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1
Ekanayake, Jagath C. "Soil water movement through swelling soils." Lincoln University, 1990. http://hdl.handle.net/10182/1761.
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The present work is a contribution to description and understanding of the distribution and movement of water in swelling soils. In order to investigate the moisture distribution in swelling soils a detailed knowledge of volume change properties, flow characteristics and total potential of water in the soil is essential. Therefore, a possible volume change mechanism is first described by dividing the swelling soils into four categories and volume change of a swelling soil is measured under different overburden pressures. The measured and calculated (from volume change data) overburden potential components are used to check the validity of the derivation of a load factor, ∝. Moisture diffusivity in swelling soil under different overburden pressures is measured using Gardner's (1956) outflow method. Behaviour of equilibrium moisture profiles in swelling soils is theoretically explained, solving the differential equation by considering the physical variation of individual soil properties with moisture content and overburden pressure. Using the measured volume change data and moisture potentials under various overburden pressures, the behaviour of possible moisture profiles are described at equilibrium and under steady vertical flows in swelling soils. It is shown that high overburden pressures lead to soil water behaviour quite different from any previously reported.
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Zhang, Guanghui, and 張廣輝. "Soil-water characteristics of sandy soil and soil cement with and without vegetation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208025.
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The use of soil cement as a growth medium was examined in this study. During the monitoring, green soil cement revealed diverse ecological values. The survival rates of plants in each soil conditions were higher than 80%,which was very promising. Furthermore, the survival rates dropped when the soil density reached95%, which means soil density might influence the survival rate of plant. Plant growth rates in sandy soil were higher than that in soil cement. In particular, low soil density facilitated plant growth in sandy soil, whereas density effect was not clear to plant growth performance in soil cement.
Experiments were undertaken to study the soil-water characteristics of sandy soil and soil cement in field and laboratory condition. The influence of vegetation and material density on the development of negative pore water pressure (PWP) and degree of saturation (Sr) in the studied materials was investigated. The field planting experiments proved a promising survival rate of Schefflera heptaphylla in both types of materials while sandy soil promoted better growth of the seedlings than the soil cement. From the field study, PWP and Sr of sandy soil responded noticeably and promptly to natural drying and wetting cycles. However, the responses in soil cement were relatively mild. When subjected to the same drying-wetting cycles, PWP responded more slowly and to a smaller magnitude compared with that of soil cement. In addition, Sr changed little in soil cement. An increase in the density of the sandy soil promoted rapid development of negative PWP, while an opposite trend was observed for soil cement. Attempts have been made to explain the observations from the perspectives of material permeability and change in water content during a drying period in both soil types. Furthermore, in sandy soil, the development of PWP (with a measurement limit of -90 kPa) was minimally affected by the presence of vegetation, while vegetation noticeably helped the development of negative PWP in the soil cement. Bounds of the soil-water characteristic curve of the studied materials were presented based on estimates from the drying and wetting scanning curves derived from the field monitoring. A complementary laboratory study was carried out in an environmental chamber with controllable temperature and humidity. Monitoring results from the laboratory agreed well with that obtained from the field.published_or_final_version
Civil Engineering
Master
Master of Philosophy
3
Bagour, Mohammed H., and Donald F. Post. "Predicting the Volumetric Water Content of Irrigated Arizona Soils at Different Soil Water Potentials." Arizona-Nevada Academy of Science, 2001. http://hdl.handle.net/10150/296584.
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Buchanan, Margaret MacNeill. "Soil Water Flow and Irrigated Soil Water Balance in Response to Powder River Basin Coalbed Methane Product Water." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/buchanan/BuchananM0505.pdf.
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A repacked soil columns experiment and a series of computer soil water balance simulations were conducted to examine potential impacts of coalbed methane (CBM) water from Montana's Powder River Basin (PRB) on soil water flow and water balance in PRB soils. CBM water is often high in sodium, which may separate soil clay particles, particularly after soil exposure to low-salinity rainfall or snowmelt, and when soils contain expansible smectite clay minerals. Aggregates in soils exposed to sodic water may swell and slake, and clays and other fine particles may disperse, clogging soil pores and slowing or preventing soil water flow. In the soil columns experiment, A and B horizon materials from sandy loam, silt loam, and clay loam soils were pre-treated with water having salinity and sodicity typical of PRB CBM water or of Powder River (PR) water currently used for irrigation in the basin. Tension infiltrometer measurements were used to determine infiltration flux, first using pre-treatment water, and subsequently deionized (DI) water, simulating rainwater. Measurements were compared by pre-treatment water, horizon, and soil type. Under pre-treatment water testing, the sandy loam and clay loam soils pre-treated with CBM water exhibited smaller infiltration flux values than when pre-treated with PR water. Only the sandy loam soil showed a greater decrease in infiltration flux with DI water on soils pre-treated with CBM relative to PR water pre-treated soils. There was no difference in infiltration flux decrease with DI water between A and B horizon soils, or between smectite and non-smectite soils. The soil water balance numerical simulations modeled potential effects of sodic irrigation waters on sandy loam, silt loam, clay loam and silty clay PRB soils under sprinkler or flood irrigation, during one growing season. Baseline soil water retention functions were constructed for the five soils, and adjusted via trends identified in the literature to create five additional functions for each soil, simulating exposure to five increasingly sodic irrigation waters. Simulation results showed greater impact of sodic irrigation under flood than sprinkler irrigation. The fine sandy loam and silty clay loam soils exhibited the fewest changes in water balance partitioning, while the silt loam and silty clay soils showed the greatest changes, especially in increased runoff and reduced transpiration.
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Alvenäs, Gunnel. "Evaporation, soil moisture and soil temperature of bare and cropped soils /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5714-9.pdf.
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Kwong, Chin Pang. "Field and laboratory experimental study of water infiltration in cracked soil /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202009%20KWONG.
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Barrett, Gary Edward. "Infiltration in water repellent soil." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28618.
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Observations made at Goat Meadows - a small sub-alpine basin located near Pemberton, British Columbia -demonstrated that a layer which is either water repellent or has only a limited affinity for water is present at most vegetated sites. The layer is typically a few centimetres in thickness, and is usually located at or near the top of the profile: it was present only in the zone of accumulation of organic matter. The spatial distribution of the layer did not appear to be related to the distribution of any particular species of plant. Sampling of sub-alpine sites in the Cascade, Selkirk, and Purcell Mountains indicated that such layers are common in the alpine - sub-alpine ecotone of southern British Columbia.
The relationship between ponding depth and infiltration rate was explored through experiments conducted on samples collected near Ash Lake, in Goat Meadows. These samples were chosen for analysis because the repellent layer was in excess of thirty centimetres thick at this site. Infiltration rates remained below 2x10⁻⁹ m/s for all samples, even given ponding depths of up to forty centimetres. Breakthrough of liquid water was not observed, even after one month, which implies that most of the infiltration occurred as vapour transfer.
