Soil Science Commons^™

The Current State Of Community Engagement In Urban Soil Pollution Science, Nicole Fernández-Viña, Yujuan Chen, Kirsten Schwarz

Agricultural and Environmental Sciences Faculty Research

Environmental burdens disproportionately impact the health of communities of color and low-income communities. Contemporary and legacy industry and land development may pollute soils with pesticides, petroleum products, and trace metals that can directly and indirectly impact the health of frontline communities. Past efforts to study environmental injustice have often excluded those most impacted, created distrust of researchers and other experts among frontline communities, and resulted in little to no structural change. Prevailing research methods value formal knowledge systems, while often dismissing the knowledge of those most harmed by environmental hazards. Community science has emerged as a process of doing science …

Influence Of Soil And Foliar Application Of Fulvic Acid On Yield Parameters Of Organically Grown Bell Peppers (Capsicum Annuum L.) Under Open-Field Conditions In Tennessee, Pinkky Kanabar, Dilip Nandwani

Student Research

Due to increased demand for healthier fresh produce by consumers, growers are seeking for environmental friendlier techniques to improve sustainability and profitability in organic vegetable production. The use of fulvic acid biostimulant coupled with different mode of application can contribute to enhanced plant growth and high-quality yield. A field experiment was conducted in a randomized complete block design with three replications at the organic farm of Tennessee State University in summer 2021. The influence of foliar and soil application of fulvic acid biostimulant on yield of organically grown bell peppers (Capsicum annuum L.) was investigated. Transplants were raised from organic …

Linking Soil Microbial Community Structure To Potential Carbon Mineralization: A Continental Scale Assessment Of Reduced Tillage, Elizabeth L. Rieke, Shannon B. Cappellazzi, Michael Cope, Daniel Liptzin, Gregory Mac Bean, Kelsey L.H. Greub, Charlotte E. Norris, Paul W. Tracy, Ezra Aberle, Amanda Ashworth, Oscar Bañuelos Tavarez, Andy I. Bary, Roland L. Baumhardt, Alberto Borbón Gracia, Daniel C. Brainard, Jameson R. Brennan, Dolores Briones Reyes, Darren Bruhjell, Cameron N. Carlyle, James J.W. Crawford, Cody F. Creech, Steve W. Culman, Bill Deen, Curtis J. Dell, Justin D. Derner, Thomas F. Ducey, Sjoerd W. Duiker, Miles F. Dyck, Benjamin H. Ellert, Avelino Espinosa Solorio, Steven J. Fonte, Simon Fonteyne, Ann-Marie Fortuna, Jamie L. Foster, Lisa M. Fultz, Audrey V. Gamble, Charles M. Geddes, Deirdre Griffin-Lahue, John H. Grove, Stephen K. Hamilton, Xiying Hao, Zachary D. Hayden, Nora Honsdorf, Julie A. Howe, James A. Ippolito, Gregg A. Johnson, Mark A. Kautz, Newell R. Kitchen, Sandeep Kumar, Kirsten S.M. Kurtz, Francis J. Larney, Katie L. Lewis, Matt Liebman, Antonio Lopez Ramirez, Stephen Machado, Bijesh Maharjan, Miguel Angel Martinez Gamiño, William E. May, Mitchel P. Mcclaran, Marshall D. Mcdaniel, Neville Millar, Jeffrey P. Mitchell, Amber D. Moore, Philip A. Moore, Manuel Mora Gutiérrez, Kelly A. Nelson, Emmanuel C. Omondi, Shannon L. Osborne, Leodegario Osorio Alcalá, Philip Owens, Eugenia M. Pena-Yewtukhiw, Hanna J. Poffenbarger, Brenda Ponce Lira, Jennifer R. Reeve, Timothy M. Reinbott, Mark S. Reiter, Edwin L. Ritchey, Kraig L. Roozeboom, Yichao Rui, Amir Sadeghpour, Upendra M. Sainju, Gregg R. Sanford, William F. Schillinger, Robert R. Schindelbeck, Meagan E. Schipanski, Alan J. Schlegel, Kate M. Scow, Lucretia A. Sherrod, Amy L. Shober, Sudeep S. Sidhu, Ernesto Solís Moya, Mervin St Luce, Jeffrey S. Strock, Andrew E. Suyker, Virginia R. Sykes, Haiying Tao, Alberto Trujillo Campos, Laura L. Van Eerd, Nele Verhulst, Tony J. Vyn, Yutao Wang, Dexter B. Watts, Bryan B. William, David L. Wright, Tiequan Zhang, Cristine L.S. Morgan, C. Wayne Honeycutt

