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Grazing Strategy Effects On Utilization, Animal Performance, Aboveground Production, Species Composition, And Soil Properties On Nebraska Sandhills Meadow, Aaron Shropshire

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

Ultrahigh stocking density (a.k.a., mob grazing) is proposed as a management tool that results in greater harvest efficiency, animal performance, aboveground plant production, species richness, and soil carbon content. The study objective was to determine grazing treatment, haying, or non-defoliated control effects on forage utilization, aboveground production, animal performance, and soil properties. In 2010, 25 ha of Sandhills meadow were divided into 2 replications of 3 grazing, a hay, and control treatment. Grazing treatments were a 120-pasture rotation with one grazing cycle (mob), a 4-pasture rotation with one cycle (4PR1), and a 4-pasture rotation with two cycles (4PR2) at stocking …

Understanding Spatial Dynamics Of Tallgrass Prairie Dominated By Tall Fescue, Callie Griffith

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

This study was conducted on restored tallgrass prairie and invaded tallgrass prairie located in the Grand River Grasslands of southern Iowa to determine differences in heterogeneity of plant structure and functional group composition at different scales. Restored tallgrass prairies were seeded with a species-rich seeding mixture and managed by burning the entire prairie, every three years. Data were collected in August 2014 and 2015 to compare heterogeneity of restoration of native plant structure and functional group composition to the heterogeneity of invaded tallgrass prairies that were managed with patch burning and conventionally grazed. Invaded tallgrass prairies were managed with patch-burning …

Generation And Evaluation Of Modified Opaque-2 (O2) Popcorn Suggests A Route To Quality Protein Popcorn (Qpp), Ying Ren

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

I have been working on a Quality Protein Popcorn breeding project where QPM conversion is carried out simultaneously for several elite popcorn germplasms. During my study in the graduate program, I led the following aspects of the Quality Protein Popcorn Breeding Project:

1. Identified suitable QPMs as opaque-2 allele donors.

2.Examined the feasibility of quick introgression of the opaque-2 allele into popcorn lines via marker-assisted selection.

3. Monitored modification by SDS-PAGE zein profiling and light box phenotypic selection to make sure multiple modifier loci for opaque-2 were incorporated each time generation advancement was carried out.

4. Carried out high throughput …

Epidemiology And Management Of Fusarium Head Blight And Foliar Fungal Diseases Of Wheat, Carlos Bolanos-Carriel

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

Fusarium head blight (FHB) caused by Fusarium graminearum, the FHB-associated mycotoxin deoxynivalenol (DON), and foliar fungal diseases are significant threats to wheat production. This research 1) evaluated the effects of fungicide chemical class, application timing, and cultivar resistance on FHB and DON under field conditions; 2) evaluated the effects of field-applied fungicide chemical class, grain moisture, and time on DON under grain storage conditions; 3) evaluated the effects of field-applied fungicide chemical class and time on trichothecene-related gene (Tri5) expression under grain storage conditions; 4) determined the optimum F. graminearum spore concentration and spike bagging period following …

Identification Of Genes/Genomic Regions Controlling Resistance To Biotic And Abiotic Stresses In Synthetic Hexaploid Wheat, Madhav Bhatta

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

Synthetic hexaploid wheat (SHW; 2n=6x=42, AABBDD, Triticum aestivumL.) is produced from an interspecific cross between durum wheat (2n=4x=28, AABB, T. turgidumL.) and goat grass (2n=2x=14, DD, AegilopstauschiiCoss.). It is reported to have a considerable amount of genetic diversity and is a potential source of novel alleles controlling abiotic and biotic stresses resistance and improving wheat quality. Therefore, the first study was to understand the genetic diversity and population structure of SHWs and compare the genetic diversity of SHWs with elite bread wheat (BW) cultivars. The result of this study identified a wide range of genetic diversity within …

Investigation Of Alternative Hosts And Agronomic Factors Affecting Xanthomonas Vasicola Pv. Vasculorum, Causal Agent Of Bacterial Leaf Streak Of Corn, Terra Marie Hartman