In order to observe the movement of liquid water through water repellent media, a plexiglas cell was constructed. A synthetic water repellent sand with uniform surface properties was used as the medium. It was found that up to some critical depth, there was no entry of water into the medium. As the ponding depth was increased in steps, the front would advance in steps: it remained stationary between these step-increases in ponding depth. As the front advanced, protuberances or "fingers" began to develop. At some critical ponding depth, a finger would grow without bound. These observations pose a challenge to existing models of infiltration, since it appears that heterogeneity at the scale of individual pores must be invoked to explain them, but it is usually assumed that the properties of a porous medium are continuous at this scale.
The thermodynamics of filling and emptying of pores is considered with emphasis on the effects of pore shape and of variations in the physicochemical properties at the scale of the pore. This thermodynamic analysis provides the conceptual basis for development of a model of infiltration in which pore-scale heterogeneity is preserved. Although it was not developed as such, the model follows the approach of cellular automata, in which local relations between pores or "cells" govern the behaviour of the system. The model replicated the observations of infiltration into synthetic water repellent porous media well: both the halting advance of the front as the ponding depth was increased and the development of fingers were simulated. The fact that such complex behaviour was predicted using only a simple set of physically based rules confirms the power of the approach.Arts, Faculty of
Geography, Department of
Graduate
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Chen, Chien-chang. "Shear induced evolution of structure in water-deposited sand specimens." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/22724.
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Miller, Christopher James. "Mechanisms of water colour release from organic soils and consequences for catchment management." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Online version available for university members only. This requires an institutional login off-campus, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=24724.
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Ward, Philip R. "Generation of water repellence in sands, and its amelioration by clay addition /." Adelaide, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phw262.pdf.
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Bobart, Hawkins Jane Madge. "Amino acids as diagnostics of soil and soil water quality." Thesis, University of Plymouth, 2004. http://hdl.handle.net/10026.1/2425.
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Information on the contribution of amino acids to dissolved organic nitrogen and carbon exported from grassland soil is scarce. Evidence from the literature for other environments, suggests that determination of amino acid patterns of distribution may be a useful method for improved understanding of the interaction of microbial synthesis and degradation of organic N in conjunction with soil physical states. A sample pre-concentration technique and an HPLC methodology were developed that enabled the determination of dissolved free (DFAA) and combined (DCAA) amino acids in natural waters at picomolar concentration. These methods were used to examine the content of amino acids and their distribution patterns in waters from 3 different settings. Firstly, field-sized lysimeters (1 ha) were used to examine dissolved free and combined amino acids in surface runoff and drainage waters from a grassland soil over 3 winter drainage periods. The waters were collected from soils beneath drained and undrained permanent ryegrass swards, receiving 280 kg N haˉ¹yrˉ¹ , permanent ryegrass receiving no mineral N input, and grass/white clover (no mineral N). Total DFAA concentration ranged between 1.9 nM - 6.1 µM and total DCAA concentration ranged between 1.3 - 87 µM. A large library of amino acid distributions was assembled and multivariate pattern analysis techniques were used to determine whether there were distinctive amino acid signatures that could be used as a diagnostics for soil management and condition. Although addition of mineral N fertilizer increased amino acid concentration in waters, there was no detectable effect of fertilizer addition on DFAA distribution patterns. In contrast, both DFAA and DCAA patterns were strongly influenced by soil hydrology alone. However, in the case of DCAA patterns, there was evidence of an interaction between hydrology and fertilizer addition. Secondly, monolith lysimeters were used to determine the DFAA in drainage waters from 4 different grassland soil types, in order to find whether there was evidence of pattern difference with soil texture. Results showed that distribution patterns vary between soil types, and contrary to what might be expected, that clay soils do not necessarily retain basic amino acids. Thirdly, the concentration and patterns of DFAA were determined hourly over a 24 hour period, for a river that received exported soil waters from the field lysimeters mentioned above. Total DFAA concentration correlated with water temperature and NH4+ Compared with exported soil waters, the concentrations of DFAA in river water were several orders of magnitude smaller, although GLY, SER, LYS and MET were in greater relative proportions. Results of the studies show that amino acids have the potential to be used as diagnostics of source, soil condition and management.
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Copeland, Stephen Mark 1955. "Soil water potential as related to the Crop Water Stress Index of irrigated cotton." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276940.
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The application of the crop water stress index (CWSI) method to irrigation scheduling is enhanced by knowledge of the relationship between CWSI and soil water potential (SWP) and how this relationship is affected by soil texture. A study using the same cultivar of cotton on three different soils was conducted in southern Arizona over a single growing season. Detailed data were collected of CWSI and soil moisture content for several treatments that scheduled irrigations at threshold CWSI values. CWSI was correlated with soil water potential values calculated from pressure plate determined moisture release curves. Spatial variability of soil characteristics necessitated use of average rather than plot specific moisture release curves. Analysis showed a linear CWSI-SWP relationship that varied greatly with soil depth and study site. The study concluded that soil profile average SWP alone does not normalize the CWSI between sites with different soil textures.
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de, la Mota Daniel Francisco Javier. "Water Fluxes in Soil-Pavement Systems: Integrating Trees, Soils and Infrastructure." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/99419.
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In urban areas, trees are often planted in bare soil sidewalk openings (tree pits) which recently are being covered with permeable pavements. Pavements are known to alter soil moisture and temperature, and may have implications for tree growth, root development and depth, drought resilience, and sidewalk lifting. Furthermore, tree pits are often the only unsealed soil surface and are important for water exchange between soil and atmosphere. Therefore, covering tree pits with pavement, even permeable, may have implications for the urban water balance and stormwater management. A better understanding of permeable pavement on tree pavement soil system functioning can inform improved tree pit and street design for greater sustainability of urban environments.
We conducted experiments at two sites in Virginia, USA (Mountains and Coastal Plain) with different climate and soil. At each location, we constructed 24 tree pits in a completely randomized experiment with two factors: paved with resin-bound porous-permeable pavement versus unpaved, and planted with Platanus x acerifolia 'Bloodgood' versus unplanted (n = 6). We measured tree stem diameter, root growth and depth, and soil water content and temperature over two growing seasons. We also monitored tree sap flow one week in June 2017 at the Mountains. In addition, we calibrated and validated a soil water flow model, HYDRUS-1D, to predict soil water distribution for different rooting depths, soil textures and pavement thicknesses.
Trees in paved tree pits grew larger, with stem diameters 29% (Mountains) and 51% (Coastal Plain) greater. Roots developed faster under pavement, possibly due to the increased soil water content and the extended root growing season (14 more days). Tree transpiration was 33% of unpaved and planted pit water outputs, while it was 64% for paved and planted pits. In June 2016, planted pits had decreased root-zone water storage, while unplanted pits showed increased storage. A water balance of the entire experimental site showed overall decreased soil water storage due to tree water extraction becoming the dominant factor. HYDRUS-1D provided overall best results for model validation at 10 cm depth from soil surface (NSE = 0.447 for planted and paved tree pits), compared to 30- and 60 cm depths. HYDRUS-1D simulations with greater pavement thickness resulted in changes in predicted soil water content at the Coastal Plain, with higher values at 10- and 30-cm depths, but lower values at 60-cm depth. At the Mountains, virtually no difference was observed, possibly due to different soil texture (sandy vs clayey).
