Life Sciences Commons^™

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 …

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 …

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 …

Nickel Speciation, Microbial Community Structure, And Chemical Attributes In The Rhizosphere Of Nickel Hyperaccumulating And Non-Accumulating Plants Growing In Serpentine Soils, James W. Morris

Theses and Dissertations--Plant and Soil Sciences

Serpentine soils are formed from weathering of serpentinite, the ultramafic parent material that provides serpentine soils with their unique identity. Weathering of serpentinite results in a plethora of edaphic factors that impose strong selection pressures on plant life, with high magnesium (Mg) to calcium (Ca) ratio, low fertility, and high levels of geologically derived metals such as cobalt (Co), chromium (Cr), and nickel (Ni). Appropriately, plant life on serpentine soils is often specialized, sparse, and endemic which in turn affects the ecosystems that develop on serpentine soils from the landscape scale down to the physiology of their inhabitants. At the …

Glyphosate Plus Dicamba Spray Solution Deposition, Coverage, And Efficacy As Influenced By Spray Nozzle Design And Weed Density, Madison Dru Kramer

Theses and Dissertations--Plant and Soil Sciences

Dicamba injury to sensitive soybean and other broadleaf crops due to drift is a major issue and label restrictions have been created to mitigate dicamba drift. One restriction is the mandated use of low drift nozzles to spray dicamba; these nozzles produce larger droplets and minimize the production of driftable fines. Experiments were conducted to evaluate herbicide coverage, deposition, and efficacy. Three spray nozzle designs and different weed densities were the main factors in the analysis. Dicamba plus glyphosate was applied to 5 to 10 cm tall weeds with a Turbo TeeJet (TT11005) nozzle and two drift reduction nozzles approved …

Evaluation Of The Influence Of Dicamba Exposure On Crop Injury And Canopy Closure Of Glufosinate Resistant Soybean, Zachary K. Perry

Theses and Dissertations--Plant and Soil Sciences

Dicamba-resistant soybean along with lower volatility dicamba formulations have been introduced in an attempt to control herbicide resistant weeds such as Amaranthus palmeri. This introduction has increased the amount of dicamba being applied later in the growing season increasing the prevalence of dicamba off-target movement. Dicamba damage was simulated by applying low rates of dicamba directly on soybeans at rates (0.5 g ae ha^-1, 1 g ae ha^-1 and 5 g ae ha^-1 dicamba) and five-exposure timings from June 1 to July 10. The experimental design was a randomized complete block with four replications at …

Using Biology To Better Inform Marestail [Conyza Canadensis (L.) Cronq.] Management, Ryan James Collins

Theses and Dissertations--Plant and Soil Sciences

The importance of sustainable weed management practices continues to grow as farmers are increasingly faced with herbicide resistant weed populations. Marestail (Conyza canadensis), also known as horseweed, is a problematic weed in soybean cropping systems that has developed resistance to multiple herbicide modes of action. A two year study was conducted in Lexington, KY, examining timing patterns of marestail emergence and different integrated weed management strategies for marestail prior to no-till soybean. Treatments contained fall and spring applied herbicides with different levels of residual activities, cover crops and combinations of the two. Additionally, yields and partial budget net …

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 …

Extracting Secondary Metabolites From Bacterial Endophytes To Suppress Or Promote Sweet Sorghum And Weeds, Mohammad R. Alsabri

Theses and Dissertations--Plant and Soil Sciences

Endophytic bacteria are ubiquitous in agricultural settings and have the potential to drastically affect plant growth both positively and negatively. These complex relationships play a key role in plant nutrition and are therefore of great interest to the agricultural community and beyond. With my dissertation work, I have had the opportunity to examine the relationship between endophytic bacteria and plants in various ways. The first part of my dissertation investigated how the microbial diversity found in soil affects the below- and above-ground traits of Sorghum bicolor. In the second section, I focused on a particular strain of bacteria that …

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 …

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 …

In Pursuit Of Understanding Barrel Variation: Surveying The Lignocellulose Composition And Content Changes In Quercus Alba Barrel Staves During Cooperage And Bourbon Whiskey Maturation, Jarrad Wade Gollihue

Theses and Dissertations--Plant and Soil Sciences

Bourbon whiskey is a distilled spirit which is a uniquely American with several legal requirements including 1) the major grain in the mash is corn, 2) must be aged in a new charred white oak barrel, and 3) made in the United States of America. Kentucky is the whiskey historical home, producing most of the bourbon in the United States. Interest in whiskey has developed a need to understand more about the underlying chemistry of bourbon. The charred white oak barrel used in bourbon production is of substantial interest because the barrel has been implicated in giving American whiskey its …

Regulatory Networks During Seed Development, Ran Tian

Theses and Dissertations--Plant and Soil Sciences

Seeds make up approximately 70% of the human diet directly so understanding regulatory mechanisms to generate a seed and the embryo it contains is fundamentally important. The LAFL genes encode transcription factors (TF) that are critical for seed development. Three members of LAFL, LEAFY COTYLEDON2 (LEC2), ABSCISIC ACID3 (ABI3) and FUSCA3 (FUS3), are B3 domain factors that bind DNA motifs called RY motifs. While LEC2 is expressed earlier in embryo development, ABI3 and FUS3 are expressed during later development. All three of these TFs can induce embryo-specific programs after completion of germination to different extents up to and including formation …

Plant-Soil Interactions Dominate Soil Microbial Respiration And Soil Organic Carbon Sequestration In A Subtropical Moist Evergreen Broadleaved Forest In China, Zhijie Yang

Theses and Dissertations--Plant and Soil Sciences

Tropical forest soils contain one-third of global soil carbon (C). The warm and moist climate in tropical forests leads to rapid soil organic carbon (SOC) decomposition, with the highest soil microbial respiration rates in the world, so even a slight change in soil C and microbial respiration could affect atmospheric carbon dioxide concentration. However, there remains a lack of understanding of the mechanisms driving microbial respiration in tropical forests, due to different climate and biophysical drivers compared to temperate or boreal forests. Furthermore, forest conversions (from natural forests to plantations) are most widespread in tropical regions, leading to a loss …