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Sisco, Nicholas D. "Unearthing Soil Science in Green Infrastructure Planning." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530270280777253.
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Brandsma, Richard Theodorus. "Soil conditioner effects on soil erosion, soil structure and crop performance." Thesis, University of Wolverhampton, 1997. http://hdl.handle.net/2436/99094.
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Riggs, Katherine Sarah. "Soil chemical changes following limestone additions to acid soils." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315889.
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Hoyle, Frances Carmen. "The effect of soluble organic carbon substrates, and environmental modulators on soil microbial function and diversity /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0050.
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Obrycki, John F. "Managing Soils For Environmental Science And Public Health Applications." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469014282.
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Mathys, Ilse Lois. "Soil health and quality concept in agricultural extension and soil science : an assessment of topsoil conditions in a long term vineyard soil management trail in Robertson, South Africa." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6544.
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Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2011.Includes bibliography.
ENGLISH ABSTRACT: The natural resource condition or health has been accepted as a valuable indicator of sustainable land use. The assessment of soil health (quality) has become a valuable tool in determining the sustainability of land management systems. This work aims to evaluate the sustainability of soil management practices in agricultural extension for vineyards in Robertson, South Africa based, on the current approach of the concept of soil health and soil quality, as well as to briefly explore the present reservations regarding the definition of the concept. The soil management treatments include a mechanical weed control, chemical weed control, annual addition of straw mulch, annual cover crop and perennial cover crop. The objective of study is to (i) identify suitable soil health (quality) indicators for vineyards in the study area; (ii) analyze the soil health (quality) indicators for different soil management treatments; (iii) evaluate the effect of various soil management treatments on the overall soil functionality, by comparing measured indicators to the soil property threshold values, for optimal vine growth; iv) establish a more consistent understanding and use of the terms health and quality, as understood and used in the general science community, with particular reference to the public health system. The soil physical, chemical and biological properties which were selected as indicators of soil health (quality) based on specific criteria similar to previous work done on the concept. The properties selected include soil texture, gravimetric water content, bulk density, soil aeration, water aggregate stability, soil pH, EC, available N,P,K , soil organic matter content, soil microbial biomass, potential mineralizable nitrogen and soil respiration. The study makes use of methods of analysis previously used for soil health and soil quality assessments, as well as soil analytical methods as accepted by experienced soil scientist within the study area. The soil was sampled on three separate events to depths of 0-200 mm for initial characterization of soil and 0-50 mm to compare soil health (quality) Between tracks and In tracks of treatment plots. The values obtained for each property were compared with the optimum for vineyards and ranked accordingly. The treatment that resulted in the most desirable soil health (quality) was the straw mulch and perennial cover crop treatments.
AFRIKAANSE OPSOMMING: Die toestand of gesondheid van natuurlike hulpbronne is aanvaar as `n waardevolle aanduiding van volhoubare grondgebruik. Die assessering van grond gesondheid (kwaliteit) is 'n waardevolle hulpmiddel in die bepaling van die volhoubaarheid van grond bestuur stelsels. Hierdie werkstuk poog om die volhoubaarheid van grond bestuurs praktyke te evalueer vir wingerde in Robertson, Suid-Afrika wat baseer is op die huidige benadering van grond gesondheid en kwaliteit. Die tesis dek ook die huidige onsekerhede oor die konsep en definisies van terme wat gebruik word in die konsep. Die grond bestuur praktyke sluit in 'n meganiese onkruidbeheer, chemiese onkruidbeheer, jaarlikse toevoeging van `n strooi deklaag, jaarlikse en meerjarige dekgewas dekgewasse. Die doel van die studie was om (i) die geskikte grond gesondheid (kwaliteit) indikators vir wingerde in die studie area te identifiseer, (ii) die grond gesondheid (kwaliteit) indikators vir verskillende bogrond bestuur praktyke te identifiseer; (iii) die effek van verskillende grond bestuur praktyke op die algehele grond funksies te evalueer, deur dit te vergelyk met die gemete indikators vir drempelwaardes vir optimale wingerd groei; iv) 'n meer konsekwente begrip en gebruik van die terme “gesondheid” en “kwaliteit” vas te stel, soos dit verstaan en gebruik word in die algemene wetenskaplike gemeenskap, met spesifieke verwysing na die openbare gesondheidsisteem. Die grond fisiese, chemiese en biologiese eienskappe wat as indikators van grond gesondheid (kwaliteit) geselekteer was, word gebaseer op spesifieke kriteria soortgelyk aan dié wat in vorige werk op die konsep gedoen was. Die eienskappe wat geselekteer is sluit in grondtekstuur, gravimetriese waterinhoud, bulk digtheid, grond deurlugting, totalle water stabiliteit, grond pH, electriese geleiding, toeganklike N, P, K, grond organiese materiaal inhoud, grond mikrobiese massa, potensiële mineraliseerbare stikstof en grond respirasie. Die studie maak gebruik van analitiese metodes wat voorheen gebruik was vir grond gesondheid en kwaliteit, sowel as die grond analitiese metodes soos gebruik deur ervare grondkundiges binne die studie gebied. Die grondmonsters was geneem op drie afsonderlike geleenthede oor dieptes van 0-200 mm vir die aanvanklike karakterisering van grond en 0-50 mm, om grond gesondheid (kwaliteit) Tussen trekkerspore en In trekkerspore van die persele te vergelyk. Die waardes verkry vir elke eienskap was vergelyk met die optimum vir wingerde en verdeel volgens kwaliteit. Die behandeling wat die mees optimale grond gesondheid (kwaliteit) getoon het, was die strooi deklaag en meerjarige dekgewas behandelings.
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Burgos, Hernández Tania D. "Investigating Soil Quality and Carbon Balance for Ohio State University Soils." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1577141132704637.
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Caniquitte, Sabine Sophie. "Soil microbial community, soil aggregation and cropping system: study of their relationship." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19278.
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The effect of six cropping systems on soil carbon, aggregation and microbial community was examined after three growing seasons. The six cropping systems involved corn, sorghum, soybean, red clover, timothy and bare fallow, and differed in terms of tillage practice, type of crop (perennial versus annual) and type, amount and quality of carbon inputs to soil. Soil structure under sorghum and timothy differed from that of bare soil. Soil total carbon content exceeded that of fallow only under the two perennial cropping systems. Microbial community size and activity, arbuscular mycorrhizal fungi, bacteria and Gram(-) bacteria were positively correlated with total carbon, mean weight diameter (MWD) of aggregates and abundance of macroaggregates, and negatively correlated with abundance of microaggregates. Fungi were positively correlated with MWD of aggregates and negatively correlated with abundance of microaggregates. Root biomass and lignin content had the greatest effects on the size and proportion of microbial groups correlated with soil structure and carbon content. The relationships between microbial community structure and soil structure, and between microbial community structure and plant material chemical characteristics were further explored with an experiment where the dynamics of soil microbial community structure and changes in soil structure during the decomposition process of soybean, corn, timothy and red clover materials were monitored for 28 weeks. Up to 53% of the variation in microbial community composition could be explained by the quality of added materials and up to 24% of the variation in soil structure could be explained by the composition of the soil microbial community. The C/N, hemicellulose, soluble CL'effet de six systèmes de culture sur le carbone, l'agrégation et la communauté microbienne du sol a été évalué après trois saisons de croissance. Les systèmes de culture comprenaient le maïs, le sorgho, le soya, le trèfle, la fléole des prés ainsi que des parcelles en jachère et étaient caractérisés par différents types de travail du sol et de plantes (pérennes versus annuelles) et par la nature, quantité et qualité des apports de carbone au sol. Comparativement à la jachère, la structure du sol a été affectée par les systèmes de culture impliquant le sorgho et la fléole des prés et le carbone total du sol n'a été augmenté que sous les plantes pérennes. La taille et l'activité de la communauté microbienne ainsi que les champignons arbusculaires mycorhiziens, les bactéries en général et les bactéries à Gram négatif ont été positivement corrélés au diamètre moyen des agrégats et à la proportion de macroagrégats du sol, mais négativement corrélés à la proportion de microagrégats. Les champignons étaient positivement corrélés au diamètre moyen des agrégats et négativement corrélés à la proportion de microagrégats. La biomasse racinaire et le contenu en lignine des racines ont eu le plus d'effet sur la taille et la proportion des groupes microbiens corrélés à la structure et à la teneur en carbone du sol. La relation entre la structure du sol et la composition de la communauté microbienne ainsi que le lien entre la qualité des matières végétales et la structure de la communauté microbienne ont été examinés davantage lors d'une expérience en laboratoire. Du sol et des tissues de maïs, de soya, de trèfle et de fléole des prés ont été incubés pendant 28 semaines
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roberts, john christopher. "Impact of Manure and Soil Test Phosphorus on Phosphorus Runoff from Soils Subjected to Simulated Rainfall." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-06162005-123000/.
