Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Soil Science" Title from author supplied metadata (automated record created on Apr. 27, 2007.) Vita. Abstract. Includes bibliographical references.

Thesis (Ph. D.)--Oklahoma State University, 2007. / Vita. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2008. / "Major Subject: Soil Science" Title from author supplied metadata (automated record created on Oct. 13, 2008.) Vita. Abstract. Includes bibliographical references.

The role of earthworms in improving soil fertility and structure is widely recognised. As a result earthworms (often single species populations) have been deliberately introduced into pasture and arable land by man in attempts to improve plant production and into degraded land in order to bring about soil amelioration. The potentioal of earthworms employed in land restoration programmes may be enhanced by inoculating sites with a combination of species from different ecological groupings which have different roles in soil processes. In order to acheive the type of success envisaged by such projects, detailed information on the ecology and interactions between candidate species is required. This research investigated inter- and intra-specific interactions in terms of growth, maturation, cocoon production and survival, between five earthworm species (Allolobophora chlorotica (Savigny), Aporrectodea caliginosa (Savigny), Aporrectodea longa (Ude), Lumbricus rubellus (Hoffmeister) and Lumbricus Terrestris (Linnaeus)) under laboratory conditions. Cultures were initially maintained under optimal environmental conditions. Selected environmental variables (e.g food poison, food particle size and soil bulk density) were manipulated in order to quantify observed species interactions and subject earthworms to condditions that could be encountered at restored sites. Results demonstrated that all species could be successfully cultured under laboratory conditions. Techniques developed during the work may have applications in commercial large-scale rearing of earthworms in addition to production of species cohorts for toxicological testing and further laboratory experimentation. All experimental species were found to co-exist under the specified laboratory conditions, however both positive and negative inter- and intra-specific interactions were recorded throughout the study. The intensity of negative (competitive) interactions was attributed to the degree of niche overlap between earthworms and was dependant upon the species present, their stage of development and ability to adapt th limiting environmental conditions. Some deep burrowing earthworm species were found to increase the production of smaller conspecifics and other smaller earthworm species. it is suggested that this type of positive (commensal) association arose from smaller individuals feeding on concentrated and easily digestible organic matter present in the castings of larger earthworms. In addition to the potential applications of culture techniques described earlier, this research has contributed to the knowledge of an important ecological group, provided data for competition theory and should also prove valuable because of its implications for soil restoration.

The ecological importance of native woodland in the Scottish Highlands and Islands is widely acknowledged and many calls for its expansion have been made. Much research into the effects of such an expansion on the above-ground ecosystem has been undertaken, but little is known about the impact it has on the underlying soils. Experimental tree plots, containing species native to western Scotland, were established on the Isle of Rum National Nature Reserve during the 1960's. This thesis seeks to assess the effects of 35 years of birch (Betula spp.), oak (Quercus spp.) and Scots pine (Pinus sylvestris) growth on the relatively fertile, mineral soils at Harris and the less fertile, organic soils at Kilmory Fank. Significant changes in soil characteristics were identified beneath all three species growing on both soil types. These changes were complex in nature. The effects of oak and birch growth could not uniformly be said to constitute soil improvement, however, the soils beneath Scots pine were significantly improved. The role of antecedent conditions in influencing the direction and type of soil change was demonstrably more important than theinfluence of the species type. The direction and nature of change was similar under oak and birch growing on the same soils, rates of organic matter decomposition were elevated but some nutrients, particularly potassium, were depleted by up to 50 kghi. This depletion appeared to represent a nutrient redistribution from soil to trees and litter, rather than a loss to the system as a whole. No clear evidence was found to suggest that one species was a more or less effective soil improver than the other Under Scots pine, plant nutrients had accumulated in the soil, particularly calcium which had increased by more than 90 kgha'. At Harris, the acidity had declined by 0.3 pH units. The net nutrient input appears to derive from marine aerosols trapped by the pine canopy and a subsequent translocation of them to the underlying soil via throughfall and stemfiow. The results are of value to forest managers who perceive the establishment of new native woodlands as a route to soil restoration. They show that many of the commonly held perceptions regarding the influence of tree growth on soils must be treated with caution. This is because the changes that occur appear to be highly site dependent, thus planting of native tree species can have widely varying effects consequent upon the original soil characteristics and prevailing environmental conditions.

