tea (T) suggest they may have applications as soil amendments for improving poor soils. Studies were conducted to determine 1) the effect of amendments on grass growth and soil properties, 2) the effect of incorporation versus surface application of amendments on soil properties, and 3) the effect of amendment application frequency on grass growth and soil properties. In the first study, amendments were mixed with sand and planted to bermudagrass. Treatments included CF, T, and peat moss (PM) mixed with sand, and 100% sand as a control. In the second …

Irrigated Zea Mays Response To Nitrogen And High Plant Population Density In Narrow Rows, Julie Baniszewski

Theses and Dissertations--Plant and Soil Sciences

Modern genetics have improved maize hybrids to better tolerate stress, use nutrients more efficiently and potentially yield higher. Management practices, such as narrow row technology and high plant population density (PPD) may further improve yields in modern maize under irrigated, non-limiting conditions. High PPD (74, 99, 124, 148 K seeds ha^-1) were tested in narrow rows with up to four nitrogen (N) rates in three locations over two years in Kentucky with a modern maize hybrid in irrigated, non-limiting conditions. Results indicate that optimal seeding rates were 99,000 to 124,000 seeds ha^-1, providing maximum yield and …

The Effects Of Manufactured Nanomaterial Transformations On Bioavailability, Toxicity And Transcriptomic Responses Of Caenorhabditis Elegans, Daniel L. Starnes

Theses and Dissertations--Plant and Soil Sciences

In recent decades, there has been a rapid expansion in the use of manufactured nanoparticles (MNPs). Experimental evidence and material flow models predict that MNPs enter wastewater treatment plants and partition to sewage sludge and majority of that sludge is land applied as biosolids. During wastewater treatment and after land application, MNPs undergo biogeochemical transformations (aging). The primary transformation process for silver MNPs (Ag-MNPs) is sulfidation, while zinc oxide MNPs (ZnO-MNPs) most likely undergo phosphatation and sulfidation. Our overall goal was to assess bioavailability and toxicogenomic impacts of both pristine, defined as-synthesized, and aged Ag- and ZnO-MNPs, as well as …