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Runoff from agricultural fields amended with animal manure or fertilizer is a source of phosphorus (P) pollution to surface waters, which can have harmful effects such as eutrophication. The objectives of this study were to evaluate the impact of soil P status and the P composition of manure sources on P in runoff, characterize the effects of manure sources on mass loss of dissolved reactive P (DRP), total dissolved P (TDP), algal available P (AAP) and total P (TP) in runoff, and enhance the PLAT database with respect to soluble P attenuating factor (SPAF) and non-soluble P attenuating factor (NSPAF) values. Soil boxes set at 5% slopes received 7.5 cm hr-1 of simulated rainfall. Study soils included a Kenansville loamy sand (loamy siliceous subactive thermic Arenic Hapludults, a Coastal Plain soil) and a Davidson silt loam (kaolinitic thermic Rhodic Kandiudults, a Piedmont soil). Soil test P concentrations ranged from 16 to 283 mg P kg-1. Sources of P included broiler litter (BRL), breeder manure (BRD), breeder manure treated with three rates of alum (Al2(SO4)3) BRD0-0 kg m-2, BRDL-3.9 kg m-2, and BRDH-7.8 kg m-2 and DAP along with an unamended control. All manure sources were applied at 66 kg P ha-1. Water extractable P (WEP) represented an average of 10 ?b 6% total P in manure. Runoff samples were taken over a 30-min period. Piedmont soil contained greater amounts of clay, Al and Fe concentrations, and higher P sorption capacities that produced significantly lower DRP, TDP, AAP, and TP losses than the Coastal Plain soil. Runoff P loss did not differ for low and high STP soils of same taxonomy with the exception of AAP mass losses for Coastal Plain soil samples. Water extractable P in manures accounted for all DRP lost in runoff with DRP correlating strongly with WEP concentration (0.9961). A weak relationship between DRP in runoff and WEP applied to soil boxes was observed (R2=0.6547) and increased when a possible outlying manure treatment, BRL, was omitted from regression data (0.9927). Overall, manures containing the highest WEP concentrations supplied the largest losses of DRP in runoff. Manure treated with 3.9 and 7.8 kg m-2 of Al2(SO4)3 (alum) decreased DRP in runoff by 29%. Values calculated for PLAT SPAF and NSPAF coefficients were higher for Coastal Plain soil than Piedmont soil and overall higher than default values in PLAT. Management based on these results should help minimize harmful effects of P in runoff.
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Steusloff, Tyler W. "Nitrogen Management Strategies to Improve Corn Growth and Reduce Soil Greenhouse Gas Emissions from Claypan Soils." Thesis, University of Missouri - Columbia, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13850753.
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Adoption of nitrogen (N) management strategies to minimize gaseous N loss from agriculture while maintaining high yield production is increasingly important for an exponentially growing population. Agricultural management on poorly-drained claypan soils in the Midwestern U.S. make corn ( Zea mays L.) production even more challenging due to the subsoil’s low permeability, which may result in wetter soil conditions and relatively larger amounts of soil N2O emissions during the growing season. The objective of this study was to determine the effects of urea fertilizer placement with and without the addition of a nitrification inhibitor (NI) on corn yield, N use efficiency (NUE), and cumulative soil N2O emissions on a Northeastern Missouri claypan soil. The fertilizer strategies utilized in this study consisted of deep-banded urea (DB) or urea plus nitrapyrin [2-chloro-6-(trichloromethyl) pyridine] (DB+NI) at a depth of 20 cm compared to urea broadcast surface applied (SA) or incorporated to a depth of 8 cm (IA). The addition of a NI with deep-banded urea resulted in 27% greater apparent N recovery efficiency than all other N treatments. Additionally, DB+NI had 54 and 55% lower cumulative soil N2O emissions than IA and SA treatments in the two combined growing seasons. These results suggest that deep placement of urea with or without nitrapyrin is an effective management strategy for increasing corn yield and reducing N loss on a claypan soil.
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Smuts, Michiel Nicolaas. "Determination of the lime requirement of sandy, organic-rich, and structured, high Mg:Ca ratio soils by the Eksteen method." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/19866.
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Thesis (MScAgric)--Stellenbosch University, 2001.ENGLISH ABSTRACT: The Eksteen method of lime requirement determination, based on the ratio of Ca+Mg:H (R-value), is widely used in the Western Cape and has proven to be extremely accurate for most soils. However, the Eksteen method is known to give erroneous predictions of lime requirement for certain soil groups. These include sandy soils (notably pale coloured sandy soils), organic-rich topsoils and strongly structured, Mg-rich subsoils. The objective of this study was to examine the nature of the Eksteen RpH relationship for these problem soils, and to develop appropriate modifications to the Eksteen method, where possible. A population of both normal and problem soils was selected and analysed, the RpH relationships of the soils were determined, and various relationships were examined. The principal findings with regard to the nature of the Eksteen RpH relationship were as follows: 1. The lime requirements of pale coloured sandy soils can be most accurately determined on an equivalent basis relative to the total extractable acidity, after the total extractable acidity has been corrected for residual lime. 2. The previously observed and acknowledged inaccuracy of the Eksteen method on organic-rich soils stems from the pH-dependant acidity component of the organic matter. The accuracy with which the lime requirement of these soils is predicted by the Eksteen method can be greatly improved by the application of an organic matter correction factor (OMCF) to the total extractable acidity, which is the parameter on which the lime requirement is then based. 3. In structured, Mg-rich subsoils the pH-neutralising capacity of Mg is considerably lower than that of Ca, a factor which is not taken into account by the Eksteen method. The Eksteen method can nevertheless be corrected to overcome this discrepancy. The high levels of Mg in the structured, Mg-rich subsoils cannot be attributed to minerals in these subsoils containing brucite interlayers. 4. Toxic levels of AI may only be expected at soil pH values below approximately 4.7 as determined in 1M KC!. Soil organic matter and CEC have marked affects on AI extractability. In accordance with the objective that appropriate modifications to the Eksteen method should be developed if possible, theoretically-based correction factors were developed which will permit the use of the Eksteen method to be confidently extended to those soil groups (pale coloured sandy soils, organicrich topsoils and strongly structured, Mg-rich subsoils) for which it was formerly considered unreliable.
AFRIKAANSE OPSOMMING: Die Eksteen metode van kalkbehoeftebepaling, gebaseer op die verhouding van Ca+Mg:H (R-waarde), word oor die algemeen wyd in die Wes-Kaap gebruik en is baie akkuraat vir meeste gronde bewys. Dit is egter bekend dat die Eksteen metode verkeerde kalkbehoeftes vir sekere grondgroepe voorspel. Hierdie sluit sanderige grande (veral lig gekleurde sandgronde), organiesryke bogrande en sterk gestruktuurde, Mg-ryke ondergronde in. Die doel van hierdie studie was om die aard van die Eksteen R:pH verwantskap vir hierdie probleemgronde te bepaal, waar moontlik. 'n Populasie van beide normaal en probleemgrande is geselekteer en geanaliseer, die R:pH verwantskap van die grande is bepaal en verskeie verwantskappe is ondersoek. Die hoof bevindinge ten opsigte van die aard van die Eksteen R:pH verwantskap was as volg: 1. Die kalkbehoefte van lig gekleurde sandgronde kan akkuraat bepaal word op 'n ekwivalente basis, relatief tot die totale ekstraheerbare suurheid, nadat die totale ekstraheerbare suurheid gekorrigeer is vir residuele kalk. 2. Die voorheen bekende onakkuraatheid van die Eksteen metode op organiesryke gronde het sy oorsprong by die pH-afhanklike suurheid komponent van organiese material. Die akkuraatheid waarmee die kalkbehoefte van hierdie grande met behulp van die Eksteen metode voorspel kan word, kan noemenswaardig verbeter word deur die totale ekstraheerbare suurheid te korrigeer met behulp van 'n organiese materiaal korreksie faktor (OMKF). Die aangepaste totale ekstraheerbare suurheid is dan die parameter waarap die kallkbehoefte gebaseer word. 3. In gestruktuurde, Mg-ryke ondergrande is die pH-neutraliseringsvermoe van Mg aansienlik laer as die van Ca, 'n faktor wat seide in berekening gebring word by die Eksteen metode. Die Eksteen metode kan tog gekorrigeer word om hierdie tekortkoming te oorkom. Die hoe vlakke van Mg in gestruktuurde, Mg-ryke ondergrande kan nie aan die teenwoordigheid van minerale in die ondergrond, wat brusiet tussenlae bevat, toegeskryf word nie. 4. Toksiese AI vlakke sal alleenlik by grond pH waardes laer as ongeveer 4.7, soos bepaal in 1M KCI, verwag word. Grand organiese materiaal en KUK het 'n noemenswaardige effek op ekstraheerbare AI. In ooreenstemming met die doelwitte om toepaslike wysigings aan die Eksteen metode aan te bring, is teoreties gebaseerde korreksiefaktore ontwikkel, wat die gebruik van die Eksteen metode verder verbreed om daardie grondgraepe (lig gekleurde sanderige grande, organies-ryke bogrande en sterk gestruktuurde, Mg-ryke ondergrande) in te sluit waarvoor dit vantevore as onbetraubaar beskou is.
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Whitacre, Shane D. "Soil Controls on Arsenic Bioaccessibility: Arsenic Fractions and Soil Properties." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244036619.
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Warren, G. P. "Available nitrogen in relation to fractions of soil nitrogen in grassland soils." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370367.
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St, Luce Mervin. "Labile organic nitrogen fractions: characteristics, dynamics and significance to soil nitrogen supply in agricultural soils." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117160.
