bluuebunny/crossref_metadata_2025 huggingface dataset:
Porewater quality of uranium tailings during laboratory aging and its relation to the solid phase
Authors: Fordham AW
Published: April 2005

After treatment to dissolve and to extract uranium, tailings from Ranger Uranium Mine had a low pH of about 1.8. However, this rose rapidly during initial stages of aging in the laboratory, due to the neutralizing effect of chloritic minerals present in the ore. Within two weeks at 22�C, the pH had reached 3.1, and it continued to rise with time and increasing temperature. The maximum value observed was 5.4 after six weeks at 70�C. Associated with (and acting against) the rise of pH was precipitation of iron, aluminium and silicon oxyhydroxides and hydroxy-sulfates from pore solution into the solid phase. These compounds acted as scavengers to reduce the concentrations of potentially toxic elements copper, zinc, cobalt, nickel, cadmium and lead in porewaters to levels which eventually became comparable to those in limed tailings. Concentrations of radionuclides were also reduced by sorption/coprecipitation reactions with these scavengers, but levels in solution were continually replenished by slow dissolution of a residual uranium mineral, probably brannerite. As a result, radioactivity in porewaters after prolonged aging was appreciably higher than that in limed tailings. Salt concentrations were high, being composed essentially of magnesium, ammonium and manganous sulfates. Ionic strengths were nominally of the order of 1.5 M, but in reality were close to that of seawater (0.7 M) if complex ion formation was taken into account. Concentrations of the major ions magnesium, ammonium, manganous and sulfate, as well as those of calcium and sodium, did not change appreciably during aging at the various temperatures. In general, porewater compositions of limed tailings were similar to those of aged acidic tailings, but the solid phase of limed tailings contained much more gypsum. Also, there appeared to be differences in the behaviour of iron and aluminium hydroxy compounds in the two systems, probably because the hydroxy compounds were precipitated very rapidly during liming and recrystallized into less hydroxylated forms with time. Porewaters from tailings neutralized with magnesium oxide rather than lime had higher total salt concentrations, because, unlike calcium, magnesium salts did not precipitate unless porewaters were further concentrated by evaporation. Manganese precipitated from porewaters at about pH 8.5, and this precipitate also helped to retain heavy metals and radioelements within the solid phase.
Barite pseudomorphs after lenticular gypsum in a buried soil from central Australia
Authors: Sullivan LA , Koppi AJ
Published: April 2005

Barite pseudomorphs after lenticular gypsum in a buried soil from central Australia are composed of loosely arranged platy crystals. These features were most probably formed by direct alteration with barium-rich solutions. The possible sources of the barium-rich solutions are briefly discussed.
Evaluation of the portable pressure transducer technique for measuring field tensiometers
Authors: Cresswell HP
Published: April 2005

The use of a portable pressure transducer system which couples to tensiometers via a syringe needle and septum stopper was assessed. Changes that occurred to pressure within the tensiometer on insertion of the needle were significant and up to 120 min was sometimes required before complete re-equilibration to the original tensiometric pressure was achieved. Tensiometer readings with less than 5% error were attained by allowing 3-4 min re-equilibration time at soil matric potentials between -1 and -25 kPa, but up to 35 min was required at -40 kPa. As well as increasing with decreasing initial pressure in the tensiometer, re-equilibration time was dependent on soil properties. The re-equilibration times reported are specific to the volume of air left in the tensiometer below the septum stopper (1.2 cm3). A larger air bubble will decrease re-equilibration time but could cause undesirable thermal errors during field use. Transducer readings should be made after allowing time for complete re-equilibration of the tensiometer following insertion of the needle. However, for practical field measurement of low matric potentials, it will be necessary to read the portable transducer before full re-equilibration and correct the reading based on previously determined re-equilibration patterns. These re-equilibration patterns should be specific to each tensiometer and should cover a range of matric potentials. It is also important that the air bubble below the septum stopper be maintained constant for each reading, and that the septum stoppers be replaced regularly. With careful use, these systems are convenient for monitoring large numbers of tensiometers spaced apart in the field.
An examination of some acid soils at Batlow, New-South-Wales
Authors: Little IP
Published: April 2005

