Agronomy and Crop Sciences Commons^™

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 …

Evaluating Spatial Variability Of Corn Yield Response To Phosphorus Fertilizer For Improved Precision Phosphorus Management, Jennifer Fridgen

Theses and Dissertations--Plant and Soil Sciences

Soil scientists did not develop soil test-based fertilizer recommendations to support precision nutrient management. Knowledge of crop responses to applied essential nutrients, such as phosphorus (P), and the processes governing these responses at high spatial resolution are necessary to improve precision agronomic recommendations. This dissertation investigates the limitations of current soil sampling methodologies and recommendation frameworks for crop response to fertilizer, with particular emphasis on P fertility in Kentucky (KY) corn production. The first study examined the relationship between the resolution of systematic grid sampling and the spatial structure of soil test variables (Mehlich-3 P (M3P), Mehlich-3 potassium (M3K), and …

Management Adaptations To Sustainably Increase Soybean Yield And Water Productivity Through Field Studies And Crop Modeling, Mounica Talasila

Theses and Dissertations--Plant and Soil Sciences

Soybean (Glycine max [L.] Merr.), a major crop in the upper U.S. Mid-South, is predominantly cultivated under rainfed conditions, where variable precipitation frequently induces water stress and limits yield potential. Consequently, irrigation adoption has been increasing across this region. Determining the optimal cultivar maturity group (MG) and planting date (PD) for both rainfed and irrigated systems is essential for maximizing yield and improving water use metrics. Evaluating crop water use efficiency (WUE; yield per unit of seasonal evapotranspiration) and total water productivity (WP; yield per unit of total water input from precipitation and irrigation) is critical to developing such …

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 …

Advancing Root Trait Measurements For A Deeper Understanding Of Soil Biogeochemistry, Brian Rinehart

Theses and Dissertations--Plant and Soil Sciences

Climate change is disrupting (agro)ecosystems, with the potential for significant losses in crop productivity and ecosystem resilience due to changes in water and biogeochemical cycling. These disruptions can also release more carbon dioxide into the atmosphere through the degradation of soil organic matter. Plant roots have emerged as a potential tool for mitigating these effects, given their roles in plant function and in driving soil biogeochemistry. While this interest is growing, our ability to implement root trait selection is limited due to constraints on characterizing roots and limited clarity on the effects of traits on plant and ecosystem function. My …

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 …

Surveys, Field Studies, And Laboratory Incubation Experiments To Improve Alfalfa Production In The Mid-South, William Fleming

Theses and Dissertations--Plant and Soil Sciences

The objective of the alfalfa survey was to determine the role of soil fertility in the alfalfa yield plateau. Soil samples at depths of 10, 15, and 30 cm and tissue samples were collected from 114 alfalfa stands across Kentucky and surrounding states. Results indicate that soil fertility is likely contributing but not driving the alfalfa yield plateau. The main objective of the polyhalite incubation study is to determine if POLY4 was soluble enough to support potassium (K) and sulfur (S) for plant growth. The design of the study included four fertilizer treatments, three soil types, and four incubation times. …

Winter Rye (Secale Cereale L.) Management And Production Profitability In Kentucky, And Heritability Of Sensory Attributes, Elzbieta Szuleta

Theses and Dissertations--Plant and Soil Sciences

Winter rye (Secale cereale L.) is a small grain crop characterized by outstanding tolerance to drought, low temperatures, soil salinity and relatively low nutritional requirements. Rye is widely used as a cover crop, well known for its deep root system and outstanding nitrogen scavenging ability. This crop is widely used as a feed for livestock but also it is beneficial in human nutrition. Because of its versatile use, nutritional benefits and unique aroma and flavor, especially for bread and whiskey, there is an increasing interest in this crop in the United States. Unfortunately, rye grain production in the United …

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 …

Molecular Analysis Of Epigenetic Memory Of Stress Establishment And Long-Term Maintenance In A Perennial Woody Plant, Jia Wen Tan

