bluuebunny/crossref_metadata_2025 huggingface dataset:
A soil catena on denuded laterite profiles in Queensland
Authors: Gunn RH
Published: April 2005

A catena comprising 10 distinct zones on variously denuded laterite profiles in central Queensland is described. Red and yellow earths occur on intact or slightly stripped uplands. On denuded weathered zones, solodized solonetz, solodic, and related soils with abrupt textural differentiation have formed on intermediate slopes and saline-alkali clay soils occur on lower slopes. Soil differences are related partly to differences in parent materials and partly to the spread of weathering and erosion products across the topographic sequence. The catena either in whole or in part is repeated over wide areas. The weathering of primary minerals in parent rocks appears to be the most likely source of salts that led to the formation of halomorphic soils. The soluble materials have been leached and redistributed by surface and subsurface seepage from denuded mottled and pallid zones upslope. The clay soils appear to have formed mainly on materials derived from shales that were originally overlain by arenaceous upper Tertiary sediments, but some reworking of these materials may have occurred. Montmorillonoid clays have been preserved from deep weathering by their impermeable nature.
Development of a red-brown earth profile
Authors: Oertel AC , Giles JB
Published: April 2005

Ratios of the concentrations of alumina, ferric oxide, and titania, of which significant fractions were present in independent forms, are used to show that translocation of clay played at most only a minor part in the development of the clay profile of the Hanwood sandy loam, a red-brown earth. Supporting evidence was obtained from particle-size analyses and the concentration of potassium oxide. The essential features of this red-brown earth profile were determined by the weathering in position of layered sediments. There is evidence for the downward movement of a very small amount of ferric oxide.
The solubility of potassium from soil illites. IV. Rates of reaction and exchange constants
Authors: Tucker BM
Published: April 2005

Potassium-sensitive cationic electrodes have been used to study the rates of release of potassium from five illitic soil clays. This release was complete within a few minutes for clay-size particles and was probably controlled by diffusion. The electrode response time of 15 sec to 0.001 pK unit was too slow to permit accurate measurement of the rate of release, as the process was more than 90% complete in this time. As expected, the chemical reaction was too fast to be measured independently of diffusion. The electrodes were also used to calculate stepwise changes in Gapon constants as potassium (or sodium) was adsorbed by the clay in competition with calcium ions. The Gapon constants for potassium decreased greatly as potassium was adsorbed, but did not reach the low values expected for external exchange sites until comparatively large amounts of potassium were taken up. Potassium ions were held much more tightly thm sodium ions until the external sites began to be filled. The continuous change of Gapon constant with potassium content precluded a sharp distinction between interlayer and external exchangeable potassium. Values of the constants corresponding to the equilibrium solubilities measured in earlier work showed that the clays had a strong preference for potassium over calcium at the potassium contents in these clay preparations, and this showed that the solubility equilibria refer to potassium in the interlayer regions of the clay minerals.
An evaluation of the phosphate potential, Truog, Olsen, and Morgan methods for measuring the availability of soil phosphate
Authors: White RE , Haydock KP
Published: April 2005

The equilibrium potentialsP was compared with three of the better conventional extractants, namely, Olsen's (0.5M NaHCO3), Truog's (0.002M H2SO4), and Morgan's (0.5M HOAc/NaOAc buffer), on a range of soils of uniform calcium status, using lucerne (Medicago sativa L.), and on soils of variable calcium status, using Phaseolus lathvoides L. Relative yield and phosphorus uptake correlated better with soil test than did absolute yield response to phosphorus, for all methods. On the soils of uniform calcium status, the equilibrium potentialSP and Olsen methods were comparable and were superior to the Truog and Morgan methods. There was little to choose between the four methods on the soils of variable calcium status, when a very acid soil containing a high level of exchangeable aluminium was excluded from the correlations. Contrary to previous findings, the predictive value of the equilibrium potentialSP was high. The discrepancy may be explained by differences in the method of measuring the potential. Of the conventional extractants, one such as Olsen's bicarbonate, which reflects primarily the intensity of the phosphate supply of a soil and does not attack phosphate unavailable to plants, is to be preferred to those that reflect quantity rather than intensity.
The sorption of cobalt by manganese minerals in soils
Authors: McKenzie RM
Published: April 2005

Measurements were made of the sorption of copper, cobalt, and nickel by finely ground manganese nodules obtained from soil samples and it was found that very large amounts of these elements were sorbed by the manganese minerals in the nodules. The initial sorption of copper was greater than that of cobalt or nickel, but extraction of the sorbed elements with acetic acid showed that, once sorbed, cobalt was the most strongly held. Weight for weight, the manganese minerals sorbed, on the average, 6 times as much copper and 20 times as much cobalt as the associated soil materials. The corresponding ratios for the non-extractable fractions were 4 for copper and 160 for cobalt. The non-extractable fraction of the cobalt further increased on aging of the mineral after sorption, but little increase was observed for copper or nickel. These results explain the high concentration of cobalt found in manganiferous materials in soils.
The reaction between monosilicic acid and aluminium hydroxide. I. Kinetics of adsorption of silicic acid by aluminium hydroxide
Authors: Hingston FJ , Raupach M
Published: April 2005