Tetraalkylammonium cation intercalation into smectites was found to be a useful tool for the study of many aspects of smectite chemistry, including the determination of their internal surface areas and the identification of the mineral composition of Alberta oil sands bitumen. The adsorption of aromatic molecules to these organoclays has given useful insights about the nature of the interlamellar pore systems of these compounds. The grafting of organic moieties to the interlayer surface of montmorillonite was achieved by the reaction of the acidified clay with 3-chloropropyltrimethoxysilane. Nucleophilic substitution of the Cl for chelating functionalities (SH and SCH$\sb2$CH$\sb2$SH) has resulted in highly effective heavy metal adsorbents, particularly for Pb and Hg. The adsorbents could be easily regenerated by leaching out the metal with HCl. Similar materials were prepared using the layered silicates magadiite and kenyaite, but were found to be ineffective for the removal of metal ions from solution because of the congestion of the interlamellar region of these minerals by the organic functionalities which has prevented the access of the metal ions to the chelating sites. Alcohols and diols were found to condense onto the the interlamellar silanols of H-magadiite and H-kenyaite upon thermal treatment. The techniques used to characterize these compounds provided strong evidence of the formation of Si-O-C linkages between the mineral template and the organic groups. The nanocomposites thus formed were found to be stable to well beyond 400$\sp\circ$C, but did not show appreciable microporosity. The grafting interlamellar region of these silicates, whose crystal structures are still unknown. The preparation of clay-based catalysts for nitric oxide decomposition was attempted by the cointercalation of organic and metal cations into montmorillonite and by the doping of Al-pillared montmorillite by metal ions. The resulting compounds were found to promote the ortho nitrosylation of phenol in the presence of NO gas, but only in very low yield (3%). Static variable temperature studies have failed to show any catalytic decomposition of nitric oxide in the presence of these materials.

The aim of this study was to investigate, at various soil water contents, the tillage effects of two different types of injectors on soil hydraulic properties of a loamy clay soil located in Winchester, Ontario, Canada. The two injectors considered are the AerWay SSD (A) and the Kongskilde Vibro-Flex (K). The soil-properties changes associated with the injectors were assessed at ten different soil water contents for both injectors. The first part of this research involves the evaluation of field saturated hydraulic conductivity (Kfs), matrix flux potential (&phis;m), bulk density (rhob) and volumetric water content (theta) for undisturbed soil (U) and for soil disturbed by injector (D). The field saturated hydraulic conductivities measured on disturbed soil for the Kongskilde (DK) were in 80% of the cases lower than those measured on undisturbed soil (UK). In contrast, Kfs measured on disturbed soil for the AerWay (DA) were higher in 90% of the cases. These results indicate that the Kongskilde reduces the infiltration capacity of the soil, which may be the result of reduced effective porosity via the smearing of the soil surface. They also indicate that the AerWay is facilitating infiltration, most likely by fracturing the soil surface. The second part of this study involves a dye tracer experiment conducted on disturbed soil to evaluate the movement pathways of water through soil. In contrast to the AerWay, no relation could be established between liquid transport variables and the water content at which the Kongskilde was run. Greatest depths of penetration observed for the AerWay treatment occurred at run average water contents above 29.7 % vol. and below 19.7 % vol. Sorptive capacity of the upper layers was maximized when soil water contents were between 21.7 % vol. and 31.3 % vol.