Tree pits with permeable pavement accelerated tree establishment, but promoted shallower roots, possibly increasing root-pavement conflicts and tree drought susceptibility. Paved tree pits resulted in larger trees, increasing tree transpiration, but reduced soil evaporation compared to unpaved pits. Larger bare soil pits surrounded by permeable pavement might yield the best results to improve urban stormwater retention. Also, HYDRUS 1D was successful at simulating soil water content at 10-cm depth and may be valuable to inform streetscape design and planning.PHD
14
Carminati, Andrea. "Unsaturated water flow through soil aggregates /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17011.
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Ng, Man-chung, and 吳敏聰. "Water infiltration in unsaturated soil slope." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B46599642.
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Johnston, Christopher R. "Soil chemical and physical changes resulting from irrigation with coalbed natural gas co-produced water effects of soil amendments and water treatments /." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1445033651&sid=10&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Fontes, Adan Fimbres 1953. "Soil Albedo in Relation to Soil Color, Moisture and Roughness." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/191203.
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Land surface albedo is the ratio of reflected to incident solar radiation. It is a function of several surface parameters including soil color, moisture, roughness and vegetation cover. A better understanding of albedo and how it changes in relation to variations in these parameters is important in order to help improve our ability to model the effects of land surface modifications on climate. The objectives of this study were 1) To determine empirical relationships between smooth bare soil albedo and soil color, 2) To develop statistical relationships between albedo and ground-based thematic mapper (TM) measurements of spectral reflectances, 3) To determine how increased surface roughness caused by tillage reduces bare soil albedo and 4) To empirically relate albedo with TM data and other physical characteristics of mixed grass/shrubland sites at Walnut Gulch Watershed. Albedos, colors and spectral reflectances were measured by Eppley pyranometer, Chroma Meter CR-200 and a Spectron SE-590, respectively. Measurements were made on two field soils (Gila and Pima) at the Campus Agricultural Center (CAC), Tucson, AZ. Soil surface roughness was measured by a profile meter developed by the USDA/ARS. Additional measurements were made at the Maricopa Agricultural Center (MAC) for statistical model testing. Albedos of the 15 smooth, bare soils (plus silica sand) were determined by linear regression to be highly correlated (r²=0.93, p>0.01) with color values for both wet and dry soil conditions. Albedos of the same smooth bare soils were also highly correlated (r²≥0.86, p>0.01) with spectral reflectances. Testing of the linear regression equations relating albedo to soil color and spectral reflectances using the data from MAC showed a high correlation. A general nonlinear relationship given by y=8.3661n(x)+37.802 r²=0.71 was determined between percent reduction in albedo (y) and surface roughness index (x) for wet and dry Pima and Gila field soils. Measurements of albedo, color and spectral reflectance at the Walnut Gulch Watershed indicated that albedo values were highly correlated with percent rock & gravel, color value and reflectance data (TM bands 1-4).
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Bellamy, Christopher A. "Sensor-based soil water monitoring to more effectively manage agricultural water resources in coastal plain soils." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1263402218/.
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Qureshi, Suhail Ahmad. "Soil water balance of intercropped corn under water table management." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23289.
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A one year water table management field study was conducted on a Soulanges sandy loam soil in Soulanges county, Quebec. Two controlled water table levels, i.e. 0.5 m and 0.75 m from the soil surface, as well as free outlet conventional drainage treatments were established in monocropped corn (Zea mays L.) and corn intercropped with ryegrass (Lolium multiflorum Lam) plots.Cropping system showed no significant effects on evapotranspiration, and on soil moisture distribution. It was observed that the 0.5 m and 0.75 m controlled water tables (CWT) provided the same soil moisture trends in both cropping systems. The soil moisture was always higher in controlled water table plots compared to freely drained plots. The water use efficiency of 0.75 m CWT in both cropping systems was high compared to 0.5 m CWT.
The soil moisture contents at three depths were only 2% to 10% less in intercropped plots compared to monocropped plots. The soil moisture was 12 to 13% higher in CWT plots compared to freely drained plots for both cropping systems. The soil moisture in 0.5 m CWT and 0.75 m CWT plots was not significantly different. The average water table levels in monocropped plots were not significantly different from intercropped plots.
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Dalton, James A. "Contribution of upward soil water flux to crop water requirements." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/344938/.
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Chang, Chao-Ting. "Soil water availability regulates soil respiration temperature dependence in Mediterranean forests." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/406082.
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The variations of ecosystem and soil respiration are mainly driven by temperature and precipitation, but the importance of temperature and precipitation could vary across temporal and spatial. At diurnal to annual temporal scales, ecosystem and soil respiration generally increase with average annual temperature, but very low or very high soil moisture has been shown to diminish the temperature response of respiration. Therefore, in water-limited ecosystem, such as the Mediterranean region where the seasonal pattern is characterized with significant summer drought, precipitation patterns are likely to play a particularly important role in regulating ecosystem and soil respiration inter annual whereas temperature may be much less factor. In this dissertation, I try to reduce the uncertainties of terrestrial net ecosystem exchange in Mediterranean region by measuring the interaction between environmental factors and soil respiration at short (i.e., diurnal) and medium (i.e., seasonal-years) temporal scales. Three in situ experiments were employed to investigate how soil respiration responds to environmental variations and management. Together, these three studies gave a consistent picture on how soil moisture strongly affects the dynamic and magnitude of soil respiration in Mediterranean forests. Results elucidated a clear soil moisture threshold; when soil moisture is above this threshold, soil temperature is the main driver of soil respiration, meanwhile, when soil moisture is below this threshold, soil respiration decoupled from soil temperature and is controlled by soil moisture. This suggests that soil moisture modified, at least in Mediterranean ecosystems, the temperature sensitivity of respiration through threshold-like response.Las variaciones de la respiración del ecosistema y del suelo son principalmente impulsadas por la temperatura y la precipitación, pero la importancia de la temperatura y la precipitación puede variar a lo largo del tiempo y el espacio. En las escalas temporales diurnas a anuales, la respiración del ecosistema y del suelo generalmente aumenta con la temperatura media anual, pero se ha demostrado que la humedad del suelo muy baja o muy alta disminuye la respuesta a la temperatura de la respiración. Por lo tanto, en ecosistemas con escasez de agua, como la región mediterránea, donde el patrón estacional se caracteriza por sequías significativas en verano, es probable que los patrones de precipitación jueguen un papel particularmente importante en la regulación de la respiración del ecosistema y del suelo. En esta tesis, intento reducir las incertidumbres del intercambio de ecosistemas netos terrestres en la región mediterránea midiendo la interacción entre los factores ambientales y la respiración del suelo a escalas temporales cortas (diurnas) y medias (estacionales). Se utilizaron tres experimentos in situ para investigar cómo la respiración del suelo responde a las variaciones y manejo del ambiente. En conjunto, estos tres estudios dieron una imagen consistente de cómo la humedad del suelo afecta fuertemente la dinámica y la magnitud de la respiración del suelo en los bosques mediterráneos. Los resultados dilucidaron un umbral claro de humedad del suelo; Cuando la humedad del suelo está por encima de este umbral, la temperatura del suelo es el principal impulsor de la respiración del suelo, mientras que la humedad del suelo está por debajo de este umbral, la respiración del suelo está desacoplada de la temperatura del suelo y controlada por la humedad del suelo. Esto sugiere que la humedad del suelo modificó, al menos en los ecosistemas mediterráneos, la sensibilidad a la temperatura de la respiración a través de la respuesta tipo umbral.
