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Iowa State University

Plant Sciences

Graduate Theses and Dissertations

Soil Science

Publication Year

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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 ...


Spatially Consistent Corn Yield Variability On The Loess Hills Of Northwest Iowa: A Critical Look, Thomas J. Lawler Jan 2016

Spatially Consistent Corn Yield Variability On The Loess Hills Of Northwest Iowa: A Critical Look, Thomas J. Lawler

Graduate Theses and Dissertations

In Iowa, precision agriculture technology continues to be embraced by the agricultural community and large volumes of data are continually being collected. One type of data collected is spatially dense georeferenced yield points that are converted into maps to show the magnitude and variability of corn yield. The first part of this thesis reports on the use of “Anselin Local Moran's I Cluster tool” to quantify spatial corn yield variability in the Loess Hills of Northwest Iowa and then validate the results using a residual method. A 32 hectare site with geo-referenced corn yield data collected from 2006-2013 was ...


Potassium And Sulfur Availability And Lime Potential Of Ash Co-Product Of Corn Cellulosic Ethanol Processing, Samuel Groenenboom Jan 2016

Potassium And Sulfur Availability And Lime Potential Of Ash Co-Product Of Corn Cellulosic Ethanol Processing, Samuel Groenenboom

Graduate Theses and Dissertations

Lignin-derived ash obtained as a co-product of corn residue used for ethanol production may have value as a soil amendment. Preliminary laboratory analyses indicated that the ash had potential lime value and higher concentrations of K and S compared with other nutrients. The value of the ash to supply K and S and to increase soil pH was evaluated at two Iowa sites compared with commonly applied sources of K (KCl) and S (gypsum) and pure CaCO3. At each site, three 2-year trials were initiated to assess the K, S, and lime values of the ash. Several rates of each ...


Validation And Application Of Close-Range Photogrammetry To Quantify Ephemeral Gully Erosion, Karl Richard Gesch Jan 2015

Validation And Application Of Close-Range Photogrammetry To Quantify Ephemeral Gully Erosion, Karl Richard Gesch

Graduate Theses and Dissertations

Agricultural soil erosion is a serious problem on farms because it contributes to crop yield declines and beyond farms because it is a source of sediment and chemical pollutants. Ephemeral gullies effectively convey runoff and connect agricultural uplands to off-site waters, so control of this phenomenon would benefit multiple societal sectors. Soil conservationists often employ predictive soil erosion models to develop conservation plans, but commonly used models cannot account for ephemeral gully erosion. Future models with the capability to simulate such concentrated flow erosion must be verified with field measurements. This work sought to quantify the measurement uncertainty of a ...


Corn Seedling Response To Silicon Amendments In Three Iowa And One Chinese Soil, Ziying Wang Jan 2015

Corn Seedling Response To Silicon Amendments In Three Iowa And One Chinese Soil, Ziying Wang

Graduate Theses and Dissertations

Silicon is an essential element in biological systems. It is required by mammals, plants, and microorganisms. It is well studied as a component of soil mineralogy, especially in the phyllosilicate (tetrahedron) structure. However, there remains a significant need to study more about how Si affects plant growth. This study seeks to address this need in a small way. Specifically this project evaluates the likely amount of Si in three Iowa soils and one Chinese soil, and whether Si influences early corn growth (seedlings) in a pot study. The soil series of interest in Iowa are Fayette, Harps and Ida. Seedlings ...


Winter Rye Cover Crop Effect On Corn Seedling Pathogens, Lara Ann Schenck Jan 2015

Winter Rye Cover Crop Effect On Corn Seedling Pathogens, Lara Ann Schenck

Graduate Theses and Dissertations

Cover crops are a valuable management tool to reduce soil and nutrient losses while retaining moisture, improving soil organic matter content, and stabilizing soil N during the winter months when the ground is normally left fallow. Cereal rye (Secale cereale L.) is commonly used as a winter cover crop in the Midwest due to its ability to withstand cold temperatures, reduce soil erosion, and scavenge soil N. However, it has been found that a cereal rye cover crop can sometimes reduce performance and yields in the following corn (Zea mays) crop. Past studies have suggested that reduced corn growth and ...


