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1
Ogunye, Festus Olubunmi. "Rain resistance of stabilised soil blocks." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243039.
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Milstone, Barry Scott. "Effects of nonhomogeneous cementation in soils on resistance to earthquake effects." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/77896.
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Small amounts of cementation in a sand increase its ability to sustain static and dynamic loads, even in a liquefaction type environment. This has been shown in previous research examining the behavior of both naturally cemented and artificially prepared samples.
Cemented sands are present in many parts of the world and can be caused by either a variety of cementing agents or by cold welding at points of grain contact. They are generally quite difficult to sample, but artificially cemented sands have been shown to aptly model the behavior of natural materials, and allow for better test controls. Consequently, artificial samples were used exclusively for the present investigation which has three major objectives: to investigate the effects of a weakly cemented lens within a stronger mass; to determine how cementation affects the volume change characteristics of statically loaded samples; and, to describe the pore pressure generation of sands subjected to cyclic loading.
Prior to commencing the test program, a number of index tests were performed on the uncemented and cemented sand used during the laboratory investigation. It was revealed that cementation leads to increased void ratios which distort relative density calculations used to compare cemented and uncemented samples of similar dry unit weight. The practice of identifying samples by dry unit weight was adopted for this report.
Static triaxial compression tests were performed on 17 samples. Test results indicate that although the magnitude of volumetric strain at failure does not seem to be dictated by the level of cementation, there is a relationship with cementation and the rate of volume change at failure. A weak lens was seen to lower the static strength of the stronger mass. 26 stress controlled cyclic triaxial tests revealed that a weak lens lowers the liquefaction resistance of the stronger mass. The cyclic strength of the nonhomogeneous material, however, is higher than the independent strength of the weak lens. A weak lens has greater influence at relatively higher levels of cyclic stress. Pore pressure generation in cemented sands are seen to be controlled by strain. At shear strain levels below about 1%, cemented sands behave similarly to uncemented sands with pore pressures increasing more rapidly beyond that amount of strain. Consequently, pore pressure development during cyclic loading is described by a broken-back curve which is defined in the early stages by existing empirical relationships for uncemented sand. Pore pressure prediction may then be achieved using an equation for cemented sand, such as that developed in the present work.Master of Science
3
Standing, James R. "Studies of the interface resistance of soil nails." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8935.
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Shu, Xin. "The mechanisms underlying the resistance and resilience of soil carbon and nitrogen cycling to environmental stresses." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=237673.
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Cycling of nutrients, such as Carbon (C) and Nitrogen (N), is one of the most important soil functions and is strongly related to the composition of the soil microbial community. However, soil is increasingly under environmental pressures that threaten its ecological functions and sustainability. To maintain soil functional sustainability, it is important to understand how soil withstands environmental stresses (subsequently referred to as resistance) and recovers from stresses (subsequently referred to as resilience). This study focused on the resistance and resilience of C and N processes and the underpinning microbial communities to a persistent Cu stress or a transient heat stress. The main advances and novel findings of this thesis are: (1) C mineralization is more resistant and resilient than ammonia oxidation and denitrification, and thus the combination of C and N processes are more informative than measuring a single process to interpret the overall resistance and resilience; (2) microbial composition and microbial physiological evolution play important roles in affecting resistance and resilience; (3) soil physico-chemical properties (e.g. organic matter, soil water and soil pH) are critically important in conferring resistance and resilience. The outcome of this study advances the understanding of the mechanisms of soil resistance and resilience of C and N cycling to environmental changes. The results generated here are an essential step for improving soil sustainability and promoting agricultural productivity under future environmental challenges.
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Woodward, Rebecca Stanton Wain. "Analysis of tetracycline resistance in compost bacilli." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259753.
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Cook, H. F. "Assessment of drought resistance in soils." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374255.
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Bellinger, Christina G. "Commercial Soils as a Potential Vehicle for Antibiotic Resistance Transmission." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503298572132004.
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Heap, John. "Increasing Medicago resistance to soil residues of ALS-inhibiting herbicides." Adelaide, Sth. Aust, 2000. http://hdl.handle.net/2440/19842.
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REZENDE, EMILIANA DE SOUZA. "STUDY OF SOIL-GEOSYNTHETIC INTERFACE RESISTANCE USING AN RAMP APPARATUS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7113@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEm obras ambientais, onde geossintéticos são utilizados como sistema de proteção e de cobertura de taludes, é de extrema importância o conhecimento do mecanismo de interação solo-geossintético, através da obtenção dos parâmetros de resistência da interface (adesão e ângulo de atrito da interface). O ensaio de laboratório mais adequado para a obtenção desses parâmetros, nestas condições, é o de cisalhamento em plano inclinado ou ensaio de rampa, pois permite simular a condição de campo onde o cisalhamento ocorre em um plano inclinado sob baixas tensões. Assim, este trabalho apresenta um estudo sobre a interação sologeossintético através de ensaios de rampa, executados em um equipamento de grandes dimensões, visando analisar a influência de alguns fatores, tais como, tipo de geossintético, tipo de solo, densidade relativa do solo e tensão confinante. Foram utilizados dois tipos de geossintéticos, uma geomembrana de PVC e uma geogrelha uniaxial e dois tipos de solo, areia e pedregulho (brita). A análise da influência da densidade relativa do solo foi realizada através de ensaios na interface areia-geossintético em duas densidades relativas diferentes (35 e 100%). A influência da tensão confinante foi estudada através de ensaios com três tensões confinantes distintas (2,1; 3,2 e 5,1 kPa). Os resultados mostram que a influência de fatores como densidade relativa do solo, tensão confinante e tipo de solo, dependem do tipo do geossintético. O aumento da densidade relativa do solo promove um acréscimo de resistência na interface para a geogrelha e uma redução para a geomembrana. O aumento da tensão confinante reduz o ângulo de rampa na ruptura, sendo este efeito mais pronunciado na interface areia-geogrelha. Em relação ao tipo de material, a interface brita-geogrelha é a que apresenta maior resistência.
In environmental works, where geosynthetics are used as protection system and of slope covering, it is of extreme importance the knowledge of the interaction mechanism soil-geosynthetic, through the obtaining of the parameters of resistance of the interface (adhesion and interface friction angle). The laboratory test more appropriate for the obtaining of those parameters, in these conditions, is it the inclined plane test or ramp test, because it allows to simulate the field condition where the shearing happens in inclined plane under low tensions. Like this, this work presents a study about the interaction soilgeosynthetic through ramp tests, executed in an equipment of great dimensions seeking to analyze the influence of some factors, such as, geosynthetic type, soil type, relative density of the soil and confinement pressure. Two geosynthetics types, a PVC geomembrane and a uniaxial geogrid, two soil types, it sand and gravel (break). The analysis of the influence of the relative density of the soil was accomplished through tests in the interface sand- geosynthetic in two different relative densities (35 and 100%). The influence of the confinement pressure was studied through tests with three different confinement pressures (2,1; 3,2 and 5,1 kPa). The results show that the influence of factors as relative density of the soil, pressure confinement and soil type, they depend on the type of the geosynthetic. The increase of the relative density of the soil promotes an increment in the interface resistance for the geogrid and a reduction for the geomembrana. The increase of the confinement pressure reduces the ramp angle in the rupture, being this more pronounced effect in the interface sand-geogrid. In relation to the material type, the interface gravel-geogrid presents larger resistance.
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Sze, Hon-yue, and 施漢裕. "Initial shear and confining stress effects on cyclic behaviour and liquefaction resistance of sands." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45700837.
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Adsero, Matthew E. "Effect of jet grouting on the lateral resistance of soil surrounding driven-pile foundations /." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2381.pdf.
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Karlowskis, Victor. "Soil Plugging of Open-Ended Piles During Impact Driving in Cohesion-less Soil." Thesis, KTH, Jord- och bergmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-156394.
