bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydraulic conductivity in surface active soils
Authors: Basak P , Madhav MR
Published: April 2005

Kozeny's equation based on a capillary tube model with constant viscosity does not give satisfactory results for fine-grained soils. When surface forces dominate over gravity forces, the pore water behaves abnormally and the physical properties of this pore water are found to be quite different from free water. Flow through saturated fine-grained soils is known to be affected by the properties and thickness of loosely and strongly bound water, whose viscosity is observed to be higher because of the modified water structure induced by clay-water interaction. An analytical solution based on a capillary tube model taking into account the changed viscosity of bound water and variation of viscosity within the bound water in relation to its thickness is attempted. The derived equation appears to be general in nature and is applicable for both surface active and inactive soils. It is shown that Kozeny's equation turns out to be the particular case of the derived equation when the thickness of the bound water is zero or when the variation of viscosity is not taken into account.
Estimation and dimulation of sheet run-off
Authors: Ive JR , Rose CW , Wall BH , Torssell BWR
Published: April 2005

Sheet run-off was estimated for a Townsville stylo-annual grass pasture with 1% slope in the northern Australian monsoonal region by using neutron hydrometry supplemented by gravimetric soil sampling, both carefully timed with respect to the rainfall event. The technique is applicable to run-off and run-on situations. An empirical model was developed and incorporated into a water balance routine in an existing growth model. It relates surface sheet run-off to the soil antecedent water content (top 20 cm) and the standard daily rainfall total; the coefficients of the empirical functions are site specific. For the rainfall events studied, run-off was 37 � 12% of the rainfall. The soil water values simulated with the run-off model included were significantly closer to the experimental values than when run-off was assumed to be zero. This improvement in simulation of soil water profiles was consistent with an improvement in subsequent dry matter simulation.
Prevention of crust formation in soils by poly(vinyl alcohol)
Authors: Oades JM
Published: April 2005

The successful field stabilization of a seedbed by poly(viny1 alcohol) (PVA) with a molecular weight close to 70000 is described. Stabilization of the 0-2 cm layer of the seedbed by spraying on PVA in aqueous solution at rates of 8-10 g m-2 was shown to increase seedling emergence, rainfall infiltration and water storage. The PVA prevented crust formation, thus reducing surface run-off and soil erosion by one-half compared with control areas. The improved infiltration led to increased leaching of mineral nitrogen down the profile. The treatment may be useful for stabilization of experimental areas, preparation of lawns or intensive horticultural practice.
Nitrate leaching and adsorption in a krasnozem from Redland Bay, QLD. I. Leaching of banded ammonium nitrate in a horticultural rotation
Authors: Black AS , Waring SA
Published: April 2005

Ammonium nitrate at a rate of 165 kg nitrogen ha-l was placed in bands 76 cm apart in a krasnozem. The fertilized plots were either kept bare or cropped using a horticultuial rotation. Soil samples were collected at various time intervals to a depth of 300 cm. The amount of leachate was estimated from the water balance equation and the relative movement of nitrate with water determined. Of the mineral nitrogen initially in the soil, 72% (201 kg nitrogen ha-1) remained as nitrate between the depths of 40 and 120 cm following a bean crop. Prolonged cover cropping with oats decreased the amount of nitrate to less than 44 kg nitrogen ha-1 (< 2 mg nitrate nitrogen kg-1) in the surface 160 cm of the profile. In the bare plots, nitrate movement per 10 mm of leachate decreased with depth, lateral movement was gradual, and vertical movement was concentration dependent below 160 cm. These results are discussed in terms of the direction of water flow, soil structural properties and nitrate adsorption.
Nitrate leaching and adsorption in a krasnozem from Redland Bay, QLD. II. Soil factors influencing adsorption
Authors: Black AS , Waring SA
Published: April 2005

Laboratory determinations of nitrate adsorption from a 0.005M potassium nitrate solution indicated that exclusion occurred in soil from 0-20 cm and that adsorption increased through the subsoil from 0.16 m-equiv./100 g at 45-90 cm to 0.45 m-equiv./100 g between 360 and 600 cm. These profile changes appeared to be related to decreases in organic matter and pH and increases in kaolinite content. Correlation studies showed a strong relation (r = 0.87) between nitrate adsorption and relative net charge as measured by �pH (pHKCl pHH2O) and a negative relation (r = -0.67) with pHH2O. Correlations with sesquioxide fractions were variable and mostly negative.
Surface charge on kaolinites in aqueous suspension
Authors: Bolland MDA , Posner AM , Quirk JP
Published: April 2005

