Digital Commons Network^™

Adhesion Index Integrates Cell And Bacterial Responses To Titanium Across Protein Conditioning And Surface Roughness, Sahar Afshari, James D. Boyd, Victoria L. Stanton, Arnold Stromberg, Katherine L. Thompson, David M. Devito, Craig S. Miller, Martha E. Grady

Mechanical Engineering Faculty Publications

Biofilm formation is a primary cause of implant-associated infections in dental and orthopedic devices. Early interactions between bacteria and host cells at the implant surface critically influence subsequent infection or successful integration. Therefore, biocompatibility screening should evaluate both biofilm formation and cell adhesion. Adhesion Index, defined as the ratio of cell adhesion to biofilm adhesion, provides a non-dimensional number to optimize towards that end. In this work, the laser spallation technique is implemented to compare the effects of implant surface characteristics (rough and smooth titanium) and protein coatings (blood plasma and fibronectin) on bacterial biofilm (Streptococcus mutans, Staphylococcus aureus) and …

Isthmus, Ahmed H. Yassin, Ethan H. Huff, Vijay B. Mohan Ramu, Bruno Tacchi, Carlos E. Américo, Tyler D. Stoffel, Savio J. Poovathingal

Mechanical Engineering Faculty Publications

ISTHMUS is a software package designed to couple voxel-based domains with surface mesh-based solvers. Voxelized geometries provide high-fidelity representations of materials but are difficult to integrate into multiphysics workflows because of jagged boundaries and the absence of robust interface mapping. ISTHMUS addresses this challenge through two key modules: motion mapping and flux mapping. The software is written in Python with performance-critical routines accelerated on GPUs via CUDA. ISTHMUS is solver-agnostic, enabling coupling of a wide range of fluid, thermal, and structural codes without requiring modifications to their discretizations.

Thermodynamics Of Binding Between Adeno-Associated Viruses And Heparin In Bulk And At Interfaces Via Isothermal Titration Calorimetry, Elizabeth Adeogun, Jude C. Obijiaku, Ronny Horax, Kayla E. Daugherty, Joshua Sakon, Xianghong Qian, Barbara Knutson, Stephen E. Rankin, Karthik Nayani

Chemical and Materials Engineering Faculty Publications

Adeno-associated viruses (AAVs) have emerged as promising vectors for gene therapy due to their non-pathogenic nature and ability to transduce various cell types efficiently. In recent years, there has been an increasing effort to optimize the production and purification of AAV to support clinical applications; however, challenges exist in affinity ligand design, synthesis, and characterization. Understanding the binding interactions of these viruses with functional molecules is pivotal for the development of affinity-based separation methods of AAVs. Classical methods to measure thermodynamic parameters such as Isothermal Titration Calorimetry (ITC) are challenging to employ in these scenarios, as the concentrations of the …

Use Of Function Diagrams In Physiology Education, Thad E. Wilson, Brian A. Jackson, B. Peter Sawaya

Physiology Faculty Publications

Function diagrams focus on physiological concepts rather than associated structures and can serve as elaboration tools and mnemonic aids. A function diagram prototype of the gastrointestinal system was recently described (Wilson TE, Barrett KE. Adv Physiol Educ 45: 264-268, 2021). In this article, a functional diagram of the glomerulus, nephron, urinary system, and bladder is proposed. Colloquially named "Nessie the Nephron" to loosely capture the looping structure and elusive understanding of renal blood flow, glomerular filtration, and epithelial transport for the student, not to mention the nearly mythical countercurrent multiplier. "Navigating the Lochs" references Nessie's possible habitat and more importantly …

Provider And Patient Perspectives On The Diagnosis And Treatment Of Alzheimer's Disease, Philippe Amouyel, Sandrine Andrieu, Angela Bradshaw, Ralph C. Carmona, Magali Dumont, Lea Tenenholz Grinberg, Takeshi Iwatsubo, Oskar Hansson, Clifford R. Jack, Gregory A. Jicha, Simin Mahinrad, Eric Mcdade, Catherine J. Mummery, Ronald C. Petersen, Shelagh Robinson, Julie A. Schneider, Lenny Shellcross, Amanda G. Smith, Heather M. Snyder, Beth Tapply, Charlotte Teunissen, Wiesje M. Van Der Flier, Bruno Vellas, David Wallon, Jeff D. Williamson, Donna Wilcock, Maria C. Carrillo

