Plant Sciences Commons^™

Xyway Lfr@Fmc Fungicide: Improving Corn (Zea Mays L.) Water Use Efficiency And Productivity Under Water-Deficit Stress And Dryland Conditions, Isha Poudel

Doctoral Dissertations

Triazole fungicide has the ability to protect crops from varying water stresses. Xyway LFR^@FMC is a triazole, at-plant fungicide and has been observed to improve plant performance under limited water conditions. A greenhouse study was conducted to assess the potential of Xyway LFR^@FMC in altering the ability of corn plants to control transpiration rates under water deficit-stress (DS) conditions. Greenhouse grown plants were treated with Xyway LFR^@FMC at 0.56, 0.77, 1.11,1.26 L ha^-1. Plants treated with 1.11 L ha^-1 reduced the amount of water loss in response to DS and had the highest fraction …

Methods To Hasten Zoysiagrass Establishment From Sprigs, Tyler Carr

Doctoral Dissertations

Zoysiagrasses (Zoysia spp. Willd.) are commonly used on golf course fairways and tees in addition to residential and commercial lawns due to lower input requirements relative to bermudagrass (Cynodon spp.). This has led to increased interest in using zoysiagrass for golf course putting greens; however, zoysiagrass establishment from sprigs is prolonged compared to bermudagrass. A series of experiments were conducted in glasshouses in Knoxville, TN in 2022 to evaluate the effects of environmental conditions and management practices on the establishment of Prizm zoysiagrass from sprigs. To determine the optimal soil temperature for Prizm zoysiagrass establishment, sprigs were exposed …

Corn (Zea Mays L.) Production In Living Mulch Systems, Grazing Potential, And Economic Viability, Marcia Peireira Quinby

Doctoral Dissertations

Living mulch (LM) is a practice in which forages are grown simultaneously with the main crop, serving as a living cover throughout the growing season. The LM systems were developed to alleviate concerns of soil depletion and finding ways to reduce tillage negative effects on soil productivity. In addition, when legumes are use can decrease the reliance on N fertilizer. The use of corn in LM have been previously studied due to the crop being a large commodity in the U.S.; In addition, the ability to graze the LM after corn production can increase the land use efficiency. To determine …

Evaluation Of Cotton Management Decisions: Cover Crops, Weed Control, And Injured Stands, Savana D. Denton

Doctoral Dissertations

Herbicide-resistant weed species have altered the challenges faced by Tennessee cotton (Gossypium hirsutum, L.) producers. While the weed control and environmental benefits of cover crops have been well-documented, the integration of cover crops into cotton production systems has presented management challenges. In-season broadcast postemergence weed control options are limited in cotton. Furthermore, off-target movement of 2,4-D and dicamba can result in additional management challenges if susceptible cotton is injured. Studies were conducted from 2018 to 2021 to evaluate: 1) cotton response to cover crop termination timings and methods; 2) postemergence weed control programs in cotton without the use of …

Interseeding Native Warm-Season Grass Pastures, Jonathan D. Richwine

Doctoral Dissertations

Cool-season annual (CSA) grass and legume species, as well as warm-season forbs, can enhance established native warm-season grass (NWSG) pastures by extending the grazing season, reducing supplemental feed costs, suppressing weeds, increasing herbage production and overall forage quality, and increasing food and cover resources for pollinators and wildlife. Therefore, two NWSG experiments were conducted near Spring Hill, TN, 2018-2020, to assess three CSA seeding options (cereal rye monoculture, a cereal rye, ‘Purple Top’ turnip, ‘Trophy’ rape, ‘Frosty’ berseem clover, and ‘Dixie’ crimson clover polyculture, or non-planted control) and two warm-season N rates (0 or 67 kg N ha^-1) …

Characterization And Management Of Glyphosate-Resistant Junglerice, Clay M. Perkins

Doctoral Dissertations

Junglerice has become a major weed in Tennessee and across the mid-south. Glyphosate resistance and dicamba antagonism has resulted in the reported control failures and rise in prevalence. Junglerice was the most prevalent weed escape in cotton and soybean fields across Tennessee from 2018 to 2020. In all, 13% of the junglerice accessions could no longer be effectively controlled with glyphosate. Due to poor in-crop control, it has been recommended to start clean when trying to control junglerice and other grasses. Therefore, research was conducted to determine the best burndown methods utilizing dicamba, glufosinate, or paraquat. A sequential application of …