The surface charge of several natural kaolinites was measured in the pH range 3-10 using an exchange technique. The positive charge was found to increase with decreasing pH and sometimes to increase with increasing ionic strength; it occurred on the kaolinites at pH values as high as 9 and 10 and was particularly evident at high ionic strengths. The positive surface charge on kaolinites is thought to be due to exposed alumina such as is found on oxide surfaces. Aluminium was found to dissolve from kaolinite at pH values beiow about 6.5. Aluminium dissolution increased with decreasing pH and time. When the proportion of dissolved aluminium ions balancing negative surface charge was taken into account, the negative and net negative surface charge on kaolinite was concluded to be largely due to pH independent charge resulting from isomorphous substitution, together with some pH dependent charge due to exposed SiOH sites. If Na+ was the index cation, dissolved aluminium ions from the clay replaced some of the Na+ balancing the negative surface charge. However, when Cs+ was the index cation, less Cs+ balancing the negative surface charge on the clay was replaced by dissolved aluminium. As the concentration of either Na+ or Cs+ was increased, less dissolved aluminium replaced the index cation as a counteraction to the negative surface charge.
M73246ssbauer spectroscopic evidence for akaganéite ( β -FeOOH) in New Zealand soils
Authors: Logan NE , Johnston JH , Childs CW
Published: April 2005

57Fe Mossbauer spectroscopy and computer-based data reduction procedures have been used to study quantitatively, the various secondary iron-containing minerals in a selection of New Zealand soils and iron-manganese soil concretions. The results indicate that akagankite (�-FeOOH), previously considered a rare mineral, is a major form of iron in these samples. Lepidocrocite (�-FeOOH), and/or goethite (�-FeOOH) with a particle size less than approximately 70 A also appear to be present in all samples. Distinction between these two latter forms was not possible, because of the super-paramagnetic effects associated with fine particles of goethite. Hematite (�-Fe2O3 with a suitably large particle size (greater than approximately 180 A) was positively identified in two of the soil samples studied. The ratios of the concentrations of the various forms of iron are given.
Subplasticity in Australian soils. Introduction.
Authors: Butler BE
Published: April 2005

NO ABSTRACT AVAILALE
Subplasticity in Australian soils. I. Description, occurrence, and some properties
Authors: McIntyre DS
Published: April 2005

The origin of the term 'subplasticity', its connotation in the description and properties of some Australian soils, and the occurrence and distribution of subplastic soils are discussed. Although the term was originally descriptive, the degree of subplasticity being determined by field texturing of soils, it has come to mean also that the soil very strongly resists dispersion into primary particles by both mechanical and chemical means. The results of some early attempts at dispersion are presented (a series of following papers describes properties in more detail), and comparison is made with various other soils, which show subplasticity and resistance to dispersion to a lesser degree, or normal dispersion properties. A high degree of subplasticity and high resistance to dispersion are associated, in the majority of cases, with soils formed in parna, an aeolian clay, as parent material.
Subplasticity in Australian soils. II. Relationships between subplasticity rating, optically oriented clay, cementation and aggregate stability
Authors: Brewer R , Blackmore AV
Published: April 2005

Subplasticity and aggregate stability have been studied in a group of red-brown earth materials from the Riverine Plain of New South Wales and, for comparison, two samples of krasnozem materials. Within the red-brown earth materials there are positive correlations between subplasticity rating, strongly oriented clay, dithionite-soluble iron oxides, and stability of aggregates; there is no correlation with carbonates. Data on the stability of coarse and fine sand-size and silt-size aggregates under increasingly severe dispersion show that the subplasticity ratings of these materials depend principally on the relative stability of the plasma of the s-matrix, even though bodies of strongly oriented clay are relatively resistant to dispersion. Cementation by iron oxides is discounted as the mechanism causing stability because of the low proportions present in all except one of these red-brown earth materials. The krasnozem materials do not contain strongly oriented clay, so the correlation with subplasticity rating does not hold between groups of different kinds of soil materials. The data suggest that subplasticity in these materials can reasonably be attributed to cementation by iron oxides.
Subplasticity in Australian soils. IV. Plasticity and structure related to clay cementation
Authors: Blackmore AV
Published: April 2005

Subplastic behaviour apparently arises from some form of cementation between clay particles and between groups of particles. Five red-brown earth subsoils from the Riverina area of New South Wales, with subplasticity ratings from SP0 to SPIII+, have been examined here in order to relate plasticity, and other physical properties which reflect structure and stability of structure, to an appropriate laboratory measure, or index, of cementation. The soils were so chosen as to minimize the number of other properties that vary among them. The properties and indexing of the soils in the laboratory show broad consistence with their range of subplasticity as described in the field. When it has been released from cementation, the clay in the more subplastic soils is highly active, having properties similar to those of a montmorillonite with calcium and sodium on the exchange surface. The structure and the high total clay content of the subplastics require a high degree of orientation of individual clay particles into packets or domains. These packets are stabilized by cementation, largely at their edges, and at the same time attached to neighbouring non-parallel packets. Water readily reaches most of the pore space and the material, although very stable, continues to display some properties which are consistent only with a large content of clay particles. Consequently it seems likely that much of the planar surface of the individual clay particle is not contaminated with a cement.
Soil profile development in some alluvial deposits of eastern New South Wales
Authors: Walker PH , Coventry RJ
Published: April 2005

