Agriculture Commons^™

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 …

Improving Baking Quality Of Soft Red Winter Wheat In Kentucky Through Breeding And Sulfur-Nitrogen Fertility Management, Maria Paula Castellari

Theses and Dissertations--Plant and Soil Sciences

Soft Red Winter (SRW) wheat is an important crop grown on about 400,000 acres in Kentucky as a pivotal cash crop in the 3-crops-in-2-years rotation of corn, wheat, and soybean. The humid environment of Kentucky generates a high yielding wheat crop, with low protein concentration and weak gluten strength. This wheat is mainly sold to millers and used by the industry for cakes, pastries, cookies, and crackers. Conversely, there is a rapidly growing interest in identifying other value-added markets for this wheat different to commodity commercialization, such as artisan-baked goods and craft-distilled beverages. Evaluating the quality characteristics of wheat grown …

Manipulating Species Diversity: Environmental Impacts In Row Crop, Livestock, And Grassland Agroecosystems, Alayna A. Jacobs

Theses and Dissertations--Plant and Soil Sciences

The diversity of living species in an agroecosystem affects both natural resources and agricultural production efficiency. The rise of managed plant monocultures has allowed agricultural yields to increase over time. However, simplifying agroecosystems affects the capacity of the system to sustainably provide clean air, water, and productive soils essential for continued food and fiber production. This dissertation manipulates species diversity in row crop and forage agroecosystems prevalent in the Eastern United States and tracks the associated environmental and agricultural production consequences.

In row crop agroecosystems, increasing plant diversity with winter cover crops has been suggested as a strategy to increase …

Epidemiology And Management Of Frogeye Leaf Spot Of Soybean: Damage Thresholds, Efficacy And Profitability Of Foliar Fungicides, Jhonatan Paulo Barro

Theses and Dissertations--Plant Pathology

Frogeye leaf spot (FLS), caused by Cercospora sojina, is an economically important disease of soybean in many parts of the world where soybean is grown, including the United States. A meta-analytic approach was used to summarize a data set of 66 uniform field research trials conducted to evaluate fungicide efficacy against FLS on soybean. The dataset spanned 10 years (2012 to 2021) of experiments conducted across eight states in the U.S., including Alabama, Arkansas, Illinois, Iowa, Kentucky, Louisiana, Mississippi and Tennessee. First, the relationship between FLS severity and soybean yield was investigated. A significant negative slope obtained through random …

An Evaluation Of Eragrostis Tef For Future Cultivar Development, Eric Wayne Luteyn

Theses and Dissertations--Plant and Soil Sciences

The many benefits of utilizing teff (Eragrostis tef) as small grain is well documented in journal publications. Over time the domestication of this species has become essential to the diets of the local population and the livestock living in the African highlands. Current research points to a high diversity of trait characteristics found in many teff populations and the potential utilization of these traits to increase desirable characteristics in both grain and forage varieties. With the overarching goal of adding to what is already known about teff, this study evaluates the different traits that are of interest to …

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 …

Incorporation Of Summer Annual Mixtures Into Grazing Systems In Kentucky, Kelly Marie Mercier

Theses and Dissertations--Plant and Soil Sciences

Utilizing summer annual grass-legume forage mixtures has the potential to improve forage yield and nutritive characteristics, and/or animal performance during times when cool-season pasture growth is limited by high temperatures. Legumes can utilize atmospheric nitrogen, which can increase crude protein and forage digestibility in mixtures. As nitrogen application generally improves both the yield and nutritive characteristics of summer annual forages, but can have a negative effect on legume competitiveness, nitrogen fertilizer recommendations for legume-containing summer annual mixtures are not well established.

