Botany Commons^™

Evaluating The Impact Of Intercropping Vegetables And Cut Flowers On Yield And Conservation Biological Control, Alliance Igiraneza

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Specialty crops such as vegetables are some of the most susceptible to yield losses and increased management difficulty over time due to pests. One of the potential solutions to this problem, which aims at ensuring the sustainability of the sector, is using conservation biological control practices such as intercropping to increase diversity, while maintaining the economic feasibility and profitability of the system. This study was conducted to evaluate the impact of this management practice using Bell pepper (Capsicum annuum var. King Arthur) as the main crop, intercropped with flowers including zinnia (Zinnia elegans var. Benary’s Giant), sunflower ( …

Cis-Variant Gene-Expression Association Analysis: A Targeted Approach To Identify Functional Cis-Regulatory Variation, Sofiya Arora

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Phenotypic diversity in plants is largely driven by changes in gene function arising from mutations in both the coding and regulatory regions. Regulatory variation is particularly pervasive because it can fine-tune gene expression without disrupting protein function and is therefore less likely to be strongly selected against in natural populations. As a result, it has played a central role in evolution and domestication. In our previous genome-wide eQTL mapping study in maize, nearly two-thirds of the expressed genes were found to harbor detectable cis-expression quantitative trait loci (cis-eQTLs) with strong local effects on gene expression. Though these cis-variants are widespread, …

Effects Of Applying Humic Acid In-Furrow At Potato Planting, Jonathan Tyler Price

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Many products are marketed towards potato farmers that purport to have a positive return on investment for yield and quality. Humic acids, which are comprised of long chained, organic molecules that can be naturally or industrially made, are currently being marketed in this way. The use of these materials is reported to improve nutrient uptake, increase soil health, encourage vigorous growth, and most importantly, increase yields.  From 2023-2025, the in-furrow application of humic acid containing commercial products was evaluated in Pennsylvania on the cultivars ‘Lehigh’ and ‘Waneta’. Black Label Zn, Duo Maxx, Fertiactyl RhiZn, Humi-flex FA, Hydra-Hume, and Monty's Liquid …

Evaluation Of Publicly Available Maize Germplasm Adaptation To Environments In Nebraska, Garrett Snodgrass

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Publicly available maize germplasm represents an important resource for breeding programs seeking to expand genetic diversity and improve hybrid performance. However, effective use requires characterization of per se phenotypic performance of parental lines and evaluation of the parental line’s hybrid progeny adaptation to a given target population of environments. Furthermore, understanding population structure and heterotic grouping is imperative for maximizing efficiency of breeding decisions. The objectives of this study were to (1) evaluate phenotypic performance of parental lines and hybrids across environments in Nebraska, and to (2) refine heterotic group classification of parental lines within the University of Nebraska-Lincoln’s Hybrid …

Hydroponics In The Classroom: Cultivating Plants, Captivating Young People, Stacy A. Adams, Christian Stephenson, Theresa James, Kim Todd

Department of Agronomy and Horticulture: Faculty Publications

Few students take the initiative to pursue coursework beyond that required for progression to graduation. Limited are opportunities that connect educational content to industry application, potentially inspiring young people towards impactful careers. The United States government has emphasized the importance of STEM education to ensure national security and to maintain economic competitiveness globally. STEM education is not a defined discipline but an approach for building knowledge through application and engagement. Developing and managing a hydroponics prototype provides numerous opportunities for embedding STEM content into a fun and interactive project. This poster provides inspiration for constructing a simple deep water culture …

Patch Mow Grazing: Investigating The Effects Of Mowing On Forage Nutritive Value, The Biomass–Nutritive Value Relationship, And Herbivore Selection, Trace R. Stauble

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Herbivore foraging behavior plays a critical role in shaping grassland structural heterogeneity, with selection often driven by forage biomass and nutritive value. Currently, it is thought that herbivores primarily select areas that are greater in nutritive value, and low in biomass. More specifically, disturbances like fire and grazing have been thoroughly studied showing that recently burned and grazed areas are not only higher in nutritive value but disproportionately selected by herbivores in comparison to undisturbed areas. However, most studies address only narrow ranges of defoliation, comparing intensely defoliated sites (< 10 cm) to those that are either not defoliated or have experienced a much longer time since defoliation, thereby decreasing grazing pressure as biomass increases. However, one of the most widely used methods of defoliation in grasslands, mowing, hasn’t been thoroughly studied for its effects on nutritive value, and how it impacts herbivore selection. Our study aimed to (1) evaluate how mowing treatments—i.e., short (5 cm), medium (18 cm), and tall (>30 cm, unmown)—affect nutritive value and herbivore selection, (2) assess …

