Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on Dec. 2, 2009). Includes bibliographical references.

Studying biological parameters of northern latitude soils is of importance because of their high capacity to sequester organic matter. A consequence of climate change and the resulting increasing temperatures in the Arctic may be the shift from such soils being carbon sinks to becoming unmanageable carbon sources. Despite the relative harshness of the climate and the limited growing season, Icelandic soils are productive when cultivated and there is evidence of the emergence of a warmer and wetter climate. A key issue will be a consideration of the impact of intensive cultivation on the soils, landscape and general environmental parameters. This thesis studied the effect of climate, land use, fertilisation and soil pedological properties on Icelandic Andosols biology. Icelandic agricultural soils biological parameters were affected by land use were fertilisation seamed to suppress nitrogen mineralisation in cultivated fields. Furthermore, there were indications that an increase in soil moisture content promoted either nitrogen immobilisation or denitrification limiting inorganic N availability to the standing vegetation. They were adapted to perform around the freezing point. Soil respiration and enzymatic activities were measured down to a soil temperature of -10°C. Around the freezing point enzymatic activities and soil respiration was governed by availability of labile carbon. The soil microbial biomass carbon pool was not affected by different climatic variables (rainfall, air and soil temperatures) or fertilisation treatments. In comparison to other soils sampled in Scotland, Icelandic soils had a considerably larger microbial biomass carbon pools but their biological activity was significantly lower. This was mainly related to their pedological properties promoting high carbon sequestration and low C availability to microorganisms.

Thesis (M.S.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references (leaves 82-92). Also available on the World Wide Web.

TPC is a 16 000 hectare estate located in Moshi, Tanzania and is currently planted under 8 800 hectares of sugarcane and produces over 60 000 tons of sugar per annum. The influence of volcanic parent material and volcanic ash over TPC, together with the alluvial nature of many of the soils, has imparted a unique combination of soil mineralogical, physical and chemical properties. Furthermore, irrigation with poor quality water has led to sodicity problems on the estate. Understanding the mineralogy and sodicity effects on soil hydraulic properties across the estate can lead to better irrigation management where it is important to prevent the build-up of salts due to over-irrigation. In response to this need, a study was carried out with the aim of characterising the mineralogical, physical and chemical properties in the five management areas of the estate (North, East, West, South and Kahe), in order to determine the relationships between various measured parameters. A total of 70 fields across TPC, as well as four sites outside the estate and two ash layers, were chosen for sampling. Undisturbed soil cores and bulk samples were collected from the A and B horizons from 45 of these fields and the four sites outside. Selected fields were sampled at more than one site to assess field variability, and where cane growth was patchy selected fields were sampled in a patch of poorly growing cane and an adjacent patch of better cane growth. Bulk soil samples were collected from the remaining fields and the two ash layers. Double ring infiltration measurements were carried out on 25 of the selected fields. X-ray diffraction, transmission electron microscopy and aluminium, iron and silica extractions were carried out to determine the mineralogy. Physical and chemical measurements included water retentivity, saturated hydraulic conductivity, bulk density, particle size distribution, organic carbon, pH (H2O), electrical conductivity, water soluble and exchangeable cations (Ca, Mg, K and Na), cation exchange capacity and clay specific surface area. The particle size distribution showed that the soils were mainly loams and sandy loams. Organic carbon values were generally greater in the A horizon compared to the B horizon and varied between 0.4 and 2.5 % in the topsoil and 0.3 and 2.1 % (with the exception of field 11 which had an organic carbon of 4.0 %) in the subsoil. X-ray diffraction patterns of sand and silt fractions were dominated by sanidine while clay patterns were weak and had high backgrounds and very broad peaks, suggesting the presence of poorly ordered material in the clay fraction. The Al and Fe extraction methods and electron micrographs indicated that this poorly ordered material was allophane. However, the dominant clay mineral across the estate was halloysite, in both tubular and spheroidal form, as well as very small (<< 0.5 μm) kaolinite particles. There was also gibbsite in some of the samples analysed. The combination of allophane, halloysite, kaolinite and gibbsite indicated that the primary volcanic minerals have weathered to various degrees across the estate. This is reflected in the alluvial nature of the soils where less weathered material has been periodically deposited onto older, more weathered material over some parts of the estate. The south and west areas had a slightly higher Alo + ½ Feo ratio than the other areas in both the topsoil (1.07 and 0.95, respectively) and the subsoil (1.16 and 1.06, respectively), a possible consequence of less weathered alluvial material that was deposited in these areas. Although the concentration of allophane was low (< 5 %), even in the south and west areas, its presence greatly increased the clay specific surface area (up to 145.94 m2 g-1) and consequently had a significant influence on the soil physical and chemical properties. Water retention across TPC was high, particularly at the lower matric potentials (between 0.13 and 0.45, and 0.09 and 0.24 m3 m-3 at -33 kPa and -1500 kPa, respectively). The high water retention is a result of allophane which gives the soils a high adsorption capacity and a porosity that is dominated by micro-pores. Generally, the south area had the highest water retention at the various measured matric potentials which corresponds to the higher allophane content. Variability in water retentivity across areas and within fields limited further interpretation and correlation with the mineralogical results. Infiltration rate was lowest in the south (60.85 mm hr-1) and highest in the Kahe area (171.20 mm hr-1). The main factor influencing the final infiltration rate was the concentration of sodium in the soil, with higher concentrations causing soil dispersion and blockage of soil pores. Clay dispersion has led to the development of calcareous surface crusts and reduced porosity, thus reducing the infiltration rate. Sodium concentration in the soil is likely to have had a dominating effect over the mineralogical composition of the soil. Poor cane growth in the south and west areas corresponded to higher pH (up to 10.32), electrical conductivity (up to 614 mS m-1), sodium absorption ratio (up to 20.63) and water soluble and exchangeable sodium (up to 53.20 mmolc l-1 and 14.87 cmolc kg-1 soil, respectively) in these areas. The soils are thus more dispersive and the combination of sodicity and allophane has resulted in “fluffy” soils with small particles clogging soil pores and thus surface crusts have formed easily. The combined effect of mineralogy and sodicity in the south is further complicated by the presence of perched water tables. High adsorption capacities and the dominance of micro-pores allow the occurrence of significant capillary rise which brings salts to the soil surface, further exacerbating the sodicity problem. Therefore, over-irrigation should be avoided where soils are prone to sodicity from a combination of irrigation with poor quality water, perched water tables and strong capillary rise action. Fields which are currently experiencing the negative effects of high sodicity, require irrigation with good quality water and adequate sub-surface drainage to ensure the leaching of salts. Further studies with specific focus on the south and west areas would be beneficial in accounting for the variability and in drawing correlations between the mineralogy and sodium content of the soils with the other measured properties. Fields which are prone to increased sodicity through over-irrigation with poor quality water, have strong capillary rise from perched water tables and which require remediation through sub-surface drains can thus be distinguished and the factors influencing sugarcane growth can be more clearly understood. Growth depends on the combination of these soil’s unique mineralogy and sodium content and the influence they have on the infiltration rate, adsorption capacity, micro-porosity and capillary rise from the water table. For future work, water movement modelling to predict saturated and unsaturated flow, as well as in situ measures of unsaturated flow, will lead to further understanding of the soil hydraulic properties and aid in improved irrigation management. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Six pedons derived from volcanic cinders from the San Francisco Volcanic Field near Flagstaff, Arizona, were studied to evaluate their physical, chemical, and mineralogical properties for inclusion in the proposed soil order Andisol. All the pedons meet the requirements for the Andic soil properties and they are thus classified as either Typic Ustivitrand or Melanic Ustivitrand Subgroups of Andisol Order. The proposed classification is discussed with respect to the guidelines presented in the ninth International Committee of Classification on Andisols (ICOMAND) letter.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 5 uppsatser.

