Agronomy and Crop Sciences Commons^™

Exploring Regenerative Vegetable Systems On The Central Coast Of California, Una S. O'Connell

Master's Theses

As climate change and current agricultural practices place pressure on the long term sustainability and resilience of food production systems, there is growing interest in whether existing agricultural systems can adapt to maintain productivity while improving environmental outcomes.

This study evaluated the effects of regenerative versus standard organic vegetable production systems on yield, insect communities, and weed suppression across three field trials conducted on California's Central Coast. In addition, I collected baseline soil health data for all trials. Trials 1 and 2 were carried out at the Cal Poly San Luis Obispo Organic Farm using cabbage and broccoli as cash …

Evaluation Of Ultraviolet-C Light For Control Of Mites And Western Tarnished Plant Bug In Strawberry & Interactive Lethal Effects Of Common Strawberry Fungicides And Adjuvants On Phytoseiulus Persimilis, Colin T. Koubek

Master's Theses

California strawberry production relies heavily on chemical pesticides to manage arthropod pests and diseases, but pesticide resistance, regulatory pressure, and the need to conserve biological control agents have increased interest in alternative pest management tools. This thesis evaluated ultraviolet-C (UV-C) light as a nonchemical management tool for key strawberry arthropod pests and assessed the compatibility of common strawberry fungicides and adjuvants with the predatory mite Phytoseiulus persimilis Athias-Henriot. The first objective was to determine the ovicidal and lethal effects of UV-C light on Lygus hesperus Knight eggs and nymphs. Laboratory and field ovicide assays were conducted using UV-C doses relevant …

Effects Of Irrigation And Nitrogen Management On Yield And Leaching Risk In Organic And Conventional Broccoli Fields, Shane Egerstrom

Master's Theses

Under regulatory pressures to reduce groundwater contamination by nitrate from fertilizer, such as those posed by the Central Coast Regional Water Quality Control Board’s Agricultural Order 4.0, a need exists to better understand interactions between irrigation and nitrogen (N) management. To increase N use efficiency (NUE), growers are encouraged to account for additional sources of N in their management plans, such as irrigation water N and preplant soil N. The availability of these N sources for plant uptake and how it is affected by other management conditions is not yet well documented. We conducted 6 field trials, 3 organic and …

Evaluating Soil Health And Crop Yield In Louisiana Agricultural Systems: Impacts Of Best Management Practices And Prediction Models, Hector J. Mendoza Lagos

LSU Doctoral Dissertations

The adoption of conservation management practices is critical for improving soil health, enhancing nutrient use efficiency, and sustaining crop productivity in row crop systems in Louisiana. This study evaluated the role of conservation agronomic practices, soil biochemical indicators, and machine learning predictive models to improve soil nutrient dynamics, soil health indicators, microbial communities (MC), and crop productivity on a corn (Zea mays L.) research plot scale and in a commercial forty-hectare cotton (Gassypium hirsutum L.)-corn-soybean (Glycine max L.) rotation system in northeast Louisiana. The objectives of the study were to evaluate soil nutrient dynamics and MCs under …

Field Pea (Pisum Sativum L.) Response To Planting Date In South Carolina Organic Cropping Systems, Tristan Lawrence

All Theses

Field peas (Pisum sativum L.) are not widely cultivated in South Carolina, resulting in limited agronomic data to support farmers interested in this crop. However, field peas hold significant promise as a cool season crop for both organic and conventional growers in the region. Most commercially available field pea cultivars are evaluated and bred for the Pacific Northwest, where environmental conditions differ substantially from those in the southeastern United States. Consequently, there is a lack of region-specific recommendations for successful cultivation in South Carolina. To address this gap, a two-year planting date study was conducted during the …

Dried Water Treatment Residuals Might Be An Option To Reduce Soluble Reactive Phosphorus Release From Soils, Katie B. Mckay

Biological and Agricultural Engineering Undergraduate Honors Theses

Nonpoint source pollution from agricultural landscapes contributes to freshwater eutrophication, with legacy phosphorus (P) in soils potentially driving soluble reactive phosphorus (SRP) losses to surface waters. The objectives of this study were to evaluate SRP adsorption by dried water treatment residuals (WTRs) produced by Beaver Water District, quantify reductions in soil SRP release across increasing WTR application rates, and compare dried WTR performance to prior WTR studies.