Two experiments were conducted to determine the feasibility of utilizing summer annual mixtures in Kentucky, USA. The first experiment …

Improving Kentucky's Winter Wheat And Double Crop Soybean Rotation, Katherine Susan Rod

Theses and Dissertations--Plant and Soil Sciences

The winter wheat double crop soybean rotation is an economically viable rotation for Kentucky farmers. Recent decreases in commodity prices has warranted the need to evaluate intensive management practices that can increase yields and profitability in this crop rotation. There were three goals of this dissertation: 1.) identify management practices that would decrease deoxynivalenol (DON) in harvested wheat grain and increase wheat heading and anthesis uniformity, 2.) evaluate double crop soybean planting timing and identify intensive management practices to increase seed yield, and 3.) determine the profitability of these management options. These studies were conducted in Princeton KY between 2016 …

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 …

Integrating Cover Crops And Herbicides For Horseweed [Conyza Canadensis (L.) Cronq.] Management Prior To Soybean [Glycine Max (L.) Merr.], Austin Sherman

Theses and Dissertations--Plant and Soil Sciences

Horseweed (Conyza canadensis (L.) Cronq.) is prevalent in Kentucky and can be difficult to control. Research has shown multiple weed control methods to be more sustainable than relying on chemical control alone, so the use of multiple methods for horseweed management was examined in this study. The main objective was to determine best practice(s) to reduce horseweed prior to soybean [Glycine max (L.) Merr.]. Treatments included: fall-planted cover crop [CC; cereal rye (Secale cereale L.) or none], fall-applied herbicide (saflufenacil or none), and spring-applied herbicides (dicamba, 2,4-D ester, or none). We hypothesized horseweed densities would be reduced …

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 …

Chemical Topping Burley Tobacco, Mitchell D. Richmond

Theses and Dissertations--Plant and Soil Sciences

The act of topping tobacco (Nicotiana tabacum L.) involves the removal of the terminal bud or inflorescence of the tobacco plant. This practice ordinarily is accomplished by manually removing the top of each tobacco plant in an entire field which is labor intensive and costly. Chemical topping utilizes sucker control products to inhibit the terminal bud and axillary bud growth without manually removing the top of the tobacco plant. There were several research objectives in order to determine the utility of a chemical topping system: 1) determine if burley tobacco could be chemically topped with currently registered suckercide products …

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 …

Using Exogenous Hormone Application To Suppress Axillary Shoot Development In Tobacco, W. Jesse Carmack

Theses and Dissertations--Plant and Soil Sciences

The variability in the number of basal axillary shoots (ground suckers) among all tobacco (Nicotiana tabacum L.) varieties, has increased since the hydroponic transplant production system became the standard. The larger root ball of hydroponically produced transplants compared to traditionally produced transplants potentially generates a difference in the ratio of auxin (inhibits axillary shoot formation) to cytokinin (promotes lateral branching), that induces basal axillary shoot development. Starting in 2014, studies were conducted to investigate whether the addition of synthetic auxins or cytokinins to hydroponic transplant production could prevent ground sucker formation. Different tobacco cultivars, with high or low ground sucker …

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 …

Tall Fescue Ergovaline Concentration Based On Sample Handling And Storage Method, Krista La Moen Lea

Theses and Dissertations--Plant and Soil Sciences

Ergovaline is produced by the endophyte Neotyphodium coenophialum (Morgan-Jones and Gams) in tall fescue (Schedonorus arundinacea (Schreb.) Dumort. = Festuca arundinacea Schreb.) and is blamed for a multitude of costly livestock disorders. Testing of pastures is common in both research and on farm situations. Since ergovaline is known to be unstable and affected by many variables, the objective of this study was to determine the effect of sample handling and storage on the stability of this compound. Homogeneous milled tall fescue sub-samples were analyzed for ergovaline concentration using HPLC after a range of sample handling procedures or storage. Ergovaline …

Boron Nutrition Of Burley And Dark Tobacco, Laura Ann Frakes Mitchell

Theses and Dissertations--Plant and Soil Sciences

The incidences of suspected Boron (B) deficiency have increased recently in Kentucky tobacco fields, potentially due to recent changes in management practices. The symptoms observed in the field include; hollow stalk, stunted growth, deformed or no bud formation, small slits on the lower leaf midrib and uncontrollable breaking of the midrib approximately two inches from the stalk. B is a micronutrient tobacco needs in minute amounts, however excessive additions of B could cause toxicity. The objectives of this work were to 1) establish critical points for B sufficiency, 2) describe and define B deficiency and toxicity symptoms and 3) develop …