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Short-term nitrogen (N) availability in agricultural soils is derived mostly from the labile organic N pool. A better understanding of N transformation processes that occur in key labile organic N fractions is necessary to recognize their role in N cycling and their relative contribution to N mineralization. The objectives of this thesis were to (1) examine, under field conditions, the influence of preceding legume and non-legume crops on microbial biomass N (MBN), water-extractable organic N (WEON), and particulate and light fraction organic matter N (POMN, LFOMN) across five sites and how these fractions supply N to canola (Brassica napus L.), as determined from N uptake and grain yield, and (2) investigate under controlled conditions, the incorporation and turnover of crop residue N through MBN, WEON, POMN and LFOMN. Labile organic N fractions were similar regardless of preceding crop but varied across sites due to soil and climatic conditions. The POMN was the best single predictor of soil N supply (R2 = 0.56 and R2 = 0.70 for yield and N uptake, respectively). Soil N supply was related to POMN, mineral N and sand content, which explained 68% of the variation in grain yield and 71% of the variation in N uptake. Sandy-loam and clay soils were incubated for 112 d with 15N-labelled faba bean (Vicia faba, C/N ratio = 29) and wheat (Triticum aestivum L, C/N ratio = 91) residues. After 3 d, most (17-30%) of the residue 15N was recovered in the POMN, with a greater proportion of the wheat than the faba bean residue recovered in the POMN fraction. The 15N recovered in the POMN fraction after 3 d was significantly related to mineral N released after 112 d (r = 0.78, P<0.001), with more 15N released as mineral N in sandy-loam than clay soil and from faba bean than wheat residue. Net N mineralization in whole soil (WS) + POM mixtures was better related to POM N concentration and less to soil mineral N, soil texture or pH, suggesting that the extent to which POM contributes to N mineralization depends on the crop residue chemistry from which it was derived. I conclude that the turnover of POMN is a major pathway through which mineral N is released in the short-term in agricultural soils. Current N fertilizer recommendations can be improved by considering POM and soil mineral N concentrations, soil texture and environmental conditions. This will help to minimize the negative impacts of N losses on the environment and make a significant step towards enhancing N-use efficiency in agroecosystems.La disponibilité à court terme de l'azote (N) dans les sols agricoles est essentiellement issue de la fraction labile du N organique. Une meilleure compréhension des processus de transformation de ces fractions est nécessaire pour connaitre leur rôle dans le cycle de l'azote et leur contribution relative à la minéralisation de N. Les objectifs de cette thèse étaient de (1) examiner, sous les conditions de champs, l'effet du précédent cultural (légumineuse vs non-légumineuse) sur la biomasse microbienne de l'azote (MBN), l'azote organique extrait à l'eau (WEON) et les fractions légère et particulaire de la matière organique (POMN, LFOMN) à travers cinq sites et comment ces fractions sont-elles liées à l'approvisionnement en N [canola (Brassica napus L.) prélèvement de N et rendement en grains] and (2) étudier, sous des conditions contrôlées, l'incorporation et le turnover de l'azote des résidus des cultures via MBN, WEON, POMN et LFOMN. Les fractions labiles du N organique étaient similaires quel que soit le précédent cultural mais varie avec les sites due aux sols et aux conditions climatiques. Le POMN était le meilleur indicateur de l'approvisionnement en N (R2 = 0,56 and R2 = 0,70 pour le rendement en grains et le prélèvement en N, respectivement). De plus, l'approvisionnement en N était premièrement relié à l'effet combiné de POMN, l'azote minéral et la teneur du sol en sable; ces paramètres expliquent 68% de la variation dans le rendement en grains et 71% de la variation dans le prélèvement en N .Deux sols, loam sableux et argileux, ont été incubés pendant 112 jours avec des résidus d'haricot (Vicia faba, C/N = 29) et du blé (Triticum aestivum L, C/N = 91) marqués à 15N. Après 3 jours, la majeure partie (17-30%) des résidus de 15N a été trouvée dans la fraction POMN par comparaison aux autres fractions. Une plus grande proportion de résidus de blé que de résidus d'haricot a été trouvée dans la fraction POMN. La forme minérale du 15N libérée a été plus élevée dans le sol laom-sableux que dans l'argile et avec l'incorporation de l'haricot comparée au blé. Le 15N incorporé au POMN après 3 jrs a été significativement relié à l'azote minéral libéré après 112 jrs (r = 0.78, P<0.001). La minéralisation nette dans le mélange au sol entier (WS) + POM est plus liée à la teneur en N du POM qu'à la teneur du sol en N minéral, sa texture et son pH. Ainsi, l'ampleur de la contribution de la fraction POM à la minéralisation de l'azote dépond de son origine. Dans l'ensemble, les résultats de cette étude suggèrent que le turnover de la fraction POMN est la principale voie par laquelle le N minéral est libéré dans les sols agricoles. Les recommandations actuellement utilisées en fertilisation azotée peuvent être améliorées en tenant compte des POMN, N minéral du sol, texture du sol et les conditions environnementales. Ces informations permettront de minimiser les impacts négatifs de la perte de N dans l'environnement and contribueront à l'amélioration de l'efficacité de l'utilisation de l'azote dans les agroécosystèmes.
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Schwertfeger, Dina. "The effects of soil leaching on metal bioavailability, toxicity and accumulation in Hordeum vulgare cultivated in copper amended soils." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115837.
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Discrepancies in ecotoxicity effects data derived from soils amended with dissolved metals in the laboratory and soils from historically aged metal-contaminated sites pose a challenge in deriving environmentally relevant soil quality criteria. In this thesis, the chemical artefacts produced by dissolved metal additions and the subsequent effects on metal bioavailability, toxicity and bioaccumulation are examined. The overall goal of this research is to advance the understanding of soil trace metal bioavailability mechanisms and improve current methods for ecotoxicity testing and bioavailability modeling.The first objective was to develop a leaching method which would minimize the "salt-effect" commonly observed in freshly-spiked soil samples. This was achieved by adapting a column leaching procedure in order to spike and leach larger volumes of test soil as a preparatory step prior to ecotoxicity assays. An experiment was set up to observe changes to leachate chemistry resulting from the dissolved Cu additions and subsequent leaching with two weak electrolyte solutions. Results showed that leaching removed the excess dissolved Cu as well as the excess acidity and base cations that were solubilized during the Cu additions. Differences between control and spiked samples of some key soil solution parameters (e.g. pH, DOC and total dissolved Ca, Mg, Al, Fe) were reduced thereby resulting in a set of spiked samples more conducive to deriving causal dose-response relationships.
A second experiment compared soil and soil solution properties of samples which underwent the spike/leach procedure to those of freshly spiked samples. Lower soil pH (up to 0.81 pH units) and DOC concentrations were observed in non-leached samples as well as up to 35-fold and 55-fold increases of dissolved Ca and Mg concentrations, typical of the salt-effect. It was estimated that the non-leached samples contained up to 100-fold greater Cu2+ and 50-fold greater Al3+ activities which, I hypothesized, could result in greater phytotoxicity of non-leached samples. Bioassays were conducted wherein Hordeum vulgare (barley) seedlings were exposed to the leached and non-leached Cu-spiked soil samples for 14 days. The leached samples were less toxic to barley and showed significant increases (up to 1.7-fold) in median inhibitory concentrations (i.e. IC50) for root elongation in two of the three test soils. The Cu2+ fraction was able to explain much of the variability in toxicity between leached and non-leached samples, as well as among the different test soils. One exception was the most acidic test soil for which plants in the leached samples showed up to 10-fold greater toxicity than plants in the non-leached samples, when exposed to similar Cu2+ activities. Soil speciation and bioaccumulation data for Cu, Al and Ca were used to deduce that Ca deficiency and possibly Al toxicity contributed to the toxicity observed in this sample set.
In a modeling exercise, the concepts of the terrestrial biotic ligand model (TBLM), which take into account ion competition at the soil solution/root interface, to describe toxic response in our samples. Results showed that the additive effects of Cu and Al toxicity estimated from the Cu-root ligand complex (Cu-BL+) and Al-root ligand complex (Al-BL2+ ) accounted for more of the variability in toxic response data than did the Cu2+ fraction or the Cu-BL+ fraction alone. The model however, could not account for the effects of the Cu-induced Ca deficiency in the most acidic test soil, thus highlighting one of the limitations of the TBLM. This thesis has contributed to the understanding of metal bioavailability mechanisms affected by soil spiking procedures and highlights the benefits of soil leaching in preparing soil samples for ecotoxicity assays which should improve trace metal risk assessment in the future.
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Dryden, Garri A. "Optimum gravel size for use as a soil surface cover for the prevention of soil erosion by water." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280469.
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Eleven series of replicated tests were conducted using 38.1 mm, 15.9 mm, and 9.5 mm gravel to determine the most effective soil surface cover to prevent soil erosion from rainfall. A sediment tray one meter square in size with an integrated rainfall simulator was used to generate data after initial trial runs had established test procedures. Various size gravels and a control with no cover were tested in a laboratory using simulated rainfall to evaluate their effectiveness in preventing erosion. Through thirty-three experiments, signature traits of specific rock sizes were identified. Experiments on 38.1 mm gravel indicated the usefulness of rock mulches in soil erosion prevention. Evaluations with 9.5 mm material indicated that erosion prevention varies inversely with particle size. Experiments with 15.9 mm gravel suggested that this material could increase erosion. This study reflects the ambivalence in the literature and points to the complexity of micro-interactions and erosion potential as influenced by gravel size. Six mechanisms governing rock mulch erosion were proposed.
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Lee, Jong-Sub. "High resolution geophysical techniques for small-scale soil model testing." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04052004-180045/unrestricted/lee%5Fjong-sub%5F200312%5Fphd.pdf.
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Benson, Kaitlyn Suzanne. "Assessment of Soil Quality Parameters of Long-Term Biosolids Amended Urban Soils and Dredge Blends." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492601621133386.
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Gentry, Terry Joe. "Molecular ecology of chlorobenzoate degraders in soil." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289936.