Electrokinetic treatment is a promising technology to remove contaminants from clayey soils. The interaction of various processes that take place simultaneously is yet to be understood, in order to better predict the efficiency of the process in a variety of soil-contaminant situations. The electrokinetic process refers to movement of water, ions, and charged particles relative to one another under the action of an applied direct current electrical field. In this research electrokinetic experiments are conducted on saturated kaolinite specimens loaded with zinc to investigate the efficiency of contaminant removal and energy expenditure during the treatment. The effect of various electrical fields on electrokinetic remediation was studied by application of constant electrical potential and current with different intensities across the specimens. The treatment duration in various tests ranged from 3 to 73 days. Electroosmotic flow, electrical gradient variation, pH, conductivity, and zinc concentration of the anolyte, catholyte and pore solution across the specimen, were measured. The calculated electroosmotic coefficients of permeability (k$\sb{\rm e}$) were within range of literature values but were not constant over time. The migration of zinc within the soil from the anode toward the cathode was significant. Almost all transported zinc was accumulated in a thin layer of soil near the cathode chamber due to high pH environment. Formation of this low conductivity layer results in higher potential drop in this region and increase in energy expenditure. In order to reduce the amount of precipitation and increase the removal of zinc in to the cathode chamber, pH enhancement technique with application of acetic acid was employed. Neutralizing the pH in the cathode chamber (pH = 6) did not lead to increase in removal efficiency of heavy metal. However, controlling the pH at lower level (pH = 4) at the cathode compartment was successful for removal of 60% zinc from soil. Effect of the position of the reference electrode on energy consumption was also studied. Experiments under controlled electrical potential field, with positioning the reference electrode close to the cathode, indicated reasonable reduction of energy expenditure during the treatment. The principal conclusions were as follows: (1) The electrokinetic technique is effective and economical for short term remediation. (2) The constant potential electrical field demonstrated lower energy consumption compared to the constant current condition, both in short term and long term remediation. (3) Controlling the pH to a value less than 4 in the cathode compartment, successfully flushed the zinc out of the sample to the catholyte. (4) Placement of the reference electrode close to the cathode (working) electrode, decreased the amount of energy expenditure significantly.

Wetland soils are highly effective ecosystems for long term storage of carbon. Prolonged periods of soil saturation stimulate high rates of productivity by appropriately adapted hydrophytic vegetation and cause a depletion of oxygen within the soil that significantly reduces the rate of mineralisation of organic material, the process that results in the release of CO2 back into the atmosphere. As a result, the rate of production exceeds the rate of mineralisation of organic material and leads to a net accumulation of soil organic carbon over time. This study aims to serve as a baseline estimate of carbon storage in wetlands of South Africa. This study was not intended to be on an extensive spatial scale but rather an intensive focus on carbon storage as well as spatial distribution, variation and factors that influence carbon storage. Three aspects of soil organic carbon were assessed for sections of four selected wetlands. Firstly, the soil organic carbon density was estimated in tons per hectare as well as the differences in soil organic carbon density of different wetland hydrological zones. Secondly, the nature and stability of soil organic carbon were assessed based on the proportion of soil organic carbon that was readily oxidised by potassium permanganate (permanganate oxidisable carbon). Lastly, correlations were assessed between soil organic carbon and the elements N, P, K, Ca, Mg, Mn, Fe, Cr, S, and Al to assess the relationships between soil concentrations of these elements and the density of soil organic carbon. Four wetlands were selected including three mineral and one organic wetland containing peat. The mean SOC densities of the three mineral wetlands at a soil thickness of 20 cm were 49.6 t ha-1 (tons per hectare), 54.5 t ha-1 and 413 t ha-1. The mean SOC density of the organic wetland was 127.0 t ha-1. There were significant differences in soil organic carbon density between different wetland hydrological zones, the highest densities found in the permanently saturated zones. A negative correlation between wetland disturbance in general and POXC content was found. Total soil N, P, and S concentration showed the highest correlation between SOC and soil POXC concentration. The soil concentrations of Fe, Mn and S did not seem to have any appreciable relationship with the oxidisability of SOC or SOC density. / Dissertation (MSc Agric)--University of Pretoria, 2019. / Plant Production and Soil Science / MSc Agric / Unrestricted

A mathematical model was developed to predict water content profiles, evapotranspiration, water flow from or to the water table, root extraction and root water potential at the surface as functions of time under unsteady state conditions. The model was tested in the field at The Hullinger Farm near Vernal, Utah, in 1970 and 1971. Comparison of water content-depth profiles show excellent agreement at the end of a 9- day run in 1970 on oats seeded to alfalfa. In 1971 with alfalfa as the crop, the data show best agreement, between predicted and computed water content-depth profiles, 48 hours after any water addition. The poorest agreement for both crops was right after irrigation. The computed cumulative ET was 4.9 em which was 0.4 em less than actual (measured) ET, during the 9- day period in 1970. In 1971, the actual and measured ET were the same for the whole season. This agreement may be partially due to the "forcing" of the water removal by ET to be the same as measured. In 1970, the computed cumulative upward flow from the water table was 2.20 em which was 0.1 em greater than the actual for the 9-day period. In 1971, the cumulative upward water flow from the water table was 4.80 em which was 3.20 em greater than the calculated for the whole season of 116 days.