Effectiveness Of A Farm Field Trip, Bonnie S. Sigmon

Theses and Dissertations--Community & Leadership Development

The annual Sigmon Farm Tour was started in 1992 as an agricultural education program where students could experience being on a farm with the goal of increasing the agricultural literacy levels of the participants. Every year the entire 4th grade student population of Rockcastle County spends the day touring the farm and participating in experiential mini lessons given by the cooperating farm service and health agencies. The program has continued for 20+ years without an evaluation as to whether it is achieving its objectives. This evaluation will also exhibit the programs strengths and weakness so it can continue to improve. …

Nitrate Reduction Coupled To Iron(Ii) And Manganese(Ii) Oxidation In An Agricultural Soil, Stephanie Pyzola

Theses and Dissertations--Plant and Soil Sciences

New evidence shows iron(II) oxidation is strongly coupled to nitrate reduction under anaerobic conditions in freshwater sediments and agricultural soils. However, the contribution of iron(II) oxidation to nitrate reduction is unknown. Furthermore, oxidation of manganese(II) by nitrate has been largely overlooked. This study investigated nitrate-dependent iron(II) and manganese(II) oxidation in an agricultural soil (Sadler silt loam) using stirred-batch kinetic techniques with native soil organic carbon (SOC) as the electron donor and included addition of amendments (hydrogen gas and wheat residue). In the presence of native SOC, nitrate-dependent Fe(II) and Mn(II) oxidation occurred at early stages of the reaction while organic …

Ecophysiological Responses Of Tall Fescue Genotypes To Endophyte Infection And Climate Change, Marie Bourguignon

Theses and Dissertations--Plant and Soil Sciences

Tall fescue is a widely used forage grass in the eastern USA and can form a symbiosis with a fungal endophyte, which can be beneficial for the plant but can cause livestock health issues. Little is known regarding the symbiotic response to predicted climate change. To address this knowledge gap, I analyzed tall fescue variety trial data collected throughout the U.S., exploring relationships between climate variables and yield for two different fescue cultivars that were either endophyte-free or infected. This study showed no endophyte or cultivar effect on fescue yield, but identified temperature, precipitation and location as significant predictors of …

Evaluating The Sustainability Of Four Organic Vegetable Production Systems, Delia W. Scott

Theses and Dissertations--Plant and Soil Sciences

A field study evaluating the sustainability of four organic vegetable production systems was conducted in Lexington, Kentucky in 2006 and 2007. The four systems included no-till, raised beds covered with biodegradable black mulch, bare ground with shallow cultivation, and bare ground with shallow cultivation and wood chip mulch. The two-year study compared yield, weed control, labor, and costs associated with each system, as well as physical, chemical, and microbiological soil characteristics. In 2006, tomatoes (Lycopersicon esculentum Mill.) were grown in the four systems, with no significant difference in yield. Summer squash (Cucurbita pepo L.) was grown in the …

Using An Active Optical Sensor To Improve Nitrogen Management In Corn Production, Donato Titolo

Theses and Dissertations--Plant and Soil Sciences

Corn nitrogen (N) applications are still done on a field basis in Kentucky, according to previous crop, soil tillage management and soil drainage. Soil tests, as well as plant analysis for N, are not very useful in making N fertilizer rate recommendations for corn. Recommended rates assume that only 1/3 to 2/3 of applied N is recovered, variability largely due to the strong affect of weather on the release of soil N and fertilizer N fate. Many attempts have been made to apply N in a more precise and efficient way. Two experiments were conducted at Spindeltop, the University of …

Small Mammal Populations In Switchgrass Stands Managed For Biomass Production Compared To Hay And Corn Fields In Kentucky, Laura Mary Jane Schwer

University of Kentucky Master's Theses

Switchgrass (Panicum virgatum), a native warm-season grass, has been investigated as a renewable energy crop that may provide viable wildlife habitat. This study investigated small mammal populations in switchgrass, hay, and corn to assess the relative habitat quality. Four, three-night trapping sessions were conducted at four locations in Kentucky using Sherman livetraps. Trapping occurred in spring (before first hay harvest), summer, fall (before switchgrass and corn harvest), and winter (post-harvest). Relative abundance of small mammals, calculated using a capture per unit effort index (per 100 trapnights), and mean taxonomic richness were used to compare habitats. Switchgrass had a …