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A series of three experiments were conducted to determine the diversity of indigenous chlorobenzoate (CB) degraders in soil and to investigate the use of different methods of bioaugmentation for remediation of contaminated soil. In the first study, soil was amended with either 500 or 1000 μg of 3-CB g⁻¹ and was either uninoculated or inoculated with the 3-CB degrader Comamonas testosteroni BR60. Bioaugmentation with C. testosteroni BR60 increased 3-CB degradation at both contaminant levels, and the increase was more pronounced at the higher level due to contaminant inhibition of indigenous 3-CB degraders. Bioaugmentation also appeared to reduce the deleterious effects that 3-CB contamination had on indigenous soil microbial populations as evidenced by changes in culturable heterotrophic bacterial populations. In the second study, two similar pristine soils were contaminated with 500 μg of 2-, 3-, or 4-CB g⁻¹ . The two soils differed in their ability to degrade the compounds with one degrading 2- and 4-CB and the other degrading 3- and 4-CB. Several hundred degraders were isolated, grouped according to DNA fingerprints, and selected degraders were identified by 16S rDNA sequences. The identity of the CB degraders differed between the two soils. The results indicated that the development of 2-, 3-, and 4-CB degrader populations was site-specific even for the soils that developed under similar soil-forming conditions. The third study also used the two soils from the second study. This project investigated the potential for use of activated soil, which contained an indigenous degrader population, as a bioaugmentation inoculant. An aliquot of a given soil that contained an indigenous 2-, 3-, or 4-CB degrader population was added to a soil that did not have an indigenous degrader population for the same contaminant. The study found that bioaugmentation with activated soil increased degradation of each 2-, 3-, and 4-CB but only if the activated soil was pre-exposed to the contaminant prior to use for bioaugmentation. The results from these three studies indicate that CB degrader populations are diverse and variable in pristine soils and, if not present in contaminated soils, appropriate degrader populations may be established via different bioaugmentation strategies.
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Sherratt, David Joseph. "Regional soil moisture modelling." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/8230.
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Zelasko, Amanda Jean. "Soil reduction rates under water saturated conditions in relation to soil properties." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-07172007-154810/.
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The success of wetland restoration projects depends in part on the length of time that a soil is in a reduced redox state. The length of time that a soil is reduced depends on how quickly reduction occurs following saturation with water. The relationship between reduction rate and various soil chemical and mineralogical properties is poorly understood, but such properties might be manipulated to improve the success of wetland restoration projects. The goals of this research were to determine soil properties that predict the rate at which soils undergo reduction when saturated, and to determine the roles of electron donors and acceptors on reduction rates. Sixteen soil samples were collected at various depths from two wetland sites, a Carolina bay (Juniper Bay) and a wetland catena (Frog Level). Soils were incubated in specially designed redox incubators to monitor reduction rates, changes in soil properties, and soil solution chemistry. Soil samples were subjected to three cycles of oxidation and reduction during the course of 36 d. Soil reduction rates were determined from the slopes of linear regression models fit to data for redox potential (Eh) over time. Reduction rates varied among soils from 1.2 to 46.2 mV h-1, and were significantly greater (p-value < 0.05) for soils with total organic carbon (TOC) > 10 g kg-1 than in soils with TOC < 10 g kg-1. Increasing amounts of dissolved Fe(II) were found at Eh values below 500 mV for pH between 4.5 and 5.1. Mineral soils with total reduction rates > 10 mV h-1 released significantly more Fe(II) into solution than mineral soils with reduction rates < 10 mV h-1 (p-value < 0.05). Regression results indicated that organic carbon, an electron donor, was the dominant factor controlling reduction rates up to 10 mV h-1, and an electron acceptor Fe(III) was the dominant factor controlling reduction rates > 10 mV h-1. For wetland restoration purposes multiple linear regression models based on our results that include TOC concentration and pH can be used along with hydrologic data to predict reduction rates in saturated soils.
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Solomon-Wisdom, Grace Oyiza. "The effect of in situ spatial heterogeneity of lead in soil on plant uptake." Thesis, University of Sussex, 2015. http://sro.sussex.ac.uk/id/eprint/54284/.
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The understanding of the spatial distribution of lead (Pb) in soil is important in the assessment of potential risks and development of remediation strategies for Pb contaminated land. In situ heterogeneity of Pb was measured at two heavily contaminated sites in the United Kingdom using the Portable X-ray Fluorescence Spectrometer (P-XRF) over a range of spatial scales (0.02 to 50 m). The pattern of the distribution of Pb was very variable, and when expressed as heterogeneity factor (HF), it ranged from 1.2 to 3.2 (highly heterogeneous). The effect of such Pb heterogeneity on plant uptake was investigated in greenhouse pot trials. Two earlier pot trials, which assessed the effect of Pb in a fixed concentration (1000 mg/kg) and in a range of concentration (100 to 10000 mg/kg) found a significant effect of the Pb added treatments, when compared to a control treatment (0 mg/kg Pb added). Biomass and uptake varied by 20 to 100% within and between 16 species/varieties. Results enhanced the selection of two species (Brassica napus and Brassica juncea) for further pot trials. A third pot experiment with Brassica napus and Brassica juncea in simplistic binary model of heterogeneity found 20 to 60% lower uptake in the binary treatment, than homogeneous the treatment. Biomass was higher by 10 to 50% in Brassica juncea and 20 to 40% lower for B. napus in the bianary treatment, when compared to the homogeneous and control treatments. The effect of a more realistic in situ heterogeneity on plant uptake was investigated in a further pot trial, which simulated low (LH), medium) (MH) and high (HH) heterogeneity treatments, compared to a homogeneous (HO) treatment. It detected a significant (P < 0.05) impact of heterogeneity on biomass and uptake between treatments and species. Four to five fold lower biomass were recorded in HH treatment, when compared to the HO treatment. Shoot and root uptake in (mg/kg) concentration increased with increasing heterogeneity with peak uptake (twice as high as HO treatment) in LH for B. napus and in HH and MH treatments for B. juncea respectively. Shoot and root Pb masses in (μg) were maximum in HO and MH treatments respectively with 50 to 70% lower Pb mass in the HH treatment. Results showed that response to heterogeneity is species specific. A sub-experiment explored the behaviour of plant roots in HH treatment and found 20 to 80% variation in root biomass between concentric patches with same nominal soil Pb concentrations. This provided insights into varied responses of these species to realistic Pb heterogeneity. The research demonstrated that the presence and extent of in situ heterogeneity of Pb in soil plays an important role in Pb uptake by plants. It also showed that the homogeneous and simplistic binary model of heterogeneity do not give reliable estimates of plant growth and Pb uptake in realistic field conditions. This work has implications for improving the efficiency of phytoremediation of Pb contaminated land, phytomining, reliability of risk assessment and models of human exposure to Pb.
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Thomas, Jacqueline Yvette. "Quantification of in situ heterogeneity of contaminants in soil : a fundamental prerequisite to understanding factors controlling plant uptake." Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6961/.
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Heterogeneity of contaminants in soils can vary spatially over a range of scales, causing uncertainty in environmental measurements of contaminant concentrations. Sampling designs may aim to reduce the impact of on-site heterogeneity, by using composite sampling, increased sample mass and off-site homogenisation, yet they could overlook the small scale heterogeneity that can have significant implications for plant uptake of contaminants. Moreover, composite sampling and homogenisation may not be relevant to target receptor behaviour, e.g. plants, and studies, using simplistic models of heterogeneity have shown that it can significantly impact plant uptake of contaminants. The alternative approach, to accept and quantify heterogeneity, requires further exploration as contaminant heterogeneity is inevitable within soils and its quantification should enable improved reliability in risk assessment and understanding variability in plant contaminant uptake. This thesis reports the development of a new sampling design, to characterise and quantify contaminant heterogeneity at scales, from 0.02m to 20m, using in situ measurement techniques, and 0.005m to 0.0005m, using ex situ techniques. The design was implemented at two contaminated land sites, with contrasting heterogeneity based upon historic anthropogenic activity and showed heterogeneity varying between contaminants and at different spatial scales, for Pb, Cu and Zn. Secondly, this research demonstrates how contaminant heterogeneity measured in situ can be recreated in a pot experiment, at a scale specific to the plant under study. Results, from 4 different plant species, demonstrated that existing simplistic models of heterogeneity are an inadequate proxy for plant performance and contaminant uptake under field conditions, and significant differences were found in plant contaminant concentrations between simplistic models and those based upon actual site measurements of heterogeneity. Implications of heterogeneity on plant roots were explored in the final experiment showing significant differences in root biomass between patches of differing contaminant concentrations.
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Mbakwe, Ikenna. "An evaluation of the effectiveness of coal ash as an amendment for acid soils." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/1897.
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Woodun, Jayashree Khanta. "Surface crusting of soils from the South Downs in relation to soil erosion." Thesis, University of Sussex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270498.
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Habte, Michael Andebrhan Civil & Environmental Engineering Faculty of Engineering UNSW. "Numerical and constitutive modelling of monotonic and cyclic loading in variably saturated soils." Awarded by:University of New South Wales. Civil and Environmental Engineering, 2006. http://handle.unsw.edu.au/1959.4/24204.