Neurology Faculty Publications

Since 2016, the Alzheimer's Association and the Fondation Alzheimer have hosted Global Alzheimer's Leadership Series (GoALS) global think tanks, with world-leading experts for innovative discussions to advance Alzheimer's disease (AD) research and care. The second GoALS think tank, held in June 2024 in Paris, focused on the relationship between biological changes and clinical manifestations of AD in the context of the evolving therapeutic landscape. Discussions spanned real-world experiences of providers, patients, and their families, theoretical considerations, and health system challenges. The lived experience perspective was central to these discussions. The importance of shared decision-making, clear and transparent communication, and the …

Frequency Of Mixed Neuropathologies In Individuals With Down Syndrome With And Without Alzheimer's Dementia, Lisi Flores-Aguilar, Thomas D. Zaikos, Isabel Rivera, Sierra T. Wright, Jerry Lou, Brianna Gawronski, Lourdes Gonzalez, Jillian V. Berry, Jeremy Rouanet, Natalie C. Edwards, Dan K. Hoang, Kevin Wood, Ann Charlotte Granholm, Elliott J. Mufson, Edwin S. Monuki, Milos D. Ikonomovic, Julia Kofler, Eric W. Doran, Ira T. Lott, Minodora O. Totoiu, Christy L. Hom, Florence Lai, William H. Yong, Frederick Schmitt, Jordan Harp, Peter T. Nelson, Jose Gutierrez, Patrick J. Lao, Donna Wilcock, Adam M. Brickman, Elizabeth Head

Neurology Faculty Publications

Individuals with Down syndrome (DS) develop Alzheimer's disease neuropathological change (ADNC) by the age of 40 years, and most develop dementia by their early 50s. The frequency of co-pathologies in clinically and neuropathologically characterized adults with DS has not been systematically characterized. We characterized the frequency of ADNC and common co-pathologies, including cerebral amyloid angiopathy (CAA), Lewy pathology (LP), limbic predominant age-related TDP-43 encephalopathy neuropathological change (LATE-NC), hippocampal sclerosis (HS), and other cerebrovascular and macroscopic findings reported in standardized National Alzheimer’s Coordinating Center (NACC) neuropathology forms in 63 adults with DS over 40 years. A secondary exploratory objective was to …

Neuropathological Measures Of Increased Tau Phosphorylation Across The Down Syndrome Lifespan, Jesse R. Pascual, Isabel Rivera, Halyma Nguyen, Phong T. Ngo, Alan Hoang, Elizabeth J. Andrews, Jeremy Rouanet, Sierra T. Wright, Lorena Sordo, Julia Kofler, Milos D. Ikonomovic, Florence Lai, Mark Mapstone, Bradley T. Christian, Benjamin L. Handen, Ira T. Lott, Eric Doran, Christy L. Hom, Jordan Harp, Frederick Schmitt, Dana L. Tudorascu, Beau M. Ances, Michael Phelan, Lei Liu, Lisi Flores-Aguilar, Elizabeth Head, Fan Zhang, Shahid Zaman, Michael A. Yassa, Badri Varadarajan, Rameshwari Tumuluru

Neurology Faculty Publications

Individuals with Down syndrome (DS) have an increased risk of developing Alzheimer disease (AD), with nearly all individuals exhibiting AD neuropathology, including amyloid beta (Aβ) plaques and neurofibrillary tangles (NFT), by age 40 years. Fluid AD biomarker studies highlight an increase in several phosphorylated tau (p-tau) epitopes in DS. However, neuropathological measures of p-tau epitopes in DS have not been examined. Therefore, our main objective was to characterize p-tau epitope burdens across the DS lifespan at autopsy. We analyzed postmortem brain samples of 98 individuals with late-onset AD (LOAD), DS with AD neuropathology (DSAD), young DS (below 40 years of …

The Ongoing Journey Of Modelling Intercropping Systems, Adam Muhammad Adam, Myriam Adam, Folkard Asch, Kenneth J. Boote, Vimbayi Grace Petrova Chimonyo, Mathias Christina, Marc Corbeels, Antoine Couëdel, Mathilde De Freitas, Tomas Della Chiesa, Frank Ewert, Gatien N. Falconnier, Kathrin Fuchs, Thomas Gaiser, Ken E. Giller, Gerrit Hoogenboom, Neil Huth, Jibrin Mohammed Jibrin, Eric Justes, Alpha Y. Kamara, Michael Kermah, Nuttapon Khongdee, Eric Koomson, David Kraus, Marcos Lana, Moritz Laub, Betha Lusiana, Carsten Marohn, Patricia Moreno-Cadena, Claas Nendel, Wanwisa Pansak, Willingthon Pavan