Soil profile data from river terrace sequences on the New South Wales coast and southern highlands have been summarized. In all sequences the profiles have a progressive increase in soil development from low alluvial benches to flood plains to terraces. The general similarity of soils among these and other alluvial sequences in eastern New South Wales is the basis of a descriptive generalization in terms of five profile stages: stratic stage on low alluvial benches; cumulic stage on flood plains; low-contrast solum stage on low terraces; high-contrast solum stage on high terraces; extended subsolum stage on highest terraces. Sufficient lack of correlation occurs between sequences to suggest that the profile stages are groupings within a continuous spectrum of profile variation, the whole representing the one pedogenetic pathway. Pedogenesis in these alluvial landscapes is considered to progress through the development, first of a biotic profile which reaches a maximum within 1000 years, which is then degraded with the onset of mineral weathering and B horizon development, to a maximum solum form within 30 000 years. The rates of change of biotic and mineral profile components are sufficiently slow that only broad limits of confidence can be applied to soil stratigraphic correlations based on field morphology alone.
Infiltration and water movement in an in situ swelling soil during prolonged ponding
Authors: Talsma T , Lelij AVD
Published: April 2005

Infiltration, swelling, and water movement were studied during ponding on a swelling clay soil. The soil was uniform in texture and clay mineralogy to 2 m depth. Most structural heterogeneity, caused by gilgai and shrinkage cracks, had been removed by grading, cultivation, and pre-ponding irrigations. Measurements were made of infiltration, moisture content, soil water potential, hydraulic conductivity, bulk density, vertical soil swelling, and the effect of overburden on tensiometer readings. Infiltration was rapid and water penetrated deeply during the first ponding day. Thereafter, qualitative agreement was found between measured infiltration and that expected from theory from 1 to 45 days after ponding. From 45 to 120 days after ponding, the development of a time-variable flow restriction near the soil surface prevented the attainment of a final, steady infiltration rate. During ponding a transient water table developed, moisture profiles were distinctly hydric, and seepage to a deep water table or aquifer was not negligible. Core sample values of hydraulic conductivity agreed with those obtained from mean flux and potential gradients, although conductivity and infiltration rate varied greatly from place to place. Measured swelling compared favourably with that calculated from bulk density changes. The maximum measured soil swelling, in the rather narrow range of moisture contents involved, was 25 mm. This is consistent with reported data on similar soils. Mean values of � = �/P near saturation at 0.2 and 0.4 m depth were between 0.20 and 0.25, indicating that the effect of overburden potential on flow was not large.
The composition of rainwater at two sites near townsville, Qld
Authors: Probert ME
Published: April 2005

Rainwater samples collected over 2 years at two sites near Townsville have been analysed. The results differ from those obtained at other near-coastal sites in Australia in that the deposition of sodium and chloride was relatively low, the sodium : chloride ratio was below that of seawater, and the samples were enriched with sulphur and calcium relative to seawater. A feature of the rainwater composition is the marked seasonal variation in the concentration of all ions, much higher values being obtained in out-of-season rains than during the wet season, but the ionic ratios were not sensitive to the seasonal distribution of rainfall. A common source for the 'excess' ions present in the rainwater could not be established.
Determining soil water diffusivities from one-step outflow experiments
Authors: Passioura JB
Published: April 2005

A simple and accurate method is developed for calculating soil water diffusivities, D(�), from one-step outflow experiments. The method is based on the assumption that d�/dt is effectively constant throughout the draining column of soil at any given time. The method is accurate to within about 15 % over most of the range of � during the outflow, providing that D increases monotonically with � through that range.
A method for computing and comparing upward flow of water in soils from a water table using the flux/unsaturated conductivity ratio
Authors: Jayawardane NS
Published: April 2005

A new method, based on an analysis of the k-h curves in relation to their use in the flow equation, is proposed for the study of steady-state upward flow of water in soils from a water table and for the computation of the pressure head profiles. This method utilizes the flux/unsaturated conductivity ratio to provide a simplified but accurate means of computing pressure head profiles, using an algebraic equation for any given rate of upward flow, between specific values of pressure heads. The values of the parameters to be used in solving this equation can be read directly from the k-h curves. In many soils, upward flow can be characterized by two parameters, namely, the slope of the k-h curve and the upper limit h,, of the critical pressure head range, thus giving a basis for direct comparison. This method can be applied to k-h curves with any integer or non-integer value of slope. Equations are also derived from which the maximum depth to water table for any rate of upward flow can be read directly from the k-h curves of certain soils. The flux/unsaturated conductivity ratio is also used to define the critical range of unsaturated conductivity, and the corresponding critical pressure head range within which the absolute values of conductivity significantly affect the shape of the pressure head profile. The use of the flux/unsaturated conductivity method, and the critical ranges for analysing k-h curves in order to predict and compare upward flow in homogeneous and layered soils, are discussed.
The nature of changes in bulk density with water content in a cracking clay
Authors: Berndt RD , Coughlan KJ
Published: April 2005

