Geoderma
The mineralogical composition of the 2–20 μm silt fraction from two soil profiles, developed upon loessial sediments in the southern Chaco region of Argentina, was studied by means of X-ray diffractometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These fine silts from the Chaco region contained more quartz and less feldspar and glass than those pointed oit for...
Existing pools of soil chemical data may be used in the investigation of conceptual models about soil chemical processes. Data from more than 2000 soil samples from German forests were pooled and interpreted to establish parameter relations that are related to soil acidification. A saturated water extract and an extraction of exchangeable cations by ammonium chloride were used. Activities in the soil...
The rates of chemical weathering within forested catchments as reported in the literature have been determined principally from input-output budgets, with outputs being measured as streamflow at a weir. In the present study an alternative method has been investigated which uses natural chloride as a tracer and does not require construction of a weir. It is shown that estimates made of weathering release...
The micromorphology and elemental composition of celestobarite crystals in a duripan from central Australia are examined. These crystals are flabellate (fan-shaped), have a Ba/Sr ratio of 11.1, and are up to 50 μm in size. The location of the celestobarite crystals within silicified roots and in close association with calcite and clay coatings indicates that these celestobarite crystals are authigenic...
The influence of microbial surfaces in the formation of short-range ordered aluminosilicates of allophanic composition was studied in the presence of citric, tannic and fulvic acids (FA) and two metals (Cd and Zn). In all bacterial cases, the pH was raised from an initial value of 4.5 to close to neutrality (6 to 7), and the bacteria produced a mineral phase in which a higher proportion of silicate...
Changes in tensile strength with clay type, clay particle size, and amounts of spontaneously and mechanically dispersible clays were assessed for dry, remoulded samples of eight Australian Vertisols and Alfisols varying in clay mineralogy. The effects of different clay content and particle size on tensile strength were also measured. The average particle sizes of whole clay, and of spontaneously...
The potassium supplying capacity of soils formed on three geological deposits along an east-west transect in the Niger Delta region of Nigeria was investigated by determining the various forms of soil K and K uptake by repeated maize croppings in pots. Soils (Inceptisols and Entisols) formed on recent alluvial materials of the Meander Belt deposits (MBD) had mica and feldspars resulting in very high...
Four large lysimeters on the San Dimas Experimental Forest, each filled with similar parent material and planted with monocultures of native species in 1946, provide a unique opportunity to quantify short-term effects of plant species on soil properties. The four species under which soils were investigated are scrub oak (Quercus dumosa Nutt.), chamise (Adenostoma fasciculatum Hook. and Arn.), ceanothus...
Soils with relatively sandy topsoils over clayey subsoils are widespread, but their genesis is not always clear. We tested the hypothesis that earthworms stimulate the formation of the sandy surface soils by producing clay-rich worm casts that are susceptible to erosion, in an undisturbed forested watershed in southwestern Ivory Coast. Soils of the watershed were strongly weathered and acidic. ...
The knowledge of the unsaturated hydraulic conductivity is one of the prerequisites to describe water flow and solute transport in soils. In this paper we examined the quality of 11 different theoretical models to predict the unsaturated hydraulic conductivity for a wide variety of soils. The hydraulic conductivity models were fitted to 44 measured curves using a quasi Newton parameter estimation...
Soil development, particularly in relation to relative age of geomorphic surfaces, was studied in a high-altitude valley on the semi-arid western side of the Andes in southern Peru. Seven major fluvial surfaces in the Colca Valley were recognized, including floodplains, stream terraces, and fans associated with the Rio Colca and its tributaries. Soils were also briefly examined on Pleistocene andesite...
Movement of mineral dust by the atmosphere has been underway for ages, but efforts to assess its magnitude and significance have come largely in the last century. Attempts to identify and understand effects of the dust on soils are even more recent, mostly in the last 30 years. Airborne movements have several forms. Dust is transported by large storms that can be spectacular. Dust is also moved...
Modern soils in south-central Nebraska may have formed in parent material made up of more than one loess unit. The aerial extent of these soils could be as much as 1.6 million ha. The presence of lithologic discontinuities within these soils complicates the explanation of their genesis. The objectives of this study were to determine if multiple loess units exist in the modern soils and to identify...
The distribution of calcitic pedofeatures within part of a buried paleosol complex on Gaolanshan Mountain, near Lanzhou in the western semi-arid part of the Loess Plateau of China, is interpreted in terms of a pedosedimentary model controlled by changes in dominance of regional climatic (monsoonal) forces. During periods of moderate loess accumulation rates and moisture availability, accretionary...
Increased soil organic matter (SOM) is associated with a reduction in K fixation by a calcareous vermiculitic soil in California. To better understand the mechanism for this effect, humic acids (HA) were extracted from this soil with and without decalcification. The HA extracted without decalcification -- the mobile HA (MHA) pool -- was dated as modern by 1 4 C-dating, while the radiocarbon...
The spatial variability of soil properties in a typical volcanic Vesuvian soil was investigated by collecting undisturbed soil samples at equal intervals of 1.5 m along a 135 m transect at a depth of 0.45 m. In this study, the spatial structure of soil hydraulic properties was examined using both statistical and geostatistical concepts. Soil hydraulic properties were determined in the laboratory...
Humification is one of the dominant pedogenic processes responsible for the development of Mollisols but systematic studies of humic acids in the whole sola were rarely documented. To further understand this process, humic acids were extracted from sola of two Mollisols in central Alberta with 0.1M Na 4 P 2 O 7 and analyzed in our laboratory. Humic acid yields decrease abruptly...
The predominant methods of measuring soil structural stability are confined to laboratory methods that, by their nature, do not quantify the field stability of the soil. An instrument is presented here for measuring the soil structural stability in situ. Stability is assessed by a method based on the change in structural characteristics that may occur when the soil is permeated by non-interactive...