Studies of the reaction between monosilicic acid and crystalline aluminium hydroxide showed that a number of layers of silicic acid could be formed on the surface of the hydroxide. Silicate is considered to be adsorbed as silicic acid rather than as silicate ions. The first layer was produced by rapid reaction of silicic acid with the surface of aluminium hydroxide. The isotherm for this initial reaction was not affected by varying the temperature from 10 to 35�C or by increasing the ionic strength of the supporting electrolyte solution. Adsorption of silicic acid resulted in increased KOH uptake by (or H2SO4 displacement from) the solid phase, which corresponded to a decrease in pH of the suspension. Subsequent layer formation was slower; the rate increased both with increasing temperature and with the ionic strength of the supporting electrolyte solution. Study of the kinetics of the reaction showed that these layers could have formed by polymerization of silicic acid on the hydroxide surface. The activation energy for the reaction increased with increasing surface coverage from 15 to 24 kcal/mole for the second layer and was about 24 kcal/mole for the third layer.
Water transport in soil with a daily temperature wave. I. Theory and experiment
Authors: Rose CW
Published: April 2005

The theory of water transport in soil is summarized for situations where flux can arise from gradients in temperature as well as in soil water suction and gravitational potential. The general differential equation describing such transport was doubly integrated to provide a form of equation suitable for the analysis of experimental data. An experiment is described in which profiles of water content and temperature were measured in the top 15 cm of bare soil for a period of 6 days and nights following saturation. High daytime radiation conditions resulted in maximum temperature gradients associated with the daily temperature wave in the soil approaching 10 degC cm-1, thus favouring vapour phase in relation to liquid phase water transport. The basic soil data necessary for the quantitative analysis of moisture fluxes into liquid and vapour components were determined. When water content at the eight sampling depths was plotted against time from saturation there was superimposed on a regular decline in water content an approximately sinusoidal fluctuation of daily period with a maximum around 0400-0600 hr local time and a minimum about 1600 hr. These results may be interpreted as indicating the existence of a vapour flux in the soil of magnitude comparable with the liquid flux. This hypothesis is examined quantitatively in Part II (C. W. Rose 1968).
The water stability of natural clay aggregates containing polyvinyl alcohol
Authors: Williams BG , Greenland DJ , Quirk JP
Published: April 2005

The effect of the adsorption of polyvinyl alcohol (PVA) by natural clay aggregates on their ability to withstand rapid wetting and shaking in water has been determined. It was found for aggregates from the B horizon of the Urrbrae loam soil (60% of < 2 � material and 0.74% of organic carbon) that between 1 and 2% by weight of PVA was sufficient to almost completely prevent breakdown into micro-aggregates. Separation of clay particles from the aggregates by abrasive forces was also largely prevented. Polymer adsorbed slowly from a dilute solution was more effective than an equal weight of polymer adsorbed rapidly from a concentrated solution. Analysis of the rate of breakdown curves enabled the initial breakdown due to rapid wetting, and the subsequent abrasive forces, to be distinguished. The results provide further support for the hypothesis previously advanced that soil aggregates are stabilized by polymer molecules that line the surfaces of the pores, binding together the clay domains which comprise the walls of the larger pores.
The uptake of nitrogen from soils in relation to solute diffusion
Authors: Clarke AL , Barley KP
Published: April 2005

When either a sand or a loam was wetted with solutions of given concentration, the apparent diffusivities of nitrate, KNO3, and ammonium, KNH3, increased with the volume of solution added. Values of KNO3 (0.5-5 x 10-3 cm2/sec) were similar to those reported previously for KCl, and were one order of magnitude higher than the values for KNH4 (0.4-3 x 10-7 cm2/sec). The rate at which wheat roots depleted the sand and loam of nitrate or ammonium was measured by two methods. In one method root mats were used, and in the other single roots were grown through a thin layer of soil. In both methods the flow of water to the roots was minimized. The uptake of nitrogen followed a very different pattern from that reported for stirred solutions. Nitrate uptake increased linearly with soil solution concentration over a wide range, 100-1000 p.p.m. of nitrate nitrogen. Also, although ammonium is generally absorbed more rapidly than nitrate from stirred solutions, nitrate was absorbed far more rapidly than ammonium when equivalent amounts were added to the soil. The observed variations in nitrogen uptake could be largely attributed to changes in the resistance that the soil offered to the diffusion of solutes.
Inositol phosphates in some Australian soils
Authors: Williams CH , Anderson G
Published: April 2005