Theses and Dissertations--Plant and Soil Sciences

Plants adapt to extreme environmental conditions through physiological adaptations, which are usually transient. Recent research has suggested that environmental conditions can activate a memory of stress that can result in a primed response to subsequent stress events. While the effect of priming has been observed in many plants, the underlying mechanisms are puzzling and seldom studied. A large body of research has been developed in the last decade linking response to stress, stress priming, and memory of stress with epigenetic mechanisms. This understanding of plant epigenetics has opened the door to the application of epigenetics to crop improvement, such as …

Building A Kentucky Baguette: Agronomic Traits, Bread Baking Quality Measurements, And Sensory Evaluation Of Modern And Landrace Wheat Cultivars Grown Under Conventional And Organic Nitrogen Management, Bryan Brady

Theses and Dissertations--Plant and Soil Sciences

The demand by artisan bread bakers across the United States for local wheat varieties has increased in recent years. The southeast is traditionally a soft winter wheat (SWW) region, producing low gluten flours more suitable for biscuits and cookies. Recently, hard winter wheat (HWW) varieties have been bred to produce acceptable yields in the high humidity environment of the southeastern United States. Artisan bread bakers in Kentucky would like to create a niche food value chain benefitting farmers, small-scale millers, bakers, consumers, and their local and regional food systems (LRFS). The increased demand and the availability of adapted hard wheat …

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 …

Optimizing Nitrogen Management In Winter Wheat Production Systems For Improved Bread Baking Quality, Ammar Sadiq Mahdi Al Zubade

Theses and Dissertations--Plant and Soil Sciences

In Kentucky, there is growing interest among farmers to produce high protein and strong gluten wheat that is suitable for bread baking to meet the demand of local artisanal bakers. Soft red winter wheat (SRW) is the most commonly wheat grown in the state and throughout the Southeastern US. Flours produced from SRW are relatively low in grain nitrogen (N) due to the region’s moderate winters and warm humid conditions during grain filling. As such, SRW is used in baking products where lower protein flours are preferred, such as cookies, cakes, pastries and crackers. Unlike SRW, hard red winter wheat …

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 …

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 …

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 …

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 …

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 …

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 …

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 …

Effect Of Management Decisions On Corn Yield Productivity And Stability In Environments With Contrasting Water Availability, Juan Ignacio Di Salvo

Theses and Dissertations--Plant and Soil Sciences

Corn (Zea Mays L.) is a grain crop with large productivity, but also elevated evapotranspiration demand, making it highly susceptible to periods of water stress occurring during critical reproductive stages. Environmental conditions in Kentucky make it possible to grow corn under rainfed conditions, but the crop is still likely to experience water stress during some times of the growing season depending on the year and location. There is limited information on the size of the yield gap due to water stress in Kentucky, and the timing and intensity of water deficit.

In addition, evaluating the interactive effects of hybrid …

Enhanced Efficiency Nitrogen Formulation Effect On Grass-Legume Pasture Productivity, Kathryn Marie Payne

Theses and Dissertations--Plant and Soil Sciences

The use of nitrogen (N) fertilizer is generally restricted on mixed species forage systems due to its stimulatory effect on grasses which increases competition with legume species. Reduced legume growth from this competition can compromise forage nutritive value and prospective yields. The controlled-release nature of several enhanced efficiency fertilizer N products holds the potential to improve legume persistence in mixed species pastures while providing supplemental N required by the grass component. The studies contained in this dissertation evaluated the effect of different enhanced efficiency N formulations (ATU, ESN, methylene urea, SuperU, and a 75% ESN: 25% urea blend) and untreated …

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 …

Effect Of Bedding Type And Soil Incorporation On Nitrogen Mineralization Rate Of Broiler Litter Amended Soils, Lydia A. Fitzgerald

Theses and Dissertations--Plant and Soil Sciences

Broiler litter (BL) is a high value manure available to Kentucky crop producers to utilize as a fertilizer. The rate of BL application, timing of application, and method of application are all important factors to take into account when utilizing BL. A laboratory incubation was conducted to observe nitrogen (N) mineralization rates of BL amended soils over time under different conditions. Different application methods, application rates, watering frequencies, and bedding materials were used to determine their influence on N mineralization. Broiler litter applied on the soil surface, at lower rates, at lower watering frequency resulted in lower mineralization rates than …

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 …

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 …