Sulfate-bearing soils are a problem in highway construction as they combine with materials used for lime stabilization to form minerals, particularly ettringite, that expand and induce heave in the stabilized soil. This research involves quantifying sulfate in soils that may be potentially used in highway construction using electromagnetic induction. The objectives are to: 1) document electrical conductivity (EC) variability within selected sites that contain sulfate-bearing materials, and 2) determine if electromagnetic induction has potential for locating hazardous levels of sulfate-bearing materials. The 0.43 ha study area is located in the Blackland Prairies and is a Vertisol known to contain gypsum at the time of site selection. Apparent EC using a model EM38 electromagnetic induction instrument was measured at 200 locations in July and November 2003, using a sampling grid with 5-m spacings. Representative rows and columns were selected from the map of apparent electrical conductivity, and soil cores taken to a depth of 1.5 m at 29 points. Soil samples were obtained by dividing cores into depth increments of 0 to 25 cm, 25 to 75 cm, and 75 to 150 cm. Laboratory analyses were run for each sample and included moisture content, EC and soluble cations and anions of the saturated paste extract, and percent gypsum. Elevation measurements were made to determine if changes in elevation related to EC measurements. Apparent EC proved to be more successful at detecting soluble salts during the dry sampling period (July) when the effect of soil moisture content was less. For July data, EC and gypsum were significantly correlated in the deepest samples (r2 = 0.51 and 0.15, respectively) to apparent EC. Further, soluble sulfate was significantly correlated to apparent EC (r2 = 0.30) at a depth of 25 to 75 cm. Results suggest that the EM38 can be used successfully to map variability of soil salinity across a field, but although correlation exists between apparent EC and sulfate-bearing materials, it is not sufficiently strong to serve as a good predictor for conditions surrounding lime-induced heave in soil.

Knowledge of the spatial distribution of soil textural properties at the watershed scale is important for understanding spatial patterns of water movement, and in determining soil moisture storage and soil hydraulic transport properties. Capturing the heterogeneous nature of the subsurface without exhaustive and costly sampling presents a significant challenge. Soil scientists and geologists have adapted geophysical methods that measure a surrogate property related to the vital underlying process. Apparent electrical conductivity (ECa) is such a proxy, providing a measure of charge mobility due to application of an electric field, and is highly correlated to the electrical conductivity of the soil solution, clay percentage, and water content. Electromagnetic induction (EMI) provides the possibility of obtaining high resolution images of ECa across a landscape to identify subtle changes in subsurface properties. The aim of this study was to better characterize subsurface textural properties using EMI mapping and geostatistical analysis techniques. The effect of variable temperature environments on EMI instrumental response, and ECa - depth relationship were first determined. Then a procedure of repeated EMI mapping at varying soil water content was developed and integrated with temporal stability analysis to capture the time invariant properties of spatial soil texture on an agricultural field. In addition, an EMI imaging approach of densely sampling the subsurface of the Reynolds Mountain East watershed was presented using kriging to interpolate, and Sequential Gaussian Simulation to estimate the uncertainty in the maps. Due to the relative time-invariant characteristics of textural properties, it was possible to correlate clay samples collected over three seasons to ECa data of one mapping event. Kriging methods [ordinary kriging (OK), cokriging (CK), and regression kriging (RK)] were then used to integrate various levels of information (clay percentage, ECa, and spatial location) to produce clay percentage prediction maps. Leave-one-out cross-validation showed that the multivariate estimation methods CK and RK, incorporating the better sampled surrogate ECa, were able to improve the RMSE by 7% and 28%, respectively, relative to OK. Electromagnetic induction measurements provide an important exhaustive layer of information that can improve the quality and resolution of soil property maps used in hydrological and environmental research.