Plant and Soil Sciences Faculty Publications

Context: The global shift toward sustainable agriculture has increased interest in using process-based models to design and optimize intercropping systems. However, these models differ fundamentally in how they represent trade-offs (competition for light, water, and nutrients) and synergies (facilitation, complementarity) in resource sharing between species. This conceptual variation creates uncertainty in model selection and application, particularly since most models were originally developed for monoculture and subsequently adapted for intercropping. Objective: In this study, we describe how current crop models represent interspecies resource-sharing mechanisms, analyse their structural differences, and synthesize findings from existing validation studies to understand how their structural differences …

Increasing Diversity Of Warm- And Cool-Season Species Enhances Aboveground And Root Carbon And Nitrogen Accumulation In Subtropical Forage Mixtures, Ricardo Henrique Ribeiro, Jeferson Dieckow, André Fischer Sbrissia, Felipe Bratti, Henrique Almeida Santos Ducheiko, Marcelo Trybek, Anibal De Moraes, Marília Barbosa Chiavegato

Plant and Soil Sciences Faculty Publications

Background and aims: This study evaluated how increasing forage species diversity affects herbage and root mass, associated C and N accumulation, and soil particulate organic matter (POM). Methods: Over three years a field experiment compared a baseline system of warm-season perennial bahiagrass (Paspalum notatum) annually overseeded with black oat (Avena strigosa) to eight mixtures containing 3 to 6 species, including legumes and grasses, differing in seasonal growth (warm vs. cool season) and life cycle (annual vs. perennial). Added legumes included warm-season forage peanut (Arachis pintoi) and cool-season white clover (Trifolium repens), while added grasses included warm-season limpograss (Hemarthria altissima) and …

Soybean Plant Population Density Recommendations Across The United States, Giovani Preza Fontes, Carrie Ortel, Emma Macham, David Moseley, Shawn Conley, Chad Lee, Mark A. Licht, Laura E. Lindsey, Haleigh J. Ortmeier-Clarke, Rachel Vann, Maninder P. Singh, Seth Naeve, Jeremy Ross, Jake Mcneal, Michael Plumblee, Shaun Casteel, Eros Francisco, Michael J. Mulvaney, Nicolas Cafaro La Menza, Andre Froes De Borja Reis, Daniela Carrijo, Emerson Nafziger

Plant and Soil Sciences Faculty Publications

Rising production costs and declining commodity prices have compelled farmers to reassess their input and management strategies. Soybean [Glycine max (L.) Merr] seed costs, in particular, have continued to increase due to advances in biotechnology, higher-yielding germplasm, and available seed treatments, accounting for 32–35% of the total operational expenses in current soybean production systems. Optimizing seeding rate is therefore one area of consideration for improving profitability and maximizing return on investment. However, soybean yield response to plant population density is influenced by the combination of several factors, including water availability, temperature, radiation interception, planting practices, and crop growth and development. …

School Renewal And School Well-Being, Jianping Shen, John Lane, Patricia Reeves, Siche Feng, Xin Ma

Educational, School, and Counseling Psychology Faculty Publications

In this longitudinal case study, we examined school well-being during the change process. We operationalized the change process as the school renewal model and viewed school well-being from the perspective of the PERMA (positive emotion, engagement, relationships, meaning, and accomplishment) model. We found that all elements of the PERMA model were manifested in the school renewal process and that the school renewal process was not dominated solely by conflict and tension, as the literature typically suggests about the change process. The findings of the study suggest the possibility of reframing tension as productive rather than detrimental in the school renewal …

Volumetric Differences Of Thalamic Nuclei Are Associated With Posttrauma Psychopathology, Nick Steele, Ahmed Hussain, C. Lexi Baird, Courtney C. Haswell, Delin Sun, Leonel Rangel-Jimenez, Chadi G. Abdallah, Michael Angstadt, Geoffrey May, Hannah Berg, Jennifer U. Blackford, Josh M. Cisler, Judith K. Daniels, Nicholas D. Davenport, Richard J. Davidson, Maria Densmore, Seth G. Disner, Wissam El-Hage, Amit Etkin, Negar Fani, Jessie L. Frijling, Evan M. Gordon, Daniel W. Grupe, Ryan J. Herringa, Anna R. Hudson, Neda Jahanshad, Tanja Jovanovic, Anthony King, Saskia B.J. Koch, Ruth Lanius, Amit Lazarov, Gen Li