Plant Tissue Analysis To Assess Phosphorus And Potassium Nutritional Status Of Corn And Soybean In Iowa, Andrew John Stammer Jan 2015

Plant Tissue Analysis To Assess Phosphorus And Potassium Nutritional Status Of Corn And Soybean In Iowa, Andrew John Stammer

Graduate Theses and Dissertations

Interest in re-evaluating the value of tissue testing to assess P and K status in corn (Zea mays L.) and soybean (Glycine max L. Merr.) is increasing. The objective of this research was to study relationships between grain yield response to P and K and the concentration of these nutrients in plant tissue. Single-year and multi-year response trials were conducted in Iowa at 30 sites for P (32 sites-years with corn and 34 with soybean) and at 53 for K (67 sites years with corn and 52 with soybean) that encompassed 17 soil series. We sampled above-ground plant parts at ...


Nitrogen Mineralization In Biofuel Cropping Systems In Soils, Yili Meng Jan 2015

Nitrogen Mineralization In Biofuel Cropping Systems In Soils, Yili Meng

Graduate Theses and Dissertations

This thesis includes two studies. The first study compared the net N mineralization rate in soils of five cropping systems (corn-soybean rotation, continuous corn, continuous corn with a winter rye cover crop, perennial prairie, and N-fertilized perennial prairie) in Iowa. To consider the effect of plant residues and freezing-thawing on net N mineralization rate, treatments with and without plant residues and with or without freezing were established and followed through a 30-day aerobic incubation. The effect of chemical characteristics of soil samples and the plant residue samples of each cropping system on N mineralization were also investigated. Overall, the cropping ...


Pedology Of Corn Productivity Indices For Selected Parts Of Southern Highland Zone Of Tanzania, Johnson Godlove Mtama Jan 2015

Pedology Of Corn Productivity Indices For Selected Parts Of Southern Highland Zone Of Tanzania, Johnson Godlove Mtama

Graduate Theses and Dissertations

Scientific investigations to determine land use planning and interpretations for corn productivity potential in the Southern Highland Zone of Tanzania were conducted. The assessment of soils corn growth potential has been conducted in four selected pedons namely; Uyole, Mbimba, Inyala and Seatondale. Pedological, physical, chemical characterization and an attempt to develop the pedotransfer functions were done. The results show that the soils have deep to very deep sola, subangular blocky structures, evidence of pedogenic clay movement, fine to coarse texture, bulk density ranged from 0.79 to 1.46 g/cm3, pH ranged from slightly acidic to slightly alkaline, cation ...


Biochar Properties And Impact On Soil Co2 And N2o Emissions, Rivka Brandt Fidel Jan 2015

Biochar Properties And Impact On Soil Co2 And N2o Emissions, Rivka Brandt Fidel

Graduate Theses and Dissertations

Biochar application to soil has been proposed as a means to sequester carbon and mitigate anthropogenic greenhouse gas (GHG) emissions. However, biochar directly influences soil GHG emissions in a complex-interactive manner that remains poorly understood, and hence further understanding of biochar-soil interactions is needed to evaluate biochar’s efficacy as a tool for greenhouse gas mitigation. The goals of this dissertation are to (1) quantify the organic and inorganic alkalis of several biochars, (2) quantify the impact of biochar properties on GHG emissions from diverse soils, and (3) identify mechanisms by which biochar properties influence GHG emissions from soils. To ...


Corn Production With Instinct Nitrification Inhibitor Applied With Urea-Ammonium Nitrate Solution And Liquid Swine Manure, Aaron Michael Sassman Jan 2014

Corn Production With Instinct Nitrification Inhibitor Applied With Urea-Ammonium Nitrate Solution And Liquid Swine Manure, Aaron Michael Sassman

Graduate Theses and Dissertations

Improving N use efficiency of applied N by corn (Zea mays L.), in order to minimize N losses from agricultural fields, is of concern to both producers and environmentalists. Use of nitrification inhibitors is thought to slow the conversion of applied NH4 to NO3, which would reduce N losses from the soil while increasing corn plant N uptake. This thesis includes two, small plot field studies designed to evaluate the effect Instinct (Dow AgroSciences, Indianapolis, IN) nitrification inhibitor had on corn production. The first study evaluated the effect of Instinct spring preplant applied with urea-ammonium nitrate (UAN) solution on corn ...


A Carbon Assessment Of Iowa State University's Land, Catherine Rosson Delong Jan 2014

A Carbon Assessment Of Iowa State University's Land, Catherine Rosson Delong

Graduate Theses and Dissertations

In 1862, Iowa State University was the first college to become a land-grant university. Today, their mission has expanded beyond the Iowa farmer to the global farmer and more broadly the agricultural world. As part of this global perspective, Iowa State University has chosen to be the first US university to evaluate itself in an environmental context through a carbon assessment of its soils. The carbon content of Iowa State's 6,392 hectares was evaluated to an 18 and 100 cm depth using two databases. The carbon flux of Iowa State University's land, given a change in management ...