Cover Crop Influence On Arthropod Biodiversity And Soil–Water Dynamics In A Semi-Arid Maize–Soybean Sequence Of The Nebraska High Plains, Carlos Eduardo De Oliveira Martins

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

With the expansion of cover crop (CC) use in semi-arid regions, producers in the Nebraska High Plains are increasingly interested in understanding how CCs influence both beneficial arthropods and soil-water within maize-soybean (Zea mays L., Glycine max [L.] Merr.) rotations. Integrating CCs in these systems can enhance soil water availability and beneficial insect activity, but potential trade-offs include higher early-season water use by CCs and the risk of increasing potential pest populations. This thesis addresses these questions through two complementary studies conducted under field conditions near Brule, Nebraska. The first study evaluated the effects of a multi-species CC mixture …

Post-Fire Soil Health Assessment Of The Grasslands And Woodlands In The Semi-Arid Nebraska Sandhills, Stephanie M. Lugo

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Grasslands in the Nebraska Sandhills are shaped by natural wildfires, which help maintain the structure and function of native grasslands. In recent decades, afforestation with ponderosa pine and eastern redcedar has introduced new woodlands that altered the region’s fire dynamics and raised important questions about the effects of wildfire on different vegetation types. As wildfires become more frequent, understanding their impacts on soil health in grasslands and woodlands becomes increasingly important. This study examines the short-term effects of the 2022 Bovee Fire on physical, chemical, and biological soil properties in native grasslands and ponderosa pine and eastern redcedar afforested woodlands. …

Evaluating Metamitron Efficacy For Glyphosate-Resistant Palmer Amaranth (Amaranthus Palmeri) Management In Sugarbeet Across The Central High Plains, Abraham Akuoko

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Herbicide-resistant (HR) Palmer amaranth (Amaranthus palmeri S. Watson) is regarded as one of the most prominent weeds within sugarbeet fields across the Central High Plains, with limited chemical control options. Although a few herbicides are available, their use is restrictive due to crop injury concerns and can only be applied at or after the 2–4 true leaf (TL) growth stage, which will provide no control for already emerged weeds. However, Palmer amaranth often emerges between sugarbeet planting and the 2 TL sugarbeet growth stage. Consequently, as of 2023, there were no herbicide options to control Palmer amaranth in sugarbeet …

Large Scale Deletion And Rebalancing Within The K1c Kafirin Family In Sorghum, Tyler W. Ferris

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Sorghum bicolor (L.) Monech (sorghum) is cultivated as food for humans and livestock and is valued for its low input requirements. However, sorghum grain protein is deficient in the essential amino acid lysine and has poor protein digestibility because of the abundance of proline-rich kafirins that constitute >70% of proteins that form low-digestibility protein bodies. To reduce kafirin expression in the endosperm, and elicit wholesale proteome rebalancing to increase non-kafirin proteins, a single-guide RNA (sgRNA) Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR/Cas9) construct was previously used to target members of the highly-repetitive alpha-kafirin family, k1C in RTx430 sorghum. The …

Soil Health In Nebraska: Exploring Practitioners' Needs And Insights From A Long-Term Organic Farm, Ingrids Isabel Mata Vigil

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Soil health is foundational to sustainable agriculture, environmental resilience, and long-term food security. Yet, the adoption of soil health assessments remains limited, often perceived as too technical, costly, or difficult to implement in real-world contexts. To better understand these challenges, the first chapter presents findings from a statewide survey of 41 soil health practitioners in Nebraska, including farmers, extension educators, NRCS staff, and conservation professionals. Respondents highlighted the need for simpler, more accessible, and context-specific tools for soil health assessment that help practitioners make informed decisions aligned with their management goals. Complementing these insights, the second chapter includes an independent, …

Catching A Fever: A Comparison Of Vachellia Xanthophloea Populations In The Limpopo And Luvuvhu River Floodplains Of The Makuleke Contractual Park, Kianie B. David

School of Natural Resources: Dissertations, Theses, and Student Research

This study investigates patterns of stand structure regeneration, growth characteristics, and coarse woody debris (CWD) patterns in Vachellia xanthophloea (fever tree) stands within the Makuleke Contractual Park (MCP), a semi-arid savanna system in northern Kruger National Park (KNP), South Africa. Fieldwork was conducted across two stand types: a monospecific fever tree stand in Rietbok Vlei and a mixed-species stand in the Western Nhlangaluwe Floodplain where fever tree is established with Faidherbia albida (ana tree). Data were collected from 20 total 1/4-acre (1,011 m²) circular plots between both stands in 2024 and 2025, including seedling root collar diameter (RCD), …