Soil Health Assessment For The Agroecosystems Of West Tennessee, Surendra Singh

Doctoral Dissertations

Soil health assessment is important for making informed sustainable management decisions in production systems. An established standardized method to quantify soil health is lacking and the validity of the existing methods across agroecoregions and cropping systems is not yet proven. Therefore, this study aims to evaluate the feasibility of widely discussed three soil health tests - Haney’s Soil Health Test (HSHT), Comprehensive Assessment of Soil Health (CASH), and Alabama Soil Health Index (ASHI) to assess soil health in diverse cropping systems of Tennessee. Since these approaches were originally developed for specific agroecoregions, we hypothesized that these tests are not sensitive …

Enhancing The Sustainability Of Integrated Biofuel Feedstock Production Systems, Amanda Joy Ashworth

Doctoral Dissertations

As use of second-generation biofuel crops increases, so do questions about sustainability, particularly their potential to affect fossil energy consumption and greenhouse gas emissions. Nitrogen (N)-fixing legumes interseeded into switchgrass (Panicum virgatum L.) may be an alternative to inorganic fertilizer in forage-feedstock systems. Research herein is divided into four general experiments: I). N replacement and feedstock impacts from legume intercrops and biochar in switchgrass; II). N-fixation rates in intercrop systems; III). impacts of biofuel systems under enhanced climate change; and, IV). projected sustainability of regional switchgrass production. Approaches included: characterization of feedstock/forage quality traits based on legume, biochar and …

Toward Direct Biosynthesis Of Drop-In Ready Biofuels In Plants: Rapid Screening And Functional Genomic Characterization Of Plant-Derived Advanced Biofuels And Implications For Coproduction In Lignocellulosic Feedstocks, Blake Lee Joyce

Doctoral Dissertations

Advanced biofuels that are “drop-in” ready, completely fungible with petroleum fuels, and require minimal infrastructure to process a finished fuel could provide transportation fuels in rural or developing areas. Five oils extracted from Pittosporum resiniferum, Copaifera reticulata, and surrogate oils for Cymbopogon flexuosus, C. martinii, and Dictamnus albus in B20 blends were sent for ASTM International biodiesel testing and run in homogenous charge combustion ignition engines to determine combustion properties and emissions. All oils tested lowered cloud point. Oils derived from Copaifera reticulata also lowered indicated specific fuel consumption and had emissions similar to the ultra-low sulfur diesel control. Characterization …

Effects Of Leaflet Orientation And Root Morphology On Physiological Traits And Yield In Soybeans., Richard Dewayne Johnson

Doctoral Dissertations

Drought is the most important abiotic stress adversely affecting soybean (Glycine max (L.) Merr.) yield. Leaflet orientation has been shown to reduce leaflet temperatures and transpiration while root morphology has been related to slower wilting phenotypes. The objective of this study was to investigate effects of leaflet orientation and rooting morphology on whole plant transpiration, yield, water use efficiency, and other physiological traits in soybeans using grafting techniques, population lines, near-isogenic lines, and restrained leaf canopy experiments. Experiments were conducted in Knoxville, TN with additional yield trial plots at Springfield, Spring Hill, and Milan, TN. Data were collected on …

Detection Of Soybean Amino Acid Qtls And Seed Yield Qtls Using Selective Genotyping, Benjamin David Fallen

Doctoral Dissertations

The U.S. Census Bureau projects the world’s population will top more than nine billion by 2050. Today, soybeans account for 56 % of the world oilseed production and 68 % of the world protein meal consumption, with U.S. soybean production accounting for 33 % of the world soybean production. So, to meet the demand of the world’s growing population and of the livestock industry improvements in both the composition and the yield of soybean is essential.

The primary objective of this project was to use molecular markers to identify genomic regions associated with amino acid composition and yield in soybean. …

Investigating Cold Hardiness And Management Practices Of Warm-Season Putting Green Species In The Transition Zone, John M. Kauffman

Doctoral Dissertations

Warm-season turf species are becoming increasingly popular for putting green use in the transition zone. Ultradwarf bermudagrass (Cynodon dactylon (L.)  C. transvaalensis Burtt-Davy) is the prevalent warm-season putting green species, but seashore paspalum (Paspalum vaginatum Swartz) and ‘Diamond’ zoysiagrass [Zoysia matrella (L.) Merr.] may also be grown in the transition zone. Warm-season species are susceptible to winter injury and may require different management regimes than cool-season species. Therefore, the objectives of this research were to assess the impacts of various management practices on warm-season putting green species and characterize the physiological basis for differences in freeze tolerance of various …