Agricultural and Environmental Sciences Faculty Research

Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical …

Effect Of Nitrogen Fertilization On Central Tendency And Spatial Heterogeneity Of Soil Moisture, Ph And Dissolved Organic Carbon And Nitrogen In Two Bioenergy Croplands, Xuehan Wang, Siyang Jian, Lahiru Gamage, Jianwei Li

Agricultural and Environmental Sciences Faculty Research

Background

Soil moisture, pH, dissolved organic carbon and nitrogen (DOC, DON) are important soil biogeochemical properties in switchgrass (SG) and gamagrass (GG) croplands. Yet their spatiotemporal patterns under nitrogen (N) fertilization have not been studied.

Aims

The objective of this study is to investigate the main and interactive effects of N fertilization and bioenergy crop type on central tendencies and spatial heterogeneity of soil moisture, pH, DOC and DON.

Methods

Based on a 3-year long fertilization experiment in Middle Tennessee, USA, 288 samples of top horizon soils (0–15 cm) under three fertilization treatments in SG and GG croplands were collected. …

Carbon-Sensitive Pedotransfer Functions For Plant Available Water, Dianna K. Bagnall, Cristine L. S. Morgan, Michael Cope, Gregory M. Bean, Shannon Cappellazzi, Kelsey Greub, Daniel Liptzin, Charlotte L. Norris, Elizabeth Rieke, Paul Tracy, Ezra Aberle, Amanda Ashworth, Oscar Bañuelos Tavarez, Andy Bary, Roland Louis Baumhardt, Alberto Borbón Gracia, Daniel Brainard, Jameson Brennan, Dolores Briones Reyes, Darren Bruhjell, Cameron Carlyle, James Crawford, Cody Creech, Steven Culman, William Deen, Curtis Dell, Justin Derner, Thomas Ducey, Sjoerd Willem Duiker, Miles Dyck, Benjamin Ellert, Martin Entz, Avelino Espinosa Solorio, Steven J. Fonte, Simon Fonteyne, Ann-Marie Fortuna, Jamie Foster, Lisa Fultz, Audrey V. Gamble, Charles Geddes, Deirdre Griffin-Lahue, John Grove, Stephen K. Hamilton, Xiying Hao, ‪Zachary D. Hayden, Julie Howe, James Ippolito, Gregg Johnson, Mark Kautz, Newell Kitchen, Sandeep Kumar, Kirsten Kurtz, Francis Larney, Katie Lewis, Matt Liebman, Antonio Lopez Ramirez, Stephen Machado, Bijesh Maharjan, Miguel Angel Martinez Gamiño, William May, Mitchel Mcclaran, Marshall Mcdaniel, Neville Millar, Jeffrey P. Mitchell, Philip A. Moore, Amber Moore, Manuel Mora Gutiérrez, Kelly A. Nelson, Emmanuel Omondi, Shannon Osborne, Leodegario Osorio Alcalá, Philip Owens, Eugenia M. Pena-Yewtukhiw, Hanna Poffenbarger, Brenda Ponce Lira, Jennifer Reeve, Timothy Reinbott, Mark Reiter, Edwin Ritchey, Kraig L. Roozeboom, Ichao Rui, Amir Sadeghpour, Upendra M. Sainju, Gregg Sanford, William Schillinger, Robert R. Schindelbeck, Meagan Schipanski, Alan Schlegel, Kate Scow, Lucretia Sherrod, Sudeep Sidhu, Ernesto Solís Moya, Mervin St. Luce, Jeffrey Strock, Andrew Suyker, Virginia Sykes, Haiying Tao, Alberto Trujillo, Laura L. Van Eerd, Nele Verhulst, Tony John Vyn, Yutao Wang, Dexter Watts, David Wright, Tiequan Zhang, Charles Wayne Honeycutt