This paper has two components. Firstly it evaluates a set of data for the apple-growing soils of the Batlow district. Secondly it makes some comments on the use of silver thiourea for the determination of exchangeable Al and Mn and the estimation of exchangeable Al by titration of 1 M KCl suspensions. A group of 21 profiles from soils used for apple-growing in the Batlow District were examined in the laboratory. It was found that many of the soils were very acidic, especially in the subsoil. Dilute CaCl2 extracted as much as 50 �g g-1 of Al and considerable exchangeable Al was extracted by silver thiourea. Exchangeable Ca levels were usually adequate for plant growth, hence low levels in apple fruit may reflect the adverse effect of Al on Ca uptake by the plant. Potassium levels were low and may be marginal in some cases and Mg tended to be low in the surface. Principal component analysis showed 77% of the variation in the data was accounted for by three independent components, one involving pH, exchangeable Ca and Al, one involving K and Mg and one involving exchangeable Mn. It was demonstrated that silver thiourea does not replace Al as effectively as the basic exchangeable cations. Also, thiourea reduces Mn so that low values will be obtained for exchangeable Al in soils with much easily reducible Mn because of the increase in pH that accompanies reduction. Silver thiourea appears to overestimate exchangeable Al in some soils with very low cation exchange capacity. Titration of clay suspensions in 1 M KCl is a satisfactory and reliable way of measuring exchangeable Al that also enables an assessment of pH-dependent charge. The method used by the USDA Soil Survey Staff, viz. equilibration of soil samples with 1 M KCl for 16 h, filtration, and determination of Al also gives reproducible results and is taken as the standard. Successive leaching with portions of 1 M KCl tends to give low values for exchangeable Al.
Forms of phosphate in soils fertilized with rock phosphate and superphosphate as measured by chemical fractionation
Authors: Kumar V , Gilkes RJ , Bolland MDA
Published: April 2005

The forms of P in three Western Australian soils that had been fertilized up to 5 years previously with rock phosphates (RP) and superphosphate were determined by a P fractionation procedure using 1 M NH4Cl, 0.5 M NH4F, 0.1 M NaOH+1 M NaCl, citrate-dithionite-bicarbonate (CDB), 1 M NaOH, and 1 M HCl. P extracted by NH4Cl and NH4F from soils fertilized with superphosphate decreased with time since application. For soils treated with apatitic RP the amounts of fertilizer P extracted by 1 M HCl decreased with time since application. This decrease was probably due to loss of apatite grains from the top soil by eluviation, bioturbation and cultivation rather than continuing dissolution of RP. For these soils most of the fertilizer P (63-67%) remained in the soil as residual apatite 5 years after fertilizer application, and this P is soluble in 1 M HCl. Over the 5 years of the experiment there was no systematic transformation of one form of P to another in soils fertilized with apatitic RP. An average amount ranging over 20-37% of added P was lost from the 0-10 cm sampling depth for different fertilizers.
Simulation of soil organic carbon and nitrogen changes in cereal and pasture systems of southern Australia
Authors: Carter MR , Parton WJ , Rowland IC , Schultz JE , Steed GR
Published: April 2005

Maintenance and improvement of soil organic matter levels is an important concern in dryland farming systems of temperate regions. The Century soil organic matter model was used to simulate changes in soil organic C and total N under long-term wheat (Triticum aestivum L.) and pasture rotations at five sites in southern Australia. Average declines in soil organic C and total N of 14 and 10%, respectively, in continuous and wheat-fallow systems over a 10 to 20 year period were closely simulated by the model at each site. Additions of N fertilizer (80 kg N ha-1), which prevented soil organic matter decline in continuous wheat systems, was also well represented by the model. Trends in soil organic matter under long-term legume pasture were not adequately simulated by the model, probably due to the 'annual' nature of subterranean clover (Trifolium subterranean L.) in dry seasons and subsequent changes in the ratio of live to dead plant biomass and shoot to root ratios. Overall, the study emphasizes the importance of adequate total plant C production to prevent a decline in soil organic C.
The dynamics of sulfur, phosphorus and iron in flooded soils as affected by changes in Eh and pH
Authors: Lefroy RDB , Samosir SSR , Blair GJ
Published: April 2005