A study was made of the total amount of inositol penta- plus hexaphosphate in a range of Australian soils. The amounts varied widely, ranging from 1.0 to 356 p.p.m. P, and accounted for 0.4-38% of the total organic phosphorus, with an average value of 16%. Neither the absolute content of inositol phosphate nor its proportion to the total organic phosphorus could be closely associated with any particular soil property. In undisturbed soil profiles the inositol phosphates tended to be concentrated near the soil surface. Inositol phosphates were shown to accumulate in soils when organic matter accumulated under leguminous pasture and to decrease when organic matter was lost from soils as a result of cultivation. The relative decrease of inositol phosphates in the cultivated soils was much smaller than that of the organic phosphorus as a whole.
On the domed structure and anisotropy of the B horizon of a solodized solonetz
Authors: Holmes JW , Stace HC
Published: April 2005

The domed columnar structure of the B horizon of solodized solonetz soils has been considered to be caused by the swelling and shrinking properties of sodium clays in the B horizon under seasonally wet and dry conditions. Such an observation, however, gives no explanation of how such soil morphology developed. With the intention of obtaining some information of the process by which the domed structure of the columns might be generated, some physical, chemical, and mineralogical characteristics of two domed columns were examined. Swelling, water retention, clay content, clay mineral species, and potassium content were some of the properties that varied systematically with position, both vertically and, more importantly, radially from the axes of the columns. That the domed columns are anisotropic was shown by these analyses. The domed structure of the columns appears to be generated by swelling strains caused partly by sand blocking the vertical cracks thereby causing horizontal confinement and partly by an increased ability to swell, even when unconfined, of the clay nearer to the axes of the columns. This increased swelling is associated with a greater degree of interstratification of the clay minerals nearer to the axes of the columns.
Ion uptake from soils by plant roots, subject to the Epstein-Hagen relation
Authors: Kautsky J , Barley KP , Fiddaman DK
Published: April 2005

Diffusion theory has been used to describe the uptake of ions from soils by single roots. Numerical solutions of the relevant differential equation are given for the case where rate of uptake is a nonlinear function of the solution concentration at the root surface. The function employed is derived from a physiological relation described by Epstein and Hagen (1962). Results are compared with those obtained using a common linear approximation.
Comparison of the effects of soil matric potential and isotropic effective stress on the germination of Lactuca sativa
Authors: Collis-George N , Williams J
Published: April 2005

The matric potential contributes positively to the isotropic effective stress operating in the solid framework of a soil system. Collis-George and Hector (1966) suggested that the matric potential may influence seed germination through its contribution to the effective stress in the solid framework surrounding the seed. Experiments are described which separate the effects of matric potential on seed germination into those that can be attributed to the free energy of the soil water and those that can be attributed to the effective stress in the soil system. The results clearly indicate that (1) seed germination is influenced by the isotropic effective stress in the solid framework of the soil system, and (2) the influence of matric potential on seed germination in the range 0 to - 400cm of water can be wholly attributed to the isotropic effective stress in the solid framework and not to the free energy of the soil water as defined by the matric potential. These conclusions are discussed in terms of the behaviour of other organisms in response to an applied matric potential.
The uptake of fluoride by Acacia georginae F.M. Bailey
Authors: Murray LR , Woolley DR
Published: April 2005

Chemical and physical measurements were made on soil samples and leaf material from Acacia georginae in order to investigate a number of factors which were considered to be possibly influencing the uptake of fluoride by the plant in the field. No correlation was found between leaf fluorine levels and any of the factors measured. The available evidence suggests that the 100-fold variation in leaf fluorine levels found is not due to variation in soil composition; this conclusion was supported by pot trials using soil from trees with high and low leaf fluorine levels. High leaf fluorine levels (> 10 p.p.m. of air dry material) were found in the field only where the tree grows over carbonate bedrock (limestone or dolomite); however, only a small percentage of the trees in such areas have elevated leaf fluorine levels.
Studies on soil polysaccharides. I. The isolation of polysaccharides from soil
Authors: Swincer GD , Oades JM , Greenland DJ
Published: April 2005

Methods for extracting polysaccharides from soil have been evaluated with respect to yield and polymer degradation. Maximum extraction with a single non-degradative treatment was obtained by shaking soil with 0.5N NaOH for 16 hr at 20�C. Pretreatment of the soil with cold dilute hydrochloric and hydrofluoric acids raised the extraction efficiency to over 40% of the total soil carbohydrate. The carbohydrates removed by 0.5N NaOH at 20�C and by hot water and other lower-yielding reagents were of comparable molecular size. Hot 0.5N NaOH treatment and acidic acetylation both removed more carbohydrate than cold 0.5N NaOH but caused considerable degradation. About 80% of the carbohydrate was removed from a range of soils by extracting first with 1N HCl, followed by 0.5N NaOH, and finally acetic anhydride containing 2.5 % conc. H2SO4. Humic materials were removed from the 0.5N NaOH by passing the extract upwards through a column of Dowex 50 (H+). Other coloured materials were adsorbed from the effluent by a water-insoluble cross-linked polyvinyl-pyrrolidone, and final purification and desalting were achieved by gel filtration. The 'purified' polysaccharide contained neutral sugars 55%, hexosamines 6%, uronic acids 10% (minimal value), amino acids 6 %, nitrogen 2.1%, and ash 1.8%. At least 10 neutral sugars, 2 hexosamines, 2 uronic acids, and 16 amino acids were present. The polysaccharides had a wide molecular weight distribution.
The use of radiation-sterilized soil to study the ammonium nutrition of wheat
Authors: Rovira AD , Bowen GD
Published: April 2005