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During impact driving of open-ended piles through cohesion-less soil the internal soil column may mobilize enough internal shaft resistance to prevent new soil from entering the pile. This phenomena, referred to as soil plugging, changes the driving characteristics of the open-ended pile to that of a closed-ended, full displacement pile. If the plugging behavior is not correctly understood, the result is often that unnecessarily powerful and costly hammers are used because of high predicted driving resistance or that the pile plugs unexpectedly such that the hammer cannot achieve further penetration. Today the user is generally required to model the pile response on the basis of a plugged or unplugged pile, indicating a need to be able to evaluate soil plugging prior to performing the drivability analysis and before using the results as basis for decision. This MSc. thesis focuses on soil plugging during impact driving of open-ended piles in cohesion-less soil and aims to contribute to the understanding of this area by evaluating models for predicting soil plugging and driving resistance of open-ended piles. Evaluation was done on the basis of known soil plugging mechanisms and practical aspects of pile driving. Two recently published models, one for predicting the likelihood of plugging and the other for predicting the driving resistance of open-ended piles, were compared to existing models. The main outcomes from the model evaluations are: • Internal shaft resistance, pile diameter and pile velocity/acceleration were found to be the primary input parameters affecting the result in the models used to predict if soil plugging is likely to occur. • The pile diameter was shown to have less influence on the calculated driving resistance in the recently published model, derived from measurements of plug length ratios, compared to in the existing model. This thesis also includes a full-scale field study conducted during the initial piling operations for the construction of the new Värtahamnen seaport in Stockholm (Sweden). The soil conditions cause the piles to be driven through very dense post glacial moraine, in which little is known about soil plugging. The drivability performance of 146 open-ended and closed-ended steel pipe piles with diameters ranging from 914-1168 mm was compared through analysis of driving records. The aim was to evaluate if open-ended piles resulted in a drivability related gain and if so during which part of the installation process. The driving records were used to quantify the performance in terms of driving time and energy required to drive the piles. The main conclusions from the field study are: • Significant time savings were achieved by using open-ended piles instead of closedended piles. The time advantage was bigger during impact driving, compared to vibratory driving, and on average the impact driving of open-ended piles took 9 minutes versus 26 minutes for closed-ended piles. • Contrary to what was expected, namely that the open-ended piles would result in lower driving resistance, the results indicate that the majority of the time savings came from open-ended piles being more stable during driving and thereby requiring fewer adjustments.Under slagdrivning av öppna pålar i friktionsjord förekommer det att den interna jordpelaren mobiliserar tillräckligt mycket internt mantelmotstånd för att förhindra inträngning av ny jord. Detta fenomen, på svenska vanligen kallat jordpluggning, medför att drivbeteendet för pålen övergår till att likna det hos en sluten och massundanträngande påle. Oförmåga att på ett korrekt sätt beakta jordpluggning medför ofta att drivmotståndet för öppna pålar antingen överskattas, vilket medför att onödigt kraftfull och kostsam utrustning används, eller underskattas vilket kan medföra att pålen pluggar och inte kan drivas till avsett djup. I dagsläget kräver drivbarhetsanalyser generellt sett att användaren måste modellera pålen som en pluggad eller opluggad påle. Detta medför att det finns ett behov att kunna utvärderajordpluggning innan drivbarhetsanalysen genomförs, samt även vid utvärdering av resultaten från drivbarhetsanalysen. Detta examensarbete fokuserar på jordpluggning vid slagdrivning av öppna pålar i friktionsjord och syftar till att öka kunskapen inom området genom att utvärdera modeller som kan användas för att uppskatta huruvida jordpluggning är sannolikt, samt modeller för att uppskatta drivmotståndet för öppna pålar. Utvärderingen av nämnda modeller skedde med utgångspunkt i kända mekanismer som förknippas med jordpluggning, samt i praktiska aspekter av påldrivning. Två nyligen publicerade modeller, en avsedd att utvärdera huruvida pluggning är sannolikt och den andra för att uppskatta det förväntade drivmotståndet, jämfördes med befintliga modeller för samma ändamål. De huvudsakliga slutsatserna av modellutvärderingen är: • Internt mantelmotstånd, pålens diameter samt pålens hastighet/acceleration var de faktorer som hade störst inverkan på resultatet hos de modeller som avser utvärdera huruvida jordpluggning är att förvänta. • Pålens diameter visade sig få mindre inverkan på beräknat drivmotstånd i den nyligen publicerade modellen, baserad på mätningar av plugglängd relativt penetrationsdjup, jämfört med i den befintliga modellen. Examensarbetet innefattar även en fältstudie genomförd under inledningen av pålningsarbetet vid uppförandet av nya Värtahamnen i Stockholm. Markförhållandena på platsen medför att pålarna drivs genom bottenmorän, ett jordförhållande där det i stor utsträckning saknas erfarenheter relaterade till jordpluggning. Med hjälp av pålprotokoll jämfördes drivbarheten hos 146 öppna och slutna pålar med diametrar 914-1168 mm. Målet var att fastställa huruvida öppna pålar medförde ökad drivbarhet och i så fall under vilket skede av drivprocessen. Pålprotokollen användes för att kvantifiera vinsten i form av drivtid samt erforderlig drivenergi. De huvudsakliga slutsatserna från fältstudien är: • Betydande tidsvinst kunde påvisas för öppna pålar, jämfört med stängda pålar. Tidsvinsten var större under slagdrivning än under vibrationsdrivning och i snitt 9 minuter jämfört med 26 minuter för stängda pålar. • I motsats till det förväntade utfallet, nämligen att de öppna pålarna inte skulle plugga, antyder resultaten att majoriteten av tidsvinsten kan kopplas till att de öppna pålarna var mer stabila under drivning vilket resulterade i färre korrigeringar
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Yusoff, Nor Azizi bin. "Effect of rate of shearing on resistance in fine grained soil." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555234.
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Geotechnical design relies on correct interpretation of field observations from site investigation, full scale testing and laboratory element strength tests. A wide spectrum of applied shear strain rates are adopted which have the potential to generate conflicting soil strength parameters. Modern geotechnical applications frequently operate at significantly higher levels of applied shear strain rate than traditional construction methods. This can often lead to overestimation of strength parameters and thus caution must be exercised when interpreting data to prevent unsafe design. A new Rowe Cell-Vane Shear apparatus has been developed to investigate the relationship between undrianed shear strength and rate effects. This apparatus is capable of providing a torque up to 20Nm and rotation rates from O.5mm/s to 400mm/s. The consolidometer was 254 mm in diameter and 126 mm high, with an aluminium base plate designed to accommodate four vanes during consolidation. Rigorous calibrations have been conducted to account for vane shaft friction and motor lag time. Three design mixes were established by using a mixture of Speswhite Kaolin, a silica flour (Oakamoor HPF3) and a silica sand (Buckland P30) at different percentages. The design mixes covered a range of Atterberg limits from low to high plasticity. Functionality of the newly developed apparatus is confirmed through the test results. Rate effects were observed for the peak undisturbed, residual undisturbed and residual disturbed strengths. The rate effects on peak undisturbed shear strength increased with decreasing LI. The results from three different soils at similar liquidity indices indicated that the rate effect was dependant on liquidity index not the plastic limit or liquid limit.
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Gebretsadik, Alex Gezahegn. "Shear Resistance Degradation of Lime –Cement Stabilized Soil During Cyclic Loading." Thesis, KTH, Jord- och bergmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141196.
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This thesis presents the results of a series of undrained cyclic triaxial tests carried out on four lime-cement stabilized specimens and clay specimen. The shear resistance degradation rate of lime-cement column subjected to cyclic loading simulated from heavy truck was investigated based on stress-controlled test. The influence of lime and cement on the degradation rate was investigated by comparing the behavior of stabilized kaolin and unstabilized kaolin with similar initial condition. The results indicate an increase in degree of degradation as the number of loading cycles and cyclic strain increase. It is observed that the degradation index has approximately a parabolic relationship with the number of cycles. Generally adding lime and cement to the clay will increase the degradation index which means lower degree of degradation. The degradation parameter, t has a hyperbolic relationship with shear strain, but it loses its hyperbolic shape as the soil getting stronger. On the other hand, for unstabilized clay an approximate linear relationship between degradation index and number of cycles was observed and the degradation parameter has a hyperbolic shape with the increase number of cycles. It was also observed that the stronger the material was, the lesser pore pressure developed in the lime-cement stabilized clay.
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Gogu, Sudhir Reddy. "Resistance and Morphology of Azotobacter Vinelandii Grown on Dialyzed Soil Agar." Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc798103/.
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The objectives of this research were to identify the form of Azotobacter as it exists in situ in the soil; to compare its resistance to that of laboratory grown cysts typical of those described in the literature; and to compare its resistance to that of cells grown on dialyzed soil agar. In addition, the morphology of the cells grown on dialyzed soil agar was examined by light and electron microscopy and then compared to the cysts grown on n-butanol Burk's medium. Dipicolinic acid and oxygen uptake rate were measured in cysts and on cells grown on dialyzed soil agar in order to determine whether the cells grown on dialyzed soil agar were endospores or other dormant form and also to measure the respiratory quotient in these cells.
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Lyons, Rebecca Louise. "Resistance Mechanisms to Soil-Borne Cereal Mosaic Virus & Soil-Borne Wheat Mosaic Virus in Wheat and Barley." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503804.
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Pankow, Christine Ann. "Effect of Soil Type, Composting, and Antibiotic Use on Fate of Antibiotic Resistance Genes and Microbial Community Composition in Dairy and Beef Manure Applied Soils." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/86672.
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Manure is a commonly used soil fertilizer, but there are concerns that this practice could affect the spread of antibiotic resistance genes (ARGs) from farm to fork. A microcosm-scale study evaluated the effect of prior antibiotic use (manure-based soil amendments generated from dairy and beef cattle with or without antibiotic administration), composting, and soil type on the quantity of ARGs and the microbial community composition of dairy and beef manure applied soil. ARGs were analyzed through novel metagenomic techniques and quantitative polymerase chain reaction of sul1, tet(W), and 16S rRNA gene, while the microbial community composition was determined via 16S rRNA amplicon sequencing. The results indicated that while prior antibiotic administration elevated the relative abundance of ARGs and changed the microbial community of raw manure applied soils, composting reduced this effect. However, compost applied soils still had a higher relative abundance of ARGs than the unamended soils and occasionally soil applied with raw manure of untreated cattle. Soil type may be a mediating factor as there were differences observed between the three soil types (sandy loam, silty clay loam, and silty loam) with sandy loam amended soils often having the least attenuation of ARGs. As the relative abundance of ARGs was still elevated and the microbial community composition still significantly different from the unamended soils after 120 days, these results suggest that 120 days is not a long enough waiting period between biological soil amendments and crop harvest for ARG dissipation.Master of Science
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Perera, Dinum. "DEVELOPING RESISTANCE TO WHITEFLY IN POINSETTIA (Euphorbia pulcherrima) USING Agrobacterium-MEDIATED TRANSFORMATION." MSSTATE, 2009. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07072009-214527/.
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The broad objective of this research was to develop transgenic poinsettia that express tryptophan decarboxylase (TDC) capable of protecting poinsettia against whitefly. An effective and efficient in vitro micro propagation and proliferation technique of poinsettia Prestige Red was successfully developed in this study and this protocol can be used for potential development of transgenic poinsettia. Poinsettia Prestige Red was successfully infected by Agrobacterium rhizogenes producing hairy roots at the site of infection. Investigations of more effective PGR concentrations are necessary in order to develop transgenic poinsettia through hairy roots. Stem disks of poinsettia Eckespoint Pollys Pink developed into somatic embryos when they were transformed by A. tumefaciens harboring TDC. A. tumefaciens-mediated transformation of poinsettia through somatic embryogenesis is cultivar dependent. Additional research into more effective PGR combinations, antibiotic concentrations and antinecrosis chemicals is required in order to develop transgenic poinsettia harboring TDC through somatic embryogenesis using A. tumefaciens.
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Qian, Leilei. "Evaluation of Antibiotic Resistance Profiles of Enteric Bacteria in Swine Feces Before and After Lagoon Treatment." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-05082007-161836/.