Precision management of cotton production can increase profitability by decreasing inputs. The overall objective of this project is to improve cotton production by minimizing seeding rates while still maximizing yields and lint quality in water-limited soils. The research for this study was conducted at the Texas AgriLife Research IMPACT Center located in the Brazos River floodplain. In 2008 and 2009, 27 measurement locations were selected in production-sized center-pivot irrigated fields and planted in cotton variety Deltapine 164 roundup ready flex / bollgard II. Sites were selected based on soil apparent electrical conductivity (ECa) values, in a low, medium, and high ECa zones. Three seeding rates (74,100; 98,800; and 123,500 seeds ha-1) were established in each of the three ECa zones with three replications. In 2009, an additional seeding rate was added at 49,400 seeds ha-1. At each measurement location, soil texture, soil moisture (weekly), lint quantity and quality (High Volume Instrument) were measured. An additional replication for each ECa zone and seeding rate was selected for lint quantity and quality (HVI) measurements. Results indicated that cotton lint yield increased as ECa values, clay content, and water holding capacity of the soil increased. The seeding rates did not consistently affect cotton lint yield or quality. Seeding rates of 74,100 and 49,400 seeds ha-1 in a low and medium ECa zone for IMPACT-08 and -09 yielded more lint (300 kg ha-1), respectively. HVI lint quality parameters, such as, micronaire, fiber length, strength, uniformity, and elongation were significantly better in ECa zone 3. While the seeding rates did not affect the amount of soil water used throughout the season, lint yield variations between ECa zones can be explained by the rate at which soil water was used. Lower rates at which soil water was used within ECa zone 3 resulted in higher lint yields when compared to ECa zones 1 and 2, which used soil water faster and at greater depths. The findings suggest that irrigation applied to the low ECa zone was not sufficient to meet the plants demand, while in a high ECa zone, irrigation could have been reduced, resulting in cost savings through reduced inputs.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-11-30T09:09:36Z No. of bitstreams: 2 Dissertação - Antônio Marcelino da Silva Filho - 2015.pdf: 2204549 bytes, checksum: 2f0941c7970eff84c86b64f4fd261cb6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-11-30T09:11:40Z (GMT) No. of bitstreams: 2 Dissertação - Antônio Marcelino da Silva Filho - 2015.pdf: 2204549 bytes, checksum: 2f0941c7970eff84c86b64f4fd261cb6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-11-30T09:11:40Z (GMT). No. of bitstreams: 2 Dissertação - Antônio Marcelino da Silva Filho - 2015.pdf: 2204549 bytes, checksum: 2f0941c7970eff84c86b64f4fd261cb6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-12-19 / This work presents the study of the relationship between soil apparent electrical resistivity ρa and the moisture content, clay content and soil compaction, for use of the ρa as a mapping tool of spatial soil variability. The values of apparent electrical resistivity are obtained by geoelectrical prospecting methods that detect the effects produced by the flow of electrical current in the soil. It is used the Wenner array and the technique of Lateral Profiling for data collection. It was held measures of ρa in different soil types, varying moisture content gradually while maintaining a constant compaction, and then varying the compaction and relating it to a constant humidity. To the study of spatial variability, it was chose two areas that would enable the change of moisture and compaction content, in order to verify the measurement capacity of ρa as methodology of identification of change in soil dynamics. The results obtained are presented and discussed. / Este trabalho apresenta o estudo das rela¸c˜oes entre a resistividade el´etrica aparente do solo ρa e o teor de umidade, teor de argila e compacta¸c˜ao do solo, para utiliza¸c˜ao de ρa como ferramenta de mapeamento da variabilidade espacial do solo. Os valores da resistividade el´etrica aparente s˜ao obtidos atrav´es de m´etodos de prospec¸c˜ao geoel´etricos que detectam os efeitos produzidos pelo fluxo de corrente el´etrica no solo. Utilizam-se o arranjo de Wenner e a t´ecnica do Caminhamento El´etrico para coleta dos dados. Realizaram-se medidas de ρa em diferentes tipos de solo, variando-se gradualmente o teor de umidade, mantendo-se constante a compacta¸c˜ao, e posteriormente variando a compacta¸c˜ao em fun¸c˜ao de valor constante de umidade. Para o estudo da variabilidade espacial, escolheram-se duas ´areas que possibilitassem a altera¸c˜ao dos teores de umidade e compacta¸c˜ao, a fim de verificar a capacidade da medi¸c˜ao de ρa como metodologia de identifica¸c˜ao de altera¸c˜oes na dinˆamica do solo. Os resultados obtidos s˜ao apresentados e discutidos.