The effect of changing water content on the bulk density of undisturbed cores of a cracking clay was examined in laboratory experiments. The results were compared with the relationship between bulk density and water content established by core sampling the same soil in the field. Over the water content range measured in the field soil, the laboratory cores shrank three-dimensionally and normally. Small departures from normal shrinkage were attributed to the formation of cracks within the cores, and to the occurrence of some structural shrinkage in cores previously wet to high water contents. Swelling of cores was approximately three-dimensional, except for some unconfined swelling which occurred in the core surface. Unidimensional swelling was induced by confining dry cores to reduce the void ratio before wetting. Subsequent shrinkage was three-dimensional, indicating that the soil particles were reoriented during the unidimensional swelling phase. While the laboratory measurements showed that the soil volume changes were essentially three-dimensional and normal, the field data indicated that unidimensional shrinkage occurred at water contents greater than 0.47 g g-1. These field results were attributed to sampling inaccuracies associated with the use of a small-diameter core sampler, the actual field bulk density relationship being considered three-dimensional.
The natural abundance of 15N in the soil water system of a small catchment area
Authors: Black AS , Waring SA
Published: April 2005

The 15N abundance in components from a 100 ha catchment was determined. �15N values for fertilizer nitrogen ranged from -4.1 to 1.9 and for nitrate nitrogen in water from 4.4 to 6.1. �15N values for total nitrogen from three sites ranged from 2.9 to 6.7 and for nitrate released during laboratory incubations from -0.2 to 4.2. The variability in �15N of nitrate released by mineralization between replicates and within each sampling site was small. The �15N for nitrate released under bare fallow was 5.5. The use of these variations in 15N abundance is discussed. The �15N values for nitrate from soil intervals to 6M increased with depth. This result is discussed in terms of fractionation in a nitrate adsorbing soil.
Measurement of the overburden component of total potential in swelling field soils
Authors: Talsma T
Published: April 2005

Methods are presented for measuring the contribution of the overburden potential, ? = �P, to total potential in swelling field soils. For this purpose the total stress, P, was varied to obtain the load factor, �. In the first method, applicable to shallow topsoil, P was assumed to be zero. This permitted calculation of � from the slope of the unloaded shrinkage curve. In two other methods, the surface load, P(0), was varied in the field above tensiometers, and in the laboratory using undisturbed samples. Values of � were then calculated assuming that loading or unloading did not substantially drain or wet the soil during the measurement period. This assumption appeared reasonable; mean values of �, at constant moisture and void ratios, agreed closely, although site variability was rather high. Within the limits of accuracy of these methods, � did not depend on P. Average values of �, measured at high moisture content on a number of swelling clay soils, were all <0.25.
Ionic adsorption on variable charge mineral surfaces. Theoretical charge development and titration curves
Authors: Bowden JW , Posner AM , Quirk JP
Published: April 2005

A completely general theory is presented which can be used to describe both anion and cation adsorption on amphoteric oxide surfaces. It takes account of the fact that both the surfaces and adsorbing species are charged and that the surfaces change their charge when ionic adsorption takes place. The theory is applicable to both specific and non-specifically adsorbed ions. It is shown to account for the pH dependent charge curves of goethite, silica and two tropical soils.
The effect of topdressed superphosphate on changes in nitrogen:carbon:sulphur: phosphorus and pH on a red earth soil during a long term grazing experiment
Authors: Kohn GD , Osborne GJ , Batten GD , Smith AN , Lill WJ
Published: April 2005

Increases in total nitrogen in a grazing experiment at Wagga Wagga (N.S.W.) over the years 1962-1966 were related to the levels of superphosphate applied (0-375 kg ha-1), the average rate of increase being 59 kg ha-1 year-1. The rate of change varied between years and was negative in a dry year. Total sulphur levels were not influenced by phosphate treatments (mean 150 ppm), but sulphate sulphur was only maintained by the highest superphosphate level. Total, aluminium, iron, calcium and 'available' phosphate increased with superphosphate levels. The level of aluminium-bound phosphate increased more rapidly than the other fractions. In the treatments without applied phosphate the aluminium bound phosphate declined more rapidly than the other fractions. Organic carbon was not influenced by treatments but showed an increase with time. The C:N ratio declined from 13 to 11.8 during the experiment. Soil pH declined by 0.18 pH units, but this was not affected by superphosphate levels. Stocking rates had no effect on these parameters of soil fertility.
Chemical fractionation of soil nitrogen in six soils from southern New South Wales
Authors: Osborne GJ
Published: April 2005

The nitrogen in six surface soils from southern New South Wales was chemically fractionated into the mineral nitrogen; hydrolysed ammonium + amino sugar; hydrolysed non-distillable acid soluble nitrogen; intercalary ammonium and insoluble humin nitrogen fractions. These fractions were determined before and after a glasshouse study in which ryegrass (Lolium perenne) was grown. There was no significant relationship between any of the fractions and the dry matter producion of ryegrass at three harvest dates. The levels of each fraction varied between the soils ; however, each fraction as a percentage of the total nitrogen showed little variation, either before or after plant growth. In four soils the hydrolysed ammonium + amino sugar fraction was increased during the glasshouse study, while the hydrolysed non-distillable acid soluble fraction was decreased on three soils, increased on two, and was unchanged in the remaining soil. Two methods of hydrolysis were compared and found to give significantly different results for some soils. On the basis of the data presented, the chemical fractionation of soil nitrogen following acid hydrolysis was of no practical value as a predictor of plant yield.
Parent material stratigraphy of an egmont loam profile, Taranaki, New Zealand
Authors: Stewart RB , Neall VE , Pollok JA , Syers JK
Published: April 2005

