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Articles 1 - 10 of 10
Full-Text Articles in Physical Sciences and Mathematics
Growth Of Methanogens In The Presence Of Perchlorate Salts: A Study For Possible Life On Mars, John Cale
Growth Of Methanogens In The Presence Of Perchlorate Salts: A Study For Possible Life On Mars, John Cale
Biological Sciences Undergraduate Honors Theses
The Phoenix Lander collected soil samples from Mars, and it detected perchlorate salts in its analysis [1]. As oxidizing agents, perchlorates pose a threat to the hypothesis that there may be microbial life on Mars. Since Mars is very dry, perchlorate may continue to accumulate in the soil. If anaerobic methanogens inhabit Mars, then they must be able to grow in the presence of perchlorate salts. There were four species of methanogens tested in this project. The methanogens were first exposed to small concentrations of calcium perchlorate, and then they were gradually tested at higher concentrations. Growth was measured by …
Examining Denitrification In Agricultural Ditch Sediments Vegetated With Rice Cutgrass (Leersia Oryzoides): Modeling Seasonal Variation Across Increasing Levels Of Nitrate Loading And Model Application To Pre-Existing Datasets, Shannon Lee Speir
Graduate Theses and Dissertations
Nitrogen (N) derived from fertilizer application in agricultural systems may contribute to significant environmental impacts, including eutrophication of fresh and coastal waters. Rice cutgrass (Leersia oryzoides) can significantly enhance denitrification potential in agricultural ditch sediments, but relationships with known drivers are not well understood. To address this, I examined effects of nitrate (NO3-) availability on dinitrogen gas (N2) and NO3- fluxes seasonally in Chapter 2. Denitrification rates were measured as N2 flux from intact vegetated sediment cores using Membrane Inlet Mass Spectrometry (MIMS). Michaelis-Menten models were developed from observations to mathematically describe N2 fluxes across the spring, summer, and fall …
Liming Characteristics Of A High-Calcium, Dry Flue Gas Desulfurization By-Product And Its Effects On Runoff Water Quality, Jason Richard Burgess-Conforti
Liming Characteristics Of A High-Calcium, Dry Flue Gas Desulfurization By-Product And Its Effects On Runoff Water Quality, Jason Richard Burgess-Conforti
Graduate Theses and Dissertations
In 2013, only 37% of the 32 million Mg of flue gas desulfurization (FGD) by-products generated in the United States were reused beneficially. If FGD by-products could be used as a beneficial soil amendment, millions of megagrams may be diverted away from surface impoundments and landfills. The purpose of this research was to identify the liming characteristics of a high-Ca dry FGD (DFGD) by-product in comparison to a Class-C fly ash (FA) and reagent-grade CaCO3, and to evaluate the effects of land application to a managed grassland on runoff, plant, and soil quality. Liming characteristics were determined by measuring the …
Soil And Plant Property Differences Among High-Yield Soybean Areas In Arkansas, Taylor Cass Adams
Soil And Plant Property Differences Among High-Yield Soybean Areas In Arkansas, Taylor Cass Adams
Graduate Theses and Dissertations
Continued achievement of soybean [Glycine max (L.) Merr.] yields greater than 6719 kg ha-1 (100 bu ac-1) will depend on decreasing the yield gap, which is contingent on gathering more information regarding the soil physical, chemical, and microbiological environment and the main plant factors contributing to high-yield soybean. Therefore, understanding the main factor differences between high- and average-yield areas may provide insight for making management decisions to increase yields. The objectives of this study were i) to evaluate the effects of region and soil depth on soil property differences between high- and average-soybean-yielding areas, ii) to determine which soil properties …
Cover Crop Establishment And Potential Benefits To Arkansas Farmers, Ashley Elizabeth Humphreys
Cover Crop Establishment And Potential Benefits To Arkansas Farmers, Ashley Elizabeth Humphreys
Graduate Theses and Dissertations
Soybean farmers in Arkansas need best management practices (BMPs) that maximize the benefits of using cover crops including planting date and fertilization recommendations. An evaluation of cover crop species, planting dates, seeding rates, fertilizer rates, and N accumulation aids in providing these BMPs. The first objective of this research is to assess the effect of planting date on biomass production, as well as looking at the interaction of seeding rate or fertilizer rate for legumes or non-legumes, respectively, using Austrian winter pea (Pisum sativum), cereal rye (Secale cereale), black oats (Avena strigosa), wheat (Triticum aestivum), and tillage radish (Raphanus sativus). …