Improving Nitrogen Management And Corn Productivity Through Enhanced Efficiency Fertilizer And Cover Crop Integration In Nebraska Cropping Systems, Madhusudhan Adhikari

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Effective nitrogen (N) management is vital for sustaining corn yield and reducing environmental impacts in Nebraska cropping systems. Three field studies were conducted to evaluate the impact of 1) fertilizer type (anhydrous ammonia [AA] with nitrification inhibitor: enhanced efficiency fertilizer [EEF] or AA without EEF) and N application timing (pre-plant vs. split with side-dress UAN) on in-season soil N availability, crop response, nitrous oxide (N₂O) emissions, residual soil N and N use efficiencies (NUEs); 2) winter cover crop (CC) species and crop rotation variability on CC biomass production, N uptake, soil N dynamics, and cash crop performance in …

Extending Cover Crop Growing Window To Improve The Health Of Environmentally Sensitive Soils, Noshin Ara Tunazzina

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Sloping and sandy soils are highly susceptible to degradation. The health of these soils could be improved with cover crops (CCs). However, CC effectiveness in improving soil health mainly depends on CC biomass production, which is often low in temperate regions. The question is: how can we increase CC biomass production? Lengthening the CC growing window can be a potential strategy. This study assessed how 1) interseeded and terminated early (2-3 weeks before crop planting) CC, 2) interseeded and terminated late (at crop planting) CC, 3) drilled (after harvest) and terminated early CC, 4) drilled and terminated late CC, and …

Evaluation Of The Global Durum Panel (Triticum Turgidum Ssp. Durum) For Wheat Streak Mosaic Virus Resistance, Winter Survival, And Seed Characteristics, Megan Engel

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The majority of durum wheat (Triticum turgidum spp. durum; AABB; 2n=4x=28) is predominantly grown in the northern Great Plains of the United States, and is used in the production of semolina, a coarse flour that makes pasta and couscous. Durum has been widely regarded for being more tolerant to abiotic stress, due to its ability to withstand drought and high temperatures. In this thesis, we conducted greenhouse, field, and lab studies, for the traits wheat streak mosaic virus (WSMV), winter survival, and single kernel characteristics of the Global Durum Panel version 2 (GDPv2 n = 976), a panel …

Genetic And Soil Influences On The Grapevine Rhizosphere Microbiome, Lauren M. Quackenbush

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

In vineyard cropping systems, the rhizosphere microbiome arises through recruitment and filtering of the bulk soil microbiome shaped over time by soil carbon and nitrogen, climate, pH and historical legacies of vineyard management. The recruitment and filtering steps occur under the genetic influences of rootstock and scion that together drive variability in rhizosphere microbiome diversity and composition.

This study compares rhizosphere microbiomes of four Pinot Noir blocks under two rootstocks (101-14 and 420A) and four scions (777, 828, Calera, Mt. Eden). Core microbiomes were consistent across all replicates. The most abundant bacterial phyla were Actinobacteriota, Proteobacteria, and Acidobacteriota …

Introduction To Hydroponics- 2025-2026 Workshop Handbook, Stacy A. Adams

Department of Agronomy and Horticulture: Faculty Publications

Hydroponically grown plants grow faster than traditional production systems, with greater productivity, greater palatability, and having optimal visual character. Three principal components of a system include the plant support platform, a nutrient solution reservoir, and an interface for the root-solution. This publication provides in-depth explanation to system design, evaluation of water quality, nutrient formulation, and prototype systems that can be easily constructed for those wanting to explore hydroponics, such as educators, organizational leaders, or home enthusiasts.

Greenhouse Management For The Smaller Structure--Educational And Hobby, Stacy A. Adams

Department of Agronomy and Horticulture: Faculty Publications

Greenhouses used for teaching or by hobbyist are smaller than those used for commercial production or found in the retail environment. Structural materials, covering, mechanical equipment, and control systems often are packaged as a kit made available through greenhouse suppliers. Supplier construction services may not be available, in which buyers must use local contractors to complete the installation. Greenhouses are unique structures that differ greatly from sheds or other outbuildings. They have coverings that allow maximum light transmittance, protected from UV degradation, and can handle wide inside to outside temperature extremes. This extension circular provides valuable information on the character, …

Terrarium- An Ecosystem In A Jar, Stacy A. Adams

Department of Agronomy and Horticulture: Faculty Publications

STEM education is supported through hand's-on activities in the classroom. Content understanding and reaffirmation of knowledge is supported through this informative STEM-Quick card that teachers or extension educators can distribute to participants for reference. Terrariums provide an example of a closed ecosystem where water and carbon cycling is demonstrated and plant growth can be observed. This card presents the steps to building and caring for an easy to create terrarium.