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Antibiotics are used in livestock production for the treatment of diseases and for improvement of feed efficiency and growth. However, agricultural use of antibiotics may be partly responsible for the emergence of antibiotic-resistant organisms. Large amounts of managed manure are land applied, which opens the door for the spread of antibiotic resistance in the environment. Thus, the goal of this project was to evaluate the effects of lagoon treatment on the persistence of antibiotic resistant enteric bacteria isolated from swine feces. Both cool season and warm season samples were collected from a swine farm located in Sampson County, NC. Each season samples included three nursery swine fecal samples, three nursery swine lagoon liquid samples, four finishing swine fecal samples, three finishing swine lagoon liquid samples, and four soil samples from both nursery and finishing swine spray field. A total of 4032 E. coli isolates and 4896 Enterococcus isolates were obtained from the samples. The antibiotic resistance profiles of the isolates were determined using a set of antibiotics at various concentrations. The antibiotic cephalothin, erythromycin, oxytetracycline, tetracycline, streptomycin, and neomycin were tested for both bacterial species, but different concentrations were applied. For E. coli, rifampicin was also tested; for Enterococcus, chlortetracycline, vancomycin, and amoxicillin were also tested. After antibiotic resistance analysis was achieved, 25 isolates were randomly selected from each sample for further evaluation by polymerase chain reaction test. Soil samples were collected; however, fecal indicator bacteria were not recovered. Additionally, E. coli was not recovered from warm season nursery lagoon samples. All isolates displayed multiple antibiotic resistance, and for the isolates from the same source, the resistance patterns were similar for the antibiotics within the same antibiotic family. Percentages of resistant isolates were greater in nursery fecal samples than in finishing fecal samples for majority of antibiotic tests. For nursery samples, percentages of antibiotic resistant isolates decreased after lagoon treatment for majority of antibiotic tests. For finishing samples, no such trend was obvious. The results indicated that antibiotic resistant isolates still persist in the lagoon liquid, which may cause potential risk to human and environmental health. And because antibiotic resistance may affect later therapeutic and subtherapeutic value of these antibiotics, management strategies of agricultural antibiotic use may be improved. The antibiotic resistance patterns and molecular banding patterns of the isolates were not unique to a specific source. The results suggest that there is considerable overlap among nursery feces, nursery lagoon, finishing feces and finishing lagoon samples. However, if combine of the feces and the lagoon isolates together and only classify isolates from nursery to finishing swine, the percentages of correctly classified isolates became larger. The results suggest that ARA and PCR would best be used for identifying fecal contamination from swine sources based on broad categories (nursery versus finishing) instead of relying on these procedures for specific identification of lagoon and feces separately.
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Brown, Rollins Patrick. "Predicting the ultimate axial resistance of single driven piles." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3025000.
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Henry-Poulter, Siobhan. "An investigation of transport properties in natural soils using electrical resistance tomography." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389933.
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Lorentz, Andrew. "Design, construction and testing of an ascending micropenetrometer to measure soil crust resistance." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/8511.
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The increasing world population is putting pressure on global food production.
Agriculture must meet these growing demands by increasing crop yields. One phenomenon
which prevents seedling emergence and damages crop yield is soil crusting. Understanding
of soil crusting and the factors which influence it is fundamental to ensuring good crop
production. An instrument which will test soil crust strength in a novel way, mimicking
seedling growth, may lead to pre-emptive agricultural soil management which could
increase crop production. This work details the process of design, construction and testing
of an ascending penetrometer to measure soil crust strength. The full design process is
discussed from concept generation and evaluation, using experimental methods and a
multi-criteria decision making tool, through to final design configuration, specification,
manufacture and testing.
Traditionally, soil penetrometers measure soil strength by forcing a probe from the surface
of the soil into the bulk soil below. To more accurately measure the direct impedance a
seedling would experience a device should measure impedance from the bulk soil upwards
and into the soil crust, mimicking what a growing seedling would experience. Results
prove that the manufactured ascending penetrometer with a force resolution of 0.01N and
displacement resolution of 0.0004mm is capable of detecting differences in soil crusts. At
these resolutions and accuracy to 0.1N and 0.1mm excellent repeatability was achieved.
The machine is therefore a useful and realistic tool for quantitatively comparing soil crusts
in soil. It is hoped that being able to compare soil crust strength will lead to improved soil
management techniques.
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Parra, Jorge R. "Evaluation of uncertainties in the resistance provided by slender reinforcement for slope stablization /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3137734.
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Herbst, Mark Alan. "Impact of Mass Mixing on the Lateral Resistance of Driven-Pile Foundations." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2353.pdf.
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Froemke, Aaron Michael. "Horseweed (Erigeron canadensis) Control in No-Till Soybean Systems on a Coarse Textured Soil." Thesis, North Dakota State University, 2020. https://hdl.handle.net/10365/31791.
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Horseweed (Erigeron canadensis) is a competitive winter or summer annual broadleaf weed. When uncontrolled, horseweed can reduce soybean (Glycine max) yields by 93%. Research was conducted to advance our knowledge on horseweed growth stage response to foliar-active and residual herbicides, fall applications, and the utility of differing herbicide technologies. Greenhouse results determined that herbicide efficacy was greatest when applied to early rosette horseweed providing an average control of 70% across herbicide treatments. Field trials determined that preventing new emergence with flumioxazin, added with dicamba or paraquat to kill existing plants in the fall, increased control to 99% the following spring. Field trials also determined that dicamba, applied PRE or POST, provided excellent horseweed control and was an effective soybean technology system for horseweed-infested fields. Saflufenacil controlled existing plants, but residual benefits were unclear. Further research must be done to investigate residual activity of PRE herbicides applied before horseweed emergence.
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Nesme, Joseph. "Characterization of antibiotic resistance genes abundance and diversity in soil bacteria by metagenomic approaches : what is the dissemination potential of the soil resistome?" Phd thesis, Ecole Centrale de Lyon, 2014. http://tel.archives-ouvertes.fr/tel-01068359.
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Environmental bacteria and especially soil bacteria are active producers of antibiotic molecules and most drugs used nowadays are isolated from saprophytic soil bacteria and these microorganisms have also evolved numerous resistance pathways leading to an arsenal of Antibiotic Resistance Genes Determinants (ARGD) known as the environmental resistome. A survey of ARGD prevalence is required in order to characterize this natural phenomenon with critical implications in our current infectious diseases management. In order to perform such analysis we compiled a set of 71 metagenomic datasets from various environmental origins: soils, oceans, lakes, human feces, indoor air, etc., and compared their sequences with a database of known antibiotic resistance gene determinants (ARGD). ARGD-annotated reads are found in every environment analyzed confirming their ubiquity. Soil is found to be the richest and shares a large part of ARGD with the human gut microbiome, indicating ARGD transfers between these environments. Experiments using qPCR and metagenomic DNA sequencing on soil samples from two sites with known and distinct antibiotic pollution history were conducted to understand how ARGD abundance and diversity in soil are affected when impacted by antibiotic molecules. The first site is a reference soil from a long-term experiment without history of antibiotic pollution (Rothamsted Park Grass, UK). Soil microcosms are setup with addition of either antibiotic-containg animal manure or pure molecules and incubated for 6 months to monitor changes in ARGD concentration following these perturbations. Our second study-site is a very remote settlement in French Guiana where antibiotics are available since recently and may have impacted the local soil microbial community. Soil samples are taken following a line-transect going from the village (antibiotic source) to 3km deep in the forest in a gradient of human-impact. Our results all confirm prevalence of ARGD in soil at significant abundance but also that ARGD distribution is more correlated to environmental factors such as soil type, microbial taxonomy composition or microcosms incubation conditions than antibiotic molecules exposure in both sites. Pathogens ARGD diversity is far lower than ARGD diversity found in the environment and not all the soil resistome is readily accessible for transfer. In order to characterize the soil mobile gene pool, a strategy is proposed to isolate specifically mobile DNA directly from the environment for sequencing purposes. Better knowledge on the microbial ecology factors limiting ARGD transfers to pathogens may greatly help us reduce the current threat on our limited medical antibiotic molecules resource.
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Hedin, Matthew Lowell. "The Effects of dairy cattle antibiotics on soil microbial community cycling and antibiotic resistance." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83227.
Full textAbstract:
Antibiotic use in agricultural ecosystems has the potential to increase resistance to antibiotics
in soil microbial communities since 40-95% of an antibiotic dose administered to livestock is
excreted intact or as metabolites. Exposure to antibiotics is also known to alter microbial
community composition, biomass, and physiology, but the potential influences of antibiotic
residues on the essential ecosystem processes that microbes regulate, e.g., carbon and
nitrogen cycling are not well understood. I investigated the effects of antibiotic residues
associated with dairy cattle operations on soil microbial communities and the ecosystem
processes they regulate. I examined the effects of antibiotic exposure on the biogeochemical
functioning of soil microbial communities by measuring the activity of extracellular enzymes
associated with organic matter processing and nutrient mineralization in soils collected from
dairy cattle operations across the United States. At each experimental station paired sites
were identified by local managers that represented sites with high and low stocking rates of
dairy cows who had been treated prophylactically with antibiotics to prevent mastitis.
Responses varied among individual enzymes, but I found an overall significant decrease in total
hydrolytic enzyme activity under high cattle stocking rates indicating a change in the
functioning of the microbial community in soils exposed to antibiotic laden manure. Principle
components analysis suggest that while some of the variation in enzyme activities are
associated with the abundance of antibiotic resistance genes, soil organic matter (total organic,
mineralizable, and particulate organic carbon) was the most significant variable accounting for
differences in enzyme activities. This reflects an inherent challenge in studies of antibiotic
exposure in agricultural landscapes: the difficulty of distinguishing direct effects of antibiotic
residues from the organic matter and nutrient subsidy associated with manure applications. To
address this concern I conducted a series of incubation experiments manipulating soils to
isolate the influences of antibiotics, manure resource subsidies, and bovine microbiome
inoculants into soils. Specifically, I examined soil respiration and antibiotic resistance gene
counts using qPCR following treatment with cephapirin, pirilimycin and a positive and negative
control. I found that pre-exposure to antibiotics and manure is important in modulating the
response of microbial communities (soil respiration, and gene copy numbers of AmpC and
TetO) to further antibiotic exposure. I conclude that antibiotics themselves have a direct effect
on soil communities and their functioning that is additive to the effect of manure (i.e., as a
resource subsidy). This effect is mediated by the history of previous exposure to antibiotics, i.e.,
cattle stocking density. These results suggest that antibiotic residues from dairy cattle
operation may have significant effects on microbial communities and the biogeochemical
cycling they regulate in agricultural ecosystems.Master of Science
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Newill, Paul Anthony. "Imaging of soil moisture in the root zone using capacitively coupled electrodes." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/imaging-of-soil-moisture-in-the-root-zone-using-capacitively-coupled-electrodes(24dbb858-3a0f-4fd7-8956-0070d2e47283).html.
