Short-term Response of Soil Iron to Nitrate Addition

The inhibition of soil Fe(III) reduction by fertilizer NO3 − applications is complex and not completely understood. This inhibition is important to study because of the potential impact on soil physicochemical properties. We investigated the effect of adding NO3 − to a moderately well-drained agricultural soil (Sadler silt loam) under Fe(III)-reducing (anoxic) conditions. Stirred-batch experiments were conducted where NO3 − was added (0.05 and 1 mM) to anoxic slurries and changes in dissolved Fe(II) and Fe(III), oxalate-extractable Fe(II), and dissolved NO3 − were monitored as a function of time. Addition of 1 mM NO3 − inhibited Fe(II) production sharply with reaction time, from 10% after 1 h to 85% after 24 h. The duration of inhibition in Fe(II) production was closely related to the presence of available NO3 −, suggesting preferential use of NO3 − by nitrate reductase enzyme. Active nitrate reductase was confirmed by the fivefold decline in NO3 − reduction rates in the presence of tungstate (WO4 2−), a well-known inhibitor of nitrate reductase. In addition, NO3 −–dependent Fe(II) oxidation was observed to contribute to the inhibition in Fe(II) production. This finding was attributed to a combination of chemical reoxidation of Fe(II) by NO2 −– and NO3 −–dependent Fe(II) oxidation by autotrophic bacteria. These two processes became more important at a greater initial oxalate-Fe(II)/NO3 − concentration ratio. The inhibitory effects in Fe(II) production were short-term in the sense that once NO3 − was depleted, Fe(II) production resumed. These results underscore the complexity of the coupled N–Fe redox system in soils

Nitrite Reduction by Siderite

Nitrate-dependent Fe(II) oxidation is an important process in the inhibition of soil Fe(III) reduction, yet the mechanisms are poorly understood. One proposed pathway includes chemical reoxidation of mineral forms of Fe(II) such as siderite [FeCO3(s)] by NO2 −. Accordingly, the objective of this study was to investigate the reactivity of FeCO3(s) with NO2 −. Stirred-batch reactions were performed in an anoxic chamber across a range of pH values (5.5, 6, 6.5, and 7.9), initial FeCO3(s) concentrations (5, 10, and 15 g L−1) and initial NO2 − concentrations (0.83–9.3 mmol L−1) for kinetic and stoichiometric determinations. Solid-phase products were characterized using x-ray diffraction (XRD). Siderite abiotically reduced NO2 − to N2O. During the process, FeCO3(s) was oxidized to lepidocrocite [γ-FeOOH(s)] based on the appearance of XRD peaks located at 0.624, 0.329, and 0.247 nm. The rate of NO2 − reduction was first order in total NO2 − concentration and FeCO3(s), with a second-order rate coefficient (k) of 0.55 ± 0.05 M−1 h−1 at pH 5.5 and 25°C. The reaction was proton assisted and k values increased threefold as pH decreased from 7.9 to 5.5. The influence of pH on NO2 − reduction was rationalized in terms of the availability of FeCO3(s) surface sites (\u3eFeHCO3 0, \u3eFeOH2 +, and \u3eCO3Fe+) and HNO2 concentration. These findings indicate that if FeCO3(s) is present in an Fe(III)-reducing soil where fertilizer NO3 − is applied, it can participate in secondary chemical reactions with NO2 − and lead to an inhibition in Fe(III) reduction. This process is relevant in soil environments where NO3 −– and Fe(III)-reducing zones overlap or across aerobic–anaerobic interfaces

Economic Optimum Rates and Returns from Nitrogen Fertilization of Coastal Bermudagrass for Hay in East Texas.

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Personal note: Working with Farhad Arbab 1990–2005

From 1990 to 2005 the author had the privilege and pleasure to work as a programmer in Farhad Arbab’s research group, initially on the development, implementation and applications of the Manifold coordination language

Fragipan Horizon Fragmentation in Slaking Experiments with Amendment Materials and Ryegrass Root Tissue Extracts

Slaking experiments were conducted of fragipan clods immersed in solutions of poultry manure, aerobically digested biosolid waste (ADB), fluidized bed combustion byproduct (FBC), D-H2O, CaCO3, NaF, Na-hexa-metaphosphate, and ryegrass root biomass. The fragipan clods were sampled from the Btx horizon of an Oxyaquic Fragiudalf in Kentucky. Wet sieving aggregate analysis showed significantly better fragmentation in the NaF, Na-hexa-metaphosphate, and ryegrass root solutions with a mean weight diameter range of 15.5-18.8 mm compared to the 44.2-47.9 mm of the poultry manure, ADB, and FBC treatments. Dissolved Si, Al, Fe, and Mn levels released in solution were ambiguous. The poor efficiency of the poultry manure, ADB, and FBC treatments was attributed to their high ionic strength, while the high efficiency of the NaF, Na-hexa-metaphosphate, and rye grass root solutions to their high sodium soluble ratio (SSR). A slaking mechanism is proposed suggesting that aqueous solutions with high SSR penetrate faster into the fragipan capillaries and generate the critical swelling pressure and shearing stress required to rupture the fragipan into several fragments. Additional fragmentation occurs in a followup stage during which potential Si, Al, Fe, and Mn binding agents may be released into solution. Field experiments testing these findings are in progress

