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Understanding Cold Acclimation In Medicago Truncatula, Babita Thapa Jan 2008

Understanding Cold Acclimation In Medicago Truncatula, Babita Thapa

Graduate Theses and Dissertations

Medicago truncatula is a close annual relative to alfalfa. Understanding cold acclimation (CA) is important for concurrently increasing autumn yield and winter survival in alfalfa. Such investigations are difficult because of its complex genetic makeup, and outcrossing with inbreeding depression. This study was conducted to understand CA in M. truncatula for determining if it could be used as a model to help dissect the genetic control of autumn yield and cold tolerance in alfalfa. Although M. truncatula has less agronomic value than alfalfa, its small genome and short generation time makes it useful as a model crop for legume genomics ...


The Effect Of Bio-Char On Soil Properties And Corn Grain Yields In Iowa, Rachel Colleen Unger Jan 2008

The Effect Of Bio-Char On Soil Properties And Corn Grain Yields In Iowa, Rachel Colleen Unger

Graduate Theses and Dissertations

An incubation study was conducted to study the effect of three different types or "qualities" of nitrogen-enriched bio-char on total nitrogen (N), extractable phosphorus (P), extractable potassium (K), nitrate-N, ammonium-N, pH, SOM, and total organic carbon (C) in two soils. The different "qualities" represent the bio-char created with three different amounts of atmospheric air (0, 10, and 25%) present in the pyrolysis reactor when the bio-char was created. A field study was conducted to study the effect of N-enriched bio-char on corn grain yields, biomass yields, and soil ammonium (NH44+-N) and soil nitrate (NO3--N) concentrations. The ...


Biotic And Abiotic Factors Associated With Fusarium Ear Rot Of Maize Caused By Fusarium Verticillioides, Michael Wayne Parsons Jan 2008

Biotic And Abiotic Factors Associated With Fusarium Ear Rot Of Maize Caused By Fusarium Verticillioides, Michael Wayne Parsons

Graduate Theses and Dissertations

Fusarium ear rot, caused by Fusarium verticillioides, is one of the most common worldwide diseases of maize, causing yield and quality reductions as well as contamination of grain by fumonisins and other mycotoxins. Drought stress and various insects have been implicated as factors affecting disease severity. Three separate field studies were conducted during 2002 and 2003.

The first field study was conducted in Woodland, CA during 2002 and 2003, to evaluate the relative influence of 1) drought stress at different stages of crop development, and 2) ear infestation by two species of insects, upon severity of Fusarium ear rot disease ...


Productivity And Nutrient Cycling In Bioenergy Cropping Systems, Andrew Howard Heggenstaller Jan 2008

Productivity And Nutrient Cycling In Bioenergy Cropping Systems, Andrew Howard Heggenstaller

Graduate Theses and Dissertations

One of the greatest obstacles confronting large-scale biomass production for energy applications is the development of cropping systems that balance the need for increased productive capacity with the maintenance of other critical ecosystem functions including nutrient cycling and retention. To address questions of productivity and nutrient dynamics in bioenergy cropping systems, we conducted two sets of field experiments during 2005-2007, investigating annual and perennial cropping systems designed to generate biomass energy feedstocks. In the first experiment we evaluated productivity and crop and soil nutrient dynamics in three prototypical bioenergy double-crop systems, and in a conventionally managed sole-crop corn system. Double-cropping ...


Effects Of Landscape Position And Age Of Reconstructed Prairies In Previously Cultivated Land On Soil Carbon Dynamics And Physical Properties, Jose German Guzman Jan 2008

Effects Of Landscape Position And Age Of Reconstructed Prairies In Previously Cultivated Land On Soil Carbon Dynamics And Physical Properties, Jose German Guzman

Graduate Theses and Dissertations

In recent years, conversion of crop and marginal land to reconstructed prairie has been gaining momentum, due to the prairies' aesthetic and environmental values. However, little attention has been given to the belowground biogeochemical processes, which have potential to reduce soil erosion, and sequester significant amounts of atmospheric CO2 in the soil. The general objectives of this study were to determine the effects of years since establishment and slope position on soil C dynamics of reconstructed prairies by (1) quantifying changes in soil organic carbon (SOC) and soil total nitrogen (TN) stocks, (2) establishing whether a site is a sink ...