Leveraging Within-Field Spatial Variability To Optimize Soybean Yield, Seed Quality, And Profitability, Marina Marly Dalla Betta

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Optimizing yield and seed quality in soybean production is critical for both profitability and meeting market demands. However, within-field variability in soil properties poses a challenge in determining optimal management strategies to maximize soybean yield, seed quality, and profitability. This work aimed to evaluate the spatial variability of soybean fields to optimize soybean seeding rates, seed quality, and profitability. Two case studies were used to carry over this research. The first study looked at the optimal economical site-specific soybean seeding rates using 11 on-farm precision experiments across Nebraska. The second study looked at the protein and oil variability within 22 …

Broad-Spectrum Resistance To Fungal Foliar Diseases In Wheat: Recent Efforts And Achievements, Amira M.I. Mourad, Asmaa A.M. Ahmed, P. Stephen Baenziger, Andreas Börner, Ahmed Sallam

Department of Agronomy and Horticulture: Faculty Publications

Wheat (Triticum spp.) is one of the most important cereal crops in the world. Several diseases affect wheat production and can cause 20-80% yield loss annually. Out of these diseases, stripe rust, also known as yellow rust (Puccinia striiformis f. sp. tritici), stem rust (Puccinia graminis f. sp. tritici), leaf rust (Puccinia recondita), and powdery mildew (Blumeria graminis f. sp. tritici) are the most important fungal diseases that infect the foliar part of the plant. Many efforts were made to improve wheat resistance to these diseases. Due to the continuous advancement in …

Disentangling Genotype And Environment Specific Latent Features For Improved Trait Prediction Using A Compositional Autoencoder, Anirudha Powadi, Talukder Zaki Jubery, Michael C. Tross, James C. Schnable, Baskar Ganapathysubramanian

Department of Agronomy and Horticulture: Faculty Publications

In plant breeding and genetics, predictive models traditionally rely on compact representations of high-dimensional data, often using methods like Principal Component Analysis (PCA) and, more recently, Autoencoders (AE). However, these methods do not separate genotype-specific and environment-specific features, limiting their ability to accurately predict traits influenced by both genetic and environmental factors. We hypothesize that disentangling these representations into genotype-specific and environment-specific components can enhance predictive models. To test this, we developed a compositional autoencoder (CAE) that decomposes high-dimensional data into distinct genotype-specific and environment-specific latent features. Our CAE framework employed a hierarchical architecture within an autoencoder to effectively separate …

Industrial Hemp Biomass Negatively Affected By Herbicide Drift From Corn And Soybean Herbicides, Milos Zaric, Bruno Canella Vieira, Barbara Houston, Guilherme Sousa Alves, Samuel E. Wortman, Julie A. Peterson, Greg R. Kruger

Department of Agronomy and Horticulture: Faculty Publications

The establishment of industrial hemp (Cannabis sativa L.) fields near row crops has raised concerns about the potential adverse effects of herbicide drift on hemp production. This study examined hemp susceptibility to drift of herbicides registered for use in corn and/or soybeans. Herbicide solutions (2,4-D, dicamba, glufosinate, glyphosate, imazethapyr, lactofen, mesotrione) were applied separately in the wind tunnel (3.6 m s⁻¹ airspeed), simulating drift scenarios, with conventional TP95015EVS (TP) and air inclusion AI95015EVS (AI) flat fan nozzles calibrated to deliver 140 L ha⁻¹ carrier volume at 230 kPa. Mylar cards and hemp plants (20–25 cm tall) were placed …

Designing A Decision-Support Tool For Fertilizer Recommendations In Oil Palm Smallholders, Rana Farrasati

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Oil palm (Elaeis guineensis Jacq.), originally from West Africa, now accounts for 42% of global vegetable oil production and mainly includes key regions cultivated in tropical regions of Southeast Asia, West Africa, South America, and Central America. Despite its economic significance, the oil palm industry faces challenges of stagnant yields and large yield gaps, particularly among independent smallholders. These issues often stem from inadequate nutrient management practices and limited agronomic knowledge. Our objective was to quantify nutrient requirements for mature oil palm plantations as a basis to design a decision support tool (DST) for fertilizer recommendations. To do so, …