Agricultural and Environmental Sciences Faculty Research

Currently accepted pedotransfer functions show negligible effect of management-induced changes to soil organic carbon (SOC) on plant available water holding capacity (θAWHC), while some studies show the ability to substantially increase θAWHC through management. The Soil Health Institute's North America Project to Evaluate Soil Health Measurements measured water content at field capacity using intact soil cores across 124 long-term research sites that contained increases in SOC as a result of management treatments such as reduced tillage and cover cropping. Pedotransfer functions were created for volumetric water content at field capacity (θFC) and permanent wilting point (θPWP). New pedotransfer functions had …

Reducing Tillage Affects Long-Term Yields But Not Grain Quality Of Maize, Soybeans, Oats, And Wheat Produced In Three Contrasting Farming Systems, Kirsten Ann Pearsons, Emmanuel Chiwo Omondi, Brad J. Heins, Gladis Zinati, Andrew Smith, Yichao Rui

Agricultural and Environmental Sciences Faculty Research

Reducing tillage has been widely promoted to reduce soil erosion, maintain soil health, and sustain long-term food production. The effects of reducing tillage on crop nutritional quality in organic and conventional systems, however, has not been widely explored. One possible driver of crop nutritional quality might be the changing soil nitrogen (N) availability associated with reduced tillage in various management systems. To test how reducing tillage affects crop nutritional quality under contrasting conventional and organic farming systems with varied N inputs, we measured nutritional quality (protein, fat, starch, ash, net energy, total digestible nutrients, and concentrations of Ca, K, Mg, …

Stimulation Of Ammonia Oxidizer And Denitrifier Abundances By Nitrogen Loading: Poor Predictability For Increased Soil N2o Emission, Yong Zhang, Feng Zhang, Diego Abalos, Yiqi Luo, Dafeng Hui, Bruce A. Hungate, Pablo García-Palacios, Yakov Kuzyakov, Jørgen Eivind Olesen, Uffe Jørgensen, Ji Chen

Biology Faculty Research

Unprecedented nitrogen (N) inputs into terrestrial ecosystems have profoundly altered soil N cycling. Ammonia oxidizers and denitrifiers are the main producers of nitrous oxide (N₂O), but it remains unclear how ammonia oxidizer and denitrifier abundances will respond to N loading and whether their responses can predict N-induced changes in soil N₂O emission. By synthesizing 101 field studies worldwide, we showed that N loading significantly increased ammonia oxidizer abundance by 107% and denitrifier abundance by 45%. The increases in both ammonia oxidizer and denitrifier abundances were primarily explained by N loading form, and more specifically, organic N …

Soil Bacteria In Urban Community Gardens Have The Potential To Disseminate Antimicrobial Resistance Through Horizontal Gene Transfer, Abdullah Ibn Mafiz, Yingshu He, Wei Zhang, Yifan Zhang

Agricultural and Environmental Sciences Faculty Research

Fifteen soil and 45 vegetable samples from Detroit community gardens were analyzed for potential antimicrobial resistance contamination. Soil bacteria were isolated and tested by antimicrobial susceptibility profiling, horizontal gene transfer, and whole-genome sequencing. High-throughput 16S rRNA sequencing analysis was conducted on collected soil samples to determine the total bacterial composition. Of 226 bacterial isolates recovered, 54 were from soil and 172 from vegetables. A high minimal inhibitory concentration (MIC) was defined as the MIC greater than or equal to the resistance breakpoint of Escherichia coli for Gram-negative bacteria or Staphylococcus aureus for Gram-positive bacteria. The high MIC was observed in …