Determination Of Optimum Fall And Spring Nitrogen Fertilizer Rate For Maximizing Grain Yield Of Soft Red Winter Wheat Sown At Variable Planting Dates, Lucas Vasconcelos Vieira
Determination Of Optimum Fall And Spring Nitrogen Fertilizer Rate For Maximizing Grain Yield Of Soft Red Winter Wheat Sown At Variable Planting Dates, Lucas Vasconcelos Vieira
Graduate Theses and Dissertations
An optimum planting date is important for winter wheat nitrogen (N) management as it dramatically changes the growing environment including temperature and moisture, ultimately affecting fertilizer efficiency and grain yield (GY). In Arkansas, high precipitation in the fall often forces farmers to delay planting and current Arkansas recommendations include the application of fall N when soft red winter wheat (SRWW) is sown later than optimum, despite the lack of data supporting this practice. This study evaluated the effect of rate and timing of N application on GY of SRWW sown at variable planting dates in Arkansas. Granular urea was split …
Validation Of N-Star Nitrogen Rate Recommendations And Evaluation Of N-Star Soil Sampling Procedures For Clay Soils In Arkansas, Jarom Thane Davidson
Validation Of N-Star Nitrogen Rate Recommendations And Evaluation Of N-Star Soil Sampling Procedures For Clay Soils In Arkansas, Jarom Thane Davidson
Graduate Theses and Dissertations
The two methods for determining N-fertilizer recommendations for rice (Oryza sativa L.) in Arkansas are the standard N recommendation (SR) based on soil texture, previous crop, and rice cultivar, and the Nitrogen-Soil Test for Rice (N-STaR) which quantifies the potentially mineralizable-N of the soil and provides a site-specific N recommendation. The N-STaR program has recently been developed, and the validation of N-STaR for clay soils is an important step in ensuring that N-STaR predicts correct N-fertilizer rates for rice under a delayed-flood production system. Small-plot trials located across Arkansas compared the N-STaR 95 and 100% relative grain yield (RGY) N …
Validation Of An Internal Camera Based Volume Determination System For Triaxial Testing, Leah D. Miramontes
Validation Of An Internal Camera Based Volume Determination System For Triaxial Testing, Leah D. Miramontes
Civil Engineering Undergraduate Honors Theses
Accurate strain and volume measurements are critical to phase relationships and strength determination for saturated and unsaturated soils. In recent years, laboratory-based photographic techniques of monitoring soil specimens have become more common. These techniques have been used to reconstruct 3D models and to determine strain and volumetric changes of triaxial specimens. A new technique that utilized digital photographs of the soil specimen, captured from within a triaxial testing cell, was utilized. Photographs were processed using photogrammetry software to reconstruct 3D models of the soil specimens. By placing camera equipment within the cell, the technique eliminated the need to account for …
Evaluation Of Rusle 2 To Estimate Soil Loss From Pastures, Stasha Katrina Balkissoon
Evaluation Of Rusle 2 To Estimate Soil Loss From Pastures, Stasha Katrina Balkissoon
Graduate Theses and Dissertations
The accurate estimation of soil erosion by the Revised Universal Soil Loss Equation version 2 (RUSLE2) is critical for several conservation assessments, least of which is its use in the Phosphorus Index (PI) to identify and rank the vulnerability of agricultural fields to phosphorus (P) runoff. Earlier versions of RUSLE reported a soil loss overestimation, which were revised to give RUSLE2, where biomass production in different climatic regions was more accurately represented. RUSLE version 2.0, which contains the new vegetative biomass production routine, was evaluated using two performance indices, the Nash Sutcliffe Efficiency Index (NSE) and Index of Agreement (D) …
Wayne E. Sabbe Arkansas Soil Fertility Studies 2015, Nathan A. Slaton
Wayne E. Sabbe Arkansas Soil Fertility Studies 2015, Nathan A. Slaton
Arkansas Agricultural Experiment Station Research Series
Rapid technological changes in crop management and production require that the research efforts be presented in an expeditious manner. The contributions of soil fertility and fertilizers are major production factors in all Arkansas crops. The studies described within will allow producers to compare their practices with the university’s research efforts. Additionally, soil-test data and fertilizer sales are presented to allow comparisons among years, crops, and other areas within Arkansas.