Bio-Based Sprayable Mulch For Weed Control In Row Crop Systems, Camila Chiaranda Rodrigues

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Improving current crop productivity levels requires transformative advancements in management, engineering, and science. One of the main challenges is the increasing difficulty of weed management due to herbicide-resistant weeds. There is a growing need for alternative weed management methods to reduce pesticide use and improve environmental safety. An emerging technology that is being developed is spray-on films which could help address these challenges. Spray-on films are liquid solutions that after spraying on the soil will dry and form a physical barrier. The overall objective of this research was to evaluate the effectiveness of a chicken feather bio-based sprayable mulch film …

Assessing The Above- And Belowground Productivity Of Fall-Planted Cover Crop Cultivars In Nebraska's Diverse Ecoregions, Bridget Mckinley

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Cover crops (CC) provide essential ecosystem services including soil conservation, nutrient cycling, and weed suppression, through the accumulation of aboveground (AGB) and belowground (BGB) biomass. While AGB has been widely studied, BGB contributions, particularly root development and distribution, remain less understood. This study evaluated fall-planted CC across three Nebraska ecoregions, assessing AGB productivity, BGB biomass, and correlations between ground cover, plant height, and AGB.

Thirty treatments, including grasses, legumes, brassicas, and mixtures, were evaluated over two fall growing seasons (2022–2023 and 2023–2024) at three UNL research centers in northeast, west central, and west Nebraska. AGB was highest at west site …

Twas Facilitates Gene-Scale Trait Genetic Dissection Through Gene Expression, Structural Variations, And Alternative Splicing In Soybean, Delin Li, Qi Wang, Yu Tian, Xiangguang Lyv, Hao Zhang, Huilong Hong, Huawei Gao, Yan-Fei Li, Chaosen Zhao, Jiajun Wang, Ruizhen Wang, Jinliang Yang, Bin Liu, Patrick S. Schnable, James C. Schnable, Ying-Hui Li, Li-Juan Qiu

Department of Agronomy and Horticulture: Faculty Publications

A genome-wide association study (GWAS) identifies trait-associated loci, but identifying the causal genes can be a bottleneck, due in part to slow decay of linkage disequilibrium (LD). A transcriptome-wide association study (TWAS) addresses this issue by identifying gene expression–phenotype associations or integrating gene expression quantitative trait loci with GWAS results. Here, we used self-pollinated soybean (Glycine max [L.] Merr.) as a model to evaluate the application of TWAS to the genetic dissection of traits in plant species with slow LD decay. We generated RNA sequencing data for a soybean diversity panel and identified the genetic expression regulation of 29 …

Summer- And Fall-Planted Cover Crops Across Nebraska: Assessing Performance Using Aerial Imagery And Evaluating Short-Term Soil Impacts, Grace Emperatriz Pacheco Jiron

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Cover crops are widely recognized for improving soil health and promoting sustainability in agricultural systems. Despite the increasing use of monitoring tools like aerial imagery, their application in evaluating summer-planted cover crops in the Great Plains remains limited, hindering effective management strategies. Fall-planted cover crops provide long-term environmental benefits, including enhanced soil quality and erosion control; however, understanding their short-term effects on soil properties is crucial for encouraging adoption. This study assessed summer- and fall-planted cover crops across Nebraska, integrating aerial imagery and soil health analyses.

Over two years, fifteen summer-planted monocultures and five mixtures were evaluated for establishment, biomass …

Dissecting The Genetic Architecture Of Sunflower Disc Diameter Using Genome-Wide Association Study, Yavuz Delen, Ravi V. Mural, Semra Palali-Delen, Gen Xu, James C. Schnable, Ismail M. Dweikat, Jinliang Yang

Department of Agronomy and Horticulture: Faculty Publications

Sunflower (Helianthus annuus L.) plays an essential role in meeting the demand for edible oil worldwide. The yield of sunflower seeds encompasses several component traits, including the disc diameter. Over three consecutive years, 2019, 2020, and 2022, we assessed phenotypic variation in disc diameter across a diverse set of sunflower accessions (N = 342) in replicated field trials. Upon aggregating the phenotypic data from multiple years, we estimated the broad sense heritability (H²) of the disc diameter trait to be 0.88. A subset of N = 274 accessions was genotyped by using the tunable genotyping-by-sequencing (tGBS) method, …

Ponca State Park Vascular Plant Species List, Robert F. Steinauer

Nebraska Game and Parks Commission: White Papers, Conference Presentations, and Manuscripts

A list of vascular plant species found in Ponca State Park. Arranged by plant family and then species name. Also included are descriptions of locations where the species is commonly found.