Assessing The Impact Of Organic Versus Conventional Agricultural Management On Soil Hydraulic Properties In A Long-Term Experiment, Abdelrahman Alfahham, Matthew T. Amato, Emmanuel Omondi, Daniel Giménez, Alain F. Plante

Agricultural and Environmental Sciences Faculty Research

Investigating the effects of various agricultural management systems on soil hydraulic properties in long-term field experiments allows farmers to evaluate their efficacy in mitigating the effects of droughts and floods, which are expected to intensify in the coming decades. This study's main objective was to quantify soil structural and hydraulic properties in plots under organic manure, organic leguminous, and conventional agricultural management and related tillage practices at Rodale Institute's Farming Systems Trial. Soil cores were collected at depths of 0–10, 10–20, and 20–30 cm and analyzed for soil water retention, saturated hydraulic conductivity (Ksat), soil organic C (SOC), bulk density, …

Can Agricultural Management Induced Changes In Soil Organic Carbon Be Detected Using Mid-Infrared Spectroscopy?, Jonathan Sanderman, Kathleen Savage, Shree R.S. Dangal, Gabriel Duran, Charlotte Rivard, Michel A. Cavigelli, Hero T. Gollany, Virginia L. Jin, Mark A. Liebig, Emmanuel Chiwo Omondi, Yichao Rui, Catherine Stewart

Agricultural and Environmental Sciences Faculty Research

A major limitation to building credible soil carbon sequestration programs is the cost of measuring soil carbon change. Diffuse reflectance spectroscopy (DRS) is considered a viable low-cost alternative to traditional laboratory analysis of soil organic carbon (SOC). While numerous studies have shown that DRS can produce accurate and precise estimates of SOC across landscapes, whether DRS can detect subtle management induced changes in SOC at a given site has not been resolved. Here, we leverage archived soil samples from seven long-term research trials in the U.S. to test this question using mid infrared (MIR) spectroscopy coupled with the USDA-NRCS Kellogg …

Soil Extracellular Oxidases Mediated Nitrogen Fertilization Effects On Soil Organic Carbon Sequestration In Bioenergy Croplands, Jianjun Duan, Min Yuan, Siyang Jian, Lahiru Gamage, Madhav Parajuli, Kudjo E. Dzantor, Dafeng Hui, Philip A. Fay, Jianwei Li

Agricultural and Environmental Sciences Faculty Research

Nitrogen (N) fertilization significantly affects soil extracellular oxidases, agents responsible for decomposition of slow turnover and recalcitrant soil organic carbon (SOC; e.g., lignin), and consequently influences soil carbon sequestration capacity. However, it remains unclear how soil oxidases mediate SOC sequestration under N fertilization, and whether these effects co-vary with plant type (e.g., bioenergy crop species). Using a spatially explicit design and intensive soil sampling strategy under three fertilization treatments in switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.) croplands, we quantified the activities of polyphenolic oxidase (PHO), peroxidase (PER), and their sum associated with recalcitrant C acquisition …

Antimony (V) Adsorption At The Hematite–Water Interface: A Macroscopic And In Situ Atr-Ftir Study, Jerzy Mierzwa, Rose Mumbi, Avedananda Ray, Sudipta Rakshit, Michael E. Essington, Dibyendu Sarkar

Agricultural and Environmental Sciences Faculty Research

The environmental mobility of antimony (Sb) is largely unexplored in geochemical environments. Iron oxide minerals are considered major sinks for Sb. Among the different oxidation states of Sb, (+) V is found more commonly in a wide redox range. Despite many adsorption studies of Sb (V) with various iron oxide minerals, detailed research on the adsorption mechanism of Sb (V) on hematite using macroscopic, spectroscopic, and surface complexation modeling is rare. Thus, the main objective of our study is to evaluate the surface complexation mechanism of Sb (V) on hematite under a range of solution properties using macroscopic, in situ …