The dynamics of Fe, P and S were studied in three soils (prairie, podzolic and krasnozem) with varying S sorption capacity (13, 32 and 132 �g S sorbed g soil-1 at 5 �g S mL-1). The soils were incubated as suspensions for 14 days at 25�C and the pH and Eh adjusted independently to four levels in the range of pH 4-8-70 and Eh from + 350 to -150 mV. In the prairie and krasnozem soils, the concentration of S in the soil solution at high pH increased as Eh was lowered to +200 mV and then decreased as Eh was lowered further. At low pH, Eh changes did not affect the concentration of S in the soil solution. The changes in the concentration of sorbed S extracted by KH2PO4 were generally similar to those for S in the soil solution. Sulfate sorption increased with a decrease in pH, with the pH effect being greater at higher Eh. At high pH and Eh, the soils released S into the solution but sulfate sorption capacity increased when Eh was lowered. At low pH, the sulfate sorption capacity of the prairie soil first increased with a lowering in Eh from +350 to about +200 mV, but then decreased with a further lowering of Eh. In the krasnozem soil, sulfate sorption capacity increased with a lowering in Eh from the highest (+350 mV) to the lowest (-150 mV) level only at the lowest pH (4.8). In the podzolic soil, the effect of pH on sulfate sorption capacity was similar at all Eh levels. The Eh effects on sulfate sorption capacity of the three soils were different.
Effect of ants on sandy soils in semi-arid eastern Australia - Local distribution of nest entrances and their effect on infiltration of water
Authors: Eldridge DJ
Published: April 2005

The influence of the funnel ant (Aphaenogaster barbigula) on water infiltration was studied on an aeolian soil in a semi-arid Callitris glaucophylla woodland in eastern Australia. At the study site at Yathong Nature Reserve, densities of up to 37 nest entrances m-2 were recorded in some areas, equivalent to a density of 88 000 entrances ha-1 over small areas or 0.9% of the surface area of the landscape. Seventy-two per cent of the entrances were actively being used by the ants. Steady-state water infiltration on soils with entrances averaged 23.3 mm min-1 which was about four times that on entrance-free soils. As the diameter of the nest entrance increased, water penetrated deeper into the soil. The results provide further evidence that ants have a marked influence on redistribution of water in semi-arid environments.
Radiological consequences of amending soils with bauxite residue gypsum mixtures
Authors: Summers KJ , O'Connor BH , Fox DR
Published: April 2005

This paper reports on the gamma (�) radiation flux from sandy soils of the Swan Coastal Plain treated with bauxite residue/gypsum at various application rates and assesses the radiological significance of soil amendment in relation to currently accepted standards. Amendment rates of up to 2000 t ha-1 of bauxite residue were used. There is a linear increase of incremental � dose with increasing rate of residue. The 1 mSv limit for incremental � dose exposure for the general public is reached for 100% occupancy at an amendment rate of 1500 t ha-1 of bauxite residue. The gamma rate of approximately 0.15 �Gy h-1 is similar to that for soils of much of the area between Bunbury and Capel in the south-west of Western Australia and is significantly lower than levels for Minninup beach where there are deposits of mineral sands.
Preliminary report on a new method for determining the shear strength of a soil surface - the resin plate method
Authors: Collis-George N , Tolmie PE , Moahansyah H
Published: April 2005

The proposed method consists of pouring a thin layer of resin onto the soil surface. This impregnates the soil to approx. 2 mm regardless of moisture content. The resultant rigid plate of resin and soil is detached from the soil beneath by applying a horizontal stress. Results for three sands and one soil are compared with those from the torsional shear box method. The method is quick, inexpensive and the results are highly reproducible. The implications of the method are discussed.
Effects of initial water content and soil mechanical strength on the runoff erosion resistance of clay soils
Authors: Govers G , Loch RJ
Published: April 2005