Dried WTRs (~98% solids) were assessed using batch sorption experiments and soil core incubations. Phosphorus sorption was measured by mixing WTRs with CaCl₂ solutions containing increasing SRP concentrations and fitting results to …

Discovering The Genetics Underlying Speciation Traits In Heuchera (Coral Bells), Tajinder Singh

Honors Theses

Hybridization is a key evolutionary mechanism for generating biological diversity, ultimately shaping diversification and adaptation of plant lineages in natural and agroecosystems.  Our understanding of the frequency, distribution, and significance of hybridization is rapidly increasing, but the external driving forces that dictate why certain species hybridize, and others do not remain obscure. The physical traits that shape gene flow and trait sharing among species are likely to be among the key factors that directly control hybridization. Gene flow in most plants is mediated by pollinating insects and thus by pollination syndromes, which are suites of floral traits that have evolved …

Genome Wide Association Study (Gwas) On Different Economic Traits And Epigenetic Stability Of Sweetpotato In Louisiana, Ajay Dhungana

LSU Doctoral Dissertations

Sweetpotato [Ipomoea batatas (L.) Lam] is a globally important food, feed, and industrial crop, yet its improvement is constrained by a complex hexaploid genome, clonal propagation, and susceptibility to multiple diseases. In Louisiana, production is threatened primarily by Fusarium oxysporum f. sp. batatas (Fusarium wilt) and Ceratocystis fimbriata (Black rot). Furthermore, the in vitro propagation methods essential for disease-free planting material and germplasm conservation can introduce epigenetic instability that undermines clonal fidelity. This dissertation integrates genome-wide association studies (GWAS), genotype by environment interaction (GEI) and DNA methylation profiling to dissect resistance mechanisms and assess epigenetic stability in Louisiana sweetpotato …

Soil Nutrient Sufficiency Versus Plant Nutrient Status In Compost-Amended Soils: Plant Tissue Analysis As A Diagnostic Tool, Chandralekha Joga Miss

Murray State Theses and Dissertations

This study evaluated whether Mehlich III soil nutrient sufficiency ratings reliably predict plant nutrient status and chlorophyll response across contrasting compost application histories. A greenhouse pot experiment was conducted with Chijimisai (Brassica rapa) planted in three treatment soils that had no compost (T1), moderate compost history (T2), and long-term hog manure compost application (T3). Plant performance was assessed through weekly shoot length and chlorophyll content (SPAD) measurements, leaf number at maturity, and leaf tissue nutrient analysis conducted at harvest. Soil test results indicated adequate to high nutrient levels across all three treatments. Leaf tissue analysis, however, revealed substantial …

An Analysis Of Systemic And Contact Herbicide Usage Trends In Illinois Corn Production Systems, Paige E. Mckittrick

Murray State Theses and Dissertations

Herbicide use is central to weed management in Illinois corn production; however, long-term changes in the balance between systemic and contact herbicides have not been well quantified at the statewide scale. This study analyzes herbicide trends in Illinois corn from 1982 to 2016 using secondary data from the USDA Agricultural Chemical Use Survey, paired with climate, regulatory, and herbicide resistance information. Herbicide active ingredients were classified into systemic and contact functional categories and grouped according to Weed Science Society of America (WSSA) mode-of-action (MOA) codes. For each survey year, total herbicide load (lb a.i./acre), functional proportions, MOA-specific contributions, and a …

Effects Of Compost Incorporated Versus Surface Applied On Soybean Yield And Soil Health, Maheshwari Kuchanapally

Theses and Dissertations

Compost application is increasingly recognized as a sustainable soil management practice that enhances soil health and crop production. However, the method of application, incorporated versus surface applied, may influence its effectiveness in improving soil properties and crop productivity. This study evaluated the effects of compost application method on soybean (Glycine max L. Merr.) yield and soil health at Illinois State University Research Farm in Lexington, Illinois, across two growing seasons, 2024 and 2025. The 2024 experiment used a Completely Randomized Design comparing incorporated versus surface-applied compost (n = 4; 8 plots). The 2025 experiment used a Randomized Complete Block Design …