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A fully coupled, effective stress based elasto-plastic model is presented for a rigorous analysis of flow and deformation in variably saturated porous media subjected to monotonic and cyclic loading. The governing equations are derived based on the effective stress concept, equations of equilibrium, and conservation equations of mass and momentum using a systematic macroscopic approach. Both elastic and elasto-plastic constitutive equations are developed. All model coefficients are identified in terms of measurable parameters. The governing equations presented are general in nature, embodying all previously presented formulations in the field. A unified bounding surface plasticity model is developed to describe the stress-strain behaviour of variably saturated soils subjected to monotonic and cyclic loading. The model is formulated incrementally within the critical state framework using the effective stress approach. The model takes into account the effects of both plastic volumetric strain and matric suction on the hardening of the bounding surface. Cyclic behaviour is captured through a new mapping rule in which the point of stress reversal is taken as the centre of projection. The effect of particle crushing at high stresses is considered through a three-segmented critical state and isotropic compression lines. A non-associative flow rule is employed to generalise application of the model to all soils. Solution to the governing equations is obtained numerically using the finite element approach, with the finite difference method employed for the time integration of the rate equations. The elasto-plastic constitutive equations are integrated explicitly using Euler???s forward and the modified Euler integration schemes. Yield surface correction schemes are adopted to improve accuracy of the solution. Essential elements of the proposed model are validated by comparing numerical predictions with experimental data from the literature for fully and partially saturated soils subjected to monotonic and cyclic loadings in drained, undrained, isotropic and deviatoric conditions. The results demonstrate capability of the coupled model to predict essential characteristics of variably saturated soils subjected to monotonic and cyclic loadings in a unified manner.
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Gershenson, Alexander. "Notes from the underground: the science and policy of soil carbon /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
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Ellis, Larry R. "Subaqueous pedology expanding soil science to near-shore subtropical marine habitats /." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0011640.
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Sakala, Godfrey Mekelani. "The effects of incorporating plant residues on soil acidity in management of tropical soils." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263047.
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Shahadha, Saadi Sattar. "Measured Soil Hydraulic Properties as RZWQM2 Input to Simulate Soil Water Dynamics and Crop Evapotranspiration." UKnowledge, 2018. https://uknowledge.uky.edu/pss_etds/110.
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Agricultural system models integrate many different processes that cannot all be measured in field experiments and help quantify soil water dynamics, crop evapotranspiration, and crop growth with high temporal resolution. Understanding soil water dynamics and crop evapotranspiration is essential to improve agricultural management of field crops. For example, the interaction between nitrogen application rate and water dynamics is not sufficiently understood. In most cases, model simulations deviate from field measurements, especially when model input parameters are indirectly and unspecifically derived. The extent to which measured soil hydraulic property inputs decrease the discrepancy between measured and simulated soil water status is not well understood. Consequently, this study: (i) investigated thr use of measured soil hydraulic properties as Root Zone Water Quality Model (RZWQM2) inputs compared to indirectly derived inputs; (ii) explored the capability of calibrating measured soil hydraulic property input parameters for one crop and using them for other crops without further calibration; (iii) studied the effect of the nitrogen application rate on the behavior of soil water dynamics and crop evapotranspiration using RZWQM2 under different rainfall amounts. To evaluate the model in different field management conditions, a field experiment with soybean, corn, wheat, and fallow soil was conducted from 2015 – 2017 to collect field data to calibrate and validate the RZWQM2 model. The model presented a satisfactory response to using measured soil hydraulic property inputs and a satisfactory capability to quantify the effect of nitrogen rates on daily crop evapotranspiration, soil water dynamics, and crop growth. With sufficient measurements of soil hydraulic parameters, it was possible to build a RZWQM2 model that produced reasonable results even without calibration.
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Dada, Yunusa Musa. "Geotechnical interpretation of soil surveys." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327803.
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Williams, Jared Dewey. "Soil Tests for Corn Nitrogen Recommendations and Their Relationships with Soil and Landscape Properties." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-05202005-073610/.
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An accurate soil nitrogen (N) test is needed to improve corn production, profitability, and reduce environmental concerns of increasing nitrate (NO3) levels in groundwater. The objectives of this study were to (i) compare soil N tests: amino sugar N (ASN), gas pressure (GP), pre-plant NO3 (PPNT), and incubation and residual N (IRN) for precision and ability to predict corn response parameters e.g., economic optimum N rates (EONR); and (ii) examine the spatial relationships of ASN with soil and landscape properties to develop a more efficient sampling strategy. Small-plot N-response trials (NRT) were conducted in 2001 to 2004 at 31 sites. Field scale (FS) ASN variability was measured in 2003 and 2004 at four sites located in the North Carolina Piedmont and Coastal Plain. The ASN test had lower coefficients of variation than the GP, PPNT, and IRN tests (10 versus 15, 30, 52%, respectively). Each tests was correlated with economic optimum N rates from NRT sites, but coefficients of determination were low for the PPNT, IRN, and GP tests. The ASN test had the strongest correlation with EONR, but only when sites were classified as well (r2 = 0.85) or poorly (r2 = 0.78) drained. A comparison of ASN and EONR regression models across years and cost ratios (different corn price and fertilizer cost) were not statistically different. Amino sugar N was positively correlated with humic matter (HM; r2 = 0.25 to 0.71) at each FS sites. Elevation was negatively correlated with ASN at the Lower and Middle Coastal Plain (r2 = 0.44 and 0.11, respectively). In the Piedmont, ASN was negatively correlated with slope (r2 = 0.10 and 0.04). Amino sugar N was positively correlated with soil texture (percent clay) for the Middle Coastal Plain (r2 = 0.56) but negatively correlated for a site in the Piedmont (r2 = 0.04). Amino sugar N is spatially sensitive to changes in soil and landscape properties, and soil sampling zones may be created using HM, soil texture, and soil type to reduce sampling costs and time. These results show that the ASN test was the best test for predicting economical optimum N rates and could be used to develop a site specific soil test based fertilizer recommendation.
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Maas, Ellen DvL. "Uncertainties in Soil Model Projections." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587396700081549.
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Habermann, Birgit. "Ways of knowing of farmers and scientists : tree and soil management in the Ethiopian Highlands." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/49648/.
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The Ethiopian Highlands have been studied extensively, hosting a large amount of research for development projects in agriculture and forestry over several decades. The encounters in these projects were also encounters of different ways of knowing that were negotiated by the actors meeting in the space provided by the projects. This research explores these encounters and the social worlds they are embedded in, drawing on actor-oriented approaches as well as theories of narratives and framing. Ways of knowing and citizen epistemologies are taken as a lens to understand the role of identities in knowledge production and use. The two case studies were agroforestry research projects in the Ethiopian Highlands. The research followed a range of qualitative and ethnographic research methods. Different types of farmers and scientists meet in the case studies. I recognise that they all have individual agency, nevertheless I use the terms ‘scientist' and ‘farmer' in this thesis. I use the terms to describe certain groups of actors who all draw on different ways of knowing, and different value systems, when interacting with each other and their environment. The results indicate that the importance of social worlds at different scales and the contexts of research projects tend to be underestimated. In spite of good intentions scientific methodologies, terminologies and narratives tend to dominate. Scientists in the case studies acknowledged the existence of farmers' ‘indigenous' knowledge, but they determined the value of knowledge by its scientific applicability and the replicability of experiments. Research systems force the scientists into a certain modus operandi with limited possibilities to experiment and to respond to the complexities and diversities of people's social worlds. Farmers in the case studies preferred observation from their parents, observing from others or the environment as a way of learning and gaining knowledge. Depending on their personalities and their life histories they also relied on alternative ways of knowing rooted in spirituality, emotions and memories. Powerful influences on ways of knowing resulted from the way languages and authority had been used. These often led to the exclusion of marginalised community members from access to knowledge and technologies. Unfortunately, common narratives prevailed in the case studies, and alternative ways of knowing were often marginalised. By acknowledging different ways of knowing and the importance of different social worlds and different ways of doing research, both scientists and farmers could benefit and develop more sustainable pathways for agricultural and forestry land use.
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Coetzee, Marina Elda. "Chemical characterisation of the soils of East Central Namibia." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/4068.
