Geoderma
Humic substances extracted from an Alfisol, Mollisol, and Histosol were sorbed to the clay (< 2 μm) suite extracted from an Alfisol Bt horizon. The clays with sorbed humic substances as well as clays with indigenous organic matter and with organic matter oxidized with H 2 O 2 were weathered by incubation in 0.05M H 2 SO 4 for 1320 h and in 0.0025M H 2 SO...
The sorption of selenite by two allophanic soils containing high amounts of variable charge materials was studied. Selenite sorption exhibited a maximum near pH 4 and decreased, although not proportionally, with increasing pH. Only negligible amounts of selenite were sorbed above pH 7.In the two soils, the addition of selenite caused a release of sulphate (SO 2 - 4 ), silicate (Si)...
Many soils of Okinawa have counterparts in the southeastern United States, some at series level. This may follow because the parent materials are continental rocks except for some fringing coral reefs and the climate is humid and subtropical. To illustrate the soils of the island and bring out the relationships, data are given on the morphology and composition of specimen profiles from Okinawa....
In addition to native or intrinsic variability, the spatial variability of a soil property at a managed site includes an extrinsic component which is due to management practices. The objective of this study was to estimate changes in the extrinsic spatial variability of Ca, Mg, K, and P in the surface soil which resulted from tillage and fertilizer application. Such changes may increase or decrease...
In southwestern Indiana Peorian loess (about 20,000 years old) thins eastward from the river valleys where it originated, and covers Sangamon paleosols developed in various parent materials. Where the loess is thick, more than about 2.5 m, the entire modern soil profile formed in loess, and where it is thin the modern soil and paleosol are contiguous, i.e., welded. The objectives of this study were...
The effect of application of liming material (CaCO 3 or CaSiO 3 ) and phosphate, on pH, exchangeable Al, effective cation exchange capacity (ECEC) and P solubility is studied in several variable-charge soils of volcanic origin from Canary Island (Spain). The amendments were added to replace 1.5x or 2.5x exchangeable Al, and P was applied at rates to provide equilibrium solution concentrations...
Siliceous calcretes in faults near Yucca Mountain, Nevada, have been interpreted by some observers as evidence of seismically-triggered eruptions of deep water. Such an origin could have important consequences if Yucca Mountain is developed as an unsaturated site for disposal of high-level nuclear waste. At odds with this hypothesis are the absence of features that should be present at fault-fed...
Humic substances strongly affect Al speciation in the soil solution of acid soils. Therefore, conditional stability constants (K 0 ) of humic-Al complexes were investigated at pH 4.0, 4.5, 5.0, and 6.0 and were used for Al speciation calculations in the presence of humic substances. The intrinsic logK o values, calculated from the Scatchard plot increased between pH 4.5 and 5.0 by...
The mineralogical and chemical composition of three types (black, yellow and red) of tuffs from Mt. Peres in northern Israel, that differ in terms of degree of weathering were determined in order to understand the weathering sequence under Mediterranean or semi-arid conditions. The black tuff is very slightly weathered and contains 62% volcanic glass, 15% primary minerals, 12% titano-magnetite, 5%...
Lateral dispersion was investigated in water unsaturated columns (length 18 or 20 cm and diameter 6 or 11 cm, respectively) at constant flow (q = 28.5 mm h - 1 ). Columns were either packed homogeneously with fine sand and coarse sand, or in horizontal or inclinded layers. A conservative dye tracer was applied as a point source in the centre of the column or as a pulse over the entire...
Three well-drained soil profiles from Anangu, Amazonian Ecuador, are described and their characteristics are discussed in relation to vegetation composition and structure within a small area of undisturbed terra firme rain forest. The soils are clayey, kaolinitic, udic, isohyperthermic, and rich in aluminium and are classified as Typic Hapludult and Typic Paleudults, with affinities to Inceptisols...
Cells of Pseudomonas fluorescens, stained with a fluorescent brightner, calcofluor white M2R, were introduced into soil aggregates at specific matric potentials. The soil was impregnated with resin and the hardened blocks cut and polished. The inocula, dispersed through the pore network as single cells, were observed to be located in soil pores of a particular size class, determined by the antecedent...
Acid neutralization, at pH 3.0, in the mineral horizons of six acid sandy soils was measured by means of pH stat column experiments. All samples have low amounts of adsorbed base cations (0.1-4.3 mmol c kg - 1 ; base saturation 2.1-9.5%), pH ranges from 4.0 in the topsoil to 4.5 in the subsoil. The amount of NH 4 -oxalate extractable Al ranged from 87-135 mol c ...
Particle size analysis of soils containing coarse fragments requires sufficient amounts of soil material. We tried to quantify the sample volume for coarse fragment measurements in a Rendzina soil with more than 50% coarse fragment content. A monolith of 50 cm 80 cm was excavated to a depth of 160 cm, hardened with an epoxy resin and cut into six cross sections. The coarse fragment contents...
Gypsum crystals occur in Vertisols on the west coast of New Caledonia. These soils are derived from the weathering of basic rocks that contain no gypsum. The sulphur isotopic ratio 3 4 S/ 3 2 S was used as tracer to identify the origin of the gypsum. A total of 26 measurements of δ 3 4 S were made on gypsum crystals from the Vertisols and compared to those of...
Cracking was studied in fifty soils located in two recent alluvial plains and it was related to soil parameters such as clay content, soil moisture content, bulk density and coefficient of linear extensibility (COLE). The total crack area per unit soil surface, the crack width and crack depth were measured by tracing them on transparent sheets. The rate of crack development was also studied in a...
Digital elevation models (DEMs) provide a good way of deriving landform attributes that may be used for soil prediction. The geostatistical techniques of kriging and cokriging are increasingly being applied to predicting soil properties. Whereas ordinary kriging (and universal kriging) utilise spatial correlation to determine the coefficients of the linear predictor, cokriging involves both inter-variable...
Currently there is a lack of quantitative data on the functional classification of soil structure, particularly in routine soil surveys, because field physical measurements of flow characteristics are slow and require expertise. A simple air permeameter was developed which allows rapid, in situ measurements to be made of the intrinsic permeability of the soil to air (k a ). Measurements...
Adjacent cultivated and never-cultivated areas of land were compared for a variety of chemical and physical properties to determine the effect of traditional cultivation practices on an Australian Rhodoxeralf. Those properties which changed most as a result of clearing and cultivation were pH, electrical conductivity, organic carbon, nitrogen and profile macroporosity. These changes are due to various...