Genetic Analysis Of Ear Development And Tassel Architecture In Maize (Zea Mays L. Ssp. Mays), Maria Laura Mayor Jan 2008

Genetic Analysis Of Ear Development And Tassel Architecture In Maize (Zea Mays L. Ssp. Mays), Maria Laura Mayor

Graduate Theses and Dissertations

Yield potential of maize (Zea mays L.) has been increased significantly during the last century. Along with genetic gains for grain yield, changes in other traits have included an increase in the number of ears per plant (i.e. fewer barren plants) and a reduction in tassel size. The objectives of this study were 1) to identify Quantitative Trait Loci (QTL) associated with number of ears per plant (EPP), growing degree units to anthesis (GDU), plant height (PH) and tassel architectural traits, and 2) to evaluate the consistency of the QTL across environments. A population of 218 recombinant inbred lines ...


Investigation Of Management Strategies For The Production Of Sweet Sorghum As A Bioenergy Crop And Preservation Of Crop Residue By The Ensiling Process, Todd Joseph Cogdill Jan 2008

Investigation Of Management Strategies For The Production Of Sweet Sorghum As A Bioenergy Crop And Preservation Of Crop Residue By The Ensiling Process, Todd Joseph Cogdill

Graduate Theses and Dissertations

The objective of this project was to investigate management practices for sweet sorghum as a bioenergy crop in Iowa and its storability as an ensiled product. A management study was conducted to evaluate the effects of planting date, seeding rate, row width, and nitrogen fertility on the growth, biomass yield, and chemical composition of sweet sorghum. In addition, a silage study was conducted to determine chemical composition and fermentation potential of pressed sweet sorghum residue as well as the effects of enzymatic pretreatments.


Soil And Fertilizer Potassium Impacts On Corn And Soybean Grain Yield, Potassium Uptake, And Within-Field Grain Yield Variation, Matthew William Clover Jan 2008

Soil And Fertilizer Potassium Impacts On Corn And Soybean Grain Yield, Potassium Uptake, And Within-Field Grain Yield Variation, Matthew William Clover

Graduate Theses and Dissertations

Two studies were conducted in Iowa to better understand how potassium (K) fertilization affects grain yield, vegetative growth, and K concentration of different parts of modern corn (Zea mays L.) hybrids and soybean (Glycine max L. Merr.) varieties. One study was based on one- to three-year strip-trials (63 site-years) conducted from 2001 to 2007 to evaluate the effects of K fertilization on corn and soybean grain yield and post-harvest soil-test K (STK) measured with the ammonium acetate extractant. Replicated treatments were 0 and 168 kg K ha-1. Potassium increased yield as evaluated by strip averages in 21 of 63 ...


Bean Pod Mottle Virus: Spatial And Temporal Dynamics At Different Spatial Scales And The Impact Of Time Of Infection On Soybean Yield And Quality, Emmanuel Byamukama Jan 2008

Bean Pod Mottle Virus: Spatial And Temporal Dynamics At Different Spatial Scales And The Impact Of Time Of Infection On Soybean Yield And Quality, Emmanuel Byamukama

Graduate Theses and Dissertations

A comprehensive state-wide soybean disease survey was carried out during the 2005- 2007 growing seasons to determine seasonal and geospatial patterns of soybean diseases in Iowa. Bean pod mottle virus (BPMV) was one of the viruses assessed in the survey. To quantify BPMV prevalence and incidence at the field and county scales, 30 soybean plants per field were sampled from 8-20 soybean fields/county using a systematic sampling design. The GPS coordinates for each soybean field sampled were recorded. Soybean plants were tested for the presence of BPMV using enzyme linked immunosorbent assay (ELISA). Field- and county-scale BPMV prevalence and ...