Effects of antecedent water content and soil strength on the resistance to erosion by overland (rill) flow were tested for two clay soils of the eastern Darling Downs, Queensland. Both shear and unconfined compressive strength of wet soil (for soil wet to saturation immediately prior to application of rill flow) mere higher for soil with initially high water contents than for soil initially air-dry. Rates of runoff erosion did not show a simple relationship with soil strength across the two soils, though for each soil, higher strength was associated with much lower rates of erosion. The results show that variations in initial water content can be associated with large chang;es in soil erodibility. Particularly for the initially wet soils of higher strength, rates of runoff erosion were controlled by rates of detachment of sediment. From size distributions of wet aggregates and of sediment, and from measured water contents of wet soil, it can be suggested that the extent of incipient failure of aggregates on wet;ting was a major factor controlling ease of detachment by rill flow, as it can be inferred that detachment of sediment involved breakdown of aggregates. Consistent with this, rates of runoff erosion across the two soils showed a direct relationship with the amount of water uptake on wetting, which appears to be a useful measure of susceptibility to detachment by rill flow. Water uptake on wetting would be an indirect measure of incipient failure and, hence, of aggregate strength.
Cycling of fertilizer and cotton crop residue nitrogen
Authors: Rochester IJ , Constable GA , Macleod DA
Published: April 2005

Mineral N (nitrate and ammonium) contents were monitored in N-fertilized soils supporting cotton crops to provide information on the nitrification, mineralization and immobilization processes operating in the soil. The relative contributions of fertilizer N, previous cotton crop residue N and indigenous soil N to the mineral N pools and to the current crop's N uptake were calculated. After N fertilizer (urea) application, the soil's mineral N content rose rapidly and subsequently declined at a slower rate. The recovery of 15N-labelled urea as mineral N declined exponentially with time. Biological immobilization (and possibly denitrification to some extent) were believed to be the major processes reducing post-application soil mineral N content; the decline could not be accounted for by crop N uptake alone. Progressively less N was mineralized upon incubation of soil sampled through the growing season. Little soil N (either from urea or crop residue) was mineralized at crop maturity. Cycling of N was evident between the soil mineral and organic N pools throughout the cotton growing season. Considerable quantities of fertilizer N were immobilized by the soil microbiomass; immobilized N was remineralized and subsequently taken up by the cotton crop. A large proportion of the crop N was taken up in the latter part of the season when the soil mineral N content was low. We suggest that much of the N taken up by cotton was derived from microbial sources, rather than crop residues. The application of cotton crop residue (stubble) slightly reduced the mineral N content in the soil by encouraging biological immobilization. 15N was mineralized very slowly from the labelled crop residue and did not contribute significantly to the supply of N to the current crop. Recovery of labelled fertilizer N and labelled crop residue N by the cotton crop was 28 and 1%, respectively. In comparison, the apparent recovery of fertilizer N was 48%. Indigenous soil N contributed 68% of the N taken up by the cotton crop.
Relationship between 137Cs in some undisturbed New Zealand soils and rainfall
Authors: Basher LR , Matthews KM
Published: April 2005

Soil samples were collected from 10 undisturbed sites in South Canterbury and Manawatu, New Zealand, to examine the relationship between 137Cs in soils and rainfall. The results were used to test a previously derived model relating cumulative deposition of 137Cs from atmospheric fallout to mean annual rainfall. There were strong correlations between mean measured levels of 137Cs in soils from the undisturbed sites and rainfall, and between the mean measured levels in soils and those predicted by the model. The moder can therefore be used to estimate input levels of137Cs for erosion studies and to verify the suitability of local measurements of the input value from sites assumed to be undisturbed. Coefficients of variation in soil-Cs at the undisturbed sites ranged up to 30%, indicating that up to 10 samples may be needed to estimate the input value with a standard error � 10%.
Assessing the adequacy of catchment streamflow yield estimates
Authors: Chiew FHS , Mcmahon TA
Published: April 2005

Rainfall-runoff models are frequently used by hydrologists to estimate runoff from rainfall and climate data, with the model adequacy assessed by comparing the level of agreement between flows simulated by the model and the recorded flows. This paper describes simple methods (visual plots, statistical parameters and dimensionless coefficients) which are commonly used to compare estimated and recorded streamflow time series and discusses their advantages and limitations. Results of a survey conducted to ascertain the required quality of flow estimates before they are considered to be satisfactory, as well as to identify preferred methods used by hydrologists in Australia to determine the adequacy of streamflow estimates, are also discussed in this paper. Information from the survey is also used to suggest objective criteria based on dimensionless coefficients that can be used as guides in assessing the adequacy of flows estimated by rainfall-runoff models. In particular, the coefficient of efficiency is a very useful indicator in assessing model adequacy.
Distribution, properties and management of sodic soils - an introduction.
Authors: Naidu DR
Published: April 2005