Soil C:N:P Stoichiometry In Tropical Forests On Hainan Island Of China: Spatial And Vertical Variations, Dafeng Hui, Xitian Yang, Qi Deng, Qiang Liu, Xu Wang, Huai Yang, Hai Ren

Biology Faculty Research

Soil carbon (C), nitrogen (N), and phosphorus (P) are three important elements. The study of stoichiometric relationships of soil C, N, and P in tropical forests on Hainan Island, China could improve our understanding of nutrient cycling and provide valuable information for forest management. Soil samples were collected at five different depths from 0 to 100 cm at 100 sites among four different forest types on Hainan Island, and total C, N, and P concentrations were measured. Soil C and N concentrations and soil C:P and N:P ratios declined from the surface soil layer to the deeper soil layers and …

Multiple Constraints Cause Positive And Negative Feedbacks Limiting Grassland Soil Co2 Efflux Under Co2 Enrichment, Philip A. Fay, Dafeng Hui, Robert B. Jackson, Harold P. Collins, Lara G. Reichmann, Michael J. Aspinwall, Virginia L. Jin, Albina R. Khasanova, Robert W. Heckman, H. Wayne Polley

Biology Faculty Research

Understanding ecosystem carbon-cycling responses to atmospheric CO₂ enrichment is critical to preserve biodiversity and maintain vital ecosystem services in grasslands impacted by global change. We conducted an 8-y experiment enriching CO₂ concentrations from preindustrial to midtwenty-first century levels on grassland plant communities on upland, lowland, and alluvial soils. CO₂ enrichment increased the CO₂ efflux from soils to atmosphere in amounts depending on whether the dominant limitation was CO₂ or feedbacks (net positive or negative) from soil moisture and plant species turnover. These findings highlight how multiple concurrent limitations, not single limitations in sequence, regulate the …

Multi-Year Incubation Experiments Boost Confidence In Model Projections Of Long-Term Soil Carbon Dynamics, Siyang Jian, Jianwei Li, Gangsheng Wang, Laurel A. Kluber, Christopher W. Schadt, Junyi Liang, Melanie A. Mayes

Agricultural and Environmental Sciences Faculty Research

Global soil organic carbon (SOC) stocks may decline with a warmer climate. However, model projections of changes in SOC due to climate warming depend on microbially-driven processes that are usually parameterized based on laboratory incubations. To assess how lab-scale incubation datasets inform model projections over decades, we optimized five microbially-relevant parameters in the Microbial-ENzyme Decomposition (MEND) model using 16 short-term glucose (6-day), 16 short-term cellulose (30-day) and 16 long-term cellulose (729-day) incubation datasets with soils from forests and grasslands across contrasting soil types. Our analysis identified consistently higher parameter estimates given the short-term versus long-term datasets. Implementing the short-term and …

Vertical Distributions Of Soil Microbial Biomass Carbon: A Global Dataset, Tingting Sun, Yugang Wang, Dafeng Hui, Xin Jing, Wenting Feng

Biology Faculty Research

Soil microbial biomass carbon (SMBC) is important in regulating soil organic carbon (SOC) dynamics along soil profiles by mediating the decomposition and formation of SOC. The dataset (VDMBC) is about the vertical distributions of SOC, SMBC, and soil microbial quotient (SMQ = SMBC/SOC) and their relations to environmental factors across five continents. Data were collected from literature, with a total of 289 soil profiles and 1040 observations in different soil layers compiled. The associated environment data collectd include climate, ecosystem types, and edaphic factors. We developed this dataset by searching the Web of Sciene and the China National Knowledge Infrastructure …

Relationships Between Vegetation And Soil Seed Banks Along A Center-To-Edge Gradient On A Tropical Coral Island, Yao Huang, Hai Ren, Jun Wang, Nan Liu, Shuguang Jian, Hongyue Cai, Dafeng Hui, Qinfeng Guo