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Mortl, Amanda E. "Monitoring soil moisture and soil water salinity in the Loxahatchee floodplain." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015734.
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Kreba, Sleem. "LAND USE IMPACT ON SOIL GAS AND SOIL WATER TRANSPORT PROPERTIES." UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/31.
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The consequences of land use choices on soil water and gas transport properties are significant for gas and water flux in agricultural environments. Spatial and temporal patterns and associations of soil water and soil gas characteristics and processes in different land uses are not well understood. The objectives of this study were to 1) characterize soil structure under crop and grass systems, 2) quantify spatial patterns and associations of soil physical characteristics in crop and grass systems, and 3) quantify spatial and temporal patterns and associations of CO2 and N2O fluxes. The research was conducted in a 60 by 80 m field divided into grass and crop systems. Sixty sampling points were distributed in four transects with 5- and 1-m spatial intervals between measurement points. Gas fluxes were measured, at two-week time intervals, 22 times during a year. Pore size distribution was more homogeneous and more continuous pores were found in the grass than in the crop system. The spatial variability of most selected soil physical characteristics was more structured in the crop than in the grass system, which reflected the impact of land use and soil structure on their spatial patterns. CO2 flux was dependent for a longer distance in the grass than in the crop system, however, the two land-use systems exhibited similar spatial ranges of N2O flux. Gas fluxes were temporally dependent for a longer period in the grass than in the crop system. The spatial associations between CO2 and N2O fluxes and selected biochemical and physical factors depended on the flux sampling season and land use. Soil temperature was the dominant controlling factor on the temporal variability of CO2 and N2O fluxes but not on the spatial behavior. Considering the spatial and temporal ranges and dependency strength of soil variables helps identify efficient sampling designs that can result in better time and resource management. Spatial and temporal relationships between the selected soil variables also improve understanding soil management and sampling soil variables. This study provides the baseline and recommendations for future investigations specifically for sampling designs, soil management, and predictions of different soil processes related to gas fluxes.
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Feeney, Deborah Siobhan. "The influence of fungi upon soil structure and soil water relations." Thesis, Abertay University, 2004. https://rke.abertay.ac.uk/en/studentTheses/2a92d2fc-b3c5-456f-8b9a-e406bd78ee84.
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The investigation of soil structural stability and soil water processes was assessed through the application of laboratory investigations and a field based analysis. The impact of an arbuscular mycorrhizal (AM) fungal exudate glomalin (a glycoprotein), proposed to be hydrophobic was assessed for a correlation with low levels of soil hydrophobicity through measures of subcritical water repellency. Initially no correlation was reported but a further temporal investigation that involved a soil inoculum detected a significant positive effect; the results indicated that a certain concentration of protein is required before an influence upon soil hydrophobicity is detected. The temporal investigation detected significant re-aggregation of previously disturbed soil; this was linked to both increases in fungal biomass and enmeshment by plant roots. Soil in the direct vicinity of plant roots showed the most significant increases in aggregated structures, indicating that plant root enmeshment was one of the predominant factors in soil aggregation. Soil water repellency was directly correlated with measures of macroaggregates (aggregates >2000 pm), indicating that increased hydrophobicity is a mechanism involved in aggregate stabilisation. Field scale sampling and analysis indicated that fertilizer applications had varied effects upon fungal populations, dependent on the particular land management applied to the soil. Undisturbed grassland where fungal biomass was likely to be the predominant microorganism present showed significant effects of fertilizer regime upon fungal biomass, with effects likely to be related to plant-fungi interactions through changes in AM fungal biomass. The influence of fertilizer regime on arable sites was less pronounced which indicated a significant influence of disturbance reducing fungal biomass and reducing the direct and indirect effects associated with fertilizer additions. The investigation of soil pore spatial distribution is essential for understanding soil processes as water flow, gas and nutrient exchanges will occur within pore space, as will many biological processes. The investigation of inter-aggregate pore space was completed upon soil aggregates < 2 mm that had been exposed to previous experimental perturbations, where increased aggregate stability, water repellency and fungal biomass were reported. A resolution of «4 pm was achieved and changes in percentage porosity and spatial pore distributions were detected as a result of direct and indirect effects of plant roots. Greatest increases in heterogeneity of pore space were reported in soil from close proximity to roots, with a reduction in this phenomenon at an increasing distance from the root zone. The mechanism proposed for these changes was localised drying from roots. The results presented provide greater understanding of controlling factors associated with soil water and stability mechanisms, along with demonstrating biologically and physically induced changes in micro and meso-scale structures as a result of different treatments. The work provides scope for further investigation of particular biological and physical factors associated with soil structural mechanisms.
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Hayat, Faisal [Verfasser], and Andrea [Akademischer Betreuer] Carminati. "Impact of heterogeneous soil water distribution on soil and plant water relations / Faisal Hayat ; Betreuer: Andrea Carminati." Bayreuth : Universität Bayreuth, 2021. http://d-nb.info/1227444591/34.
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Jiang, Pingping. "Variability of soil hydraulic properties and estimation of plant-available water on claypan-soil landscapes." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4783.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 25, 2007) Vita. Includes bibliographical references.
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Al-Ali, Mahmoud. "Soil water conservation and water balance model for micro-catchment water harvesting system." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10941.
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A simple water balance model was applied to a micro-catchment water harvesting system for a semi-arid area in the North-Eastern part of Jordan. Two Negarim micro-catchment water harvesting systems were built at Al-Khanasri research station. A Randomized complete block design (RCBD) in factorial combination was used with six treatments and three replicates. Each plot was divided into two parts; a runoff area, and a run-on area. Two different treatments were used for the catchment area, these were: compacted (T1) and Natural treatments (T2). Three treatments were used for the run-on area, these were: disturbed (S1), stones (S2), and crop residue mulch (S3). Soil water content was measured over a depth of 0-1 m during the seasons 96-97 in these micro-catchments. In this model; daily rainfall, runoff, and evaporation were used. Runoff was calculated by the curve number method; evaporation was calculated by the Penman equation, the Priestley and Taylor method and the Class A pan approach. The least squares method was used for optimizing model parameters. The performance of the model was assessed by different criteria, such as root mean square error, relative root mean square error, coefficient of determination and the Nash-Sutcliffe efficiency method. The performance of the micro-catchments system was also evaluated. Results showed that with limited but reliable hydrological data good agreement between predicted and observed values could be obtained. The ratio of water storage in a one meter soil depth to the rainfall falling on each catchment indicated that T1S2 and T1S3 have the highest values in size1 plots while T2S1 and T2S2 have the highest values in size 2 plots. Modelling results showed that for all the size 1 plots, the required ratio of the cultivated to catchment area, (C/CA), required to ensure sufficient harvested water, was less than the actual ratio used in the experimental design. For the size 2 plots this was only true for the T1 treatments. Consequently for the majority of plot sizes and treatments, the results showed that a smaller catchment area is capable of providing sufficient harvested water to meet crop growth requirements. The experimental ratio was based on a typical yearly design rainfall for the region having either a 50% or 67% probability of occurrence. Results also indicated that using stones and crop residue as mulch on the soil surface in the cultivated area was effective in decreasing the evaporation rate. S3 was more efficient than S2 as it stored more water due to the higher infiltration rate (12.4 cm/hr) when compared to S2 (4.1 cm/hr).