Overwinter Survival Of Sclerotium Rolfsii And S. Rolfsii Var. Delphinii, Screening Hosta For Resistance To S. Rolfsii Var. Delphinii, And Phylogenetic Relationships Among Sclerotium Species, Zhihan Xu Jan 2008

Overwinter Survival Of Sclerotium Rolfsii And S. Rolfsii Var. Delphinii, Screening Hosta For Resistance To S. Rolfsii Var. Delphinii, And Phylogenetic Relationships Among Sclerotium Species, Zhihan Xu

Graduate Theses and Dissertations

In this study, three aspects of plant-pathogenic Sclerotium fungi were investigated: overwinter survival of Sclerotium rolfsii and S. rolfsii var. delphinii; development of a rapid method for detecting resistance of hosta cultivars to petiole rot disease; and clarification of phylogenetic relationship among pathogenic Sclerotium species. To test the hypothesis that differential tolerance to climate extremes affects the geographic distribution of S. rolfsii and S. rolfsii var. delphinii, overwinter survival of these fungi was investigated in the northern and southeastern U.S. At each of four locations, nylon screen bags containing sclerotia were placed on the soil surface and buried at ...


Long-Term Rotation With Monoculture Cover Crops Increases Yield Of Strawberry, Reduces Weed Populations, And Maintains Soil Chemical, Physical, And Biological Characteristics During Strawberry Production, Dennis Nicklas Portz Jan 2008

Long-Term Rotation With Monoculture Cover Crops Increases Yield Of Strawberry, Reduces Weed Populations, And Maintains Soil Chemical, Physical, And Biological Characteristics During Strawberry Production, Dennis Nicklas Portz

Graduate Theses and Dissertations

Proliferation of weed seeds and pathogenic organisms in the soil can cause a decline of yield of strawberry grown continuously on the same site. Rotations with cover crops or tillage have been found to mitigate this problem, but data are needed on the relative effectiveness of various potential rotations. Conventional management of weeds and soil pathogens in strawberry can cause detrimental effects to the chemical, physical, and biological components of the soil and subsequently reduces plant vigor. Previous research suggests that rotating cover crops with strawberry reduces weeds and soil pathogens and maintains the chemical, physical and biological components of ...


Freezing Tolerance And Cold Acclimation In Guava (Psidium Guajava L.), Wei Hao Jan 2008

Freezing Tolerance And Cold Acclimation In Guava (Psidium Guajava L.), Wei Hao

Graduate Theses and Dissertations

Guava (Psidium guajava L.) is a tropical, woody perennial with nutritious fruit. It exceeds most tropical and subtropical fruit plants in adaptability and productivity. This thesis focused on the physiology of freezing tolerance and cold acclimation in guava. Freezing tolerance tests, growth and leaf relative water content measurements, anthocyanin content analyses, and protein analyses were performed on nonacclimated and cold-acclimated leaves of guava cultivars Lucknow-49 and Ruby y Supreme. The freezing tolerance of nonacclimated leaves were -2.3 yC and 2.7 yC, and enhanced to -4.2 yC and -4.6 yC after cold acclimation for `Lucknow-49' and `Ruby ...


Perceptions Of Managers And Spanish-Speaking Employees In The Iowa Horticultural Industry, Emilie Justen Jan 2008

Perceptions Of Managers And Spanish-Speaking Employees In The Iowa Horticultural Industry, Emilie Justen

Graduate Theses and Dissertations

Labor intensive tasks, seasonal positions, low wages, and a decreasing supply of domestic labor have contributed to Iowa horticultural firms hiring foreign-born workers. The majority of these workers are Spanish-speaking Latinos who arrived to the United States from Mexico and other parts of Latin America and find jobs in golf course maintenance, landscape installation, and nursery production. Addressing the educational and other employment needs of both Latino workers and their managers was anticipated to improve working conditions, job satisfaction, and productivity of both employees and the companies that hired Latino workers. This study assessed educational needs, communication gaps and technical ...