The recolonization by Nitrosomonas and Nitrobacter of a soil sterilized by gamma radiation was extremely slow compared with the rates of recolonization by heterotrophic bacteria and fungi. As a consequence, ammonium N formed during and following irradiation was not nitrified for at least 11 weeks and plants growing on irradiated inoculated soil were ammonia fed. Under these conditions plant growth was better in irradiated-inoculated soil than in unsterilized soil. After 3 weeks, wheat from irradiated inoculated soil had three times the asparagine content found in wheat from unsterilized soil. Soil that has been irradiated then inoculated could be a useful tool for studying both nitrogen turnover in soil and the availability of nitrate and ammonium to plants growing in soil under nearly natural conditions.
Steady flow experiments in saturated clays
Authors: Smiles DE
Published: April 2005

When Darcy's law is applied to steady flow of water in saturated clay pastes it is found in general that the flux density of water is not simply proportional to the imposed water pressure difference. This arises because of the dependence of the void ratio of the clay on the pressure difference. In addition, the nature of the flux density/pressure difference curve depends on the way in which the experiment is performed.
Pseudogley in Gundaroo Subsola, Southern Tablelands, New South Wales
Authors: Van Dijk DC
Published: April 2005

The genesis is discussed of a range of pedological differentiations which occur unusually deep in the soil and characterize low, but not the lowest, catenary segments of the Gundaroo pedomorpholith. This soil layer forms a large part of the soil mantle on the Southern Tablelands and is of considerable age. The deep-seated differentiations have developed as separate 'accessory' features below red-yellow and meadow podzolic, prairie soil, and red-earth sola of normal depth (2-4 ft). The zone in which they occur is termed the 'subsolum'. The features are dominated by vertical patterns related to planar and tubular voids. They include, besides a range of sesquioxidic forms, conspicuous clay differentiations comprising pronounced cutans and up to 1-1 1/2 in. wide vertical clay veins and well-developed pedality with thick colloid coatings. These features are believed to represent 'descendant' pseudogley and to be related to an unusually dynamic palaeoclimatic regime.
Activity of sulphur-oxidizing microorganisms in some Australian soils
Authors: Vitolins MI , Swaby RJ
Published: April 2005

The percentage oxidation of sulphur and the activity of Thiobacillus thiooxidans in a red-brown earth and a chernozem were followed at monthly intervals over a period of a year, but no obvious seasonal pattern emerged, and neighbouring sites rarely synchronized. Th. thiooxidans occurred more often in the red-brown earth than in the chernozem. In a survey of 273 composite samples of Australian soils oxidation of sulphur was good in approximately one-third only, moderate to poor in a half, and nil in the remaining one-sixth. There was no obvious correlation between sulphofication and several soil properties tested; but it was often higher in soils containing sulphides and lower in more alkaline soils. Th. thiooxidans was not detected in one-third of 288 soils examined, and it was seldom very active in the remaining two-thirds. There was no relationship between the incidence of these bacteria and the Great Soil Group or the locality from which the sample came, and only poor correlations between initial pH, final pH, and titratable acidity of incubated samples. The most numerous sulphur-oxidizing organisms were heterotrophs, including nine bacterial genera and two yeasts. Facultative autotrophic thiobacilli were encountered more often than obligately autotrophic species. Green or purple sulphur bacteria were seldom isolated from arable soils. Seventy-five isolates were tested for their ability to oxidize thiosulphate and sulphur, with and without peptone, and in general heterotrophs were inferior to autotrophs and facultative autotrophs. Autoclaved soils when reinoculated with autotrophic or heterotrophic bacteria or mixtures of both types oxidized most sulphur when Th. thiooxidans and Th, thioparus were present. Soil inoculum could be imitated by a mixture of autotrophic and heterotrophic bacteria. No photochemical oxidation of sulphur was detected in soil exposed to sunlight. After enrichment of soil with seven inorganic sulphur compounds only sodium thiosulphate and sodium sulphite stimulated subsequent oxidation of elementary sulphur, while two organic sulphur compounds, cysteine and particularly methionine, were inhibitory. Starch supplement had no effect on sulphur oxidation, but asparagine depressed it. Preliminary incubation of soil for 1 to 4 weeks prior to the addition of sulphur accelerated its oxidation. The incidence of Th. thiooxidans was unaffected by eight sulphur compounds, was reduced by methionine, also by asparagine and starch, and was increased by periods of incubation prior to the addition of elemental sulphur.
Sorption and precipitation of iron of kaolinite. I. Factors involved in sorption equilibria
Authors: Fordham AW
Published: April 2005