A porção sul do Leque Aluvial do Taquari, chamada Nhecolândia, é uma sub-região do Pantanal Mato-Grossense, que apresenta um complexo sistema de lagoas arredondadas, vazantes, cordilheiras, corixos e pequenas depressões. Estudos anteriores mostraram que os fluxos de águas subsuperficiais dependem da intensidade das cheias, e da presença e forma dos horizontes verdes argilosos, localmente cimentados, que limitam fortemente a permeabilidade, e comandam os fluxos laterais. Inicialmente associados a ambientes alcalinos das salinas, esses horizontes também ocorrem em ambientes diluídos, como as pequenas depressões. O objetivo geral deste trabalho é compreender o funcionamento hídrico de três pequenas depressões, em relação com as características morfológicas dos solos. Métodos de indução eletromagnética foram utilizados para mapear a condutividade elétrica aparente (CEa); complementados por métodos de descrições das características morfológicas dos solos, e de análises granulométricas e mineralógicas em laboratório. Estes trabalhos foram complementados por análises físico-químicas das águas nas depressões; e pelo monitoramento do nível do lençol freático entre uma depressão e uma baía. O horizonte verde argiloso, mais ou menos endurecido, aparece na base das sequências de solos nas três pequenas depressões, ao qual se superpõem horizontes arenosos superficiais e subsuperficiais. As principais diferenciações morfológicas observadas referem-se aos processos de redistribuição de ferro e da matéria orgânica, ligados ao regime hídrico. No período seco, quando ocorre um rebaixamento do nível freático, o horizonte verde argiloso funciona como uma soleira e fragmenta o lençol, que passa a funcionar como dois segmentos, um ligado à Depressão Fechada, e outro à Baía. Ao longo do ano, a Depressão Fechada acumula água apenas temporária e fugazmente. Na maior parte do tempo, ela funciona como área dispersora de água às unidades morfológicas adjacentes, salientando sua importância funcional na Nhecolândia. / The southern part of the Taquari alluvial fan, called Nhecolândia, is a sub-region of the Pantanal of Mato-Grosso exhibiting a complex of round shape lakes, draining fields, forested sandy areas, small watercourses and small depressions. Former studies have shown that the sub-superficial water fluxes depend on the intensity of the flood and on the presence and shape of a sandy clay loam greenish horizon, locally cemented, which acts as an impervious layer and drives lateral fluxes. Although its presence has always been associated to the alkaline-saline parts of this singular landscape, it also occurs below small freshwater depressions. The objective of this study is to understand the hydrological functioning of these small depressions in relation to the soil cover layout. Electromagnetic induction methods were used to draw apparent electrical conductivity (CEa) maps, crossed with direct auger holes and pits observations, and laboratory analysis (grain size distribution and mineralogy). Physico-chemical analysis of the ground water in the depressions and a monitoring of the groundwater fluctuation along one year were also performed. The greenish horizon, more or less cemented, occurred at the base of the soil system in all the studied depressions. It was overlaid by more sandy horizons. The main pedological differentiation was organic matter and iron redistribution along the soil sequences, in relation with the hydrological regime. During the dry season, the watertable goes down and the greenish horizon acts as a threshold, disconnecting various watertables in the different parts of the landscape. Along the year, the closed depressions accumulate the water only temporarily and fleetingly. Most of the time, they work as areas of water redistribution towards the surrounding landscape units, and therefore have a essential function in the Nhecolândia.

A porção sul do Leque Aluvial do Taquari, chamada Nhecolândia, é uma sub-região do Pantanal Mato-Grossense, que apresenta um complexo sistema de lagoas arredondadas, vazantes, cordilheiras, corixos e pequenas depressões. Estudos anteriores mostraram que os fluxos de águas subsuperficiais dependem da intensidade das cheias, e da presença e forma dos horizontes verdes argilosos, localmente cimentados, que limitam fortemente a permeabilidade, e comandam os fluxos laterais. Inicialmente associados a ambientes alcalinos das salinas, esses horizontes também ocorrem em ambientes diluídos, como as pequenas depressões. O objetivo geral deste trabalho é compreender o funcionamento hídrico de três pequenas depressões, em relação com as características morfológicas dos solos. Métodos de indução eletromagnética foram utilizados para mapear a condutividade elétrica aparente (CEa); complementados por métodos de descrições das características morfológicas dos solos, e de análises granulométricas e mineralógicas em laboratório. Estes trabalhos foram complementados por análises físico-químicas das águas nas depressões; e pelo monitoramento do nível do lençol freático entre uma depressão e uma baía. O horizonte verde argiloso, mais ou menos endurecido, aparece na base das sequências de solos nas três pequenas depressões, ao qual se superpõem horizontes arenosos superficiais e subsuperficiais. As principais diferenciações morfológicas observadas referem-se aos processos de redistribuição de ferro e da matéria orgânica, ligados ao regime hídrico. No período seco, quando ocorre um rebaixamento do nível freático, o horizonte verde argiloso funciona como uma soleira e fragmenta o lençol, que passa a funcionar como dois