Psychiatry Faculty Publications

Background: Previous investigations of whole thalamus and thalamic nuclei volumes in posttrauma psychopathology have been sparse and limited in scope and have yielded inconsistent results. To address this, volumetric estimates of whole thalamus and thalamic nuclei were obtained from structural brain magnetic resonance imaging scans from 2058 participants across 20 worldwide sites in the ENIGMA (Enhancing Neuro Imaging Genetics through Meta Analysis) Posttraumatic Stress Disorder (PTSD) working group. Methods: Thalamic volumes were compared in trauma-exposed participants with PTSD (n = 238), major depressive disorder (MDD) (n = 184), and comorbid PTSD+MDD (n = 618) and in trauma-exposed control participants (n …

Alterations Of Cerebral Extracellular Vesicle Microrna Profiling Potentially Disrupts Brain Homeostasis Following Myocardial Infarction, Md Monowarul Islam, Shouyi Liang, Lijun Sun, Guoku Hu, Neha Dhyani, Lie Gao, Tara L. Rudebush, Xue Xu, Jinpeng Liu, Irving H. Zucker, Changhai Tian

Markey Cancer Center Faculty Publications

Cognitive impairment (CI) is prevalent among heart failure (HF) patients. Although the brain injury in HF is multifactorial, oxidative stress and neuroinflammation are common pathological features of neurological disorders and are increasingly recognized as key mechanisms underlying CI. Extracellular vesicles (EVs) are well-established mediators of biological signaling in myocardial function and are widely recognized for transporting a variety of microRNAs. However, whether myocardial injury alters the miRNA profiles of brain EVs, potentially contributing to cognitive impairment (CI) by disrupting brain homeostasis, remains poorly understood. Using a rodent myocardial infarction (MI) model, we isolated brain EVs and characterized their miRNA profiling …

Cardioprotective Effects Of 1,3 Butanediol In Masld Via Reversal Of Cardiac Lipid Accumulation And Suppression Of Cardiac Fibrosis, Olufunto O. Badmus, Landon D. Parrow, Karis E. Mcgowen, La Brenda Bell, Jennifer R. Greer, Marcela De Carvalho Cruz, Terry D. Hinds, David E. Stec

Markey Cancer Center Faculty Publications

Metabolic dysfunction-associated steatotic liver disease (MASLD) is highly associated with the development of cardiovascular disease (CVD); however, the mechanisms responsible are currently unknown. We have developed a model of MASLD due to the loss of hepatocyte peroxisome proliferator-activated receptor α (PPARα^HEPKO). We found that plasma beta-hydroxybutyrate (BHOB) levels were significantly reduced in PPARα^HEPKO mice and aimed to investigate the therapeutic potential of restoring BHOB levels in the development of CVD in these mice. Thirty-week-old PPARα^HEPKO and control PPARα^FL/FL mice were randomized to receive 1,3 butanediol (1,3-BDO), a precursor of BHOB, in drinking water for 6 …

Antioxidant Therapy Reverses Hepatotoxicity Induced By Microcystin-Lr In A Cellular Model Of Metabolic Dysfunction-Associated Steatotic Liver Disease (Masld), Apurva Lad, Jason Kindle, Prajwal Hegde, Gabriel G. Kleer, Andrew L. Kleinhenz, Johnna A. Birbeck, Judy Westrick, Nicholas J. Peraino, Terry D. Hinds, Neeraja Purandare, Andrew M. Fribley, Steven T. Haller, David J. Kennedy

Markey Cancer Center Faculty Publications

Microcystin-LR (MC-LR) is a potent hepatotoxin that has been shown to cause liver damage even at doses lower than the established Low Observable Adverse Effect Level (LOAEL) of 200 μg/kg in animal models. We have previously observed that low-dose exposure to MC-LR in animals with diet-induced Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) and subsequent treatment with antioxidants like N-acetylcysteine (NAC) and the Na⁺/K⁺ ATPase-Src kinase inhibitor pNaKtide significantly alleviated hepatic infiltration of immune cells, downregulated markers of inflammation and hepatotoxicity, increased the breakdown of the toxin molecule, and restored phase I and II drug metabolism pathways, including …