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Thesis (MScAgric (Soil Science)--University of Stellenbosch, 2009.ENGLISH ABSTRACT: A number of chemical and physical features of Namibian soils in a 22 790 km2, two degree-square block between 17 – 19 oE and 22 – 23 oS in eastern central Namibia, had been investigated, and the fertility status established. In 80 % of samples the nitrate, nitrite, and sulfate concentrations of the saturated paste extract are 0 – 54.6 mg l-1 NO3 -, 0 – 24.7 mg l-1 NO2 -, and 5.4 – 20.9 mg l-1 SO4 2- respectively. In 90 % of samples the plantavailable phosphorus is below 12 mg kg-1, which is low for a soil under natural grassland, but in line with the prevailing semi-arid climate and low biomass production of the study area. In 80 % of samples the extractable calcium, magnesium, potassium, and sodium concentrations are 0.61 – 5.73 cmolckg-1 Ca (122 – 1 146 mg kg-1 Ca), 0.12 – 2.28 cmolckg-1 Mg (15 – 278 mg kg-1 Mg), 0.13 – 0.54 cmolckg-1 K (51 – 213 mg kg-1 K) and 0.05 – 0.38 cmolckg-1 Na (11 – 87 mg kg-1 Na) respectively, while the exchangeable calcium, magnesium, potassium, and sodium concentrations are 0.21 – 6.02 cmolckg-1 Ca, 0.12 – 2.01 cmolckg-1 Mg, 0.12 – 0.49 cmolckg-1 K and 0 – 0.13 cmolckg-1 Na respectively. The mean ± 1 standard deviation is 3.57 ± 3.57 cmolckg-1 for cation exchange capacity, 3.48 ± 3.61 for sum of exchangeable bases and 4.53 ± 4.39 for sum of extractable bases. The cation exchange capacity and the sum of exchangeable bases are virtually identical, which indicate the almost complete absence of exchangeable H+ and Al3+ in the soils of the study area, as expected from a semi-arid climate. None of the profiles were classified as saline or sodic. In 80 % of samples the plant-available iron, manganese, zinc and copper concentrations are 7.2 – 32.8 mg kg-1 Fe, 13.6 – 207.5 mg kg-1 Mn, 0 – 1.80 mg kg-1 Zn and 0 – 4.0 mg kg-1 Cu respectively. Soil organic matter content of the study area soils ranges between 0.05 – 2.00 %, with most (80 % of samples) containing 0.25 – 1.20 % organic matter. This is considerably lower than values reported in literature, even for other southern African countries. The reason lies with the hot, semi-arid climate. The pH distribution is close to normal, with 80 % of samples having pH (H2O) of 5.54 – 8.18, namely moderately acid to moderately alkaline. Sand, silt and clay content of most (80 %) samples varies between 60.3 – 89.7 % sand, 4.6 – 25.2 % silt and 3.5 – 19.1 % clay. The soils of the study area are mainly sandy, sandy loam and loamy sand. In 80 % of samples the coarse sand fraction ranges from 3.5 – 34.5 %, the medium sand fraction from 20.5 – 37.3 %, the fine sand fraction from 38.7 – 54.5 % and the very fine sand fraction from 0.0 – 12.9 % of all sand. The fine sand fraction, thus, dominates, with very fine sand being least abundant. The topsoil contains relatively more coarse sand and less very fine sand than the subsoil. Instances of sealing, crusting and hardening occur sporadically in the study area. Cracking is only found in pans, while self-mulching is not evident. No highly instable soils were encountered in the study area. The water-holding capacity is generally low, with depth limitations in the western highlands, the Khomas Hochland, and texture limitations in the eastern Kalahari sands. The central area has soils with a somewhat better water-holding capacity, but it is still very low when compared to arable soils of temperate, sub-humid and humid zones elsewhere in southern Africa. Soil characteristics are perceptibly correlated with climate, parent material, topography, degree of dissection of the landscape and position in the landscape. The most obvious differences are between soils formed in schistose parent material of the Khomas Hochland in the west and those of the Kalahari sands in the east. The soils of the study area are unsuitable to marginally suitable for rainfed crop production, due to low iv fertility. The study area is climatologically unsuited for rainfed crop production, so the present major land use is extensive livestock production on large farms. The natural vegetation is well adapted to the prevailing conditions. The methodology followed to delineate terrain units, with a combination of procedures involving digital elevation data and satellite imagery, seems to work well in the Namibian landscape. This study thus served as a successful proof-of-concept for the methodology, which can in future be rolled out for the remainder of the country. The site and analytical information is available in digital format as spreadsheets and in a geographical information system, as well as in a variety of digital and printed maps.
AFRIKAANSE OPSOMMING: ‘n Aantal chemiese en fisiese eienskappe van Namibiese gronde in ‘n 22 790 km2, 1o x 2o blok tussen 17 – 19 o Oos en 22– 23 o Suid in oostelike sentraal-Namibië is ondersoek en die grondvrugbaarheidstatus bepaal. In 80 % van monsters is die nitraat-, nitriet- en sulfaatkonsentrasies van die versadigde pasta ekstrak 0.0 – 54.6 mg l-1 NO3 -, 0.0 – 24.7 mg l-1 NO2 -, en 5.4 – 20.9 mg l-1 SO4 2-onderskeidelik. In 90 % van monsters is die plant-beskikbare fosfor minder as 12 mg kg-1, wat laag is vir gronde onder natuurlike grasveld, maar dit is verklaarbaar deur die heersende semi-ariede klimaat en lae biomassa produksie in die studiegebied. In 80 % van monsters is die konsentrasies van ekstraheerbare kalsium, magnesium, kalium en natrium 0.61 – 5.73 cmolckg-1 Ca (122 – 1 146 mg kg-1 Ca), 0.12 – 2.28 cmolckg-1 Mg (15 – 278 mg kg-1 Mg), 0.13 – 0.54 cmolc kg-1 K (51 – 213 mg kg-1 K) en 0.05 – 0.38 cmolckg-1 Na (11 – 87 mg kg-1 Na) onderskeidelik, terwyl die uitruilbare kalsium, magnesium, kalium en natrium konsentrasies onderskeidelik 0.21 – 6.02 cmolckg-1 Ca, 0.12 – 2.01 cmolckg-1 Mg, 0.12 – 0.49 cmolckg-1 K and 0.0 – 0.13 cmolckg-1 Na is. Die gemiddelde ± 1 standaardafwyking is 3.57 ± 3.57 cmolckg-1 vir katioonuitruilvermoë, 3.48 ± 3.61 vir die som van uitruilbare basisse en 4.53 ± 4.39 vir die som van ekstraheerbare basisse. Die katioonuitruilvermoë en som van uitruilbare basisse is feitlik identies, wat ‘n feitlik algehele afwesigheid van uitruilbare H+ and Al3+ in die gronde van die studiegebied aandui, soos verwag word weens die semi-ariede klimaat. Geeneen van die profiele is geklassifiseer as soutbrak of natriumbrak nie. In 80 % van monsters is die plant-beskikbare yster, mangaan, sink en koper konsentrasies onderskeidelik 7.2 – 32.8 mg kg-1 Fe, 13.6 – 207.5 mg kg-1 Mn, 0.0 – 1.80 mg kg-1 Zn en 0.0 – 4.0 mg kg-1 Cu. Grond organiese material inhoud in die studiegebied wissel tussen 0.05 – 2.00 %, met 80 % van monsters wat 0.25 – 1.20 % organiese material bevat. Dit is aansienlik laer as die waardes gevind in literatuur, selfs vir ander Suider-Afrikaanse lande. Die oorsaak is die warm, semiariede klimaat. Die pH verspreiding is feitlik normaal, met 80 % van monsters wat pH (H2O) van 5.54 – 8.18 het, met ander woorde matig suur tot matig alkalies. Sand, slik en klei inhoud van die meeste (80 %) monsters varieer tussen 60.3 – 89.7 % sand, 4.6 – 25.2 % slik en 3.5 – 19.1 % klei. Die gronde van die studiegebied is hoofsaaklik sand, sand-leem en leem-sand. In 80 % van monsters beslaan die growwe sandfraksie 3.5 – 34.5 %, die medium sandfraksie 20.5 – 37.3 %, die fyn sandfraksie 38.7 – 54.5 % en die baie fyn sandfraksie 0.0 – 12.9 % van die totale sandfraksie. Die fyn sandfraksie is dus dominant, terwyl die baie fyn sandfraksie die skaarsste is. Die bogronde bevat relatief meer growwe sand en minder baie fyn sand as die ondergronde. Gevalle van verseëling, korsvorming en verharding kom sporadies in die studiegebied voor. Krake kom net in panne voor en self-omkering is nie opgemerk nie. Geen hoogsonstabiele gronde is in die studiegebied gevind nie. Die waterhouvermoë is in die algemeen laag, met dieptebeperkinge in die westelike hooglande, die Khomas Hochland, en tekstuurbeperkinge in die oostelike Kalahari sande. Die sentrale gedeelte het gronde met ‘n ietwat beter waterhouvermoë, maar dis steeds baie laag in vergelyking met akkerbougronde van gematigde, sub-humiede en humiede sones elders in Suider- Afrika. Grondeienskappe is ooglopend verwant aan klimaat, moedermateriale, topografie, graad van gebrokenheid van die landskap en posisie in die landskap. Die duidelikste verskille kom voor in die gronde wat van vi skisagtige moedermateriaal van die Khomas Hochland in die weste en dié wat in die Kalahari sande in die ooste gevorm het. Die gronde van die studiegebied is ongeskik tot marginaal geskik vir droëland akkerbou, weens die lae vrugbaarheid. Aangesien die studiegebied klimatologies ongeskik is vir droëland akkerbou, is die huidige hoof landgebruik ekstensiewe veeproduksie op groot plase. Die natuurlike plantegroei is goed by die heersende omstandighede aangepas. Die metodiek wat gevolg is om terreineenhede af te baken, wat ‘n kombinasie van prosedures met digitale hoogtedata en satellietbeelde is, blyk goed te werk vir die Namibiese landskap. Hierdie studie dien dus as ‘n suksesvolle bewys-van-konsep van die metodiek, wat in die toekoms uitgebrei kan word na die res van die land. Die veld- en ontledingsinligting is beskikbaar in digitale formaat, in ‘n geografiese inligtingstelsel en ‘n verskeidenheid digitale- en gedrukte kaarte.
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Lucas, Shawn T. "MANAGING SOIL MICROBIAL COMMUNITIES WITH ORGANIC AMENDMENTS TO PROMOTE SOIL AGGREGATE FORMATION AND PLANT HEALTH." UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/24.
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The effects of managing soil with organic amendments were examined with respect to soil microbial community dynamics, macroaggregate formation, and plant physio-genetic responses. The objective was to examine the possibility of managing soil microbial communities via soil management, such that the microbial community would provide agronomic benefits. In part one of this research, effects of three amendments (hairy vetch residue, manure, compost) on soil chemical and microbial properties were examined relative to formation of large macroaggregates in three different soils. Vetch and manure promoted fungal proliferation (measured via two biomarkers: fatty acid methyl ester 18:2ω6c and ergosterol) and also stimulated the greatest macroaggregate formation. In part two of this research, effects of soil management (same amendments as above, inorganic N fertilization, organic production) on soil chemical and microbial properties were examined relative to the expression of nitrogen assimilation and defense response genes in tomato (Solanum lycopersicum L.). Soil management affected expression of a nitrogen assimilation gene (GS1, glutamine synthetase) and several defense-related genes. The GS1 gene was downregulated with inorganic N fertilization, expression of the pathogenesis-related PR1b gene (which codes for the pathogenesis-related PR1b protein) was increased in plants grown in soil amended with compost, vetch, and N fertilizer, and expression of three other defense-related genes coding for chitinase (ChiB), osmotin (Osm), and β-1,3-glucanase (GluA) were decreased in plants from soil amended with manure and in plants from the organically managed soil. Differential expression of defense-related genes was inversely related to the relative abundance of Gram-negative bacteria. The relative abundance of the 18:1ω7c Gram‑negative bacterial biomarker was greatest in manure treated soil and in organically managed soil (which recieves seasonal manure applications). These treatments also had the lowest expression of ChiB, Osm, and GluA, leading to speculation that manure, through increases in Gram-negative bacteria, may have suppressed populations of soil organisms that induce a defense response in plants, possibly allowing for less-stressed plants. Outcomes of this research may be useful for those interested in developing management strategies for maintaining or improving soil structure as well as those interested in understanding management effects plant physio-genetic responses.