Full textAbstract:
This research explores the use of insulated electrodes to determine electrical impedance distributions within soil cores. It is used to infer the effect of roots on soil moisture which, in turn, can provide knowledge relating to crop breeding programmes. These programmes are becoming increasingly important in order to address challenges posed by global population growth and climate change. Direct contact electrical impedance measurements in soil are frequently used but these are vulnerable to electrochemical effects and corrosion. Insulated electrodes are used in the present work to overcome these difficulties and a modified electrode model has been proposed. Measurements require the acquisition of spectroscopic complex impedance and extraction of the real impedance to infer soil moisture content. Calculated and simulated impedance, from the analytical solution and an FEM model respectively, were compared to measurements performed within a parallel-plate test cell containing saline solutions. The effects of moisture, compaction and temperature on soil impedance measurements have been explored. Finally, two growth trials using maize plants and control vessels were performed to create 2D images of impedance distributions, from which moisture placement was inferred. Results show that for saline electrolytes, the insulated electrode method was capable of estimating the impedance of tap water to within 10% of calibrated laboratory equipment. For soil based measurements, the variation of moisture content from 5-30% resulted in a 1000-fold decrease in impedance. The change was most significant in drier soils. For compaction based testing, at 5% moisture content soil impedance decreased by approximately 40%, compared to only 20% in the wettest samples. Temperature testing revealed an impedance change of approximately 2%/ °C, in agreement with earlier reports. Plant growth trials revealed increases in electrical impedance due to soil drying from an initial value of 1-2kΩ when the soil was wetted to field capacity, to as much as 60kΩ when dry. Only small changes were evident in the control vessels. It was also found that areas exposed to potential evaporation, such as at the surface closest to the plant stem, suffered significant losses in moisture content, reaching as high as 15-20kΩ. This research utilises a measurement technique which has not previously been used to measure soil impedance to infer moisture content. The research also found that the scaling of a thin layer within an FEM model can significantly reduce computational demands, while retaining accuracy, and allow more complex FEM simulations to be performed on a less powerful computer.
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Springer, Yuri P. "Epidemiology, resistance structure, and the effects of soil calcium on a serpentine plant-pathogen interaction /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2006. http://uclibs.org/PID/11984.
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Mirzoyan, Artak Davit. "Lateral Resistance of Piles at the Crest of Slopes in Sand." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2088.pdf.
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Almeida, Cinara Xavier de [UNESP]. "Qualidade física de um latossolo vermelho sob sistema de semeadura direta e cultivo convencional." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/105136.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O estudo de indicadores de qualidade dos solos é fundamental para avaliar o nível de degradação imposta pelo uso agrícola e para estabelecer estratégias de manejo sustentáveis. O objetivo geral deste trabalho foi avaliar a qualidade de um Latossolo Vermelho distrófico típico sob cultivo convencional (CC) e sistema de semeadura direta (PD), por meio de indicadores físicos e da avaliação da produção das culturas da soja e do milho. Os objetivos específicos foram: i) comparar a eficiência de funções de pedotransferência para a curva de resistência do solo à penetração presentes na literatura, por meio do ajuste de dados obtidos com o penetrômetro de impacto e também com o penetrômetro eletrônico; ii) determinar a resistência do solo à penetração (RP) durante o ciclo das culturas relacionando-a ao conteúdo de água no solo (Ug); e, iii) determinar alguns indicadores de qualidade física do solo, relacionando-os com as características agronômicas das culturas. Os sistemas de uso e manejo do solo foram: CC e PD por sete e oito anos consecutivos (solo de textura média) e CC e PD por nove e dez anos consecutivos (solo de textura argilosa). Foram determinadas a RP, a porosidade total, a macroporosidade, a microporosidade, a retenção de água no solo, o índice S, a densidade, a densidade do solo máxima e também a densidade do solo relativa. Nas culturas da soja e do milho foram avaliadas: massa seca das raízes, altura das plantas, altura de inserção da primeira vagem/espiga, número de vagens por planta de soja, massa seca da parte aérea do milho e produtividade. As Equações ; ; e não diferiram e foram as mais precisas e acuradas na predição da RP. Dentre os sistemas de manejo, embora o CC tenha apresentado melhores resultados em relação aos indicadores de qualidade física do solo, o PD foi o que proporcionou maior produção de milho
The study of indicators of soil quality is essential to assess the level of degradation imposed by agricultural use and to establish sustainable management strategies. The aim of this study was to evaluate the quality of an Oxisol under conventional (CC) and no-tillage (NT), through soil physical indicators and assessing the soybeans and corn crops yield. The specific objectives were: i) compare the efficiency of pedotransfer functions due to soil resistance to penetration curve in the literature, by adjusting the data obtained with the impact penetrometer and also with the electronic penetrometer), ii) monitoring the soil resistance to penetration (PR) during the crop cycle relating it to the soil water content (Wc), and iii) determine some soil physical indicators, relating them to the agronomic characteristics of crops. The management systems were: CC and NT to seven and eight years consecutives (sandy loam soil) and CC and NT to nine and ten years consecutives (clayey soil). The PR, total porosity, macroporosity and microporosity, soil water retention, index S, soil bulk density, maximum dry bulk density, and also the relative bulk density were determined. The agronomic characteristics of soybean and corn crops have been evaluated: roots dry mass, height plant, insertion of the first spike height/pod, pods per soybean plant number, corn shoot dry mass and yield. The equations ; ; e did not differ and were the most precise and accurate in prediction of soil resistance to penetration. Among the management systems, although the CC has shown better results in relation to soil physical indicators, the NT was that the highest corn yield
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Dirbák, Štefan. "Návrh a realizace plošného měření rezistivity půdy." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-413053.
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This diploma thesis deals with research and study of soil impedance measurement and soil resistivity. Currently, the issue of measuring and determining soil resistance is ensured through the gradual measurement of certain soil parameters at individual points of the surface (or depth of the ground). This thesis focuses on the idea of measuring soil resistance on a certain area using a network of electrodes through a suitably designed test, measurement and evaluation system. Such an approach may find application in the need to determine soil parameters (such as resistivity) on a specific demarcated area (or depth). The prospect of such an application can be seen in saving time, energy and money needed to measure the soil resistivity of a certain area (as opposed to gradual point measurements). The configuration possibilities of OMICRON CPC 100 measuring instrument were used for the design and implementation of the measuring system for the mentioned purpose. The work is completed by verification of the proposed solution by real measurement with evaluation of the results.
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Archundia, Peralta Denisse. "Etude du devenir et de l’impact des antibiotiques à l’échelle d’un bassin versant : application au bassin versant du Katari (Bolivie)." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAU016/document.
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L’Altiplano Nord bolivien est soumis naturellement à des conditions climatiques et pédologiques contraignantes. Il est particulièrement impacté par des activités humaines variées tels que l’exploitation minière, l’agriculture et plus récemment l’urbanisation. Le bassin versant (BV) du Katari englobe une variété d’activités anthropiques et englobe la plus grande ville de l’Altiplano (El Alto). Cette ville s’est développée avec un aménagement territorial minimal et une réglementation insuffisante. A ce jour, peu d’études ont caractérisé les résidus pharmaceutiques et leur devenir dans les conditions extrêmes comme celles de l’Altiplano. Les antibiotiques sont des micropolluants organiques et comptent aujourd’hui comme un des groupes les plus importants parmi les polluants émergents. Tout d’abord une évaluation de l’état général de la pollution du BV a été réalisée. Les résultats ont mis en évidence que la ville d’El Alto est la principale source de pollution en nutriments (en particulier phosphate), éléments trace métalliques, composés antibiotiques et gènes de résistance bactérienne. La suite des travaux s’est focalisé sur les processus influençant le devenir du e Sulfamethoxazole, choisi comme composé modèle car il est couramment détecté dans les milieux naturels et est présent à des concentrations importantes dans le site d’étude. La sorption est le paramètre principal influant sur son devenir dans les sols du BV et est liée à la spéciation pH-dépendante du SMX et les caractéristiques physicochimiques des sols. Les interactions hydrophobes, la sorption sur la matière organique et les échanges ioniques sont les principaux processus impliqués. Le transfert vertical du composé étudié est facilité par la présence des sols plutôt perméables, ce qui explique sa présence dans les eaux souterraines étudiés. Le taux de photodégradation du SMX s’est révèle être faible dans les eaux chargées en ions et matière organique, mais reste le paramètre principal expliquant sa dissipation dans les eaux de surface étudiées. Le SMX peut être potentiellement biodégradé dans la majorité des sols étudiés, en relation avec leur taux de matière organique et à la présence de communautés microbiennes pré-adaptées à la présence du SMX. Les impacts du SMX sur la structure et l’abondance relatives des espèces de populations bactériennes du sol sont liés à la texture et à l’usage des sols étudiés (sols de montagne, sols urbains ou sols agricoles) ainsi qu’à la présence des populations microbiennes pré-adaptés. L’ajout du SMX n’a pas entrainé le développement des gènes de résistance spécifiques à cet antibiotique (gènes sul) suggérant la présence de mécanismes moins spécifiques et probablement efficaces contre une grande variété de composés. Le modèle GREAT-ER a été utilisé avec succès pour la simulation des concentrations environnementales de SMX et l’évaluation du risque environnemental, montrant que le risque écotoxicologique est plus important dans les zones du réseau hydrographique à l’aval des activités urbainesThe Altiplano North Bolivian is naturally subject to climate and soil limiting conditions. It is particularly impacted by various anthropogenic activities such as mining, agriculture and more recently urbanization. The Katari watershed encompasses a variety of human activities and includes the largest city of the Altiplano (El Alto), which has developed with a minimal land planning and insufficient regulation. To date, few studies have characterized the pharmaceutical residues and their fate in the extreme conditions of the Altiplano. Antibiotics are organic micro-pollutants considered as one of the most important groups of emerging pollutants. First, an assessment on the general state of pollution of the watershed was performed, as it is known that antibiotics may interact with other molecules (e.g. trace metal elements). Further work was carried out with the Sulfamethoxazole antibiotic as model compound, as it is commonly detected in natural environments as well as in the study site. The results showed that the city of El Alto is the main source of pollution in nutrients (especially phosphate), trace metal elements, bacteria, antibiotics and antibiotic resistance genes. Sorption is the main parameter affecting its fate in the study site which is linked to the pH-dependent speciation of SMX and the physicochemical characteristics of studied soils. Main involved processes are hydrophobic interactions, sorption on organic matter and ion exchange. SMX vertical transfer is facilitated by the presence of rather permeable soils, explaining its presence on studied ground waters. Observed SMX photodegradation rate was found to be low but remains the main factor explaining its dissipation in studied surface waters. SMX may be potentially biodegraded in most of studied soils in relation to their organic matter content and the presence of pre-adapted microbial communities to its presence. SMX impacts on bacterial populations were linked to the location, texture and use of studied soils (mountain, urban or agricultural soils) and the presence of pre-adapted microbial populations. We observed a change in the structure of microbial communities and on the relative abundance of bacterial soil species. The addition of SMX has not led to the development of specific resistance genes to this antibiotic (sul genes), suggesting the presence of less specific mechanisms which can be effective against a wide variety of compounds. The GREAT-ER model has been successfully used for the simulation of SMX environmental concentrations and the environmental risk assessment. Ecotoxicological risk is greater in areas under urban influence
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Fogler, Kendall Wilson. "Effect of Soil Amendments from Antibiotic Treated Cows on Antibiotic Resistant Bacteria and Genes Recovered from the Surfaces of Lettuce and Radishes: Field Study." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/92587.