Chemical Structure Representation Standardization Is Needed To Generalize Metabolite-Pathway Involvement Prediction Across Kegg, Reactome, And Metacyc Knowledgebases, Erik D. Huckvale, Hunter N.B. Moseley

Markey Cancer Center Faculty Publications

Background/Objectives: Due to the utility of knowing the pathway involvement of metabolites detected in biological experiments, knowledgebases such as the Kyoto Encyclopedia of Genes and Genomes (KEGG), Reactome, and MetaCyc have annotated compound entries to specific pathways defined by the knowledgebase. However, these compound-pathway annotations are largely incomplete and are costly to obtain experimentally or curate from published scientific literature. This metabolite-pathway annotation incompleteness problem is amenable to machine learning (ML)-based solutions. But to date, no machine learning model has been trained on all three knowledgebases to maximize its performance and robustness. This may be due to inconsistencies in chemical …

GαQ Is A Heterotrimeric G-Protein Subunit That Directs The Selectivity Of Pparγ-Induced Gene Pathways Toward Energy-Related Processes Rather Than Adiposity, Evelyn A. Bates, Zachary A. Kipp, Wang Hsin Lee, Genesee J. Martinez, Sally N. Pauss, Philipp E. Scherer, Terry D. Hinds

Markey Cancer Center Faculty Publications

Background/Objectives: Signaling mediators of PPARγ influence pathways involved in adipogenesis, lipid storage, inflammation, energy-related processes, and glucose utilization. Recent research indicates that PPARγ coregulators, recruited or released during ligand binding, govern specific gene pathways. It was recently discovered that Gα_q, a heterotrimeric G protein subunit, also signals to PPARγ and may significantly affect adipogenesis and glucose sensitivity. Methods: To explore Gα_q’s role in adipocytes, we generated CRISPR-mediated Gα_q (Gnaq) knockout (Gnaq KO) and scramble control cells from 3T3-L1 preadipocytes. Results: The absence of Gα_q resulted in increased lipid accumulation and elevated serine 273 (but …

In Situ Molecular Organization And Heterogeneity Of The Legionella Dot/Icm T4ss, Przemysław Dutka, Yuxi Liu, Stefano Maggi, Debnath Ghosal, Jue Wang, Prashant P. Damke, Stephen D. Carter, Wei Zhao, Sukhithasri Vijayrajratnam, Joseph P. Vogel, Carrie L. Shaffer, Grant J. Jensen

Markey Cancer Center Faculty Publications

The Dot/Icm type IV secretion system (T4SS) is essential for Legionella pneumophila infection, but its in situ architecture and mechanism remain incompletely understood. Using cryo-electron tomography, we performed subtomogram averaging and 3D classification to resolve structural heterogeneity within the complex. We identified multiple assembly states of the inner membrane complex, including a fully assembled form with a hexamer-of-dimers DotO ATPase and symmetry mismatches between subcomplexes. A composite in situ model revealed a central channel above the inner membrane, likely used for substrate secretion. Imaging of infected macrophages showed T4SSs tethered to host vacuoles and extracellular vesicle release, suggesting additional effector …

Understanding The Role Of Age And U.S. Acculturation Factors On The Relationship Between Allostatic Load And Cancer Mortality Risk In Hispanic Americans, Jessica Amezcua, Valeria Miranda, Melissa Lopez-Pentecost, Jessica Y. Islam, Marlo M. Vernon, Kathleen O’Connor, Justin Xavier Moore

Markey Cancer Center Faculty Publications

Purpose: Despite growing recognition of stress-related health inequities, the role of nativity and acculturation in shaping the relationship between chronic stress and cancer outcomes among Hispanic populations remains poorly understood. The purpose of this study was to examine whether nativity factors (United States (US) citizenship status and length of time residing in the US modify the association between allostatic load (AL), a measure of chronic physiologic stress, and cancer mortality among Hispanic adults. Methods: We performed a prospective cohort analysis using data from the National Health and Nutrition Examination Survey (NHANES) 1999 – 2010, linked to National Death Index with …