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Alghamdi, Rashad Saeed. "Soil Warming and Drying and the Consequence to Crop Yields among Conservation Tillage Practices in Frigid Corn-Soybean Fields." Thesis, North Dakota State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10605433.
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Concerns over delayed soil warming and drying have hindered adoption of conservation tillage practices in frigid environments. Our objectives were to evaluate the effects of chisel plow (CP), vertical tillage (VT), strip tillage with coulters (STC), and strip tillage with shanks (STS) on soil warming and drying and their potential consequences to crop yields. A two-year study was conduct at three full-scale, producer-managed, corn-soybean fields in the Red River Valley of eastern North Dakota and western Minnesota. Tillage treatments were assessed to measure crop residue cover, soil temperatures, soil volumetric water contents, crop yields, and other metrics. Our study indicated significant differences for many soil physical and chemical parameters, but little to none for soil warming and crop yields. Yield differences were attributed to varying fertilizer management practices, timing, and application method. These findings emphasize the importance of field management practices that compliment conservation tillage for obtaining competitive crop yields.
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Pang, Mei-yee. "The nature and magnitude of soil compaction in different human-modified habitats in Hong Kong." Click to view the E-thesis via HKUTO, 2001. http://sunzi.lib.hku.hk/hkuto/record/B42576520.
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Pan, Feifei. "Spatial and temporal structures of soil moisture fields." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/32842.
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Jackson, Robert B. "Soil Heterogeneity and its Exploitation by Plants." DigitalCommons@USU, 1992. https://digitalcommons.usu.edu/etd/6512.
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In this dissertation I first examine the ability of individual plants in the field to garner localized soil nutrients. I then measure actual soil variability around perennial plants and use various statistics to quantify the scale and degree of that variability.
Soil patches on opposite sides of Pseudoroegneria spicata tussocks were treated with distilled water or a nutrient solution containing N, P, or K in three field experiments. When P was augmented in the enriched soil patches, rates of P uptake increased significantly for roots from enriched patches compared with roots in control patches. Rates of ammonium and potassium uptake were apparently unchanged. When N was augmented in the enriched patches, rates of ammonium and potassium uptake increased significantly. When K was augmented in the enriched patches, no changes were seen for any of the nutrients.
Plant shading was found to limit the ability of Agropyron desertorum tussocks to increase rates of nutrient uptake in enriched soil microsites. Roots of unshaded plants selectively increased phosphate uptake capacity in enriched patches by up to 73%, but shading limited this response. Enrichment of the soil patches resulted in significantly greater phosphate concentrations in roots of both shaded and unshaded plants.
Nutrient heterogeneity in the soil at a native sagebrush-steppe site was quite high, with ammonium and nitrate varying by over two orders of magnitude and phosphate and potassium close to one order of magnitude within a 10x12- m area. Within 0.5x0.5-m subplots around individual plants, ammonium and nitrate varied by an average factor of 11 and 12, respectively, with less average variation for phosphate and potassium. Geostatistical semivariograms showed that soil ammonium, nitrate, phosphate, potassium, pH, and organic matter all showed detectable autocorrelation only at scales of less than 1.0 to 1.5 m. Indices of microbial activity showed no detectable autocorrelation even at the smallest measurement scale of 12.5 cm. From the degree and scale of heterogeneity encountered, I conclude that root plasticity and active foraging in a heterogeneous soil environment are likely to be important to the nutrient balance of many plants.
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Chacón, Montes de Oca Paula. "Effect of Land Use, Climate and Soil Structure on Soil Organic Carbon in Costa Rican Ecoregions." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1252995403.
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Turpin, Karine. "Macropore flow and soil hydraulic properties as affected by manurebiosolids injector implements under variable soil physical conditions." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27062.
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The aim of this study was to investigate, at various soil water contents, the tillage effects of two different types of injectors on soil hydraulic properties of a loamy clay soil located in Winchester, Ontario, Canada. The two injectors considered are the AerWay SSD (A) and the Kongskilde Vibro-Flex (K). The soil-properties changes associated with the injectors were assessed at ten different soil water contents for both injectors.
The first part of this research involves the evaluation of field saturated hydraulic conductivity (Kfs), matrix flux potential (&phis;m), bulk density (rhob) and volumetric water content (theta) for undisturbed soil (U) and for soil disturbed by injector (D). The field saturated hydraulic conductivities measured on disturbed soil for the Kongskilde (DK) were in 80% of the cases lower than those measured on undisturbed soil (UK). In contrast, Kfs measured on disturbed soil for the AerWay (DA) were higher in 90% of the cases. These results indicate that the Kongskilde reduces the infiltration capacity of the soil, which may be the result of reduced effective porosity via the smearing of the soil surface. They also indicate that the AerWay is facilitating infiltration, most likely by fracturing the soil surface.
The second part of this study involves a dye tracer experiment conducted on disturbed soil to evaluate the movement pathways of water through soil. In contrast to the AerWay, no relation could be established between liquid transport variables and the water content at which the Kongskilde was run. Greatest depths of penetration observed for the AerWay treatment occurred at run average water contents above 29.7 % vol. and below 19.7 % vol. Sorptive capacity of the upper layers was maximized when soil water contents were between 21.7 % vol. and 31.3 % vol.
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Viloria, Jesus Arnaldo. "The inter-relation between soil survey and soil information systems : optimization of the data gathering procedures." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292653.
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Gomes, Carolyn. "Spatial distribution of B horizon properties in a pine flatwood landscape New Hanover County, NC /." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3/gomesc/carolyngomes.pdf.
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Van, Zijl George Munnik. "An investigation of the soil properties controlling gully erosion in a sub-catchment in Maphutseng, Lesotho." Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4197.
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Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Lesotho is a country with an international reputation for the severe degree of soil erosion in its landscape. Despite several national soil conservation projects, soil erosion continues at an astounding rate. One of the reasons for this is possibly that the interactions between soil properties and erosion in Lesotho are not understood. Soil erosion is a site specific, cyclic phenomenon, controlled by geomorphological thresholds. To control soil erosion, the processes and soil properties which influence soil erosion in the specific place must be understood. In this study the soil properties of a highly eroded sub-catchment in Maphutseng, Lesotho was investigated. The gully extent in the sub-catchment, in 1957 and 2004 respectively, was mapped from aerial photos. These maps show where in the landscape gullies developed during this time. The gully maps were superimposed on maps of several soil erosion factors, to correlate the spatial distribution of the erosion factors with that of the gully distribution. A soil map was especially drawn for this. The spatial analysis shows that gully development between 1957 and 2004 was primarily confined to the area where duplex soils occur. The rest of the sub-catchment underwent negligible differences in gully extent during this time. The initiation of the gullies on the duplex soil area is ascribed to tunnel erosion. The high dispersibility of the duplex soil samples, sink holes which occur in this area and previous observations by researchers in this area gave evidence to this hypothesis. In the second part of the study the soil properties of seventeen soil profiles from across the study site were analysed. The difference in gully distribution between the duplex soils area and the rest of the catchment is ascribed to the high dispersibility of the duplex soils. No strong correlations could be found between the dispersion index and other determined soil properties. Segmented quantile regression was used to analyse the data further. Soil samples with moderate levels of total carbon (1.17%), iron oxide (0.9%) and effective cation exchange capacity (13.7 cmolc/kg), have below average dispersibility. When none of these stabilising agents are present in moderate amounts, soils with even low exchangeable sodium percentage values (0.68%) are dispersive. Furthermore, soils which have developed in colluvial material from basaltic origin were found to be less dispersive, presumably because of the amorphous clay minerals present in the volcanic material. The colour and increase in clay content between the A and B horizons of a soil can indicate the tunnel erosion potential of the soil. Dark coloured soils (values less than 4 and chromas less than 3) were found to have low dispersibility and free water can accumulate in the subsoils where the B horizon has much more clay than the A horizon. The accumulation of free water in the subsoil is necessary for tunnel formation. Thus soils with dark colours and/or a low clay accumulation index have low tunnel erosion potential.