Sorption of low concentrations of ferric iron (10-5M or less) by kaolinite, under conditions excluding precipitation, was affected by iron originally present in the clay. The extent of interference (measured by isotopic dilution) was examined after extraction by several methods, including a new one in which ascorbic acid was used. Only after the most exhaustive extractions could the influence of native iron on sorption equilibria be neglected. Irregular effects of clay : solution ratio upon iron uptake were observed when clays were extracted with reducing agents. Although only partially rectified by oxidative pretreatment, these irregularities could be fully suppressed by the presence of oxidizers during the measurement of iron uptake. To a lesser degree, iron uptake by various sorbing materials not previously treated with reducing agents was influenced by the addition of oxidizers to the reaction medium. This additional effect was attributed to an increase in the oxidation potential of the otherwise weakly poised systems examined. To obtain valid sorption isotherms, all the above factors must be taken into account.
The calibration of soil tests for fertilizer requirements
Authors: Jardine R
Published: April 2005

The predictability, from soil test measurements, of principal components of yield responses to superphosphate was examined using data previously published (by J. D. Colwell). On assessing the overall predictions of principal components by the adjusted coefficient of determination, approximately 45% of the variability was so accounted for. Since this is approximately 9% greater than that accountable for by Colwell's procedure, it is suggested that a calibration procedure for soil tests (to yield fertilizer requirements) could be based on such prediction equations, and is worth further consideration.
Infiltration from semi-circular furrows in the field
Authors: Talsma T
Published: April 2005

Experiments on a number of field soils have provided data to check the applicability of recently proposed theory on infiltration from semi-circular furrows. Although spatial variability of soil properties was rather high, the theoretical solutions adequately described cumulative infiltration. The effect of gravity on flow, which is dependent on furrow radius and the ratio of hydraulic conductivity to sorptivity, is not necessarily greatest in soils of high hydraulic conductivity. In most soils gravity effects were pronounced. Qualitative agreement was found between the observed advance of wet fronts and those the theory predicts. Steeper moisture gradients exist near the furrow than would occur near the surface during one-dimensional flow in the same soil. Some factors of relevance to furrow irrigation, and estimation of final infiltration rates from 'short furrow' tests, are discussed.
Moisture uptake by surface-applied superphosphate and movement of the phosphate and sulphate into the soil
Authors: Williams CH
Published: April 2005

Capillary uptake of soil water appeared to be more important than hygroscopic uptake of moisture by monocalcium phosphate in the wetting of surface-applied superphosphate particles. For hygroscopic uptake of water a relative humidity greater than 89% was found necessary, but particles on the soil surface are exposed to atmospheric humidity which is frequently well below 89%. This may prevent uptake of moisture from soils of low moisture content. The rate of moisture uptake from the vapour phase by superphosphate increased directly with increase in relative humidity above 89%. The rate of uptake was also influenced by temperature and surface area of the particle. Capillary uptake of soil water was influenced by soil moisture content, density of the particles, and the degree of contact between soil and particle. Movement of phosphate from the moist particle into the soil was rapid but the rate was affected by soil moisture, temperature, contact with the soil, and certain physical properties of the particle. In contrast to phosphate, movement of sulphate into the soil was slow because of the low solubility of calcium sulphate, and was greatly influenced by particle size. Leaching by rainfall may be an important factor in the movement of sulphate from coarse particles.
Mineral losses during soil formation in granitic material
Authors: Ellis RC
Published: April 2005

The productivity of forest stands on four soils is related to the degree of weathering of the soils as measured by the ratio of free ferric iron to total iron for the entire profile. Losses of phosphorus, potassium, and soil bulk increase with the degree of weathering, which commences at a considerable depth. Most of the phosphorus and potassium is lost from the material before it comes within the reach of tree roots.
Influence of active aluminium oxides on water movement in soils
Authors: Tweneboah CK , Kijne JW , Greenland DJ
Published: April 2005

Active aluminium oxides were removed from several soils by treatment with 0.5M calcium chloride or lM sodium chloride at pH 1.5. Soil-water retention and soil-water diffusivity were determined and contrasted with the values for these properties obtained after treatment with neutral salts. The changes resulting from the removal of aluminium oxides were relatively small in calcium saturated systems, but in sodium saturated systems soil-water diffusivity was drastically reduced by the prior removal of aluminium oxides. The results are discussed in terms of the influence of aluminium oxides on the stability of soil pores at different soil-water contents.
The penetration of clays by fine probes and root tips
Authors: Cockroft B , Barley KP , Greacen EL
Published: April 2005