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Cattle are commonly treated with antibiotics that may survive digestion and promote antibiotic resistance when manure or composted manure is used as a soil amendment for crop production. This study was conducted to determine the effects of antibiotic administration and soil amendment practices on microbial diversity and antibiotic resistance of bacteria recovered from the surfaces of lettuce and radishes grown using recommended application rates. Vegetables were planted in field plots amended with raw manure from antibiotic-treated dairy cows, composted-manure from cows with different histories of antibiotic administration, or a chemical fertilizer control (12 plots, n=3). Culture-based methods, 16SrDNA amplicon sequencing, qPCR and shot-gun metagenomics were utilized to profile bacteria and characterize the different gene markers for antibiotic resistance. Culture-based methodologies revealed that lettuce grown in soils amended with BSAs had significantly larger clindamycin resistant populations compared to control conditions. Growth in BSAs was associated with significant changes to the bacterial community composition of radish and lettuce. Total sul1 copies were 160X more abundant on lettuce grown in manure and total tet(W) copies were 30X more abundant on radishes grown in manure. Analysis of shotgun metagenomic data revealed that lettuce grown in manure-amended soils possessed resistance genes for three additional antibiotic classes compared to other treatments. This study demonstrates that raw, antibiotic-exposed manure may alter microbiota and the antibiotic resistance genes present on vegetables. Proper composting of BSAs as recommended by the U.S. Department of Agriculture and Environmental Protection Agency is recommended to mitigate the spread of resistance to vegetable surfaces.MSLFS
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Stolte, Rhett L. "THE INFLUENCE OF SOIL-APPLIED HERBICIDE AND PATHOGEN INTERACTION ON UPREGULATION OF SYSTEMIC ACQUIRED RESISTANCE IN SOYBEAN." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2533.
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Exposure of crop plants to stress or injury, such as soybean injury by PPO-inhibitor herbicide, may stimulate the upregulation of Systemic Acquired Resistance (SAR) and reduce plant susceptibility to other stressors, such as disease-causing pathogens. Field and laboratory studies were initiated to evaluate the upregulation of SAR, examining the effects of PPO-inhibiting herbicide treatment on Sudden Death Syndrome incidence and severity in soybean and the relationship of disease incidence and severity related to stand count and yield with various population densities. A two-year field study was established in Shawneetown, IL to evaluate grain yield and disease potential of soybean cultivars which are either sensitive or tolerant to protoporphyrinogen oxidase (PPO)-inhibitor herbicides, with seed either treated with insecticide, thiamethoxam and fungicides, fludioxonil and mefanoxam (Upshot) and biological fungicide Bacillus amyloliquefaciens strain D747 (Avonni) (biological fungicide) or non-treated. The seeds were planted at six different seeding rates: 197,684; 247,105; 296,526; 345,947; 395,368; 444,789; with the controls planted at a density of 345,947 seeds ha-1 in a 2x2x7 factorial study design. Field experiments were planted on April 25, 2016 and May 6, 2017 in 76 cm, 4-row plots measuring 3m by 7m, and herbicide was applied to treated plots over the center 2 rows. Data collection included crop injury at 14, 28 and 56 days after treatment (DAT), stand count at 14 and 28 (DAT), plant height and node count at end-of-season (EOS), and disease incidence and severity ratings beginning at the onset of symptomology. Yield data was collected from the center two treated rows. All plots, except the non-treated controls, received an application of sulfentrazone + cloransulam-methyl (316 g ai ha-1). In 2016 the greatest crop injury, categorized by stunting, at 14 DAT occurred in the PPO-tolerant seed variety without a fungicide and insecticide seed treatment at 4.2% planted at 444,789 seeds/ha. At 28 DAT with means pooled over seed treatment and seed variety, we observed the 197,684 seeds/ha plots having greatest crop injury at 5.25%, and lastly at 56 DAT, the 197,684 and 247,105 seeds/ha plots containing untreated, PPO-sensitive seed were the most injured at 12% crop injury. In 2017, 14 DAT was excluded from the analysis, as there was no injury at the time of rating. At 28 DAT, the PPO-sensitive seed variety, pooled over seed treatment, at 197,684 seeds/ha resulted in greater crop injury at 8.6%, similar to 2016. At 56 DAT, similar results were observed as in 2016, at 12% crop injury in the PPO-sensitive seed variety without a seed treatment planted at 197,684 seeds/ha. There were differences in stand count by seeding rate at 14 and 28 DAT, but no interactive effects between the factors in 2016; seed treatment and seed variety were not significant. However, in 2017, there were differences in stand count by seed variety and seed treatment at 14 and 28 DAT, but again, no interactive effects between factors. Relationships between stand count and seeding rate indicated a threshold at which the environment cannot sustain higher planting densities. Environmental conditions were more favorable for crop growth in 2016 than 2017. Rainfall 10 days following planting was recorded at 67 mm and 290 mm in 2016 and 2017, respectively. Soybean node counts in 2016 were greater in the PPO-tolerant variety were seed was treated with a fungicide and insecticide seed treatment. In 2017, node counts were not influenced by seed treatment or seed variety; however, the greatest number of nodes were in the 444,789 seeds/ha planting population. Disease was more prominent in the high-density plots than in the low-density plots, as would be expected because of the effects of competitive stress on plant susceptibility to pathogens as well as more plants to be infected by the pathogen. Sudden Death Syndrome disease incidence (scale of 0 to 100%) in 2016 ranged from 1.2 to 25.5 across rating dates, while severity (scale of 0 to 9 based on leaf symptomology) ranged from 0.3 to 2.2 across rating dates. In 2017 disease incidence ranged from 0 to 25.0 across all rating dates, and disease severity ranged from 0 to 1.6 across all rating dates. Yield in 2016 ranged from 3,449.8 kg/ha to 4,060.3 kg/ha with the highest yield in the PPO-tolerant variety and the lowest in the -sensitive variety. However, in 2017, yield was lowest in the 197,684 plants/ha treatments at 1,509.1 kg/ha and highest in the 444,789 plants/ha treatments at 4,053.9 kg/ha. Significant varietal and seed treatment differences were also noted in 2017.
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Pokharel, Janak. "CYCLIC LOAD RESISTANCE AND DYNAMIC PROPERTIES OF SELECTED SOIL FROM SOUTHERN ILLINOIS USING UNDISTURBED AND REMOLDED SAMPLES." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1545.
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The liquefaction resistance of undisturbed soil samples collected from a selected location in Carbondale, Southern Illinois was evaluated by conducting cyclic triaxial tests. Index property tests were carried out on the sample for identification and classification of the soil. Cyclic triaxial tests were conducted on undisturbed sample after saturation, undisturbed sample at natural water content and remolded samples prepared by compaction in the lab. The results were used to evaluate the effect of saturation and remolding on liquefaction resistance of the local soil. Effect of effective confining pressure on dynamic properties of soil (Young's Modulus and Damping ratio) was also studied. Forty five stress controlled cyclic triaxial tests were performed. Three different values of initial effective confining pressure (5 psi, 10 psi and 15 psi) were used and cyclic stress ratio was varied from 0.1 to 0.5 in order to apply different cyclic shear stresses. The results show that the cyclic load resistance of soil decreases as a result of remolding. Saturated undisturbed samples show increase in resistance to liquefaction with increase in initial confining pressure. Remolded samples were prepared by compaction in the lab keeping unit weight and water content equal to that of undisturbed samples. Remolded samples show increase in liquefaction resistance with increase in confining pressure. Undisturbed samples at natural water content show increase in resistance to develop axial strain with increase in confining pressure. Both the rate of excess pressure development and axial strain development increase significantly as a result of remolding. While investigating the effect of saturation of undisturbed samples on liquefaction resistance of soil, interesting observations were made. The excess pressure buildup rate was faster in case of saturated undisturbed samples compared to that in samples with natural water content. On the other hand, rate of strain development was significantly high in case of sample with natural water content compared to that in saturated sample. Also, results obtained from cyclic triaxial tests on saturated undisturbed samples were compared with results obtained from similar tests on Ottawa Sand (Lama 2014) sample. The comparison shows that the saturated undisturbed soil samples of the selected local soil have very high resistance to liquefaction both in terms of initial liquefaction and development of 2.5% and 5% axial strain. Modulus of Elasticity and damping ratio were studied as important dynamic properties of soil. Young's Modulus was observed to decrease significantly at higher strain levels for all three types of samples. Young's modulus increased with increase in effective confining pressure, the effect of confining pressure being large at low strain level and almost insignificant at higher strain level. Damping ratio was highest in undisturbed sample at natural water content and smallest in remolded sample and damping ratio for saturated undisturbed sample falls in between. The damping ratio did not show any definite correlation with strain and confining pressure at lower strain level. But, for strain higher than 1% double amplitude axial strain, damping ratio significantly decreases with increase in strain. Damping ratio increases with increase in confining pressure as observed at high strain for all samples.