segmentos, um ligado à Depressão Fechada, e outro à Baía. Ao longo do ano, a Depressão Fechada acumula água apenas temporária e fugazmente. Na maior parte do tempo, ela funciona como área dispersora de água às unidades morfológicas adjacentes, salientando sua importância funcional na Nhecolândia. / The southern part of the Taquari alluvial fan, called Nhecolândia, is a sub-region of the Pantanal of Mato-Grosso exhibiting a complex of round shape lakes, draining fields, forested sandy areas, small watercourses and small depressions. Former studies have shown that the sub-superficial water fluxes depend on the intensity of the flood and on the presence and shape of a sandy clay loam greenish horizon, locally cemented, which acts as an impervious layer and drives lateral fluxes. Although its presence has always been associated to the alkaline-saline parts of this singular landscape, it also occurs below small freshwater depressions. The objective of this study is to understand the hydrological functioning of these small depressions in relation to the soil cover layout. Electromagnetic induction methods were used to draw apparent electrical conductivity (CEa) maps, crossed with direct auger holes and pits observations, and laboratory analysis (grain size distribution and mineralogy). Physico-chemical analysis of the ground water in the depressions and a monitoring of the groundwater fluctuation along one year were also performed. The greenish horizon, more or less cemented, occurred at the base of the soil system in all the studied depressions. It was overlaid by more sandy horizons. The main pedological differentiation was organic matter and iron redistribution along the soil sequences, in relation with the hydrological regime. During the dry season, the watertable goes down and the greenish horizon acts as a threshold, disconnecting various watertables in the different parts of the landscape. Along the year, the closed depressions accumulate the water only temporarily and fleetingly. Most of the time, they work as areas of water redistribution towards the surrounding landscape units, and therefore have a essential function in the Nhecolândia.

No description available.

Das Wurzelwachstum von Winterweizen wurde erfasst und modelliert, um teilflächenspezifisches Boden- und Düngemanagement zu verbessern. Die Variation von Wurzellängendichten im Feld wurde über zwei Vegetationsperioden hinweg an zwei unterschiedlichen Standorten in Ostdeutschland untersucht. Zur Auswertungserleichterung der hohen Anzahl an Wurzelproben, wurde eine halbautomatische Methode zur Bildanalyse von Wurzeln entwickelt. Der Einfluss von Änderungen bezüglich Bodenwasserstatus und Bodendichte bzw. Durchdringungswiderstand auf das Wurzelwachstum wurde untersucht. Die erhobenen Felddaten dienten gleichzeitig dazu, die Bodenwasser- und Wurzelwachstumsberechnung des Modells CERES-Wheat zu validieren. Das Modell simulierte die unterschiedlichen Bodeneigenschaften sowie die Wurzellängendichten und Bodenwassergehalte nur unzureichend. Der Effekt von Änderungen der Niederschlagsmengen auf die Simulationen von Wurzellängendichten und Bodenwassergehalten wurde anhand einer Unsicherheitsanalyse getestet und war extrem gering. Des Weiteren wurde eine Methode für praktische Zwecke entwickelt, mit der die Generierung von räumlich hoch aufgelösten Bodeninformationen unter Verwendung limitierter Eingangsdaten möglich ist. Die Modellkalkulationen basieren auf der Dempster-Shafer-Theorie. Anhand von multitemporal und multimodal erfassten Bodenleitfähigkeitsdaten, die Eingangsdaten für den Modellansatz sind, wurden Bodentypen und Texturklassen bestimmt. Das Modell generiert eine digitale Bodenkarte, die flächenhafte Informationen über Bodentypen und Bodeneigenschaften enthält. Die Validation der Bodenkarte mit zusätzlich erhobenen Bodeninformationen ergab gute bis sehr gute Ergebnisse. / Winter wheat root growth was measured and modelled to improve site-specific soil and fertilizer management in commercial wheat fields. Field variations in root length densities were analysed at two contrasting sites in East-Germany during two vegetation seasons. A semi-automated root analysing method was developed to facilitate analyses of large numbers of samples. Influences of variations in soil water states, bulk densities and penetration resistances on spatial distributions of roots were quantified. Differences in soil characteristics were large between the two sites and affected root growth considerably. The same field data was used for validating the soil moisture and root growth calculations of the widely applied growth model CERES-Wheat. Simulations of root length densities, soil physical properties and soil water contents were inadequate. The effects of changes of rainfall variabilities on simulated root length densities and soil water contents were tested by uncertainty analysis but were negligible low. A methodology for generating soil information for practical management purposes at a high degree of spatial resolution using limited input information was developed. The corresponding model calculations were carried out based on the Dempster and Shafer theorem. Soil types and texture classes were determined with multimodally and multitemporally captured data of soil electrical conductivities which are required input data of the new model approach. The model generates a digital map with extensive information of spatial variations in soil properties. The validation of the generated soil map with soil data from independent measurements yielded close correlation between measured and calculated values.