Penetration tests were conducted in a saturated clay using fine probes and pea radicles. The point resistance encountered by fine probes, Qp, was related inversely to the rate of penetration of the probe. The resistance increased exponentially with decreasing voids ratio, ew,; at any given value of ew more resistance was offered by clay that had been remoulded than by finely aggregated clay. When radicles grown through a bed of soil crumbs encountered cores of moderately consolidated saturated clay, they merely indented the clay before turning and growing horizontally. When their tips were inserted in channels that had been formed in the cores, they were unable to penetrate directly through moderately consolidated remoulded clay (ew < 1.10), but grew along horizontal fissures that developed in the clay. No fissures developed in the aggregated clay, and the radicles were unable to elongate at ew < 0.81. The results of the penetration tests are interpreted with the aid of a mathematical model taking into account the strength and compressibility of the clay. In addition, multiple exposure photography was used to show the paths of motion followed by clay particles near the tip of the probe and the radicle. Qualitative information on friction between the root tip and the clay was obtained by matching the local deformation of the clay around the root tip with the deformations produced by probes of known roughness. The root tips tended to compress the clay 'cylindrically', whereas the probe tips compressed the clay 'spherically'. There appeared to be little friction between the root tip and the clay.
The respiration of the soil beneath some Eucalyptus forest stands as related to the productivity of the stands
Authors: Ellis RC
Published: April 2005

The respiration of the soil in situ was studied during a period of 15 months in four Eucabpbus stands of diverse physiognomy and productivity. Respiration rates were low in winter, and during periods of drought in summer; they were high in spring, and were stimulated by precipitation during the summer. Although soil respiration rates were not directly related to the organic matter content of the soil, to the amount of litter fall, or, in general, to the productivity of the stands as measured in terms of tree growth, the magnitude of the spring flush of respiration and the levels of respiration that were maintained during periods of summer drought were found to be related to stand productivity. The pattern of variation of the carbon dioxide content of the soil air differed markedly between stands, and there was a positive relationship between the productivity of the stands and the depth in the soil to which biological activity occurred.
Erosional modification of a lateritized landscape over sedimentary rocks. Its effect on soil distribution
Authors: Churchward HM
Published: April 2005

Erosional modification of a landscape, originally mantled by laterite, has been studied in the Perth Sedimentary Basin of Western Australia. A basis for understanding the soil pattern has thus been provided. This pattern depends on the variation in parent material resulting from the differential stripping of the lateritic mantle which in turn is related to a sequence of changes from a gently undulating upland to broad valleys. Yellow sands, derived by colluviation from the surficial horizons of the lateritic mantle, dominate the upland surface. Lower down yellowish brown and reddish brown sands, having as their source the deeper horizons of the laterite, occupy areas of increased relief. Along the sides of broad valleys, brown and dark red sands dominate areas downslope from ferruginous sandstone exposed as a consequence of even more effective erosion. The laterite mantle appears to have been developed in a landscape already showing relief including a system of valleys. Evidence suggests subsequent uplift. However, rejuvenation of the drainage system consequent on this has had only very limited influence on the area. Rather, it is to climatic fluctuation that erosional processes have responded. The magnitude of these processes is related to landscape features, notably the sequential changes up along this ancient valley system.
Pedogenesis of a solodized solonetz, based on duplicate soil profiles
Authors: Oertel AC , Blackburn G
Published: April 2005

Physical and chemical analyses of duplicate soil profile samples of a solodized solonetz, taken at sites 1.2 m apart, revealed some sizable differences in composition. These differences were most pronounced between the two lots of clay-sized fractions. Analytical results for zirconium indicated differences between the parent materials of the supposed A and B horizons. This suggested that the horizons were not pedogenic. All observations made on the soil are in accord with an hypothesis that its A and B horizons are no more than the end-products of the weathering of distinct sedimentary layers.
Fixed ammonium in soils developed on some Queensland phyllites and its relation to weathering
Authors: Martin AE , Gilkes RJ , Skjemstad JO
Published: April 2005

Analyses for native fixed ammonium and for other constituents are reported for four soil profiles developed on Permian phyllite. While total nitrogen contents decreased with depth, fixed ammonium nitrogen increased and reached very high values in each subsoil (one contained 7.7 m-equiv. fixed ammonium nitrogen per 100 g dry soil, or 0.108 % N). Nitrogen-15 enrichments of the fixed ammonium nitrogen were not significantly different from those of N2, in the atmosphere. Fixed ammonium nitrogen in one surface soil was unavailable as a source of nitrogen for Setaria sphacelata. Total potassium also increased with depth and was highly correlated with fixed ammonium nitrogen. On the basis of these results and from clay mineral analyses presented it is suggested that the fixed ammonium nitrogen is present in interlayer sites in illite formed front mica in the parent material. The ammonium/potassium molecular ratio differs for each profile but does not change during the weathering sequence mica -> illite -> vermiculite in any one profile.
Properties of deep sandy soils and the growth of Lovegrass, Eragrostis curvula (Schrad.) Nees
Authors: Farrington P , Campbell NA
Published: April 2005