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Bonita, John Anthony. "The Effects of Vibration on the Penetration Resistance and Pore Water Pressure in Sands." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29417.
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The current approach for using cone penetration test data to estimate soil behavior during seismic loading involves the comparison of the seismic stresses imparted into a soil mass during an earthquake to the penetration resistance measured during an in-situ test. The approach involves an indirect empirical correlation of soil density and other soil related parameters to the behavior of the soil during the loading and does not involve a direct measurement of the dynamic behavior of the soil in-situ. The objective of this research was to develop an approach for evaluating the in-situ behavior of soil during dynamic loading directly through the use of a vibrating piezocone penetrometer.
Cone penetration tests were performed in a large calibration chamber in saturated sand samples prepared at different densities and stress levels. A total of 118 tests were performed as part of the study. The piezocone penetrometer used in the investigation was subjected to a vibratory load during the penetration test. The vibratory units used in the investigations were mounted on top of a 1m section of drill rod that was attached at the lower end to the cone penetrometer. Pneumatic impact, rotary turbine, and counter rotating mass vibrators were used in the investigation. The vibration properties generated by the vibratory unit and imparted into the soil were measured during the penetration test by a series of load cells and accelerometers mounted below the vibrator and above the cone penetrometer, respectively. The tip resistance, sleeve friction and pore water pressure were also measured during the test by load cells and transducers in the cone itself.
The vibration and cone data were compiled and compared to evaluate the effect of the vibration on the penetration resistance and pore water pressure in the soil mass. The results of the testing revealed that the influence of the vibration on the penetration resistance value decreased as the density and the mean effective stress in the soil increased, mainly because the pore water pressure was not significantly elevated throughout the entire zone of influence of the cone penetometer at the elevated stress and density conditions. An analysis of the soil response during the testing resulted in the generation of a family of curves that relates the soil response during the vibratory and static penetration to the vertical effective stress and density of the soil. The data used to generate the curves seem to agree with the proposed values estimated through the empirical relationship. An evaluation of the effects of the frequency of vibration was also performed as part of the study. The largest reduction in penetration resistance occurred when the input vibration approximated the natural frequency of the soil deposit, suggesting that resonance conditions existed between the input motion and the soil. An energy-based approach was developed to compare the energy imparted into the soil by the vibrator to the energy capacity of the soil. The input energy introduced into the soil mass prior to the reduction in penetration resistance agrees well with the energy capacity of the soil, especially in tests at the low effective stress level where a high excess pore water pressure was observed.Ph. D.
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Almeida, Cinara Xavier de. "Qualidade física de um latossolo vermelho sob sistema de semeadura direta e cultivo convencional /." Jaboticabal : [s.n.], 2011. http://hdl.handle.net/11449/105136.
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Orientador: José Frederico CenturionBanca: Elias Nascentes Borges
Banca: Ednaldo Carvalho Guimarães
Banca: Teresa Cristina Tarle Pissarra
Banca: Renato de Mello Prado
Resumo: O estudo de indicadores de qualidade dos solos é fundamental para avaliar o nível de degradação imposta pelo uso agrícola e para estabelecer estratégias de manejo sustentáveis. O objetivo geral deste trabalho foi avaliar a qualidade de um Latossolo Vermelho distrófico típico sob cultivo convencional (CC) e sistema de semeadura direta (PD), por meio de indicadores físicos e da avaliação da produção das culturas da soja e do milho. Os objetivos específicos foram: i) comparar a eficiência de funções de pedotransferência para a curva de resistência do solo à penetração presentes na literatura, por meio do ajuste de dados obtidos com o penetrômetro de impacto e também com o penetrômetro eletrônico; ii) determinar a resistência do solo à penetração (RP) durante o ciclo das culturas relacionando-a ao conteúdo de água no solo (Ug); e, iii) determinar alguns indicadores de qualidade física do solo, relacionando-os com as características agronômicas das culturas. Os sistemas de uso e manejo do solo foram: CC e PD por sete e oito anos consecutivos (solo de textura média) e CC e PD por nove e dez anos consecutivos (solo de textura argilosa). Foram determinadas a RP, a porosidade total, a macroporosidade, a microporosidade, a retenção de água no solo, o índice S, a densidade, a densidade do solo máxima e também a densidade do solo relativa. Nas culturas da soja e do milho foram avaliadas: massa seca das raízes, altura das plantas, altura de inserção da primeira vagem/espiga, número de vagens por planta de soja, massa seca da parte aérea do milho e produtividade. As Equações ; ; e não diferiram e foram as mais precisas e acuradas na predição da RP. Dentre os sistemas de manejo, embora o CC tenha apresentado melhores resultados em relação aos indicadores de qualidade física do solo, o PD foi o que proporcionou maior produção de milho
Abstract: The study of indicators of soil quality is essential to assess the level of degradation imposed by agricultural use and to establish sustainable management strategies. The aim of this study was to evaluate the quality of an Oxisol under conventional (CC) and no-tillage (NT), through soil physical indicators and assessing the soybeans and corn crops yield. The specific objectives were: i) compare the efficiency of pedotransfer functions due to soil resistance to penetration curve in the literature, by adjusting the data obtained with the impact penetrometer and also with the electronic penetrometer), ii) monitoring the soil resistance to penetration (PR) during the crop cycle relating it to the soil water content (Wc), and iii) determine some soil physical indicators, relating them to the agronomic characteristics of crops. The management systems were: CC and NT to seven and eight years consecutives (sandy loam soil) and CC and NT to nine and ten years consecutives (clayey soil). The PR, total porosity, macroporosity and microporosity, soil water retention, index S, soil bulk density, maximum dry bulk density, and also the relative bulk density were determined. The agronomic characteristics of soybean and corn crops have been evaluated: roots dry mass, height plant, insertion of the first spike height/pod, pods per soybean plant number, corn shoot dry mass and yield. The equations ; ; e did not differ and were the most precise and accurate in prediction of soil resistance to penetration. Among the management systems, although the CC has shown better results in relation to soil physical indicators, the NT was that the highest corn yield
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Saussus, Denis. "Probabilistic distributions of ultimate axial pile resistance derived from propagation of epistemic and aleatory material and model uncertainties." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/32819.
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Willms, Inka [Verfasser]. "Assessment of antibiotic resistance in soil and its link to different land use types and intensities / Inka Willms." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1213974968/34.
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Cavallini, Maria Cecília [UNESP]. "Correlação entre a produtividade e teor de proteína bruta do capim-Marandu com atributos físicos e químicos de um latossolo do cerrado brasileiro." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/98779.
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Em sistema de integração lavoura-pecuária, os diversos cultivos em sistema plantio direto alteram os atributos do solo, refletindo na produtividade e na composição do vegetal. O objetivo foi selecionar entre os atributos do solo aqueles que melhor expliquem a variabilidade da produtividade e teor de proteína da Brachiaria brizantha. Foram analisadas as correlações lineares e espaciais entre as produtividades de massa fresca (MF) e massa seca (MS) e teor de proteína bruta (PB) da Brachiaria brizantha cv. Marandu e de alguns atributos físicos e químicos de um Latossolo Vermelho Distroférrico, em três profundidades (0,00- 0,10m; 0,10-0,20m; 0,20-0,30 m). Para tanto, foi instalada a malha geoestatística para a coleta das informações, contendo 124 pontos amostrais, numa área de 4000 m2. A produtividade de forragem e o teor de proteína bruta não variaram aleatoriamente, e apresentaram alcances da dependência espacial entre 41,1 e 63,1 m. A densidade da partícula na primeira camada (DP1), a densidade do solo em todas as camadas (DS1, DS2 e DS3), a macroporosidade nas primeiras camadas (MA1 e MA2), a microporosidade em todas as camadas (MI1, MI2 e MI3), a porosidade total determinada em todas as camadas (PTd1, PTd2 e PTd3), o teor de fósforo nas últimas camadas (#P2 e P3), a resistência mecânica à penetração na última camada (RP3), a umidade volumétrica nas primeiras camadas (UV1 e UV2), o pH na primeira camada (pH1), o teor de matéria orgânica em todas as camadas (MO1, MO2 e #MO3), também apresentaram dependência espacial com alcances variando entre 6,4 e 73,5 m. A análise das correlações lineares simples de atributos da planta versus do solo revelou que com o aumento da RP, na camada de 0,10-0,30 m, correspondeu à mais baixa produção de MS, entretanto, com o aumento do teor de P em profundidade ocorreu aumento...
In crop-livestock integration the several crops in no tillage system interfere on the attributes of soil, altering the productivity and vegetable composition. Therefore, the objective this study was to select among the researched attributes of the soil those that best explain the variability of the productivity and crude protein content of the Brachiaria brizantha. The linear and space correlations were analyzed between the productivity of fresh mass (MF), dry mass (MS) and crude protein (PB) of the Brachiaria brizantha and of some attributes of a Dystroferric Red Latosol (Oxisol), in three depths (0.0-0.10; 0.10-0.20; 0.20-0.30 m). A geostatic grid was installed for collecting data, containing 124 points in an area of 4,000 m2. The attributes of the plant did not vary randomizing with reaches of the space dependence between 41.1 and 63,1 m. To soil attributes there was space dependence (DP1, DS1, DS2, DS3, MA1, MA2, MI1, MI2, MI3, PTd1, PTd2, PTd3, #P2, P3, RP3, UV1, UV2, pH1, MO1, MO2 and #MO3), with reaches varying between 6,4 and 73.5 m. For simple linear correlations analysis with the increase of RP3 there was reduction of the MS, and with increasing content of P in depth was increased dry mass of Brachiaria brizantha. Already for the space correlations, between the attributes of the plant and soil there were positive and negative interactions between cause and effect, and PTd3 behaved as an appreciable indicator of the physical quality of the soil for the estimate of MS of the Brachiaria brizantha.