The Egmont loam of Taranaki, New Zealand, is regarded as a classic andosol developed in andesitic tephra (a yellow-brown loam in the N.Z. genetic soil classification or an entic dystrandept in the US. Soil Taxonomy). Variations in grain size distribution and mineralogy within a representative profile show it to consist of two distinct units, an upper unit of andesitic tephra and a lower unit, containing up to 30% quartz, which is interpreted as a tephric loess. Correlation of peaks in andesitic glass distribution within the profile with eruptions from Mt Egmont suggest an accumulation period of circa 10000 years for the tephra unit, while the presence, in places conducive to its preservation, of the Aokautere Ash, a rhyolitic ash of widespread distribution in the Central North Island, dates (NZ1056A) the base of the profile at less than 19 850 � 310 years B.P. Peaks in distribution of the minor rhyolitic glass component in the tephra unit are correlated with three major post-glacial rhyolitic eruptions from the Central North Island; the Taupo eruption of 1840 � 50 years B.P. (NZ1548A), the Waimihia eruption of 3440 � 70 years B.P. (NZZA), and the Rotoma eruption of 7330 � 235 years B.P. (NZ1199A). Variations in the rate of quartz accumulation in the silt fraction of the Egmont profile are correlated with climatic changes, a higher rate of quartz accumulation occurring during the colder climate of the last stadial, in contrast with a lower rate of quartz accumulation occurring during the warmer climate of post-glacial time.
Spectral analysis of gilgai soil
Authors: Webster R
Published: April 2005

Spatial variation in gilgai soil mas studied on a transect across typical gilgai terrain of the Bland Plain of New South Wales. The soil was sampled at 4 m intervals over a distance of 1.5 km at Caragabal (33�50�S, 147�40�E). Soil morphology was recorded to 1 m and samples taken for laboratory determination of pH, electrical conductivity and chloride content from 0-10, 30-40 and 80-90 cm. Bulk density was determined for the 0-10 cm depth also. All soil properties, when graphed against their sampling positions, appear very erratic; but when filtered by a five-point moving average show recurrent short range variation, associated to some extent with the visible elements of the gilgai pattern. Block variance increases steadily with increasing block size to approximately 32 m for conductivity, pH at 80-90 cm, colour hue and chroma, depth to gypsum and the first principal component. Thereafter the rate of increase is less. Spectral densities were computed from correlograms for each property. Spectra for the properties above showed more or less strong peaks at 0.12 cycles, equivalent to a wavelength of 33.3 m. Gilgai evidently recurs sufficiently regularly on the transect for spectral analysis to reveal a periodicity, and the technique is judged to be sufficiently sensitive for analysing records made directly by data logger.
Exchangeable calcium, magnesium and sodium and the dispersion of illites in water. II. Dispersion of illites in water
Authors: Emerson WW , Chi CL
Published: April 2005

Samples of illites, two extracted from soils, one from a shale, prepared with a range of exchangeable calcium, magnesium, sodium were immersed dry into water. The extent of dispersion with time was estimated visually and also deduced from the O.D. of the suspensions derived from the dispersed clay. The dispersion of wet calcium and magnesium soil illites sheared at a given water content and then immersed in water was also assessed visually. The dispersion of all three illites was enhanced when magnesium was the dominant cation rather than calcium. For the soil clays a lower ESP was required to initiate dispersion of the dry clay when immersed in water. Both calcium and magnesium forms of the shale illite dispersed partially over a period of several days when immersed dry into water, the magnesium to a greater extent than calcium. The magnesium form of the coarser of the two soil illites also dispersed slowly. By comparing the calcium-magnesium and calcium-sodium forms of the last clay, it was deduced that about 10 times the equivalent concentration of exchangeable magnesium as sodium was needed to cause the same degree of dispersion. For the other soil illite the water content for dispersion of the wet, sheared magnesium clay was found to be less than for the calcium clay. The O.D. of suspensions of the clays was found to decrease with increasing ESP and when magnesium was the dominant cation rather than calcium. This is explained in terms of particle aggregation. The ease of dispersion of the illites was correlated with particle size. Possible reasons for this, and the effect of magnesium, as opposed to calcium, on the forces between the clay particles are discussed.
Solubility relationships of iron, manganese, copper and zinc in alkaline and calcareous soils
Authors: Sinha MK , Dhillon SK , Dhillon KS , Dyanand S
Published: April 2005