Les sols humifères des “Hautes Terres” du massif des Nilgiri peuvent être considérés comme le résultat d'une évolution polycyclique : les altérites ferrallitiques correspondent à une ancienne pédogenèse sous climat tropical chaud et humide ; la pédogenèse actuelle n'expliquant que la formation des horizons humifères supérieurs.<br />Les sols les plus humifères sont caractérisés par la présence de grandes quantités d'associations organo-métalliques et vérifient les nouveaux critères d'appartenance aux Andosols des classifications des sols et sont, de plus, non-allophaniques.<br />Les Andosols des Nilgiri, développés sur un matériau ferrallitique ancien, présentent une pédogenèse originale. En l'absence de verres volcaniques et d'autres minéraux altérables dans le matériau ferrallitique de profondeur, les sources potentielles d'aluminium et de fer sont constituées par des oxydes. La gibbsite et les oxydes de fer, considérés comme minéraux ultimes de l'altération ferrallitique, sont instables en milieu acide et organique. La formation des associations organo-métalliques est due à l'acido-complexolyse de la gibbsite et des oxydes de fer. Du fait des fortes teneurs en oxydes, les associations organo-métalliques sont pourvues d'une forte charge métallique et s'accumulent dans le profil, ce qui conduit à l'apparition des propriétés andiques.<br />Les datations au 14C et la détermination du delta13C des horizons humifères ont mis en évidence que l'accumulation de matière organique était à relier à l'existence d'une période plus froide à la fin du Pléistocène sous une végétation graminéenne. <br />L'étude de ces sols présente un intérêt certain pour la compréhension des processus d'accumulation de carbone dans les sols à différentes époques, et montre que la caractérisation des associations organo-métalliques à différentes échelles permet de comprendre les mécanismes d'interaction entre la matière organique et les cations métalliques, clé de la stabilisation de la matière organique.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2008. / Härtill 4 uppsatser.