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Figueiredo, Getúlio Coutinho. "Avanços metodológicos e instrumentais em física do solo." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-21062010-110626/.
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Os ecossistemas naturais e agropecuários dependem fundamentalmente do solo como recurso básico para sua funcionalidade. Neste contexto, a qualidade do solo tem tido uma crescente importância global. Os objetivos deste estudo consistiram em propor modificações metodológicas e/ou instrumentais visando determinações mais acuradas dos indicadores da qualidade física do solo mediante o desenvolvimento de (i) um sistema eletro-mecânico que permite a obtenção de amostras indeformadas de solos sem aplicação de golpes; (ii) um penetrômetro estático automatizado, de baixo custo e portátil, para medidas de resistência à penetração (RP) e resistência tênsil (RT) sob regime de velocidade constante de 1,55 mm s-1; (iii) um consolidômetro, de baixo custo e de maior portabilidade, para determinações da curva de compressão do solo, da RP e da RT utilizando propulsão pneumática e (iv) melhorias instrumentais em um permeâmetro de carga constante de ar pela redução de oscilações durante a medição do gradiente de pressão bem como a otimização da seleção de diferentes níveis de vazão mássica de ar. Os resultados obtidos mostraram que (i) o sistema eletromecânico garantiu a preservação da estrutura do solo em amostras coletadas comparado com a amostragem por golpes, principalmente no solo mais argiloso; (ii) a RP e a RT puderam ser determinadas com elevada acurácia à velocidade constante de 1,55 mm s-1; (iii) a curva de compressão do solo foi sensível às diferenças entre os tratamentos (linha e entrelinha da cultura) e a utilização de propulsão pneumática não influenciou os resultados da RP e da RT e (iv) a instrumentação utilizada no permeâmetro de carga constante de ar permitiu realizar determinações da permeabilidade do solo ao ar tanto em campo quanto em laboratório com rapidez e elevada acurácia.Natural and agricultural ecosystems rely fundamentally on soil as a basic resource for their functionality. In this context, soil quality has had a growing global importance. The objectives of this study were based on proposing methodological and/or instrumental modifications aiming to obtain more accurate determinations of soil physical quality indicators by developing: (i) an electro-mechanical system that allows the extraction of undisturbed soil samples without mechanical impact (no-hammering); (ii) a low cost and portable static automatic penetrometer, for measuring soil penetration resistance (PR) and tensile strength (TS) at a constant speed of 1.55 mm s-1; (iii) a low cost and portable consolidometer, for determination of soil compression curve, PR and TS using pneumatic propulsion and (iv) instrumental improvements to a constant head air permeameter by reducing the oscillation during measuring the pressure head gradient and the optimization of the selection of different levels of air mass flow. The results showed that (i) the electro-mechanical system ensured the preservation of soil structure in undisturbed samples in comparison to samples extracted by hammering procedures, especially in clayey soil; (ii) PR and TS could be determined with high accuracy at the constant speed of 1.55 mm s-1; (iii) the soil compression curve was sensitive to differences between treatments (crop row and inter-row) and the use of pneumatic propulsion did not influence the results of PR and TS, and (iv) the instrumentation used in the constant head air permeameter allowed determination of soil air permeability either on the field or in the laboratory with high speed and accuracy.
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Kohrt, Jonathon. "Expression of Glyphosate Resistance in Two Amaranthus Species as Influenced by Application Variables of Glyphosate." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1119.
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The expression of glyphosate resistance can vary within single field populations of common waterhemp and Palmer amaranth. This variability in expression can translate into control ranging from 20 to 80%, which could be the difference in a minor versus a major failure in weed management. Certain application parameters that have been previously associated with glyphosate efficacy, such as glyphosate application time of day and plant stress may exacerbate this variability and lead to failed control of plants on the lower end of the resistance spectrum. Greenhouse research was conducted in 2011 to determine the influence of glyphosate application time of day on the expression of resistance in common waterhemp and Palmer amaranth. Control of both glyphosate-susceptible (GS) and -resistant (GR) weed species showed similar trends in response to glyphosate with respect time of application. Decreased sensitivity of all Amaranthus biotypes was greatest at 9:00 pm and may be attributed to an observed shift in leaf orientation from horizontal to vertical at the time of glyphosate application in response to low-light conditions. The altered leaf orientation most likely reduced herbicide spray coverage. The magnitude of resistance, the difference in the sensitivity of the resistant versus susceptible biotypes, was unaffected by glyphosate application time of day; however, these results indicate that even in resistant populations glyphosate applied at suboptimal times of day such as the evening can cause a further increase in weed escapes from glyphosate. Greenhouse and field experiments were conducted in 2011 and 2012 to determine the influence the soil nutrient amendments on glyphosate sensitivity and growth rate and of GS and GR common waterhemp and Palmer amaranth. In both the GR and GS biotypes of common waterhemp the sensitivity to glyphosate was increased as fertilizer was introduced. However, only the sensitivity of the susceptible biotype of Palmer amaranth was increased with the addition of fertilizer. The lack of response in the GR Palmer amaranth population to fertilizer can be associated with the fact that due to carrier volume limitations enough glyphosate could not be applied to achieve 50% control. The magnitude of resistance was decreased numerically with the addition of fertilizer in both weed species; however, only in common waterhemp was the magnitude of resistance significantly different with the use of high rates fertilizer. The use of fertilizer also had an influence on the growth rate and dormancy of axillary buds. Lateral branching (broken dormancy in axillary buds) was increased in both common waterhemp and Palmer amaranth with the addition of fertilizer. Converting dormant buds to active meristems favors glyphosate translocation and could be responsible for increased glyphosate efficacy. In the field, glyphosate efficacy in GR common waterhemp and Palmer amaranth was also increased with addition of fertilizer; however, this effect was variable. Optimizing the efficacy of glyphosate when applied to even mixed populations of GS and GR Palmer amaranth and common waterhemp can reduce surviving weeds that can produce seed and perpetuate the frequency of glyphosate resistance in the field. Furthermore, greater efficacy of glyphosate may translate into relatively less significant failures in glyphosate applications allowing for successful rescue herbicide treatments and minimal impact on crop yield compared with a complete glyphosate failure with dramatic implications on reduced crop yield and increased weed seed production.
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Viking, Kenneth. "Vibro-driveability -a field study of vibratory driven sheet piles in non-cohesive soils." Doctoral thesis, KTH, Civil and Architectural Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3358.
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Boncu, Altan. "Structural Fire Safety Of Standart Circular Railroad Tunnels Under Different Soil Conditions." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12609537/index.pdf.
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In many tunnel designs, reinforced concrete tunnel lining design is selected based on construction requirements rather than design loads. A constant cross-section is typically used along a tunnel even if the design loads change from one location to another, especially for tunnels constructed by tunnel boring machines (TBM). Factor of safety against failure is not constant along the length of tunnel and is typically high at shallow depth regions. Factor of safety during a rare event is usually much less than the ones set for service load states. Rare events such as earthquake, train derailment, explosion and long duration fires do not happen daily and generally a minor reparable damage is targeted at the structure during those types of events. The focus of this study is to analytically investigate structural fire safety of reinforced concrete circular tunnel linings in terms of reduction in service load safety and to develop recommendations for preliminary assessment of structural fire endurance of circular tunnel linings. Analytical methods accounting for thermal non-linearity, material degradation, tunnel lining-ground interaction and fire time stages are available to assess the structural fire safety of the concrete tunnel linings. Analytical results are determined to be in good agreement with tunnel key segment hydrocarbon fire test.
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Cavallini, Maria Cecília. "Correlação entre a produtividade e teor de proteína bruta do capim-Marandu com atributos físicos e químicos de um latossolo do cerrado brasileiro /." Ilha Solteira : [s.n.], 2009. http://hdl.handle.net/11449/98779.
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Orientador: Marcelo AndreottiBanca: Morel de Passos e Carvalho
Banca: Francisco Antonio Monteiro
Resumo: Em sistema de integração lavoura-pecuária, os diversos cultivos em sistema plantio direto alteram os atributos do solo, refletindo na produtividade e na composição do vegetal. O objetivo foi selecionar entre os atributos do solo aqueles que melhor expliquem a variabilidade da produtividade e teor de proteína da Brachiaria brizantha. Foram analisadas as correlações lineares e espaciais entre as produtividades de massa fresca (MF) e massa seca (MS) e teor de proteína bruta (PB) da Brachiaria brizantha cv. Marandu e de alguns atributos físicos e químicos de um Latossolo Vermelho Distroférrico, em três profundidades (0,00- 0,10m; 0,10-0,20m; 0,20-0,30 m). Para tanto, foi instalada a malha geoestatística para a coleta das informações, contendo 124 pontos amostrais, numa área de 4000 m2. A produtividade de forragem e o teor de proteína bruta não variaram aleatoriamente, e apresentaram alcances da dependência espacial entre 41,1 e 63,1 m. A densidade da partícula na primeira camada (DP1), a densidade do solo em todas as camadas (DS1, DS2 e DS3), a macroporosidade nas primeiras camadas (MA1 e MA2), a microporosidade em todas as camadas (MI1, MI2 e MI3), a porosidade total determinada em todas as camadas (PTd1, PTd2 e PTd3), o teor de fósforo nas últimas camadas (#P2 e P3), a resistência mecânica à penetração na última camada (RP3), a umidade volumétrica nas primeiras camadas (UV1 e UV2), o pH na primeira camada (pH1), o teor de matéria orgânica em todas as camadas (MO1, MO2 e #MO3), também apresentaram dependência espacial com alcances variando entre 6,4 e 73,5 m. A análise das correlações lineares simples de atributos da planta versus do solo revelou que com o aumento da RP, na camada de 0,10-0,30 m, correspondeu à mais baixa produção de MS, entretanto, com o aumento do teor de P em profundidade ocorreu aumento... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In crop-livestock integration the several crops in no tillage system interfere on the attributes of soil, altering the productivity and vegetable composition. Therefore, the objective this study was to select among the researched attributes of the soil those that best explain the variability of the productivity and crude protein content of the Brachiaria brizantha. The linear and space correlations were analyzed between the productivity of fresh mass (MF), dry mass (MS) and crude protein (PB) of the Brachiaria brizantha and of some attributes of a Dystroferric Red Latosol (Oxisol), in three depths (0.0-0.10; 0.10-0.20; 0.20-0.30 m). A geostatic grid was installed for collecting data, containing 124 points in an area of 4,000 m2. The attributes of the plant did not vary randomizing with reaches of the space dependence between 41.1 and 63,1 m. To soil attributes there was space dependence (DP1, DS1, DS2, DS3, MA1, MA2, MI1, MI2, MI3, PTd1, PTd2, PTd3, #P2, P3, RP3, UV1, UV2, pH1, MO1, MO2 and #MO3), with reaches varying between 6,4 and 73.5 m. For simple linear correlations analysis with the increase of RP3 there was reduction of the MS, and with increasing content of P in depth was increased dry mass of Brachiaria brizantha. Already for the space correlations, between the attributes of the plant and soil there were positive and negative interactions between cause and effect, and PTd3 behaved as an appreciable indicator of the physical quality of the soil for the estimate of MS of the Brachiaria brizantha.