The solubility relationships of the native forms of iron, manganese, copper, and zinc in alkaline and calcareous soils were determined by a modification of the chelate equiIibrium method proposed by Norvell. The experimentally determined activity product (Fe3+)(OH-)3 in soils was found to vary within the reported range of solubility products of amorphous hydrous ferric oxides. Soils which undergo alternate cycles of reversible, oxidation-reduction processes were found to maintain higher solubility of iron and manganese than other soils. Soil pH and organic matter content were found to significantly affect the solubilities of all the four micronutrient cations. The solubility relationships of manganese, copper, and zinc have been expressed as a function of soil solution pH. Probable mechanisms controlling the solubility of these metals in alkaline and calcareous soils are discussed.
Arylsulphatase clay interactions. II. The effect of kaolinite and montmorillonite on arylsulphatase activity
Authors: Hughes JD , Simpson GH
Published: April 2005

The reduction in arylsulphatase activity in the presence of kaolinite and montmorillonite was shown to be related to the total surface area of clay available for adsorption. Adsorption of arylsulphatase by kaolinite was confined to external surfaces, but with montmorillonite, interlattice sites were also involved. Evidence was presented that arylsulphatase held as a monolayer on exterior surfaces ('primary surface' adsorption), as well as that intercalated by montmorillonite, lost its activity. The remainder ('secondary surface' adsorption) retained its activity and could be removed from the clay-enzyme complex by elution.
Properties of biologically formed manganese oxide in relation to soil manganese
Authors: Bromfield SM , David DJ
Published: April 2005

Manganese oxide, produced from the oxidation of manganous ions by bacteria at pH 6.5, was extracted with solutions commonly used to estimate the availability of soil manganese to plants. Reducing agents at pH 7.0 completely dissolved the manganese oxide as did sodium ethylene diaminetetra-acetate (EDTA) solutions more acid than pH 6.0. Other acidic solutions extracted part of the manganese in amounts in proportion to the amount of oxide present. Neutral salts extracted only traces of manganese; however, the addition of copper or zinc salts to neutral M ammonium acetate resulted in the release of appreciable amounts of manganese from the oxide. The fact that sodium EDTA solutions and solutions containing copper and zinc released manganese from the bacterial manganese oxide indicates that the practice of extracting soils with these solutions to estimate of organically bound manganese is unsound. The oxide, when pre-heated from 50 to 108�C, became progressively more soluble in neutral M ammonium acetate. Manganese was also rapidly released when the pH of the oxide in suspension was lowered from pH 7 to pH 4. Conversely the oxide rapidly adsorbed manganous ions as the pH was raised from pH 4 to 7. These changes in manganese solubility parallel those reported for soils receiving similar treatments, and it is postulated that the active manganese oxides in soil are similar to bacterial manganese oxide. It is also suggested that the acid-replaceable manganese associated with the oxide plays an important part in the availability of manganese in soils.
The release of phosphorus from plant material added to soil
Authors: Blair GJ , Boland OW
Published: April 2005

An experiment was conducted to study the release of 32P from white clover plant residues in the presence and absence of growing oats plants in both low and high phosphorus status soils. Net reutilization of phosphorus from the added plant material after 48 days was highest in the high phosphorus system in the presence of plants (29.3 %) and least in the low phosphorus system in the absence of plants (0.6%). Watering to field capacity daily, every 3 days, or every 6 days, had no significant effect on reutilization rates. Evidence from the soil inorganic phosphorus data suggests that the addition of plant material resulted in a significant immobilization of soil phosphorus only in the low phosphorus soil in the absence of plants. The significance of these findings is discussed in relation to the large number of incubation studies conducted to study phosphorus turnover rates in soil.
The availability to wheat of copper from various sources including copper superphosphate
Authors: Gilkes RJ , Sadleir SB
Published: April 2005

This study compared the availability to wheat of copper supplied as CuOSP (copper ordinary superphosphate), CuSO4.5H2O, CuO, CUEDTA and a synthetic copper phosphate similar to that occurring in commercial CuOSP. The various sources were finely ground, thoroughly mixed with the soil, and compared with an OSP treatment. Plants were harvested after 40 days and at maturity. All copper sources produced a major response relative to the OSP treatment, with copper uptake by plant tops increasing with increasing rates of application. A 12-fold difference in the water solubility of the copper sources had no effect on dry weight of plant tops and copper uptake.
Soil-tree relationships in a forest of Pinus radiata with micronutrient deficiencies
Authors: Raupach M , Clarke ARP
Published: April 2005