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

Xanthomonas vasicola pv. vasculorum, causal agent of bacterial leaf streak of corn, was first reported in the U.S. in 2016 on Nebraska corn leaf samples. Prior to this report, the pathogen had only been reported on corn in South Africa. After the Nebraska report, the pathogen was reported on corn in Argentina, Brazil, and several U.S. states. This pathogen has an extensive host range, which includes sugarcane (Saccharum officinarum), grain sorghum (Sorghum bicolor), palm species (Dictyosperma album, Roystonea regia, and Areca catechu) and broom bamboo (Thysanolaena maxima). Plants commonly found in …

Biological Activity Of A Tertiary Amine Plant Growth Regulator, Bmve, In Arabidopsis Thaliana And Wheat (Triticum Aestivum), Jaspinder Singh

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

Plant growth regulators are synthetic compounds that influence plant growth and development and can increase growth, yield, and nutritive value of food crops. Research in the past has shown that a class of plant growth regulators known collectively as substituted tertiary amines have the potential to increase crop productivity, photosynthetic efficiency, and overall plant vigor. However, earlier efficacy studies that involved spraying plants were sometimes inconsistent or showed only minimal benefits. A new delivery method involving seed application of tertiary amines before sowing has shown promise in field trials for multiple crop species (US patent 9464283) (Yokoyama, Chan, Oyama, & …

Canavalia Gladiata And Dolichos Lablab Extracts For Sustainable Pest Biocontrol And Plant Nutrition Improvement In El Salvador, Carlos Martinez

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

Botanical repellents and pesticides are now being rediscovered as new tools for integrated pest management in order to reduce the use of toxic chemicals in crop production. Canavalia gladiata and Dolichos lablab are two Fabaceae very well adapted to farmlands of El Salvador, effective as living barriers and mostly as cover crops, however, they are not yet very well disseminated. This document describes the potential for using the liquid extracts and the dry flour of raw seeds of those plants for economic benefit and practical convenience for pest management in Salvadorian agriculture under field conditions. Seed extracts were useful when …

The Effect Of Physical Application Parameters On Herbicide Efficacy And Droplet Size., Andre De Oliveira Rodrigues

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

One of the largest challenges in agriculture is weed management. Improper or sub-optimal application techniques can cause decreased weed control and increased environmental contamination. Effective weed management is highly correlated with the product and the application method. Herbicide performance are affected by environmental conditions; they influence the physiology and growth of a plant and as well the herbicide performance. Among all environmental factors, rain shortly after herbicide application is one of the most harmful issues to the performance of the herbicide. Droplet size is a key factor in pesticide applications in regards to both drift and efficacy. Droplet size can …

The Effects Of Fungicide And Genetics On Fungal Diseases On Wheat In Nebraska With Emphasis On Stem Rust, Javed Sidiqi

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

Foliar fungal diseases of wheat (Triticum aestivum L.) pose a serious threat to wheat production. Despite the significant progress that has been made limiting major fungal diseases by developing resistant cultivars, these diseases challenge the economic sustainability of wheat production. The objectives of this research were (1) To determine the effect of fungal plant pathogens on grain yield in eastern NE, released and pre-release winter wheat genotypes were studied in fungicide treated and untreated plots from 2015 to 2017. (2) To determine if Sr7b is present using allelism tests in ‘Gage’ wheat as previously hypothesized.

Sixty genotypes were planted …

Evaluation Of Bacillus Strains For Plant Growth-Promotion Potentials On Corn (Zea Mays), Wheat (Triticum Aestivum), And Soybean (Glycine Max)., Rufus John Akinrinlola

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

Plant growth-promoting rhizobacteria (PGPR) can increase plant growth and yield by facilitating nutrient availability, hormone production, and inhibiting plant deleterious microorganisms. Twelve strains of bacillus (endospore-forming bacteria belonging to the genera Bacillus, Paenibacillus and Lysinibacillus) isolated from wheat rhizospheres were assessed for plant-growth promotion attributes in greenhouse and laboratory experiments. The objectives were to assess each strain’s potential to promote growth in corn, wheat, and soybean; and to determine whether the physiological traits expressed in vitro by the strains related to their effectiveness in promoting plant growth. Greenhouse experiments to assess growth-promotion potential were conducted by applying the strains …

Replacing Herbicides With Groundcovers To Enhance Vineyard Sustainability, Benjamin A. Loseke