Surface-Based Morphometry Reveals Divergent Aging Trajectories In Veterans With And Without Traumatic Brain Injury, Michelle C. Eliason, Amrutha Bindu Nagella, Cristian Cuadra, David S. Wack, Ghazala T. Saleem, Balebail Ashok Raj, Kristin Fargher, Amanda Smith, Lisa Raudin, Gloria Chaing, Norman Relkin, Karen Elizabeth Smith, Hyungsub Shim, Laura L.Boles Ponto, Susan K. Schultz, Antero Sarrael, Raymundo Hernando, Nunzio Pomara, Dick Drost, Andrew Kertesz, John Rogers, Irina Rachinsky, Stephen Pasternak, Elizabether Finger, David Bachman, Kenneth Spicer, Jacobo Mintzer, Bruce L. Miller, Howard J. Rosen, Stephen Correia, Paul Malloy

Radiology Faculty Publications

This study investigates how traumatic brain injury (TBI) alters cortical aging by comparing cortical thickness (CT) and surface area (SA) in 34 brain regions between TBI survivors and age-matched controls. Using a cross-sectional retrospective design, 105 Vietnam Veterans (32 with moderate-to-severe TBI, 73 controls) were analyzed via surface-based morphometry. Principal Component Analysis (PCA) reduced dimensionality, and Multivariate Analysis of Covariance tested group differences while controlling for age, education, depression, Post-Traumatic Stress Disorder, and intracranial volume. Findings revealed divergent morphometric signatures of aging: the proportion of SA variance explained by the first principal component (PC1) was lower in the TBI cohort …

Implementation And Assessment Of A Postreprocessing Endoscope Surveillance Program At The University Of Kentucky, 2019-2024, Court Desmond, Faith Fursman, Derek Forster, Julie A. Ribes, Sandra L. Mills, Kimberly Blanton, Kevin Hatton, Rachel Howard, David Olafsson, Sean Mctigue, Nicholas Van Sickels, Sherese Hinton, Deborah R. Flomenhoft, Takaaki Kobayashi

Surgery Faculty Publications

We evaluated an endoscope surveillance culture program at a tertiary academic center from 2019-2024. Postreprocessing culture positivity was highest for esophagogastroduodenoscopy (25.9%). Carbapenem-resistant organism matches between endoscope and patient isolates occurred in 5% of positive cultures.

Weaning Stress Induced Alterations To The Hypothalamic-Pituitary-Thyroid And -Adrenal Axes In Swine, Isabel B. Walpole, Alyssa A. Smith, Kaylyn G. Rudy, Dayeon Jeon, J. Scott Radcliffe, J. Alex Pasternak

Animal and Food Sciences Faculty Publications

Combined modulation of the hypothalamic–pituitary–thyroid (HPT) and hypothalamic–pituitary–adrenal (HPA) axes is known to play a critical role in maintaining physiological stability in response to stress. In this study, stress induced modulation of these axes was examined using 20 pigs/treatment either weaned (WN), weaned with feed/water restriction 9 h (FR), transported 9 h (TRANS), or remaining with sow (SOS) and euthanized at 32 or 56 h post-weaning. Serum cortisol, thyroxine (T4), and triiodothyronine (T3) were measured before weaning and after 24, 32, and 56 h with no difference in cortisol concentrations among treatments at any timepoint. However, both T3 and T4 …

Fate Of Nitrogen Applied To Grassland In Animal Wastes, M Sherwood

IGC Proceedings (1977-2023)

The experiment was designed to determine the effects of land spreading of animal manures on the nutrient content of surface runoff water and infiltrating soil water. This report deals only with nitrogen (N) and attempts to quantify the losses through runoff, leaching, and volatilization of ammonia (NH3) as well as N uptake in the grass over a 3-year period. Experimental plots sited on grassland, on two soil types (a moderately drained loam and an impermeable gley), were equipped to collect surface runoff water. Ceramic probes were installed in each plot at 15-, 30-, 60-, and 100-cm depths to extract in­filtrating …

Annual Losses Of Ammonia From A Grazed Pasture Fertilized With Urea, V R. Catchpoole, L A. Harper, R J.K Keyers

IGC Proceedings (1977-2023)

Nitrogen-balance studies have shown losses of applied nitrogen (N) from grazed pastures in southeastern Queensland. Losses as high as 80% have been observed from urea N broadcast at 376 kg N/ha/yr over 8 years on a Setaria sp1uu:elata cv. Nandi pasture. Management techniques aimed at reducing this loss and thereby increasing the efficiency of use of N by pastures cannot be devised until the pathways of loss are known. The objective of this research was to estimate the annual ammonia (NH3) loss by convective transport from a urea-fertilized pasture at Samford Pasture Research Station in southeastern Queensland. Urea was broadcast …