Evaluating Soil And Plant Health In A Wide-Row Maize (Zea Mays L.) Production System Integrated With Perennial Cover Crops And Turkey (Meleagris Gallopavo), Sovika Bhattarai

All Graduate Theses, Dissertations, and Other Capstone Projects

In regions dominated by intensive maize (Zea mays L.) production systems, such as the US Midwest, sustainable agricultural practices such as cover crops and livestock integration are gaining interest for their potential to improve soil, plant, and environmental health. Traditionally, annual cover cropping systems (ACCs) have been used to maintain soil quality and crop performance without compromising ecosystem services. However, the high establishment and management costs of ACCs highlight the need for alternative approaches, such as perennial cover crops (PCCs). Grown as companion crops with maize, PCCs provide extended soil cover and can improve soil biochemical properties (e.g., total C …

Impacts Of Management Practices And Soil Properties On Free-Living Nitrogen Fixation In Eastern South Dakota, Laura Galvan Nuevo

Electronic Theses and Dissertations

Free-living nitrogen (N) fixation (FLNF) may represent a sustainable pathway to supplement crop N demand in agroecosystems, yet edaphic and management factors regulating this process under field conditions remain poorly understood in the Northern Great Plains. Using 15N2 direct method to quantify potential FLNF (pFLNF) and baseline FLNF (bFLNF), this thesis investigates how crop rotations (2-, 3-, and 4-year systems), tillage management (conventional vs. no-till), cover cropping, and soil properties affect the potential of free-living diazotrophs to supply N via FLNF in a long-term no-till corn-based system in Southeastern South Dakota. A two-year field study evaluated pFLNF across four growing …

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 …

Investigation Of Perennial Clover Living Mulch And Reduced Tillage Effects On Weed Suppression, Crop Metrics, And Yield Of Organic Cabbage And Sweet Corn In The Northern Great Plains, Kristina Harms

Electronic Theses and Dissertations

Vegetable farmers often face weed management and soil health challenges, such as nitrate leaching, soil compaction, and top-soil loss. Sustainable agriculture is a forefront of innovation compared to conventional agriculture. Living mulches, non-cash crops grown alongside cash crops, have demonstrated weed suppression and impact on the promotion of sustainable agriculture. Yet studies have not evaluated established living mulch systems on cash crop quality and yield. This study conducted in 2023, 2024, and 2025 at SDSU Southeast Research Farm, Beresford, SD, USA evaluates the impact of established ‘Dynamite’ red clover (Trifolium pratense), ‘Domino’ white clover (T. repens), and ‘Aberlasting’ white × …

Regenerative Farming Practices Effects On Invertebrates In Wheat Systems, Daniel J. Pecenka

Electronic Theses and Dissertations

The modern agricultural system is based upon the Green Revolutions principle of creating more food. However, this came at a cost of invertebrate declines through habitat loss, pollution, and the introduction of agrochemicals. Here I address knowledge gaps in biological inventory of invertebrates across north, northwestern, and central North America. These invertebrates were identified and given a size scale and a dietary guild. We also examined how regenerative and conventional agricultural practices can affect invertebrate populations within the same crop. We also examined whether regenerative management wheat fields fostered great invertebrate communities while limited pest presence. Invertebrate populations were negatively …

Feasibility Of Corn Stover For Biogas Production In Northwestern Illinois: A Case Study Of Jo Daviess And Carroll Counties, Anthony Amotoe-Bondzie

Masters Theses

The growing demand for renewable energy and sustainable waste management has intensified interest in agricultural residues such as bioenergy feedstocks. This study evaluated the feasibility of converting corn stover into biogas through anaerobic digestion (AD) in Jo Daviess and Carroll Counties, Illinois, with consideration of the Savanna Industrial Park as a potential centralized processing hub. Although corn stover represents one of the largest biomass resources in the United States, this research identifies a critical gap between theoretical availability and practically recoverable feedstock. Using a mixed-methods framework, the study integrates biomass quantification, methane yield modeling, economic analysis, and policy assessment. Results …

