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Iowa State University

Plant Sciences

Graduate Theses and Dissertations

Nitrogen

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A Statistical Analysis Of Zea Mays Grain Yield Response To Nitrification-Inhibitor Amendments Under Field Conditions Utilizing Parametric And Non-Parametric Techniques, Elliot H. Sully Jan 2019

A Statistical Analysis Of Zea Mays Grain Yield Response To Nitrification-Inhibitor Amendments Under Field Conditions Utilizing Parametric And Non-Parametric Techniques, Elliot H. Sully

Graduate Theses and Dissertations

Nitrification is a matter of economic and ecological importance in nitrogen-tensive agricultural practices such as corn (Zea mays) grain production. When ammonium is bacterially oxidized into nitrate it becomes more susceptible to leaching and denitrification as nitrous oxide. The nitrification process not only adds to water and air pollution but also impacts on farm productivity by reducing grains yields and increasing fertilizer demands. Nitrification inhibiting fertilizer amendments can potentially improve grain yields by retarding the growth of nitrifying soil bacteria. Multiple field studies conducted across various locations and timespans have generated mixed results regarding the grain yield difference attributed to ...


Drivers Of Yield And Nitrogen-Loss Tradeoffs: Cropping System Evaluations With Process-Based Modeling, Rafael Alejandro Martinez-Feria Jan 2018

Drivers Of Yield And Nitrogen-Loss Tradeoffs: Cropping System Evaluations With Process-Based Modeling, Rafael Alejandro Martinez-Feria

Graduate Theses and Dissertations

The Midwest is one of the most productive agricultural regions, but mitigating loss of nitrogen (N) from cropland is needed to improve environmental quality. Tradeoffs between crop yield and N loss have been linked largely to the inefficient use of N fertilizers, but the contributions of more systemic factors such as soil characteristics, crop sequences, and genotypes have not been thoroughly studied. This dissertation examines and quantifies the impact of various genetic, environmental and management drivers of crop yield and N-loss tradeoffs in the maize and soybean cropping systems of the US Midwest, and identifies potential management strategies to lessen ...


Nitrogen Pools And Fluxes In Diversified Cropping Systems, William Robert Osterholz Jan 2016

Nitrogen Pools And Fluxes In Diversified Cropping Systems, William Robert Osterholz

Graduate Theses and Dissertations

Achieving high crop yields requires a large supply of plant available nitrogen (N), yet losses of inorganic N from agriculture are deleterious to environmental quality. A significant portion of agricultural N losses could be prevented if large soil inorganic N pools were not needed to satisfy crop N demand. Alternative N management strategies that consider N fluxes like gross N mineralization in addition to N pools should be investigated, as they could conceivably reduce the size of soil inorganic N pools while still providing sufficient N for crop production. Diversified cropping systems may be able to utilize such alternative N ...


Cover Crop Options And Mixes For Upper Midwest Corn-Soybean Systems, Seth R. Appelgate Jan 2016

Cover Crop Options And Mixes For Upper Midwest Corn-Soybean Systems, Seth R. Appelgate

Graduate Theses and Dissertations

The implementation of cover crops in Iowa has the potential to decrease soil erosion, weed density, and nitrate leaching while increasing soil organic carbon. This study investigated nine potential cover crops; winter rye (Secale cereale L.), winter triticale (Triticale hexaploide Lart.), two winter canola (Brassica napus L.) varieties, winter camelina [Camelina sativa (L.) Crantz], spring barley (Hordeum vulgare L.), spring oat (Avena sativa L.), purple top turnip (Brassica rapa L.), and hairy vetch (Vicia villosa Roth). Cover crops were planted as sole crops and selected binary and trinary mixtures. A control treatment of no cover crop was included. Cover crops ...


Integration Of Summer And Fall Cover Crops In Vegetable Cropping Systems, Raymond Albert Kruse Jan 2015

Integration Of Summer And Fall Cover Crops In Vegetable Cropping Systems, Raymond Albert Kruse

Graduate Theses and Dissertations

The demand for locally produced vegetables is growing in the Midwest, including Iowa. However, since vegetables are a small fraction of total cropland in the state, little research exists on approaches and techniques to increase the sustainability of vegetable production systems. Including cover crops in vegetable crop rotations can contribute to sustainability in vegetable cropping systems. This research investigated the integration of summer and fall cover crops in vegetable cropping systems to reduce weeds and nutrient leaching, improve soil chemical and biological properties, and enhance crop growth, yield, and produce quality. Cover crops studied in this research included buckwheat (Fagopyrum ...