AFRIKAANSE OPSOMMING: Lesotho is ‘n land met ‘n internasionale reputasie vir die ernstige graad van gronderosie waaronder die landskap gebuk gaan. Ten spyte van verskeie nasionale grondbewaringsprojekte duur die erosie teen ‘n verstommende tempo voort. Een van die redes hiervoor is heel moontlik dat die interaksies tussen grondeienskappe en erosie in Lesotho nie verstaan word nie. Gronderosie is ‘n plekspesifieke, sikliese verskynsel, wat deur geomorfologiese drempelwaardes beheer word. Om gronderosie te bekamp moet die prosesse en grondeienskappe wat gronderosie in die spesifieke plek beïnvloed, geïdentifiseer en verstaan word. In hierdie studie is die grondeienskappe van ‘n hoogs geërodeerde opvanggebied in Maphutseng, Lesotho ondersoek. Die dongaverspreiding in die opvanggebied, in 1957 en 2004 respektiewelik, is vanaf lugfoto’s gekarteer. Die kaarte wys waar in die landskap dongas gedurende hierdie tyd ontwikkel het. Die dongakaarte is op kaarte van verskeie gronderosie faktore gesuperponeer om die ruimtelike verspreiding van die erosie faktore met die donga verspreiding te korreleer. ‘n Grondkaart is spesiaal vir hierdie doel opgestel. Hierdie analise het gewys dat donga-ontwikkeling tussen 1957 en 2004 hoofsaaklik op die area waar dupleks gronde voorkom plaasgevind het. Die res van die opvanggebied het weinig verskille in donga verspreiding in hierdie tyd ondergaan. Die ontstaan van die dongas in die dupleksgronde word toegeskryf aan tonnelerosie. Die hoë dispergeerbaarheid van die dupleks grondmonsters, sinkgate wat in die area voorkom en vorige waarnemings deur navorsers in die area verleen bewyse aan hierdie hipotese. In die tweede deel van die studie is die grondeienskappe van sewentien grondprofiele van regoor die opvanggebied ontleed. Die verskil in donga verspreiding tussen die dupleksgrond area en die res van die opvanggebied is toeskryfbaar aan die hoë dispergeerbaarheid van die dupleks gronde. Geen sterk korrelasies is tussen die dispersiwiteits indeks en ander bepaalde grondeienskappe gevind nie. Gesegmenteerde kwantiel regressie is gebruik om die data verder te ontleed. Hierdie ontleding het gewys dat grondmonsters met matige vlakke van totale koolstof (1.17%), ysteroksied (0.9%) en effektiewe katioonuitruilkapasiteit (13.7 cmolc/kg), ondergemiddelde dispergeerbaarheid toon. Waar nie een van hierdie stabiliserings agente in matige hoeveelhede voorkom nie, is selfs gronde met baie lae uitruilbare natriumpersentasie waardes (0.68%) dispersief. Daar is ook gevind dat gronde wat vanuit kolluviale basaltiese afsettings ontwikkel het, minder dispersief is. Die kleur en verskil in klei persentasie tussen die A en B horison van ‘n grond kan as aanduiding dien van die grond se potensiaal vir tonnelerosie. Donker grondkleure (waarde laer as 4 en chroma laer as 3) wys op ‘n lae dispersiwiteit terwyl vrywater in die ondergrond van gronde waar die B horison veel meer klei as die E horison bevat kan akkumuleer. Die aansameling van vrywater in die ondergrond is noodsaaklik vir tonnelvorming. Dus het donker gronde en gronde met ‘n lae klei akkumulasie indeks ‘n lae potensiaal vir tonnelerosie.
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Wimaladasa, G. D. "Some aspects of the chemistry and mineralogy of soil potassium in Sri Lankan acid tea soils and Scottish soils under a range of crops." Thesis, University of Aberdeen, 1989. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU020940.
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The Sri Lankan acid tea soils, collected from six different agro-ecological regions and from the long-term field experiments in St. Coombs, were subjected to a detailed mineralogical investigation with particular reference to the understanding of the chemistry of soil potassium and K fertiliser applications. These extremely weathered soils contained predominantly kaolinite, Al-chlorite, gibbsite and goethite, but K-fixing minerals like smectite and vermiculite were absent. Small quantities of micaceous minerals were only found in the fine and coarse sand fractions of these soils, except in the Hantana soil which contained substantial quantities of micaceous minerals in the clay, silt and sand fractions. The clay and silt fractions of the Scottish soils of the Countesswells and Foudland soil series comprised 60% to 70% of mica and mica-weathered products of interstratified mica/vermiculite and vermiculite/chlorite. The rate of transformation of the micaceous minerals and the concentration of hydroxy-Al 'islands' in the Countesswells soil series increased with decreasing soil pH. The Foudland soil contained more weatherable micaceous minerals, and spring barley, winter wheat, potatoes and ryegrass/clover in a crop rotation field experiment produced optimum crop yields in the absence of K fertilisers, due to the release of substantial amounts of non-exchangeable K. The Countesswells soil was unable to supply sufficient non-exchangeable K for ryegrass/clover growth in order to achieve the same yield as that with K fertiliser. A mixed NH4- and Cl- ion exchange resin method for extraction of soil K was developed, which was capable of estimating the amounts of short-, medium- and long-term K reserves that are available to ryegrass, grown in different soil types covering a wide range of soil pH and K-bearing minerals, without destroying the mineral matrix, but K-bearing minerals in both soils and pure minerals were found to either transform or dissolve progresively as mineralogical changes took place at the soil/root interface. A new perspex cell was constructed to hold a 4mm layer of soil or mineral, for in situ studies of root morphology, and for study of the mineralogical changes in soils or pure K-bearing minerals, due to the uptake of both exchangeable and non-exchangeable K by ryegrass, within a 2mm radius of the root surface. This study showed that there were more total, primary and lateral ryegrass roots growing in a soil of higher K status, compared with one of lower K status. The numbers of dead or decomposed roots were greater in the lower K status soil. Interstratified smectite, mica/vermiculite and vermiculite/chlorite minerals were formed in the soil within a 2mm radius of the root surface, due to K uptake by ryegrass. These mineralogical changes were not observed in the same soil under intensive cropping with ryegrass in the glasshouse in bigger cylindrical pots or after 21 years of continuous growth of ryegrass in the field. Dissolution of the 2:1 layer silicate mineral structure occurred in soils and vermiculite in the perspex cells, due to the production of H3O- ions, particularly where root growth was greatest. This dissolution mechanism may override the diffusion mechanism of K release to plant roots within a 2mm radius of the root surface, and may help explain the wide range of diffusion coefficients of soil K, (10-10 to 10-23)cm2 sec-1, which appear in the literature. The new techniques of extraction of soil K by use of a mixed NH4- and C1- ion exchange resin and of studying root growth in a perspex cell, which were developed in this thesis, merit further investigation.
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Anderson, Richard Hunter. "Soil Physical And Chemical Property Effects On Toxicity And Bioaccumulation Of As (V), Cd, Pb, And Zn By Herbaceous Plant Receptors." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1220465478.
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Albert-Ayolagha, Gaskin. "Comparison of various soil survey techniques." Thesis, University of Aberdeen, 1988. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186014.
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A Field Survey and mapping was conducted after photo interpretation at a scale of 1:11,000 in an area of Northeast Scotland having varying geological features, physical conditions and land use. Mineralogical and Micromorphological analysis of modal pedo-units samples were carried out. Two Transects were marked out for land cover classification and soil mapping using the following remote sensing techniques: Aerial Photo-Interpretation (API), Landsat MSS and Airborne Thematic Mapper (ATM). MSS bands 4, 5, 7 and the corresponding ATM bands 3, 5, 6 were used in order to highlight the effects of spatial resolution. Five image classification techniques, Density Slicing (DS), Unsupervised Cluster Analysis (CL), Box Classification (BX), Maximum Likelihood (ML) and Visual Interpretation (VS) were used to separate six major land classes (urban, forest, agricultural land, moorland, bare soil and water). For soil survey and mapping the land cover classifications were compared with the various soil units in the study area. There is a weak correlation between the mineralogy and the soil types but the micromorphology correlated well with the soil types. Accuracy test for MSS August shows that ML has the highest classification accuracy having 70.0-75.6%. For MSS April computer aided VS having 72.1-77.6% is the most accurate. For the ATM the Unsupervised algorithm cluster analysis is the most effective having accuracy range of 86.6-90.6%. The comparison of the three remote sensing techniques shows that for land cover classification API is the most accurate having 93.3% followed by ATM bands (3, 5 and 6) CL having 86.6-90.1%. Landsat MSS had only 72.1-72.6%. The lower than expected value for the ATM is probably due to inappropriate and inadequate waveband selection (3 out of 11 bands). For soil survey the ATM CL analysis is the most effective. Accuracy for API and ATM are 70.6-76.2% and 86.9-90.9% respectively. It is expected that higher classification accuracy can be obtained from the ATM data by adequate waveband selection. Those suggested are bands 2, 3, 4, 5, 7, 10 and 11.
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Lucas, P. W. "Fertilizer phosphate-ammonium interactions in soil." Thesis, University of York, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374186.
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Jahiruddin, Md. "Zinc reactions and availability in soil." Thesis, University of Aberdeen, 1986. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU367676.
Full textAbstract:
The requirement of zinc (Zn) for normal plant growth was first recognized in the late nineteenth century, but acceptance of this element as an essential plant nutrient did not occur until the early 1930s. Since then, Zn deficiency has been identified throughout the world on numerous crops grown on widely varying soils under a variety of management practices. Many soils contain appreciable amounts of Zn that plants are unable to utilize. The addition of Zn compounds to soils can also prove to be of limited benefit, as most of the Zn becomes "fixed" by soil components. The mechanisms responsible for Zn "fixation" or "release" have not been fully elucidated. An understanding of the controls on the concentration of Zn in soil solutions is of great significance to the art of maintaining and improving the fertility of soils, and is of rapidly growing importance in understanding the development of Zn deficiency in plants. Certainly a better understanding of soil Zn chemistry and availability, and plant-soil relations will help improve agronomic practices for efficient crop production. With a better understanding of the Zn-deficiency problem in crops in mind, a project has been undertaken on 'zinc reactions and availability in soil'. The work in the project concentrates mainly on evaluation of zinc extractants, identification of soil variables responsible for Zn unavailability, mechanisms involved in Zn fixation at elevated pH and response of barley to Zn and Cu application.