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Khandker, Md Humayun Kabir. "Crop growth and water-use from saline water tables." Thesis, University of Newcastle Upon Tyne, 1994. http://hdl.handle.net/10443/580.
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How much water can a crop abstract from below a saline water table and how does the salinity affect yield? These questions are important because shallow groundwater may represent a substantial resource in flat, low-lying areas, but may also represent a threat to sustainability where salinity is high. A series of experiments in a glasshouse aimed to elucidate irrigation management practice under salinity conditions and to develop a root uptake model under both osmotic and matric stresses. The extraction of soil water and groundwater by lettuce and perennial ryegrass crops were measured in three instrumented lysimeters. Water table depths were 0.6,0.9 and 1.2 rn below the soil surface. The lysimeters were initially saturated with saline water (electrical conductivity 4.5 dS m- 1 for lettuce, 9.4 dS m- I for the first crop of ryegrass and 0.4,7.5 & 15.0 dS m-1 for the second crop of ryegrass) and drained until an equilibrium soil water profile was attained. Water with the same electrical conductivity was then supplied by Marione siphons to maintain the constant water table. The water table contribution was recorded and water losses from the soil profile were estimated from daily readings of soil water potential using tensiometersa; nd gypsum blocks. Solute samples were extracted periodically for salinity measurement. The cropping period of lettuce was 90 days from sowing and the lst & 2nd cropping periods of ryegrass were 223 & 215 days respectively. The first ryegrass experiment showed that the water table depth (60,90 and 120 cm) did not have significant contribution (37,36 and 36 mm) on either total soil moisture use or groundwater contribution. Similar results were found for total soil moisture use for lettuce, though the groundwater contribution varied significantly. The second ryegrass experiment showed that salinity at the water table strongly influenced total soil moisture use, but the total groundwater contribution varied only slightly. The overall crop experiments show that the groundwater contribution was within the range of 25-30% of the total water use, except for the 15 dS m7l treatment where the contribution was greater than the soil moisture use. Groundwater contribution rate was higher when the plants were subjected to more osmotic and matric stresses. Yield component data show that increasing salinity leads to a reduction in total yield, but the drymatter proportion was higher. Higher salinities occurred in the upper 15 cm of the root zone, because of the greater soil moisture depletion. Below that depth the salinization rate was smaller, because of the greater groundwater contribution in the later part of the season. There is reasonable agreement between measured and estimated (based on convective transport theory) values soil salinity. Salinities increased in the root zone by about 3-fold of initial salinity for lettuce and around 4-fold for ryegrass in the top 5 cm depth, but below 15 cm depth it was less than 2 fold. Finally, a simplified model was developed to describe the interaction of root-zone salinity and water uptake, considering salinity and water stress as additive. The model shows that the higher the root-zone salinity stress, the higher the predicted water uptake while plant uptake considered -1.5 MPa. This variation is ranged from 4 to 17% for 0.4 to 9.4 dS m-1 and 30 % for 15 dS m-1. The model was developed in a climate with low atmospheric demand, but needs testing in a more severe environment.
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Gärdenäs, Annemieke. "Soil organic matter in forest soils : effects of climate and water balance /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1998. http://epsilon.slu.se/avh/1998/91-576-5530-8.gif.
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McClelland, James H. "Soil and landscape effects on water table depth in three Indiana soils." Virtual Press, 1994. http://liblink.bsu.edu/uhtbin/catkey/917043.
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Depth to water table in soils influences soil properties such as color and horizon thickness and, in some cases, determines soil classification under Soil Taxonomy. The objective of this study was to determine the depth to water table in three Indiana soil series and to evaluate the effect of soil series and landscape on water table levels. The three soils studied were moderately well drained Glynwood, somewhat poorly drained Blount, and poorly drained Pewamo soil series. The effect of soil horizon on water table levels was also examined.Data were collected from 3/21/94 to 6/6/94 at the Hults Environmental Learning Center in Albany, Indiana. The effect of soil type on water table levels was observed as measurable differences in drainage characteristics in the three soil series. Soil horizon had limited effect on water table fluctuations. Water percolated easily through all A horizons. Water temorarily perched upon the B horizon in the Glynwood soils. Landscape position appeared to play a limited role in water table fluctuations.Department of Natural Resources and Environmental Management
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Zhang, Xiaoxian. "Simulating water flow in variably saturated soils containing fractures and soil pipes." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285396.
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Poon, David. "Re-conceptualizing the soil and water assessment tool to better predict subsurface water flow through macroporous soils." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119707.
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Efforts to manage eutrophication of surface waters should recognize that macropore flow transports significantly more phosphorus (P) to surface waters via tile drains than water that percolates through the soil matrix. For the watershed-scale SWAT (Soil and Water Assessment Tool) model to describe phosphorus transport through tile drains, SWAT needs to partition percolation into macropore flow and matrix flow. The objective of this study was to evaluate the effects of a new macropore flow algorithm on the partitioning of hydrological flows, using input data that are readily available, consistent with the current approach to SWAT modeling. The algorithm was evaluated in a proof of concept outside of SWAT and within a re-conceptualized version, SWAT-QC2. The proof of concept reproduced episodic macropore flows, which increased with greater daily rainfall if infiltration exceeded a threshold that was lower for finer-textured soils. Although the algorithm did not improve predictions of streamflow of an agricultural subwatershed in southern Quebec (30 km2), the algorithm improved SWAT's partitioning between surface runoff and subsurface flow. SWAT-QC2 also predicted reasonably the separation between macropore and matrix components of subsurface flow, upon comparison with results from a chemical-based hydrograph separation of the subwatershed's streamflow. As in the proof of concept, the predicted amount of macropore flow into tile drains was greater under finer-textured soils than coarser-textured soils. By describing the portion of percolation that flows through macropores and potentially controls subsurface P transport, the macropore flow algorithm provides a framework for future developments of SWAT that describe macropore transport of P to tile drains. To improve the partitioning between macropore and matrix flows, future developments of SWAT-QC2 should account for dynamic macropore connectivity and the effects of soil moisture on macropore flow, but more research is needed to determine experimentally the spatiotemporal variation of macropore flow in agricultural soils.Les stratégies d'intervention ciblées sur la prévention de l'eutrophisation des eaux de surface en milieu agricole devraient prendre en compte que relativement plus de phosphore chemine vers les drains souterrains par les macropores du sol qu'en cheminement matriciel. Afin de décrire les phénomènes de transport de phosphore aux drains, le modèle hydrologique SWAT (Soil and Water Assessment Tool) doit être en mesure de distinguer ces processus de transfert. La présente étude avait pour objectif d'évaluer la performance d'un nouvel algorithme séparant les écoulements matriciels et préférentiels, en mettant à profit des jeux de données existantes et suivant une démarche compatible avec l'approche de modélisation inhérente à SWAT. L'algorithme a d'abord profité d'une validation conceptuelle, hors du modèle SWAT, puis d'une évaluation suivant son intégration à une nouvelle version du modèle hydrologique, SWAT-QC2. La validation conceptuelle de l'algorithme a démontré que les flux matriciels épisodiques prédits augmentent avec les précipitations journalières, à la condition que le taux d'infiltration ait atteint un seuil limite, relativement moins élevé en sol argileux. Bien que l'algorithme n'ait pas amélioré la prédiction du débit total d'un petit bassin versant du Sud du Québec (30 km2), il a néanmoins amélioré la performance du modèle SWAT à répartir les écoulements de surface et souterrains. La comparaison des prédictions du modèle hydrologique avec les résultats de séparation des hydrogrammes à l'exutoire du même bassin versant suivant une méthode chimique témoigne d'une performance réaliste de SWAT-QC2 à prédire la répartition des flux souterrains préférentiels et matriciels. A l'instar de la validation conceptuelle de l'algorithme, les flux préférentiels prédits sont relativement plus importants en sol argileux qu'en texture plus grossière. En décrivant la proportion des écoulements souterrains qui emprunte la voie préférentielle, et qui contrôle potentiellement les transferts souterrains de P, l'algorithme d'écoulement en macropores constitue une assise pour le développement ultérieur de SWAT intégrant une description des transferts souterrains de phosphore vers les drains souterrains. Afin d'améliorer la performance de SWAT-QC2 à séparer les flux préférentiels et matriciels, les développements futurs du modèle hydrologique devraient prendre en compte la nature dynamique de la connectivité des macropores, de même que les effets de l'humidité du sol sur l'écoulement préférentiel. Cette démarche appelle cependant à une meilleure caractérisation expérimentale de la variabilité spatio-temporelle des flux préférentiels en sols agricoles.