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

In many Midwestern vineyards a three to four-foot weed-free strip is maintained directly beneath the vines to reduce vine-weed competition. Conventionally, this strip has been conserved with repeated applications of herbicide, mainly glyphosate. The necessity for this weed-free strip to reduce vine-weed competition has been well documented in more arid climates. However, in areas with higher soil fertility and adequate rainfall, this strip may be unnecessary. Moreover, stand establishment and early vine growth have not been well documented when planting groundcovers (GC) immediately following the vine planting. The main objective of this project is to assess the severity of competition …

Influence Of Multispecies Interference Of Common Ragweed (Ambrosia Artemisiifolia L.) And Common Waterhemp (Amaranthus Rudis Sauer) On Soybean [Glycine Max (L.) Merr.] Growth And Yield Under Variable Water Supply In Nebraska, Koffi Badou Jeremie Kouame

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

Common ragweed (Ambrosia artemisiifolia L.) and common waterhemp (Amaranthus rudis Sauer) are two problematic weeds for soybean producers in the United States. Both weeds have evolved resistance to many herbicides, including glyphosate. It is therefore essential to understand how these weeds in mixture impact soybean growth and yield and also how they deplete soil moisture in rainfed and irrigated cropping systems. The objectives of this research were to: (i) understand the influence of variable water supply on soybean yield loss in mixture with ragweed and waterhemp, (ii) quantify the influence of variable water supply on soybean growth in …

Exploration Of Soybean Nodule Microbiome For Plant Health Management, Serkan Tokgöz

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

Root nodule is a unique environment formed in the legume roots through a highly specific symbiotic relationship between leguminous plants and nodule inducing bacteria. Over the years, Rhizobia have been thought as the only group of bacteria residing within the nodules. However, this consideration has been recently changed with the discovery of other groups of bacteria besides Rhizobia within the legume nodules. In an effort to identify beneficial bacteria for plant disease control and growth promotion, soybean nodules were studied as the source of nodule-associated bacteria. Metagenomics analysis of a single soybean nodule was conducted to determine the bacterial diversity …

The Use Of Grape By-Products As A Nutrient Rich Cattle Feed, Zachary Christman

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

In this article you will learn about how to use the grape stems, skins and pulp that are generated by the wine industry. Ruminant animals such as cattle can digest this inexpensive yet nutrient rich material. The complete process from wine press to cattle feed is covered in this article. The historical background of using grape by-products and methods to preserve this food source is also presented.

Breeding For Resistance In California Strawberry To Verticillium Dahliae, Zachary Christman

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

This article focuses on breeding resistant strawberries to the fungus Verticillium dahliae, common name Verticillium wilt. This is a serious fungal disease that can result in a loss of 50% or more of a strawberry harvest when grown in infested soil. The main goal is to provide an example of how a cultivar can be made more resistant to a plant pathogen with the use of plant breeding methods.

Since 1930 the University of California, Davis, has been developing strawberry cultivars that are adapted to the agricultural industry and regional farms. Developing cultivars that require fewer inputs are of …

Integrating Management Zones And Canopy Sensing To Improve Nitrogen Recommendation Algorithms, Joel D. Crowther

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

Fertilizer nitrogen use efficiency (NUE) in maize (Zea mays L.) production is historically inefficient, presenting significant environmental and economic challenges. Low NUE can be attributed to poor synchrony between soil N supply and crop demand, applying uniform rates of N fertilizer to spatially variable landscapes, and failure to account for temporal variability in crop response to N. Innovative N management strategies, including crop canopy sensing and management zones (MZ), are tools that have proven useful in increasing NUE. Several researchers have proposed that the integration of these two approaches may result in further improvements in NUE and in profitability …

Plant Community Response To Disturbances In Nebraska Sandhills Upland Prairie, Josiah D. Dallmann

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

Historically, disturbances shaped prairie ecosystems both directly through events like fire and soil moving by animals, as well as indirectly through dynamic rainfall patterns and periodic flux in seed availabilities. We hypothesized that the implementation of several distinct disturbance events in Nebraska Sandhills upland prairie would have measurable effects on plant community composition. We implemented mid-spring fire, soil disturbance in the form of disking, seed addition of native forbs on disked plots, as well as early summer supplemental watering (to mimic minor rainfall events during abnormally dry periods) during 2016 and 2017. Plant community response during the first and second …