Biology Faculty Research

Few studies have focused on the relationships between vegetation and soil seed banks on small islands. To better understand the pattern and regeneration potential of seed banks on tropical coral islands, we measured environmental factors and the species composition, and species richness of soil seed banks and vegetation along a gradient from the center to the edges on East Island in the South China Sea. The results showed that the similarity between the species composition of vegetation and seed banks increased from the center to the edge. In the center, species richness in both vegetation and seed banks was positively …

Constitutive Model Of Lateral Unloading Creep Of Soft Soil Under Excess Pore Water Pressure, Wei Huang, Kejun Wen, Xiaojia Deng, Junjie Li, Zhijian Jiang, Yang Li, Lin Li, Farshad Amini

Civil and Architectural Engineering Faculty Research

Presented in this paper is a study on the lateral unloading creep tests under different excess pore water pressures. The marine sedimentary soft soil in Shenzhen, China, was selected in this study. The results show that the excess pore water pressure plays a significant role in enhancing the unloading creep of soft soil. Higher excess pore water pressure brings more obvious creep deformation of soft soil and lower ultimate failure load. Meanwhile, the viscoelastic and the viscoplastic modulus of soft soil were found to exponentially decline with creep time. A modified merchant model and a combined model of the modified …

Effects Of Nitrogen Fertilization And Bioenergy Crop Type On Topsoil Organic Carbon And Total Nitrogen Contents In Middle Tennessee Usa, Jianwei Li, Siyang Jian, Chad S. Lane, Yuehan Lu, Xiaorui He, Gangsheng Wang, Melanie A. Mayes, Kudjo E. Dzantor, Dafeng Hui

Agricultural and Environmental Sciences Faculty Research

Nitrogen (N) fertilization affects bioenergy crop growth and productivity and consequently carbon (C) and N contents in soil, it however remains unclear whether N fertilization and crop type individually or interactively influence soil organic carbon (SOC) and total N (TN). In a three-year long fertilization experiment in switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.) croplands in Middle Tennessee USA, soil samples (0–15cm) were collected in plots with no N input (NN), low N input (LN: 84 kg N ha-1 yr-1 in urea) and high N input (HN: 168 kg N ha-1 yr-1 in urea). Besides SOC …

Nitrogen Fertilization Restructured Spatial Patterns Of Soil Organic Carbon And Total Nitrogen In Switchgrass And Gamagrass Croplands In Tennessee Usa, Jianwei Li, Siyang Jian, Chad S. Lane, Chunlan Guo, Yuehan Lu, Qi Deng, Melanie A. Mayes, Kudjo E. Dzantor, Dafeng Hui

Agricultural and Environmental Sciences Faculty Research

Nitrogen (N) fertilizers can potentially alter spatial distribution of soil organic carbon (SOC) and total nitrogen (TN) concentrations in croplands such as switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.), but it remains unclear whether these effects are the same between crops and under different rates of fertilization. 13C and 15N are two important proxy measures of soil biogeochemistry, but they were rarely examined as to their spatial distributions in soil. Based on a three-year long fertilization experiment in Middle Tennessee, USA, the top mineral horizon soils (0–15 cm) were collected using a spatially explicit design within …

The Cation Exchange Behavior Of Tylosin In Loess-Derived Soil, Jaime J. Call, Michael E. Essington, Sudipta Rakshit

Agricultural and Environmental Sciences Faculty Research

Tylosin (Tyl) is a veterinary antibiotic commonly used in swine and poultry production. Due to metabolic inefficiencies, it enters the environment through manure applications. Ion exchange is an important retention mechanism for Tyl, particularly for smectite clay. The objectives of this study are to characterize the exchange interactions of Tyl with common soil cations in subsoil horizons that contain smectite and to investigate the interactions using in situ Fourier transform infrared (FTIR) spectroscopy. Adsorbed Tyl in pH neutral, smectitic subsoil horizons is divided into exchangeable and nonexchangeable forms. The percentage of adsorbed Tyl that is exchangeable varies from 36% to …