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Tucker, Alison. "The effects of cyclic freeze-thaw on the properties of high water content clays /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63372.
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Coltman, Kenna Maria. "Water table management effects on water quality: a soil column study." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1195165287.
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Coltman, Kenna Marie. "Water table management effects on water quality : a soil column study /." Connect to resource, 1992. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1195165287.
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Keller, Thomas. "Soil compaction and soil tillage - studies in agricultural soil mechanics /." Uppsala : Dept. of Soil Sciences, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/a489.pdf.
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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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Klopp, Hans Walter. "Soil Salinity and Sodicity Impacts on Soil Shrinkage, Water Movement and Retention." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27879.
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Saline, sodic, and saline-sodic ground waters are problematic throughout the Northern Great Plains and Red River Valley. High sodium adsorption ratio (SAR) and low electrical conductivity (EC) of soil solution and irrigation waters are known to create issues with saturated soil hydrologic conductivity. Our objective was determine the impact of saline, sodic and saline-sodic solutions on soil shrinkage and soil hydrologic properties. Soil shrinkage, water retention, and hydraulic conductivity were determined on a variety of soil textures following saturation with salt solutions of variable EC and SAR combinations. Data were fitted with simple theoretical models then model parameters statistically compared. Increasing SAR and decreasing EC of increased soil shrinkage, decreased hydraulic conductivity, and increased water retention near saturated conditions (i.e., > -100 cm H2O). Whereas saline-sodic waters resulted in the greatest rate of decline in saturated conductivity over time such as when salts would be managed without maintaining divalent cations.
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Mampana, Reedah Makgwadi. "Cropping system effects on soil water, soil temperature and dryland maize productivity." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/43165.
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Improved soil water conservation has become an important subject in semi-arid areas due to low and erratic rainfall which is often combined with higher temperatures to provide unsuitable conditions for successful crop productivity. Dryland agriculture remains vulnerable to yield losses in these areas. This calls for implementation of conservation agricultural practices that would improve dryland maize productivity. An on-station field trial was started in 2007 at Zeekoegat experimental farm (24 kilometers north of Pretoria), to establish the effect of different conservation agriculture practices on soil and plant properties. The experimental lay-out was a split-plot randomized complete block design, replicated three times, with each replicate split into two tillage systems (whole plots) and then each whole plot (reduced tillage (RT) and conventional tillage (CT)) was subdivided into 12 treatments (two fertilizer levels x 6 cropping patterns). The present study explored the impacts of different tillage practices, cropping patterns and fertilization levels on soil water content, soil temperature and dryland maize productivity during the 2010/11 and 2011/12 growing seasons. To improve the quality of soil water content (SWC) data, the effect of correction for concretions on soil bulk density and the relationship between volumetric soil water content (SWC) vs neutron water meter (NWM) count ratios was also investigated. Corrections for concretions on soil bulk density did not improve NWM calibrations in this study. In all seasons, significantly higher mean SWC was found under RT treatment than in CT at all depths except at 0-300 mm. For example, during the 2010/11 growing season, SWC under RT was 1.32 % and 1.10 % higher than CT for the 300 – 1350 mm and 0 – 1350 mm soil profiles, respectively. The mean weekly SWC was consistently higher for RT throughout both the growing seasons. Significantly higher SWC was also found under monoculture at all soil depths (except at 0-300 mm during 2011/12) compared to treatments under intercropping. For example, during 2010/11, at 0-300mm, SWC under maize monoculture was 1.72 % higher than under intercropping. The maximum and minimum soil temperatures were significantly higher at 100 and 400 mm soil depths under CT than under RT during 2010/11. During 2011/12, significantly higher minimum soil temperatures at 100 mm depth and lower temperature differences (maximum – minimum soil temperatures) at 400 mm depth were observed under intercropping. Despite the higher SWC and reduced soil temperature under RT, the maize seeds emergence rate was lower and plant stand was reduced. This is attributed to other factors associated with RT systems such as increased soil penetration resistance which often leads to poor root development. The lower soil temperatures under RT were generally within the range that would not be expected to inhibit growth and uptake of nutrients. Slower growth under RT resulted in lower biomass and grain yield. Plants that received high fertilizer rates grew more vigorously than plants under lower fertilizer levels when water was not a limiting factor, but produced lower grain yield due to water shortage in March, especially in 2011/12. The harvest index was therefore lower for treatments that received high fertilizer levels. Maize biomass under monoculture x low fertilizer level was significantly lower compared to other fertilizer x cropping pattern treatments. Maize plant growth under intercropping was improved throughout the seasons, which led to significantly higher grain yield than under maize monoculture. It is therefore recommended that farmers in dryland areas take the advantage of intercropping maize with legumes to obtain higher maize productivity. Further research should focus on investigating the possibility of roots restrictions occurring under RT conditions and under various environmental and soil conditions.Dissertation (MScAgric)--University of Pretoria, 2014.
lk2014
Plant Production and Soil Science
MScAgric
Unrestricted
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Makris, Konstantinos Christos. "SOIL AND COLLOIDAL PHOSPHORUS DYNAMICS IN THREE KY SOILS: BIOAVAILABILITY, TRANSPORT AND WATER QUALITY IMPLICATIONS." UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_theses/408.