Advancing Louisiana's Cropping Systems: Sustainable Bioenergy Production, Cover Crops, And Technology Integration, Pedro R. Carrillo

LSU Doctoral Dissertations

The adoption of cover crops in Louisiana is lower than the national average, underscoring the need for region-specific research to address environmental challenges and demonstrate the short-term benefits of these practices within existing production systems. This research evaluated the integration of cover crops (CC) in energy cane (Saccharum spp.) and no-till cotton systems, focusing on their effects on soil health, nitrogen (N) management, and biomass production. Soil health indicators (SHIs), including enzymatic activities (β-glucosidase, β-glucosaminidase, and urease), protein N, inorganic N concentrations (nitrate and ammonium), soil organic matter (SOM), and microbial community composition assessed through ester-linked fatty acid …

Breeding For Disease Resistance In Melon And Watermelon, Venkata Rao Ganaparthi

All Dissertations

Watermelon and cantaloupe are two widely consumed cucurbits, but their acreage in the United States reduced by nearly 50% in last two decades. Fusarium wilt caused by a soil borne pathogen Fusarium oxysporum f. sp. niveum(Fon) race 2 is a major limiting factor in watermelon production as it reduces yields by 80%. Grafting watermelon plants onto the root stock of wild, disease-resistant varieties like ‘Carolina Strongback’ is the best strategy to manage Fon race 2. Though effective, this approach increases production costs.

Part of this dissertation focused on finding more sustainable, cost-effective solutions to control Fusarium wilt …

Establishment Of Native Warm-Season Forages Using Organic Practices, Kolten Ray Wright

Graduate Theses and Dissertations

Abstract Grassland agriculture is seen as a particularly sustainable form of agriculture. Many opportunities are known to use organic production methods or incorporate native warm-season grasses (NWSG) to accomplish both production goals and environmental or social outcomes. Environmental concerns have led some practitioners to question the use of organic methods to establish NWSG. As limited work has been accomplished in the northern bermudagrass belt, this project sought to compare organic establishment strategies for common NWSG species. A field trial conducted at the USDA ARS Dale Bumpers Small Farms Research Center in Booneville, AR found that NWSG establishment success in the …

Management Of Herbicide-Resistant Italian Ryegrass Using Cover Crop And Fall Residual Herbicide, Connor T. Mckoin

LSU Master's Theses

A field study was initiated in the fall of 2023 and repeated in 2024 at the LSU AgCenter Northeast Research Station near St. Joeseph, LA, to determine the impact of fall-applied soil residual herbicide at different growth stages (spike and one-leaf stage) on grass cover crop species, cereal rye and black oats. In most instances, clomazone (631 g ai ha^-1) and treatments containing the higher rates of metribuzin (263 g ai ha^-1)resulted in the greatest amount of cover crop injury both years, with biomass impacted by clomazone both years and in one of two years with …

Uav Remote Sensing For Assessment Of Conservative Management Practices In Maize-Soybean Cropping System, Aakriti Poudel

LSU Master's Theses

Sustainable agriculture practices promote cover cropping, which enhances nutrient management and impacts subsequent crop productivity in field crop rotations. Precision agriculture technology, particularly Unmanned Aerial Vehicle (UAV) remote sensing, enables a detailed evaluation of crop management. The studies were conducted in a maize-soybean rotation system with winter cover cropping and fallow management. The maize experiment investigated the effect of nitrogen application rates and cover cropping, using UAV-derived Normalized Difference Red-Edge (NDRE) to monitor crop performance. NDRE effectively captured the N response and the effect of cover cropping across growth stages, particularly during mid-season (55-81 DAP), where it showed a strong …

Integrating Cereal Rye Cover Crop And Herbicide Programs To Manage Glyphosate-Resistant Italian Ryegrass In The Midsouth, Bhupesh K. Dhaka