Identification Of Qtl Associated With Nitrogen Metabolism In A Maize (Zea Mays L. Ssp. Mays) Testcross Population, Ignacio Trucillo Silva Jan 2015

Identification Of Qtl Associated With Nitrogen Metabolism In A Maize (Zea Mays L. Ssp. Mays) Testcross Population, Ignacio Trucillo Silva

Graduate Theses and Dissertations

Maize is a widely cultivated crop in the world and its production relies heavily on nitrogen (N) fertilization. N is an essential mineral nutrient for plant growth and development. However, during the last decades excessive quantities of N have been applied by farmers, a surplus to what maize plants can uptake, and several problems have arisen, such as pollution of the ecosystem and an economic loss to farmers. Breeding maize hybrids that are more efficient in the use of N is a long term goal for plant breeders. Nonetheless, previous to breeding, the genetic basis of N-metabolism in maize would ...


Biosynthetically Produced Amino Acid Byproducts Can Replace Nitrogen Fertilizers For Corn Production, Juan Carlos Quezada Rivera Jan 2015

Biosynthetically Produced Amino Acid Byproducts Can Replace Nitrogen Fertilizers For Corn Production, Juan Carlos Quezada Rivera

Graduate Theses and Dissertations

Commercial biosynthesis of the amino acids tryptophan (TRP) and lysine (LYS) results in byproducts that are rich in both organic and inorganic compounds. Their nitrogen (N) content may have value as fertilizer N replacement in corn (Zea mays L.) production. We conducted a two-year field study where soil applied pure TRP, its biosynthesis byproduct and LYS byproduct were evaluated as replacements for synthetic N fertilizers in corn production. In-season plant measurements leaf area index , normalized difference vegetation index, grain quality (grain protein and oil concentration) and total N accumulation were not affected by N treatments. Additionally, TRP and LYS biosynthesis ...


Genetic Analysis Of The Ibm2syn10-Dh Maize Population For Response To Low And High Nitrogen Input, Pedro José Gonzalez-Portilla Jan 2014

Genetic Analysis Of The Ibm2syn10-Dh Maize Population For Response To Low And High Nitrogen Input, Pedro José Gonzalez-Portilla

Graduate Theses and Dissertations

Maize growth and development depends highly in the capacity of the plants to absorb Nitrogen (N) from the soil. Producing a high-yielding maize crop that requires less N input is currently one important goal of maize breeding programs. In order to understand the dynamics of N use in maize, the study of phenotypic and genetic response to N deficiency must be performed. Using lines from the high resolution IBM2Syn10-DH population, the goals of this study were: 1) to identify the phenotypic response of the root system architecture (RSA) of 14-day old maize seedlings grown under contrasting levels of N; 2 ...


Utilization Of Active Canopy Sensors For Nitrogen Fertilizer Management In Corn, Daniel W. Barker Jan 2011

Utilization Of Active Canopy Sensors For Nitrogen Fertilizer Management In Corn, Daniel W. Barker

Graduate Theses and Dissertations

The purpose of this research project was to provide much needed information for the development of active canopy sensors as a N fertilizer management decision tool in corn production. Active sensors can be used as an information source regarding plant N status and, can be calibrated to help adjust in-season N applications when corn N deficiencies exist. The adoption of precision farming technology, such as active sensors, is growing in Iowa and much of the U.S. Corn Belt. This Ph.D. dissertation is presented as a series of five chapters. The first chapter is an overview of the dissertation ...


Native Warm-Season Grasses: Species, Nitrogen Fertilization, And Harvest Date Effects On Biomass Yield And Composition, Naroon Waramit Jan 2010

Native Warm-Season Grasses: Species, Nitrogen Fertilization, And Harvest Date Effects On Biomass Yield And Composition, Naroon Waramit

Graduate Theses and Dissertations

For traditional forage use, native warm-season grasses are highly productive in the summer months and are suited for a complementary role with cool-season forages in full-season forage systems of the Midwest. For renewable energy sources, these grasses can be used to produce biofuels, an alternative energy source in the future for fossil fuel which is becoming less available. Farmers may integrate forage and biomass cropping for flexibility and diversity in their farming systems. For dual-purpose crops (forage or biomass), the production of warm-season grasses would provide farmers some protection against the market failure of a single purpose. The goals for ...


Horticultural Evaluation Of Zein-Based Bioplastic Containers, Matthew Steven Helgeson Jan 2009

Horticultural Evaluation Of Zein-Based Bioplastic Containers, Matthew Steven Helgeson

Graduate Theses and Dissertations

Environmental problems caused by petroleum-based plastics have led to interest in alternatives made from biodegradable polymers (bioplastics), but little effort has been made to evaluate horticultural containers made from these materials. Containers were fabricated from polymers of the corn (Zea mays L.) protein, zein. My first objective was to determine the longevity of zein-based containers under conditions typical of horticultural production. Zein containers of two wall thicknesses were filled with either a peat-based, soilless potting substrate or coarse perlite, and they were irrigated every 2 or 4 days. After 10 weeks, weight loss of containers was determined as a measure ...