Multiple regressions of tree height and diameter on foliar nutrient contents of a second rotation 9-yearold Pinus radiata forest in an area with a history of micronutrient problems at Clover Hill (S.A.), showed low levels of copper and manganese and high chloride in trees with less height and larger diameter than normal. Areas which were swampy and had failed in the first rotation were better stocked than their surroundings in the second. Such areas were, however, more subject to disorder symptoms. The soils of the forest integraded and were: yellow podzolic, podzol, solodized solonetz and terra rossa. Swampy phases were observed in the podzol and particularly the solodized solonetz soils. Trees on the various soils had different foliar levels of copper, zinc, manganese, potassium, phosphorus, nitrogen, sodium and chloride. On increasingly swampy phases of the podzol, foliar copper and manganese decreased but nitrogen and sodium increased. The multiple regressions differed for the various soils; tree height increased and diameter decreased with higher foliar copper, manganese and nitrogen, whereas both increased with higher foliar zinc and sodium. On some soils the multiple regressions contained quadratic terms, enabling an estimate to be made for a 20% reduction in height (less than 1.5 ppm copper) or a similar increase in diameter due to tree malformation (less than 1.8 ppm copper). A similar reduction in height was also indicated when the foliar chloride was greater than 0.68 to 0.8%. Foliar phosphorus was unusually high at about 2.5 times the levels found in healthy trees in other forests. Statistical interactions between foliar nutrients did not contribute to the multiple regressions. Soil surveys to delineate saline and previously swampy areas should be part of future forestry investigations in the south-east of South Australia.
Hydraulic properties of a red-brown earth determined from in situ measurements
Authors: Olsson KA , Rose CW
Published: April 2005

Hydraulic conductivity characteristics are described for the soil profile of a red-brown earth exhibiting swelling properties. These were determined from in situ measurements of water content and suction during the redistribution of water following the irrigation of a non-vegetated field plot. Greater water contents were required for the same hydraulic conductivity in the subsoil than for the surface soil below cultivation depth. At a given suction, hydraulic conductivity was generally lower in the subsoil. In a field check on the theory of hydrostatics in swelling soils, values of the overburden potential (�) were derived from theory in terms of readily measurable parameters; these were shown to be in good agreement with values determined independently from the measured change in soil-water suction following the removal of overburden.
The effect of two manganese dioxides on the uptake of lead, cobalt, nickel, copper and zinc by subterranean clover
Authors: McKenzie RM
Published: April 2005

The uptake of lead, cobalt and to a lesser extent nickel by subterranean clover grown in pots on lead-contaminated soils was reduced by the addition of two varieties of manganese dioxide, while there was little or no effect on the uptake of copper and zinc. The results were consistent with the previously determined distribution of these elements between the manganese and iron oxides in soils.
A comparison of evapotranspiration measurements of crop communities using lysimeters and assimilation chambers
Authors: Puckridge DW
Published: April 2005

A sensitive weighing lysimeter which can be constructed largely of common materials is described. The mechanical structure of the balance is similar to that of McIlroy, but it has a different sensing system. It is suitable for short or long term measurements of evapotranspiration (E(t)). Measurements of E(t) for a wheat crop growing on the lysimeters were compared with E(t) measured with air-conditioned field assimilation chambers (enclosures) placed over the lysimeters and on other plots. The results indicate that the enclosure method is reasonable for comparative measurements of water use by plots with different treatments, particularly where water use cannot be determined with other methods. The enclosure technique is not affected by advection and is therefore useful for small plot work.
Preferential solute movement through larger soil voids. I. Some computations using simple theory
Authors: Scotter DR
Published: April 2005

Viscous solution flow down vertical cylindrical channels and planar cracks, with simultaneous molecular diffusion of the solute into the surrounding soil, was modelled. Chloride and phosphate were chosen as representative of non-sorbed and adsorbed ions respectively. In channels at least 0.2 mm in diameter, and cracks at least 0.1 mm wide, almost instantaneous preferential movement of both chloride and phosphate was predicted. Little or no preferential movement was predicted in smaller channels or cracks. For example phosphate was predicted to move to a depth of 200 mm within 10 min in saturated soil containing 0.2 mm diameter continuous channels. However, it would take phosphate over 2 months to reach the same depth in similar soil with the same hydraulic conductivity, but containing only 0.05 mm diameter channels. Channels and cracks permitting preferential solute movement would be solution-filled only at pressure potentials above - 0 2 m, so such movement can only occur in near saturated soil. Although highly idealized soil-void geometries were assumed, the results have a number of practical implications related to the movement of nutrients and pollutants in field soils.
The effect of soil conditioners on pore size distribution and water retention of a calcareous soil
Authors: Khoury MH , Sayegh AH , Atallah NJ
Published: April 2005

The application of soil conditioners on a calcareous soil resulted in an increase in the diameter of pores and a decrease in the available water. A diameter of 140 �m was suggested to be the dividing point between micropores and very fine pores.
The influence of organic matter extracted from humified clover on the properties of amorphous aluminosilicates.II. Phosphate retention
Authors: Perrott KW
Published: April 2005

Freshly formed water soluble organic matter extracted from humified clover leaves was used to treat a range of amorphous aluminosilicates and hydrous alumina. Phosphate retention isotherms were determined on the resulting organomineral complexes. These isotherms revealed the influence of the organic matter on phosphate retention by amorphous aluminosilicates. The organic treatment was found to reduce phosphate retention by hydrous alumina and amorphous synthetic aluminosilicates with high and low Al/(Al+Si) mole ratios. There was no depression of phosphate retention with amorphous aluminosilicates of intermediate composition. Similarly, the phosphate retention capacity of an allophanic soil clay of intermediate Al/(Al+Si) mole ratio was not reduced by organic treatment. These results appear to be related to the degree of polymerization of charge balancing hydroxy-aluminium in the aluminosilicates.
Soil morphological properties in relation to depth to the groundwater table in a sandy landscape near Perth
Authors: Mcarthur WM , Russell WGR
Published: April 2005