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Particulate P constitutes a significant portion of the total P found in surface runoff water. Water dispersed P-containing particles can travel long distances via surface runoff and reach water bodies causing decrease in water quality. The main objective of the study was to evaluate the potential facilitation of P transport by the water dispersed soil colloids (WDC) using three KY soils with a long-term record of poultry manure, and fertilizer P applications. Sequential fractionation for both whole soils and colloidal samples revealed that the WDC had a greater total and labile P content than the soil as a whole. Also, application of manure and fertilizer P seemed to decrease colloidal organic P fractions and increase the inorganic P fractions over the period of a growing season (May to September). Laboratory settling kinetics experiments were set up for the clay-colloidal fractions of the soils. It was shown that particulate P fractions paralleled WDC settling kinetics whereas dissolved P fractions remained in solution even after 36 hours. Field taken intact soil cores were leached with colloidal suspensions to test the effect of WDC on the vertical P movement. Results illustrated the preferential flow of particulate P though the macropores. When water was applied to the manure amended soil, dissolved P levels increased significantly over the control. WDC additions lowered dissolved P levels to the manure-amended columns, by sorbing to the WDC particles, but still greater than the dissolved P levels of the columns that had not been applied with manure.
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Eriksson, Mikael. "Biodegradation of hydrocarbons in soil and water /." Stockholm : Tekniska högsk, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3072.
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Abou, Nahra Joumana. "Modeling phosphorus transport in soil and water." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102946.
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The main objective of this project was to investigate and model phosphorus (P) transport in soil column studies. A model named HYDRUS-NICA was developed, by coupling a hydrological and transport model (HYDRUS-1D model) with an aqueous chemical model (non-ideal competitive adsorption - NICA), to improve the predictions of P transport in soil and water. The HYDRUS-NICA model was developed by replacing the non-linear empirical (Freundlich and Langmuir) equations of the HYDRUS-1D model with the NICA model equations. The numerical accuracy of the HYDRUS-NICA model was then evaluated by comparing the relative errors produced by the HYDRUS-NICA and HYDRUS-1D models. The results showed that the numerical schemes of the HYDRUS-NICA code are stable.The ability of the NICA model to describe phosphate (PO4) adsorption to soil particles was tested using soils collected from agricultural fields in southern Quebec. The surface charge and PO4 adsorption capacity of these soils were measured. Results were used to estimate the NICA model parameters using a non-linear fitting function. The NICA model accurately described the surface charge of these soils and the PO4 adsorption processes.
The HYDRUS-1D model was applied to simulate water flow and PO4 transport in re-constructed soil column experiments. The HYDRUS-1D model was calibrated based on physical and chemical parameters that were estimated from different experiments. Overall, the HYDRUS-1D model successfully simulated the water flow in the columns; however, it overestimated the final adsorbed PO4 concentrations in the soil. The discrepancies in the results suggested that the HYDRUS-1D model could not account for the differences in the soil structure found in the columns, or that the Freundlich isotherm could not adequately describe PO4 adsorption.
The HYDRUS-NICA model was calibrated and validated with results from re-packed column experiments. The simulated results were then compared with results obtained by the HYDRUS-1D model. The overall goodness-of-fit for the HYDRUS-1D model simulations was classified as poor. The HYDRUS-NICA model improved significantly the prediction of PO4 transport, with the coefficient of modeling efficiency values being close to unity, and the coefficient of residual mass values being close to zero. The HYDRUS-NICA model can be used as a tool to improve the prediction of PO4 transport at the field scale.
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Husman, S. H., M. J. Ottman, K. L. Johnson, and R. J. Wegener. "Durum Response to Soil Water Depletion Levels." College of Agriculture, University of Arizona (Tucson, AZ), 1999. http://hdl.handle.net/10150/205173.
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Research has not been conducted in Arizona to determine when to irrigate wheat based on soil water depletion levels. The purpose of this work is to establish the optimum irrigation timing based on depletion of plant available water in the soil. A field experiment was conducted at the Maricopa Agricultural Center testing irrigation of wheat at 35, 50, 65, and 80% depletion of plant available water in the soil for two durum varieties, Kronos and Westbred 881. Grain yields averaged over the two varieties were 6479, 5099, 4283, and 4145 lbs/acre for the 35, 50, 65, and 80% depletion levels, respectively. The results of this study indicate that more frequent irrigations may be required than is typically practiced to optimize wheat grain yields in Arizona. This work will be repeated during the 1999-2000 growing season and the results from both years will be evaluated before general conclusions are drawn.
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Ward, Philip R. "Generation of water repellence in sands, and its amelioration by clay addition / Philip R. Ward." Thesis, Adelaide, 1993. http://hdl.handle.net/2440/21659.
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Speirs, Simon Douglas. "Characterising soil structural stability and form of sodic soil used for cotton production." Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/5817.
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In eastern Australia, Vertosols are widely utilised for the production of irrigated cotton (Gossypium hirsutum) due to their inherent fertility and large water–holding capacity. However, irrigated agriculture in eastern Australia is faced with a decline in the availability of good quality irrigation water sources i.e. waters with low electrolyte concentrations and small Na+ contributions. Consequently, alternative water resources that contain larger contributions of Na+ are becoming increasingly relevant as potential irrigation sources. It is known that the application of Na+ rich waters as irrigation has the potential to increase the Na+ content of the soil, and that this will affect the structural condition of Vertosols. However, the extent to which these poor quality water resources will influence the structural characteristics of different Vertosols is unknown. In addition to this knowledge gap, there is currently no suitable predictor of dispersive behaviour for this soil type, particularly where Vertosols are irrigated with different water quality solutions. The research conducted in this study aimed to characterise the impact of different increments of water quality on the structural stability of different Vertosols. Once this was concluded, the study looked to assess the impact of irrigation water quality on the structural stability, structural form and soil water retention properties of intact soil columns. Knowledge of the structural stability of the soils investigated was then used to derive a model describing the impact of water quality on the structural stability of different cotton producing soils. To achieve the aims nine different soil profiles were sampled from the Bourke, lower Gwydir, Hillston and lower Namoi cotton–producing regions. Eight of these soils are Grey and Black Vertosols with clay phyllosilicate suites dominated to different extents by 2:1 expanding clays, and the ninth soil is an illitic Red Vertosol containing small contributions of 2:1 expanding clays. The soils investigated have ESPs that range between 1 and 10, ECs of 0.1 to 1.2 dS m-1 and CECeff values that are largest for those soils that contain more 2:1 expanding clays. This study shows that the clay phyllosilicate suite of different Vertosols is the primary determinant of structural stability, structural form and soil water retention properties. For example, the Gwydir and Namoi soils contain more 2:1 expanding lattice phyllosilicate clays, have the largest CECeff values of all nine soils and are the most dispersive after all applied immersion treatments. The Bourke and Hillston soils contain less 2:1 expanding lattice clay, have smaller CECeff values and are generally more stable. Irrigation of structurally–intact soils with solutions of larger SARw resulted in larger exchangeable Na+ contents for each soil (and larger ESPs) and smaller contributions of exchangeable Ca2+ and Mg2+. For each soil, larger ESPs are reflected by decreased stability, but generally the soils dominated by 2:1 expansive clays are much less stable than the soils containing smaller contributions of these clay mineral types. Irrigating the structurally–intact Vertosols dominated by 2:1 expansive clays generally resulted in structural form attributes that do not indicate any impact of the applied water treatments, but the Vertosols with less of these mineral types tend to have less desirable structural form attributes after irrigation with solutions of larger Na+ content. Similarly, where the water retention properties of two soils were assessed, the illitic Red Vertosol has less structural pore space after treatment using the large SARw solutions, while the other soil (a Black Vertosol dominated by 2:1 expansive clays) does not show any differences between water retention properties that can be linked to irrigation water quality. These results were clarified for the water retention properties by the assessment of pore–solid space relations, which show both these soils to contain less solid space after irrigation with clean water or solutions of large SARw. This is attributed to increased swelling of clays in the presence of larger Na+ contributions, but both soils have different structural arrangements as shown by the water retention properties and structural form assessment. The red illitic Vertosol shows signs of structural collapse, while the black Vertosol maintains its structural arrangement. Finally, a model describing the structural stability of different Vertosols was developed from the stability assessment of soils, both in different water quality treatments and after the irrigation of structurally–intact columns. The model presented uses a surface response function to describe the impact of increased ECw and SARw of irrigation solutions on soil stability after immersion according to specific soil physico–chemical attributes. In this model increased exchangeable Na+, SAR and a larger CECeff (and consequently, an increased proportion of 2:1 swelling clays) are associated with increases in clay dispersion, while a smaller Ca2+:Mg2+ ratio, EC and less total clay are associated with decreases in clay dispersion.