The relationships between soil properties and the annual yield of lovegrass were studied on deep sandy soils near Meckering, Western Australia. Mean annual rainfall of the area is 378 mm, most of which falls between May and September. At sites with a water table a close relationship was established between annual yield and two properties-the depth to a water table, and the silt and clay content in the 30-60 cm layer. The relationship accounted for at least 87% of the between-site variation in yield, and was maintained between years, and over a range of nutrition levels. At sites without a water table, yield was closely related to soil mechanical composition. Where the coarse sand content in the profile exceeded 70%, survival of the grass was poor. The importance of soil moisture supply to growth of the grass in these soils is discussed, and the success of the 'edaphic' trial technique is briefly assessed.
Relationships between trace element contents and other soil variables in some Papua New Guinea soils as shown by regression analysis
Authors: Bleeker P , Austin MP
Published: April 2005

Multiple linear regression has been used to examine the relationships between total trace element contents and a number of other soil variables in horizons of six texture-contrast soils from Papua-New Guinea. The results indicate that the trace elements can be divided into three groups on the basis of both regression analyses and profile distribution: namely copper, zinc, and nickel; cobalt and manganese; and chromium. With the copper concentration in the soil as the dependent variable a regression equation having an index of determination (R2) of 0.89 was obtained containing as major independent variables copper concentration in the parent material and percentage clay of the soil horizon. Zinc and nickel showed a similar relationship to percentage clay as copper but the major variability of these elements remains unexplained. Manganese and cobalt were found to be mainly related to the presence of a fluctuating water table occurring in three of the six profiles (R2 = 0.59), while chromium was principally related to the percentages of the 50-75, 150-210, and 420-1200 � sand fractions (R2 = 0.84).
Peculiar features of soil development in parna deposits in the Eastern Riverina, N.S.W
Authors: Beattie JA
Published: April 2005

Attention is drawn to unusual features of red earth and red-brown earth soils associated with layered parna deposits in the Eastern Riverina, N.S.W., which facilitate identification and tracing of individual layers, modern soils, and paleosols in different landscapes, and subsequent elucidation of distribution, stratigraphic relations, and relative age of these and associated deposits and soils. These features include mechanical composition, subplasticity, and the occurrence of secondary calcite, magnesian calcite, barytes, dolomite, and palygorskite.
Tropical weathering in the territory of Papua and New Guinea
Authors: Haantjens HA , Bleeker P
Published: April 2005

Pure physical weathering is rare in New Guinea, but three main types of physicochemical weathering are recognized. These are skeletal weathering, in which physical changes such as fragmentation, exfoliation, disaggregation, and softening outweigh the associated chemical/mineralogical changes, and immature and mature weathering in which chemical/mineralogical changes predominate. Immature and mature weathering are subdivided, according to the kind of clay minerals formed, into smectite weathering (montmorillonite, illite, vermiculite), kandite weathering (kaolinite, halloysite, allophane), and sesquox weathering (gibbsite, goethite). In New Guinea mature weathering is uncommon despite the generally favourable climatic and lithological conditions. This is due to youthful and unstable land forms, and in the highest areas also to low temperatures. Equilibrium between rapid weathering and erosion maintains skeletal to immature weathering profiles on most slopes, and outcrops of fresh rock are rare. Kandite weathering is by far the most common type, and is often associated with gibbsite sesquox weathering in very wet areas and mainly in immature stages. Only two instances of goethite sesquox weathering have been observed, both on ultrabasic rock. Smectite weathering is rare and associated with low rainfall, basic or calcareous rock, and low topographic position. Strong weathering can mostly be related to old land surfaces, and is characterized by parallel zonation from mature weathering down to bedrock. More complex patterns can arise from renewal of weathering after dissection, differential weathering of rocks, burial of weathered profiles, or remain unexplained. The maximum depth of weathering recorded is only 32 m, but on the other hand weathering to a depth of less than 3 m is uncommon on consolidated rocks except limestone. Very limited data on the rate of weathering suggest that immature weathering requires at least 5000 years to develop, while mature weathering requires at least 20,000 years. Whereas weathering at depth appears to occur under conditions of constant volume, there is evidence near the surface of strong expansion in kandite weathering, and of moderate to very great volume decreases in sesquox weathering. Examples of the chemical changes occurring during weathering are presented in a triangular diagram relating percentages of SiO,, (Al2O3, Fe2O3), and (K2O, Na2O, CaO, MgO), and in a diagram relating the weathering potential index to the weathering direction or product index. The position of materials in these diagrams is strongly related to the clay minerals present. Deviations in the trends are caused by rejuvenation by volcanic ash, pedogenetic clay migration, sedimentary discontinuity, and differences in quartz content.
Some aspects of three-dimensional infiltration
Authors: Talsma T
Published: April 2005

Laboratory and field experiments on infiltration from hemispherical cavities have provided data to test proposed approximate solutions for cumulative infiltration. Within the limits of possible experimental errors, the theory appears to be adequate. Gravity effects are relatively unimportant in three-dimensional infiltration. The analysis of flow from cavities therefore provides a useful means of measuring sorptivity in situ, especially where hydraulic conductivity is high relative to sorptivity. Final, steady, infiltration rates, observed in most experiments within half an hour, depended strongly on capillary properties as well as on hydraulic conductivity. The present analysis is used to interpret results reported from ring infiltrometer studies.
Infiltration into columns of swelling soil as studied by high speed photography
Authors: Collis-George N , Lal R
Published: April 2005