In an area of about 500 ha, in a sandy landscape, 154 soil profiles were classified according to colour, consistence, and thickness of horizons, and the resulting six classes were shown to be associated with depth to groundwater table. Where depths were > 11 m profiles had an A2 horizon which was not bleached. Where depths were < 7 m profiles included a bleached A, horizon and possibly an organic B horizon. Also profiles having a B horizon hue of 7.5YR were associated with greater depths to water than those with hues of 10YR and 2.5Y.
Accretion of organic carbon, nitrogen and phosphorus in sand and silt fractions of a red-brown earth under pasture
Authors: Oades JM , Turchenek LW
Published: April 2005

Organic carbon, nitrogen and phosphorus were determined in particle size and density fractions of a red-brown earth under a wheat-fallow rotation and an old pasture. In the soil under pasture organic carbon, nitrogen and phosphorus had accumulated particularly in sand fractions in the form of plant fragments and in particles 1-20 �m diameter as microbial debris.
Some factors affecting the extraction of soil 'available' phosphate
Authors: Batten GD
Published: April 2005

Twenty soils from southern New South Wales were analysed for acid extractable phosphate in 1971, and again in 1977 when it was found that an increase had occurred. These same samples were also analysed using reciprocating shakers with different distances of travel. More phosphate was extracted when a shaker with a greater distance of travel was used and when more soil, but at the same soil : solution ratio, was placed in a large vessel. It is suggested that such variations in technique contribute to inter-laboratory error in soil tests for phosphate.
Specific and non-specific sorption of cadmium by soil clays as influenced by zinc and calcium
Authors: Tiller KG , Nayyar VK , Clayton PM
Published: April 2005

The sorption of low concentrations of cadmium by the calcium-saturated <2 �m fraction of four soils was studied in the presence of variable concentrations of calcium and zinc, as a model of reactions in contaminated soils. The sorbed cadmium and zinc was determined by radioisotopic procedures and partitioned experimentally into specifically and non-specifically sorbed forms. With cadmium the non-specifically sorbed form usually exceeded specifically sorbed. Specific sorption of cadmium was depressed by competition with zinc but not the reverse. The non-specifically sorbed component of sorbed cadmium, as defined by rapid exchange with calcium nitrate solution, was preferred over calcium by the clay exchanger, with separation factors of 4-10 for cadmium saturations of <1% CEC. Some implications for the management of soil as a sink for heavy metal pollutants are discussed.
Overland flow on a steep, forested infiltrating slope
Authors: Bren LJ , Turner AK
Published: April 2005

The generation of overland flow was measured on a steeply sloping, densely forested site having a soil of high infiltration capacity. The results indicate that the volume of overland flow generated by a given storm is mainly a function of the rainfall quantity, and is not determined by the length of slope above the point of measurement. Increased rates of overland flow are consequent upon increased rainfall intensities. Less than 0.005 of the rainfall impinging on the studied slope reached the stream as overland flow. The results are explained as a special case of the kinematic wave theory of shallow flows, where the minimum slope length acceptable by the theory is specified, and the 'depth' of overland flow includes a component for rainfall splash.
Effect of salt solution composition on moisture release curves of soil
Authors: Jayawardane NS , Beattie JA
Published: April 2005

A pore size index was used to express quantitatively the relative decrease in size of common pore of confined columns of krasnozem, red-brown and alluvial soils, with reduction in electrolyte concentration of percolating solutions of a given sodium absorption ratio (SAR). The pore size index of red-brown and alluvial soils decreased markedly with reduction in electrolyte concentration, especially in solutions of high SAR. In the krasnozem soil the pore size index remained fairly constant for a wide range of salt solutions. Moisture release curves of red-brown soil for solutions of decreasing electrolyte concentration and constant SAR and for solutions of increasing SAR and constant electrolyte concentration can be used in combination to obtain moisture release curves of this soil for solutions at any intermediate values of SAR and electrolyte concentration. They also reveal the pattern of volume change of different sized pores.
Exchangeable sodium, subplasticity and hydraulic conductivity of some Australian soils
Authors: McIntyre DS
Published: April 2005

The hydraulic conductivities of beds of packed fragmented material from a variety of clay soils (mostly normal plastic but including some subplastics) and some non-clay soils, have been measured using high quality water. The degree of swelling of each packed bed (originally air-dry) was also determined. The data have been examined in relation to the exchangeable sodium percentage (ESP), clay content and type, and the degree of subplasticity. For the normal plastic soils, ESP influenced the hydraulic conductivity more than any other property. Its influence was independent of clay content and type. The results support the premise that an ESP much less than 15 should be accepted as the value above which soils can be adversely affected physically; a value of 5 would be more relevant. For the subplastic soils, the hydraulic conductivity was independent of ESP, and swelling was small considering their clay contents.