Responses Of Soil Carbon Sequestration To Climate-Smart Agriculture Practices: A Meta-Analysis, Xiongxiong Bai, Yawen Huang, Wei Ren, Mark Coyne, Pierre-Andre Jacinthe, Bo Tao, Dafeng Hui, Jian Yang, Chris Matocha

Biology Faculty Research

Climate-smart agriculture (CSA) management practices (e.g., conservation tillage, cover crops, and biochar applications) have been widely adopted to enhance soil organic carbon (SOC) sequestration and to reduce greenhouse gas emissions while ensuring crop productivity. However, current measurements regarding the influences of CSA management practices on SOC sequestration diverge widely, making it difficult to derive conclusions about individual and combined CSA management effects and bringing large uncertainties in quantifying the potential of the agricultural sector to mitigate climate change. We conducted a meta-analysis of 3,049 paired measurements from 417 peer-reviewed articles to examine the effects of three common CSA management practices …

Experiment Study Of Lateral Unloading Stress Path And Excess Pore Water Pressure On Creep Behavior Of Soft Soil, Wei Huang, Kejun Wen, Dongsheng Li, Xiaojia Deng, Lin Li, Haifei Jiang, Farshad Amini

Civil and Architectural Engineering Faculty Research

The unloading creep behavior of soft soil under lateral unloading stress path and excess pore water pressure is the core problem of time-dependent analysis of surrounding rock deformation under excavation of soft soil. The soft soil in Shenzhen, China, was selected in this study. The triaxial unloading creep tests of soft soil under different initial excess pore water pressures (0, 20, 40, and 60 kPa) were conducted with the K0 consolidation and lateral unloading stress paths. The results show that the unloading creep of soft soil was divided into three stages: attenuation creep, constant velocity creep, and accelerated creep. The …

Sampling Soils In A Heterogeneous Research Plot, Jianwei Li

Agricultural and Environmental Sciences Faculty Research

Soils are highly heterogeneous. In general, the number of soil samples required for soil research has always been determined arbitrarily and the associated accuracy is unknown. Here, we present a detailed protocol for efficient and clustered soil sampling in a research plot and, relying on a pilot sampling using this design, for demonstrating soil spatial heterogeneity and informing reasonable sample sizes and associated accuracy for future study. The protocol mainly comprises four steps: sampling design, field collection, soil analysis, and geostatistical analysis. The step-by-step procedure is modified according to former publications. Two examples will be presented to demonstrate contrasting spatial …

Reduced Carbon Use Efficiency And Increased Microbial Turnover With Soil Warming, Jianwei Li, Gangsheng Wang, Melanie A. Mayes, Steven D. Allison, Serita D. Frey, Zheng Shi, Xiao-Ming Hu, Yiqi Luo, Jerry M. Melillo

Agricultural and Environmental Sciences Faculty Research

Global soil carbon (C) stocks are expected to decline with warming, and changes in microbial processes are key to this projection. However, warming responses of critical microbial parameters such as carbon use efficiency (CUE) and biomass turnover (rB) are not well understood. Here, we determine these parameters using a probabilistic inversion approach that integrates a microbial-enzyme model with 22 years of carbon cycling measurements at Harvard Forest. We find that increasing temperature reduces CUE but increases rB, and that two decades of soil warming increases the temperature sensitivities of CUE and rB. These temperature sensitivities, which are derived from decades-long …

Influence Of Phosphate On Tungstate Sorption On Hematite: A Macroscopic And Spectroscopic Evaluation Of The Mechanism, Bryan Sallman, Sudipta Rakshit, Grégory Lefèvre