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Speirs, Simon Douglas. "Characterising soil structural stability and form of sodic soil used for cotton production." Faculty of Agriculture, Food and Natural Resources, 2006. http://hdl.handle.net/2123/5817.
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Doctor of Philosophy(PhD)In eastern Australia, Vertosols are widely utilised for the production of irrigated cotton (Gossypium hirsutum) due to their inherent fertility and large water–holding capacity. However, irrigated agriculture in eastern Australia is faced with a decline in the availability of good quality irrigation water sources i.e. waters with low electrolyte concentrations and small Na+ contributions. Consequently, alternative water resources that contain larger contributions of Na+ are becoming increasingly relevant as potential irrigation sources. It is known that the application of Na+ rich waters as irrigation has the potential to increase the Na+ content of the soil, and that this will affect the structural condition of Vertosols. However, the extent to which these poor quality water resources will influence the structural characteristics of different Vertosols is unknown. In addition to this knowledge gap, there is currently no suitable predictor of dispersive behaviour for this soil type, particularly where Vertosols are irrigated with different water quality solutions. The research conducted in this study aimed to characterise the impact of different increments of water quality on the structural stability of different Vertosols. Once this was concluded, the study looked to assess the impact of irrigation water quality on the structural stability, structural form and soil water retention properties of intact soil columns. Knowledge of the structural stability of the soils investigated was then used to derive a model describing the impact of water quality on the structural stability of different cotton producing soils. To achieve the aims nine different soil profiles were sampled from the Bourke, lower Gwydir, Hillston and lower Namoi cotton–producing regions. Eight of these soils are Grey and Black Vertosols with clay phyllosilicate suites dominated to different extents by 2:1 expanding clays, and the ninth soil is an illitic Red Vertosol containing small contributions of 2:1 expanding clays. The soils investigated have ESPs that range between 1 and 10, ECs of 0.1 to 1.2 dS m-1 and CECeff values that are largest for those soils that contain more 2:1 expanding clays. This study shows that the clay phyllosilicate suite of different Vertosols is the primary determinant of structural stability, structural form and soil water retention properties. For example, the Gwydir and Namoi soils contain more 2:1 expanding lattice phyllosilicate clays, have the largest CECeff values of all nine soils and are the most dispersive after all applied immersion treatments. The Bourke and Hillston soils contain less 2:1 expanding lattice clay, have smaller CECeff values and are generally more stable. Irrigation of structurally–intact soils with solutions of larger SARw resulted in larger exchangeable Na+ contents for each soil (and larger ESPs) and smaller contributions of exchangeable Ca2+ and Mg2+. For each soil, larger ESPs are reflected by decreased stability, but generally the soils dominated by 2:1 expansive clays are much less stable than the soils containing smaller contributions of these clay mineral types. Irrigating the structurally–intact Vertosols dominated by 2:1 expansive clays generally resulted in structural form attributes that do not indicate any impact of the applied water treatments, but the Vertosols with less of these mineral types tend to have less desirable structural form attributes after irrigation with solutions of larger Na+ content. Similarly, where the water retention properties of two soils were assessed, the illitic Red Vertosol has less structural pore space after treatment using the large SARw solutions, while the other soil (a Black Vertosol dominated by 2:1 expansive clays) does not show any differences between water retention properties that can be linked to irrigation water quality. These results were clarified for the water retention properties by the assessment of pore–solid space relations, which show both these soils to contain less solid space after irrigation with clean water or solutions of large SARw. This is attributed to increased swelling of clays in the presence of larger Na+ contributions, but both soils have different structural arrangements as shown by the water retention properties and structural form assessment. The red illitic Vertosol shows signs of structural collapse, while the black Vertosol maintains its structural arrangement. Finally, a model describing the structural stability of different Vertosols was developed from the stability assessment of soils, both in different water quality treatments and after the irrigation of structurally–intact columns. The model presented uses a surface response function to describe the impact of increased ECw and SARw of irrigation solutions on soil stability after immersion according to specific soil physico–chemical attributes. In this model increased exchangeable Na+, SAR and a larger CECeff (and consequently, an increased proportion of 2:1 swelling clays) are associated with increases in clay dispersion, while a smaller Ca2+:Mg2+ ratio, EC and less total clay are associated with decreases in clay dispersion.
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Grover, Samantha Patricia Power. "Carbon and water dynamics of peat soils in the Australian Alps /." Access full text, 2006. http://www.lib.latrobe.edu.au/thesis/public/adt-LTU20070627.172842/index.html.
Full textAbstract:
Thesis (Ph.D.) -- La Trobe University, 2006.Research. "A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy, [to the] Centre for Applied Alpine Ecology, Department of Agricultural Sciences, School of Life Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora". Includes bibliographical references (leaves 172-186). Also available via the World Wide Web.
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Park, Won-Jae. "Effect of miscibility and soil water content in movement of mixed waster." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/18204.
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Fotovat, Amir. "Chemistry of indigenous Zn and Cu in the soil-water system : alkaline sodic and acidic soils." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phf761.pdf.
Full textAbstract:
Copies of author's previously published articles inserted. Bibliography: leaves 195-230. In this study the soil aqueous phase chemistry of Zn and Cu in alkaline sodic soils are investigated. The chemistry of trace metal ions at indigenous concentrations in alkaline sodic soils are reported. Metal ions at low concentrations are measured by the graphite furnace atomic absorption spectrometry (GFAAS) technique.
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Makris, Konstantinos Christos. "Soil and colloidal phosphorous dynamics in three KY soils bioavailability, transport and water quality implications /." Lexington, Ky. : [University of Kentucky Libraries], 2002. http://lib.uky.edu/ETD/ukypssc2003t00069/KCMakris%5FMS%5FThesis.pdf.
Full textAbstract:
Thesis (M.S.)--University of Kentucky, 2002.Title from document title page. Document formatted into pages; contains xiii, 163 p. :ill. Includes abstract. Includes bibliographical references (p. 152-162).