Evaluation of ductile-brittle transition temperature of anisotropy material by small punch test with U-shaped notch

Miniature and standard specimens, were cut from the anisotropy materials with axial, central and radial directions to study the mechanical property. In the paper, main research focused on the small punch test (SPT) with un-notched and U-shaped notched specimen in low temperature. Through the small punch energy variation with temperature, the ductile-brittle transition temperature by the small punch test (TSP) can be determined. The results indicated that there was no obvious difference among three different directions in transformation temperature of SPT with un-notch specimens, and it cannot represent upper plateau impact energy of three different directions. And the SPT with U-shaped notched specimens can determine the differences of upper plateau fracture energy of three different directions. Therefore, SPT with U-shaped notch specimens was more useful to evaluate the material anisotropy

Attitudes Toward COVID-19 and COVID-19 Vaccinations Among Athletic Trainers

Purpose: Following the beginning of the pandemic brought about by the novel coronavirus which causes COVID-19, the first COVID-19 vaccination received emergency use authorization in the United States of America in December of 2020. Current research has shown the authorized COVID-19 vaccines are safe and effective at preventing severe illness, hospitalizations and death have a good safety profile. Additionally, the side effects associated with these vaccines are typically mild to moderate while the protection against hospitalization and severe disease is substantial. (https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html). At the time of this study, there appears to be a paucity in the research related to the attitudes toward COVID-19 and COVID-19 vaccines among athletic trainers. The purpose of this study is to describe the attitudes toward COVID-19 and COVID-19 vaccines among athletic trainers. Methods: A total of 186 athletic trainers (age= 43 ± 11, years of certified experience = 20 ± 11) opened and completed the survey. Participants were sent an electronic survey via email that collected demographic information and assessed attitudes toward COVID-19 and COVID-19 vaccines. Data was downloaded and analyzed using a commercially available statistics package. Results: The majority of athletic trainers surveyed had received a COVID-19 vaccination at the time of this study (94.1%, n=175). Most athletic trainers also agreed that the health of their patients was more important than disruption of their competition season due to COVID-19 (82.3%, n=153). In general, the most common reason for vaccine hesitancy was the speed with which currently available COVID-19 vaccines were developed. Conclusions: The findings of this study show the majority of surveyed athletic trainers had received a COVID-19 vaccine. The primary reason for athletic trainers not receiving a COVID-19 vaccination appeared to be the speed at which the currently available COVID-19 vaccines were developed. Given the available information on the new mRNA COVID vaccines, this may indicate a lack of education on the development of the COVID-19 vaccines. As athletic trainers continue to work in day-to-day patient care, it is imperative to determine the best methods for educating athletic trainers on the potential benefits of COVID-19 vaccinations

Detecting Recent Crop Phenology Dynamics in Corn and Soybean Cropping Systems of Kentucky

Accurate phenological information is essential for monitoring crop development, predicting crop yield, and enhancing resilience to cope with climate change. This study employed a curve-change-based dynamic threshold approach on NDVI (Normalized Differential Vegetation Index) time series to detect the planting and harvesting dates for corn and soybean in Kentucky, a typical climatic transition zone, from 2000 to 2018. We compared satellite-based estimates with ground observations and performed trend analyses of crop phenological stages over the study period to analyze their relationships with climate change and crop yields. Our results showed that corn and soybean planting dates were delayed by 0.01 and 0.07 days/year, respectively. Corn harvesting dates were also delayed at a rate of 0.67 days/year, while advanced soybean harvesting occurred at a rate of 0.05 days/year. The growing season length has increased considerably at a rate of 0.66 days/year for corn and was shortened by 0.12 days/year for soybean. Sensitivity analysis showed that planting dates were more sensitive to the early season temperature, while harvesting dates were significantly correlated with temperature over the entire growing season. In terms of the changing climatic factors, only the increased summer precipitation was statistically related to the delayed corn harvesting dates in Kentucky. Further analysis showed that the increased corn yield was significantly correlated with the delayed harvesting dates (1.37 Bu/acre per day) and extended growing season length (1.67 Bu/acre per day). Our results suggested that seasonal climate change (e.g., summer precipitation) was the main factor influencing crop phenological trends, particularly corn harvesting in Kentucky over the study period. We also highlighted the critical role of changing crop phenology in constraining crop production, which needs further efforts for optimizing crop management practices