Columns of aggregates of a soil, which slakes into microaggregates of about 30 � diameter as well as swelling on quick wetting, were examined by high speed photography during infiltration. Because of the collapse of the original structure of surface layers, the supply of water to deeper layers is restricted. Examination of motion pictures and magnified stills for the depth zone just below the collapsed surface layer provides a description of the phenomena occurring during the advance of the front. These phenomena are discussed in terms of limitations of the procedure used, the mechanism of wetting, the displacement of particles, infiltration behaviour, and the nature of swelling and slaking in these systems.
The effect of wall lubricants and column confinement on the infiltration behaviour of a swelling soil in the laboratory
Authors: Bridge BJ , Collis-George N , Lal R
Published: April 2005

The effect of wall lubrication in reducing the frictional drag between soil particles and the retaining wall of a column during infiltration into a swelling soil was studied for five lubricants, polybutene oil (RP7), fluorocarbon telomer (F.E.T.), silicone mold release, silicone rubber liners, and a block polymer surfactant. Only silicone rubber liners resulted in a significantly higher infiltration capacity. However, this result could be attributed to imperfect adherence of the liner to the wall of the column which allowed some lateral swelling of the soil during infiltration, rather than to a reduction in interaction between the walls and the swelling soil. By contrast, the use of expanding thin-walled cylindrical rubber sleeving for infiltration columns greatly increased the infiltration capacity of the swelling soil above that observed in the rigid tubes. The effect of column diameter on infiltration into the expanding columns was similar to that observed in rigid columns. The relevance of these findings to the design of laboratory infiltration experiments attempting to reproduce field behaviour of swelling soils is discussed.
Soil temperatures under grass fires
Authors: Scotter DR
Published: April 2005

A simplified mathematical model describing soil temperatures under grass fires is presented. It is assumed that, for grass fires that are short-lived in any one spot, the soil temperature just beneath the surface does not rise above 100�C. Data are presented for two experiments in which temperatures just above the soil surface and at depths ranging from 0.3 to 4 cm were measured. These results are compared with the results predicted by the theory and reasonable agreement is found. Predicted maximum temperature profiles for two soil thermal diffusivities and two fire durations are given.
Some properties of the krasnozems of Southern Victoria, Australia
Authors: Sargeant IJ , Skene JKM
Published: April 2005

Data are presented for mechanical composition, pH, organic matter, exchangeable cations, iron oxide distribution, and types of clay minerals in a range of profiles representative of the krasnozems in southern Victoria. Variability in these properties is discussed in the paper. Seven of the krasnozems are developed on Eocene (older) basalts, three on Pliocene-Pleistocene (newer) basalts, and one on Silurian mudstones. In all of the profiles, the clay minerals detected were kaolin, chloritized vermiculite, oxides of iron, variable amounts of illite, and small amounts of quartz. The degree of chloritization of the vermiculite component in the krasnozems derived from basalt is greatest in the most weathered profiles.
Infiltration behaviour of structurally unstable soils under ponded and non-ponded conditions
Authors: Collis-George N , Laryea KB
Published: April 2005

The infiltration behaviour of unstable soils under ponded and non-ponded conditions are compared with a stable soil and a sand. When an unstable soil is ponded and the surface layers are at a moisture potential of zero or near zero, the soil structure collapses. As a result, the infiltration rate and the rate of movement of the wetting front are small compared with those of stable porous materials. The moisture content and pore water pressure changes with time indicate three main zones during infiltration into unstable soils, viz: (i) a saturated zone where the original aggregate structure has been destroyed and hydraulic conductivity is low; (ii) a transmission zone where moisture content is not quite constant and where both moisture potential gradient and gravitational potential contribute to the movement of water; (iii) a wetting front. These zones have traditionally been identified with infiltration into stable soils, but in stable soils the saturated zone retains its original structure to a large extent, and the transmission zone is saturated (or is near saturation after allowing for air entrapment), and transmission of water in this zone is by gravitational potential alone. By contrast, the infiltration behaviour of unstable soils with restricted supply rates, which do not develop surface ponding, is similar to that of structurally stable materials under the same restricted supply rate, in that the structure is not destroyed. If the unstable soils were wetted slowly, the aggregates retained their identity when subsequently ponded. This system provided a maximum value of hydraulic conductivity to compare with the restricted supply rates. If the restricted supply rates for the most unstable soil were larger then 1/20 of maximum hydraulic conductivity ponding still occurred, but the incidence of ponding was delayed the smaller the restricted supply rate. In addition, structural deterioration was reduced, and in some circumstances this resulted in greater water storage and greater depth of wetting than with immediate ponding.