Mestre
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Farnsworth, Zachary Paul. "Lateral Resistance of Grouped Piles Near 20-ft Tall MSE Abutment Wall with Strip Reinforcements." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8694.
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A team from Brigham Young University and I performed full-scale lateral load tests on individual and grouped 12.75x0.375 inch pipe piles spaced at varying distances behind an MSE wall. The individually loaded pile which acted as a control was spaced at 4.0 pile diameters from the wall face, and the three grouped piles which were loaded in unison were spaced at 3.0, 2.8, and 1.8 pile diameters from the wall face and transversely spaced at 4.7 pile diameters center-to-center. The purpose of these tests was to determine the extent of group effects on lateral pile resistance, induced loads in soil reinforcements, and MSE wall panel deflections compared to those previously observed in individually laterally loaded piles behind MSE walls. The computer model LPILE was used in my analysis of the measured test data. The p-multipliers back-calculated with LPILE for the grouped piles were 0.25, 0.60, and 0.25 for the grouped piles spaced at 3.0, 2.8, and 1.8 pile diameters from the wall, respectively. These values are lower than that predicted for piles at the same pile-to-wall spacings using the most recent equation for computing p-multipliers. I propose the use of an additional p-multiplier for grouped piles near an MSE wall, a group-effect p-multiplier, to account for discrepancies between individual and grouped pile behaviors. The group effect p-multipliers were 0.35, 0.91, and 0.74 for the grouped piles spaced at 3.0, 2.8, and 1.8 pile diameters from the wall, respectively. The average group-effect p-multiplier was 0.66. Additionally, I used LPILE to analyze test data from Pierson et al. (2009), who had previously performed full-scale lateral load tests of individual and grouped shafts. In said analysis, the group of three 3-foot diameter concrete shafts spaced at 2.0 shaft diameters from the wall face and transversely spaced at 5.0 shaft diameters center-to-center had an average group effect p-multiplier of 0.78. As in previous studies, the induced forces in soil reinforcements in this study were greatest either near the locations of the test piles or at the MSE wall face. The most recent equation for calculating the maximum induced force in a soil reinforcement strip was reasonably effective in predicting the measured maximum loads when superimposed between the test piles, with 65% and 85% of the data points falling within the one and two standard deviation boundaries, respectively, of the original data used to develop the equation. Deflection of the MSE wall panels was greater during the grouped pile test than was previously observed for individually loaded piles under similar pile head deflections--with a maximum wall deflection of 0.31 inch compared to the previous average of 0.10 inch for pile head deflections of about 1.25 inches.
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Lyman, Noah J. "Incorporating Shear Resistance into Debris Flow Triggering Model Statistics." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2254.
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Several regions of the Western United States utilize statistical binary classification models to predict and manage debris flow initiation probability after wildfires. As the occurrence of wildfires and large intensity rainfall events increase, so has the frequency in which development occurs in the steep and mountainous terrain where these events arise. This resulting intersection brings with it an increasing need to derive improved results from existing models, or develop new models, to reduce the economic and human impacts that debris flows may bring. Any development or change to these models could also theoretically increase the ease of collection, processing, and implementation into new areas.
Generally, existing models rely on inputs as a function of rainfall intensity, fire effects, terrain type, and surface characteristics. However, no variable in these models directly accounts for the shear stiffness of the soil. This property when considered with the respect to the state of the loading of the sediment informs the likelihood of particle dislocation, contractive or dilative volume changes, and downslope movement that triggers debris flows. This study proposes incorporating shear wave velocity (in the form of slope-based thirty-meter shear wave velocity, Vs30) to account for this shear stiffness. As commonly used in seismic soil liquefaction analysis, the shear stiffness is measured via shear wave velocity which is the speed of the vertically propagating horizontal shear wave through sediment. This spatially mapped variable allows for broad coverage in the watersheds of interest. A logistic regression is used to then compare the new variable against what is currently used in predictive post-fire debris flow triggering models.
Resulting models indicated improvement in some measures of statistical utility through receiver operating characteristic curves (ROC) and threat score analysis, a method of ranking models based on true/false positive and negative results. However, the integration of Vs30 offers similar utility to current models in additional metrics, suggesting that this input can benefit from further refinement. Further suggestions are additionally offered to further improve the use of Vs30 through in-situ measurements of surface shear wave propagation and integration into Vs30 datasets through a possible transfer function. Additional discussion into input variables and their impact on created models is also included.
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Pollok, Jill. "Reproduction of a root-knot nematode population on flue-cured tobacco homozygous for Rk1 and/or Rk2 resistance genes and the effect of soil temperature on resistance gene efficacy." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/56597.
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Utilizing resistant cultivars is a main control strategy for root-knot nematodes in flue-cured tobacco (Nicotiana tabacum L.). Most commercial cultivars possess the Rk1 gene, providing resistance to races 1 and 3 of Meloidogyne incognita and race 1 of M. arenaria. This initiated a shift in root-knot populations to other species and races, creating a need for resistance to those populations. Numerous cultivars possess a second resistance gene, Rk2. Greenhouse experiments investigated whether possessing both Rk1 and Rk2 increases resistance to a variant of M. incognita race 3 compared to either gene alone, and if high soil temperatures impact their efficacy. Root galling, numbers of egg masses and eggs, and the reproductive index were compared from roots of Coker 371-Gold (susceptible), NC 95 and SC 72 (Rk1Rk1), T-15-1-1 (Rk2Rk2), and STNCB-2-28 and NOD 8 (Rk1Rk1 and Rk2Rk2). The same data were analyzed from plants in open-top root zone cabinet growth chambers set to 25ºC, 30ºC, and 35ºC to examine if resistance is temperature sensitive. Despite variability, Rk1Rk2 entries conferred greater resistance than entries with Rk1 or Rk2 alone. Entries with Rk1 alone reduced galling and reproduction compared to the susceptible control, whereas T-15-1-1 (Rk2) did not, but often suppressed reproduction. An apparent reduction in nematode reproduction was observed at 25ºC and 30ºC on entries possessing Rk1 and Rk1Rk2 compared to the control and Rk2. However, no apparent differences in reproduction occurred on Rk1 and/or Rk2 entries at 35ºC compared to the control, indicating parasitism increased on resistant entries at higher temperatures.Master of Science in Life Sciences
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Rideout, Steven Lewis. "The Effect of Nematode Isolate and Soil Environment on the Tobacco cyst Nematode (Globodera tabacum solanacearum), a Pathogen of Flue-cured Tobacco and Other Solanaceous Crops." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36056.
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Tobacco cyst nematodes (TCN), Globodera tabacum solanacearum, are one of the most serious pests for Virginia flue-cured tobacco (Nicotiana tabacum L.) farmers. These nematodes continue to spread to new farms every year and are now reported in 11 Virginia counties, seven North Carolina counties, and one farm in Maryland. The objectives of this study were to determine the ability of different populations of TCN to reproduce upon both a susceptible (K326) and resistant (NC567) cultivar, to compare TCN reproduction in non-infested soils with currently TCN-infested soils, and to examine reproduction and pathogenicity of TCN on other solanaceous crops.
Tobacco cyst nematode reproduction on the TCN-resistant cultivar NC567 was significantly reduced when compared to the TCN-susceptible cultivar K326. Although significant differences among the populations were detected on both cultivars, the differences were not consistent across experiments. Results indicate similar pathogenicity among TCN populations on resistant and susceptible flue-cured tobacco cultivars. Plant breeders may use one population of the tobacco cyst nematode to screen tobacco germplasms for TCN resistance.
Significant differences were noted in TCN reproduction among the various soils used in this study. However, the differences were inconsistent, making correlations between TCN reproduction and soil edaphic characteristics unreliable. Sterilizing the soils did not increase TCN reproduction. Reproduction in non-infested soils indicates that TCN will continue to spread throughout tobacco producing regions.
Although traditionally an exclusive pest of tobacco, TCN's spread may threaten production of other solanaceous crops. Eggplant (Solanum melongena L.), pepper (Capsicum spp. L.), and tomato (Lycopersicon spp. L.) were confirmed to be hosts of TCN under field conditions. Eggplant was highly susceptible to TCN reproduction and yield suppression, exhibiting a 64% yield reduction in plots not treated with a nematicide compared to fumigated plots. Tomato allowed high rates of TCN reproduction but did not suffer yield loss. Tobacco cyst nematode reproduction was suppressed on pepper compared to the other two crops. No crop loss was noted in nontreated pepper plots compared to plots treated with a nematicide. Results would indicate that tobacco rotations including tomato or eggplant would be unacceptable due to high TCN reproduction rates. The tobacco cyst nematode does not seem to jeopardize the production of tomato and pepper in the southeastern United States, but does threaten profitability of eggplant production in this area.
Master of Science