Agricultural and Environmental Sciences Faculty Research

The environmental fate of the tungstate (VI) oxyanion [ e.g. mono tungstate and several polytungstate, generally expressed by W (VI)] is largely controlled by sorption on soil minerals, especially on iron oxide minerals. Molecular scale evaluation of W (VI) retention on iron oxides in the presence of competing oxyanions is scarce in literature. Here we report surface interaction mechanisms of W (VI) on hematite in the presence of phosphate (P) using macroscopic and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic experiments. Batch sorption experiments were conducted using 2 g L−1 hematite and 100 μM W (VI) and …

Differential Responses Of Carbon-Degrading Enzyme Activities To Warming: Implications For Soil Respiration, Ji Chen, Yiqi Luo, Pablo García-Palacios, Junji Cao, Marina Dacal, Xuhui Zhou, Jianwei Li, Jianyang Xia, Shuli Niu, Huiyi Yang, Shelby Shelton, Wei Guo, Kees Jan Van Groenigen

Agricultural and Environmental Sciences Faculty Research

Extracellular enzymes catalyze rate-limiting steps in soil organic matter decomposition, and their activities (EEAs) play a key role in determining soil respiration (SR). Both EEAs and SR are highly sensitive to temperature, but their responses to climate warming remain poorly understood. Here, we present a meta-analysis on the response of soil cellulase and ligninase activities and SR to warming, synthesizing data from 56 studies. We found that warming significantly enhanced ligninase activity by 21.4% but had no effect on cellulase activity. Increases in ligninase activity were positively correlated with changes in SR, while no such relationship was found for cellulase. …

Long-Term Antagonistic Effect Of Increased Precipitation And Nitrogen Addition On Soil Respiration In A Semiarid Steppe, Hongyan Han, Yue Du, Dafeng Hui, Lin Jiang, Mingxing Zhong, Shiqiang Wan

Biology Faculty Research

Changes in water and nitrogen (N) availability due to climate change and atmospheric N deposition could have significant effects on soil respiration, a major pathway of carbon (C) loss from terrestrial ecosystems. A manipulative experiment simulating increased precipitation and atmospheric N deposition has been conducted for 9 years (2005–2013) in a semiarid grassland in Mongolian Plateau, China. Increased precipitation and N addition interactively affect soil respiration through the 9 years. The interactions demonstrated that N addition weakened the precipitation-induced stimulation of soil respiration, whereas increased precipitation exacerbated the negative impacts of N addition. The main effects of increased precipitation and …

Modeling The Movement Of Septic Water Chloride Through A Soil Profile, Shawkat Kochary, Tom Byl, Bahzad Noori

Civil and Architectural Engineering Faculty Research

The purpose of this study was to investigate the movement of chloride through a vadose zone located under failed and non-regulated septic tanks of Duhok city, Kurdistan of Iraq, potentially contaminating its groundwater. A physical vadose model (PVM) of a vertical flow direction was built in the laboratory to represent the city soil profile. The size of the PVM was 210 × 122 × 9.7 cm (height, width, and depth). Preliminary soil tests were conducted to better represent the lithology of study area. The PVM was then packed with regional silt clay soil, after modifying its texture, using an innovative …

Responses Of Terrestrial Ecosystem Phosphorus Cycling To Nitrogen Addition: A Meta-Analysis, Qi Deng, Dafeng Hui, Samuel Dennis, Chandra Reddy

Agricultural and Environmental Sciences Faculty Research

Aim

Anthropogenic additions of nitrogen (N) are expected to drive terrestrial ecosystems toward greater phosphorus (P) limitation. However, a comprehensive understanding of how an ecosystem's P cycle responds to external N inputs remains elusive, making model predictions of the anthropogenic P limitation and its impacts largely uncertain.

Location

Global.

Time period

1986-2015.

Major taxa studied

Terrestrial ecosystems.

Methods

We conducted a meta-analysis including 288 independent study sites from 192 articles to evaluate global patterns and controls of 10 variables associated with ecosystem P cycling under N addition.

Results

Overall, N addition increased biomass in plants (+34%) and litter (+15%) as …