Nitrogen Losses From Urine-Affected Areas Of A New Zealand Pasture, Under Contrasting Seasonal Conditions, P R. Ball, D R. Keeney

IGC Proceedings (1977-2023)

Grazing ruminants aggregate large quantities of forage nitrogen (N) into urine patches. Pasture plots treated with urine N were studied to assess its fate under contrasting seasonal conditions: cool-moist (representing winter-spring); warm-moist (late spring-early summer), and warm-dry (late summer-autumn). A permanent ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) sward on free-draining alluvial soil was studied. 'freatments were replicated in randomized blocks. Urine N was applied at 30 or 60 g N/m2• Relevant measurements were then continued until treatment differences disappeared. Apparent N balances for urine treatments were compiled. Fixation by white clover was always greatly reduced in …

Effects Of Grazing Management On Seasonal Variation In Nitrogen Fixation, J L. Brock, J H. Hoglund, R H. Fletcher

IGC Proceedings (1977-2023)

Using the acetylene reduction assay, field studies in recent years have investigated the variation in N fixation in grazed systems, and some of the principles involved in the interaction with available soil N have been described. This experiment ex­tends this work to include the effect of grazing management on the factors influencing N fixation. Two self-contained sheep-grazed units, one a 10-paddock rotationally grazed system and the other set stocked, were estab­lished on a high-fertility ryegrass-white clover pasture, with a basic stocking rate of 22 sheep/ha. Over the 1975-1978 period, both units were monitored for pasture growth, N fixation, and associated …

Symbiotic Nitrogen Fixation Of Alfalfa, Birdsfoot Trefoil, And Red Clover, G H. Heichel, C P. Vance, D K. Barnes

IGC Proceedings (1977-2023)

Forage legumes such as alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus comiculatus L.), and red clover (Trifolium pratense L.), grown in crop rotations, can provide an inexpensive source of nitrogen (N) to succeeding crops. Few quantitative measurements of seasonal patterns of N fixation in managed communities of perennial forage legumes have been undertaken, chiefly because of the lack of satisfactory methods. Therefore, there is little knowledge of how N fixation varies with crop development, yielding ability, and weather patterns. Quantitative measurements of N fixation are important in choosing the appropriate legume for use in a crop rotation and for …

Photosynthate Supply And Nitrogen Fixation In Forage Legumes, P M. Murphy

IGC Proceedings (1977-2023)

Photosynthate supply is known to limit nitrogen fixation in legumes, and the resulting shortfall in energy supply necessary for maximum crop production may be aggravated by the energy-wasteful process of hydrogen (H2) evolution by the legume N2 fixing system. There is less information available on these aspects of the nitrogen-fixing process in forage legumes, such as white clover (Trifolium repens). The objectives of the present work were to determine how N2(C2H2) fixation and H2 production are in­fluenced by carbohydrate supply in forage legumes.

Plants were grown under controlled environmental conditions, and nodule energy supply was varied by adjusting …

Selection Of Rhizobium Strains For Enhanced Dinitrogen Fixation In Forage Legume Production, C Hagedorn, W E. Knight

IGC Proceedings (1977-2023)

A set of procedures for the selection of Rhizobium strains for enhanced dinitrogen fixation in forage legumes is presented. Although forage legumes are among the most efficient members of the Leguminosae regarding biological nitrogen fixation (BNF), they are generally neither productive nor persistent without effective nodulation by appropriate rhizobia. The following methods define a selection and evaluation process to obtain appropriate Rhizobium strains. These include (1) regional survey of the production area, (2) strain collection and soil analyses, (3) strain characterization, (4) strain selection and manipulation, and (5) field evaluation of strains. The initial procedure is to survey the region …

Interactions Between Grasses And Rhizosphere Nitrogen-Fixing Bacteria, M H. Gaskins, D H. Hubbell, S L. Albrecht

IGC Proceedings (1977-2023)

Sorghum and Digitaria cultivars grown in soil or nutrient solutions were inoculated with a strain of Azospirillum in short-term greenhouse experiments. Carbon compounds lost by roots in solution culture experiments were determined in order to estimate the quantity of energy substrates that might be obtained by rhizosphere organisms from growing plants. Other plants were treated with plant growth hormones, and responses were compared to those of plants treated with killed Azospirillum cells. The similarity of the responses suggests that growth-hormone production by the inoculant organism, rather than nitrogen (N) fixa­tion, is responsible for part or all of the increase in …