Nozzle Type And Arrangement Alternatives For Improved Application Of Suckercides In Burley Tobacco (Nicotiana Tabacum L.), Beau Robert Neal

University of Kentucky Master's Theses

Maleic hydrazide (MH) applications have been standard practice for sucker control in burley tobacco (Nicotiana tabacum L.) production for the last half-century because it is relatively inexpensive, effective and easy to apply. Non-MH suckercides such as fatty alcohols and local systemics can be utilized to reduce or replace MH and lower undesirable residues in the cured leaf. The objective of this study was to evaluate various nozzle types and arrangements for efficiency to determine if sucker control with fatty alcohol could be consistently improved over the currently used TG3-5-3 arrangement, as well as examine sprayer positioning (center vs. off-center) …

Restoration Of Tall Fescue Pastures To Native Warm Season Grasslands: Does A Fungal Endophyte Symbiosis Play A Role In Restoration Success?, Sarah Lynn Hall

University of Kentucky Doctoral Dissertations

Tall fescue, a cool-season grass native to Europe, central Asia, and northern Africa, has been widely distributed throughout the U.S. for use as turf and forage. Following its widespread planting, its ability to associate with a toxic fungal endophyte, Neotyphodium coenophialum, was discovered. Research has linked this fescue-endophyte association with increased biotic and abiotic stress resistance in endophyte-infected (E+) versus endophyte-free (E-) plants, and these differences may affect the ability of land managers to eradicate tall fescue and restore native grasslands. I conducted three studies to examine whether E+ tall fescue plants respond differently to management than E- plants, …

Evaluating The Effects Of Organic And Conventional Inputs On Soil Chemical And Biological Properties In A Four-Year Vegetable Rotation And The Investigation Of Soil Microbial Properties On Plant Gene Expression, Audrey Law

University of Kentucky Doctoral Dissertations

The objective of this research was to determine the effects of conventional inputs on soil chemical and biological properties compared to organic systems in a four year vegetable rotation. Tillage and cover crops were the same in all treatments to avoid confounding factors often present in similar research. Additional experiments investigated plant gene expression in organic and conventional management systems and in soils with decreased microbial diversity. Experimental plots were prepared in the spring of 2004; four replications of three management treatments, organic, low-input and conventional, were arranged in a randomized complete block design. The rotation consisted of edamame soybean, …

Map-Based Cloning Of An Anthracnose Resistance Gene In Medicago Truncatula, Shengming Yang

University of Kentucky Doctoral Dissertations

Anthracnose, caused by the fungal pathogen Colletotrichum trifolii, is one of the most destructive diseases of alfalfa worldwide. Cloning and characterization of the host resistance (R) genes against the pathogen will improve our knowledge of molecular mechanisms underlying host resistance and facilitate the development of resistant alfalfa cultivars. However, the intractable genetic system of cultivated alfalfa, owing to its tetrasomic inheritance and outcrossing nature, limits the ability to carry out genetic analysis in alfalfa. Nonetheless, the model legume Medicago truncatula, a close relative of alfalfa, provides a surrogate for cloning the counterparts of many agronomically important genes in …

Sexual And Asexual Reproductive Characteristics Of The North American Pawpaw [Asimina Triloba (L.) Dunal], Sheri Beth Crabtree

University of Kentucky Master's Theses

The North American Pawpaw [Asimina triloba (L.) Dunal] shows great potential as a new fruit crop. Kentucky State University in Frankfort, Ky. is the site for the USDA National Clonal Germplasm Repository (NCGR) for Asimina species. Both the fruit and the trees themselves are of high value to growers and nursery producers. Pawpaw cultivars are currently propagated by grafting or budding onto seedling rootstock; no method currently exists to clonally propagate pawpaw on its own roots. Three methods of layering were attempted in this study to clonally propagate pawpaw: trench layering, pot layering, and mound layering. Both trench layering …