LSU Master's Theses

Glyphosate-resistant (GR) Italian ryegrass (Lolium perenne ssp. multiflorum) has become an economically significant weed management challenge in Louisiana row crop production systems. The problem is further exacerbated by the occurrence of biotypes with resistance to acetyl-CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors—herbicide sites of action (SOAs) commonly used for ryegrass control in soybean (Glycine max) and cotton (Gossypium). Field, greenhouse, and laboratory experiments were conducted during the 2023–2024 and 2024–2025 growing seasons at the LSU AgCenter Northeast Research Station in St. Joseph, LA, and at the LSU AgCenter Weed Science facilities in Baton …

Understanding Glufosinate Resistance In Palmer Amaranth And Examination Of Additives For Improved Weed Control, Pamela Carvalho-Moore

Graduate Theses and Dissertations

The aim of this dissertation was to: 1) provide an in-depth review about the potential use of natural and synthetic glutathione S-transferase (GST) inhibitors to enhance herbicidal activity or induce crop safety; 2) determine if the addition of metabolic inhibitors to glufosinate is an effective approach to enhance weed control; 3) investigate the mechanism conferring resistance to glufosinate in a highly-resistant Palmer amaranth accession; 4) characterize the genomic rearrangement involved in glutamine synthetase 2 amplification in a Palmer amaranth accession resistant to both glufosinate and glyphosate; 5) quantify the distribution of glufosinate resistance among Palmer amaranth accessions within a 15-km …

Modeling U.S. Corn Production Archetypes In The Agricultural Policy/Environmental Extender Model To Generate Life Cycle Assessment Inventory Data, Brandon Taylor

Graduate Theses and Dissertations

Corn (Zea mays) is an important crop grown across the US for many uses such as grain for animal feed, bio-ethanol production, food products, and industrial products. Corn is produced in almost every state in the US, but most corn production is concentrated in the Corn Belt Region including Iowa, Illinois, Ohio, Indiana, Minnesota, and Nebraska. Although technologies and production practices are improving corn production efficiency primarily through increased yields (improved land use), corn production at this scale greatly impacts the environment through emissions from fertilizer and pesticide runoff and leaching, soil degradation due to improper field practices, as well …

Assessing Grafted Triploid Watermelon And Yellow Nutsedge Growth In Saline Agroecosystems, Joseph F. Bazzle

All Theses

In an effort to better understand how saltwater intrusion events will impact watermelon growers a field trial was conducted to study how saline irrigation water will impact weed growth and seedless watermelon productivity at a joint Clemson University and USDA ARS facility. Weed management has always been a hurdle in vegetable crop production systems, requiring extensive labor even in a conventional setup. For organic growers, often the only economical approach is a combination of mechanical weed control techniques, including plastic mulches, tarps, and hand weeding. For watermelon growers, plastic mulch remains the most effective form of organic weed control available. …

The Effects Of Incremental Application Of Chemical Defoliants On Cotton Fiber Quality, Aashish Karki

All Theses

Leaf shedding is a natural process as cotton matures; however, this does not synchronize with harvest timing; therefore, defoliants are used to remove these leaves and improve harvestability of the bolls. A tractor-mounted boom sprayer is typically used to apply defoliants. However, this approach results in low penetration to the bottom canopy, poor defoliation, and, consequently, lower fiber quality. An autonomous robotic spraying system equipped with pulse width modulation technology enables targeted side-spraying of defoliants, overcoming the limitations of conventional over-the-top applications. However, limited information on staggered defoliation timing and its effect on cotton fiber quality is available. Thus, field …

Heterogeneous Yield Effects Of Cover Crop Adoption In U.S. Corn And Soybean Systems, Ethan Kendall

Graduate Theses and Dissertations

Identifying the conditions where cover crops will succeed or fail is crucial for advancing conservation agriculture. Cover crops have been widely accepted as a conservation practice that can improve soil health and might improve or stabilize crop yields, though these benefits are not consistent across different regions. This study examines how heterogeneous factors can shape the effectiveness of cover crops on corn and soybean yields across the United States. Using the National Commodity Crop Productivity Index (Index) to measure soil productivity, this study examines how cover crop impacts vary across different levels of soil quality. A county level, 16- year …