Over 28% of the total land area of Australia is sodic and it is likely that over 50% of arable land has sodicity related problems. Sodic soils present structural, nutritional and potential related problems. These soils disperse leading to massive erosion, pollution of the water ways and extensive waterlogging.
How do sodic soils behave - the effects of sodicity on soil physical behavior
Authors: So HB , Aylmore LAG
Published: April 2005

A model has been presented to illustrate the way in which the influence of exchangeable Na on the fundamental processes of dispersion and flocculation on Na-Ca systems affects the various soil physical properties in the field. Most cultivated soils slake (breakdown into microaggregates) when subjected to rapid wetting, giving rise to a surface seal and a reduction in infiltration rate. However, slaking alone may not neccessarily reduce the soil's productivity, e.g. surface aggregates of the highly productive self-mulching black earths slake even when in the virgin state. If dispersion follows slaking, in most cases it will lead to poor physical properties which may manifest as poor drainage, surface crusting, hardsetting and poor trafficability or workability of the soil and eventually lead to reduced crop yields. It is the dispersion phase that is affected by the presence of excessive sodium on the exchange complex of the soil, and this may have a profound effect on the soil's physical properties and behaviour.This paper reviews the possible mechanisms by which excessive sodicity may manifest in undesirable soil physical behaviour. It also attempts to relate observations made in the laboratory on pure Na-Ca-clay systems to the behaviour of the soil in the field. The effect of sodium on the dispersive behaviour of a soil is discussed in relation to its hydraulic conductivity and the processes of infiltration, redistribution and evaporation of water which in turn affects the subsoil water storage in a soil profile. The presence of sodium is also discussed in relation to changes in soil strength characteristics, the soils workability and ease of tillage and ultimately the soil's productivity. Data are presented which show that the validity of a threshold ESP and the exclusive use of ESP as a measure of sodicity are open to question.
Ion interactions and constraints to plant nutrition in Australian sodic soils
Authors: Naidu R , Rengasamy P
Published: April 2005

Many of the arable soils in Australia are affected by salinity and/or sodicity. Nutrient deficiency and ion toxicity may occur in both saline and sodic soils. Ho-ever, the mechanism for these constraints on plant growth in sodic soils differs from that of saline soils. Fertility of sodic soils with low nutrient reserves is compounded by the low supply of water and oxygen to roots in profiles with dispersive clays. Nutrient constraints in sodic soils are created by the electron and proton activities (pE and pH) in an environment of degraded soil structure. Australian sodic soils accumulate relatively low levels of organic matter. High sodium, high pH and low biological activity, commonly found in these soils, are not conducive for both the accumulation of organic matter and its mineralization. As a result, these soils are deficient in N and S. Australian soils are highly weathered and have moderate to low reserves of many plant nutrients such as Cu, Mn, Mo, Zn and P. Solubility of phosphorus is generally increased in sodic soils. Poor leaching conditions accumulate boron in soil layers. Higher concentrations of sodium than of calcium in these soils are the major cause of both physical and nutritional problems. Therefore, amelioration of sodicity is the logical first step in improving the chemical fertility of sodic soils. However, fertilizer application and improvement of soil organic matter are essential to increase yields to match the potential yield predictable from climate.
Irrigation and sodicity
Authors: Rengasamy P , Olsson KA
Published: April 2005

The productivity of irrigated agriculture in Australia is low for most crops and one important factor is the physical and chemical constraints caused by sodicity in the rootzone. Over 80% of the irrigated soils are sodic and have degraded structure limiting water and gas transport and root growth. Irrigation, without appropriate drainage, leads to the buildup of salts in soil solutions with increased sodium adsorption ratio (SAR) and can develop perched watertables due to a very low leaching fraction of the soil layers exacerbated by sodicity. Therefore, irrigation management in Australia is closely linked with the management of soil sodicity.The inevitable consequence of continued irrigation of crops and pastures with saline-sodic water without careful management is the further sodification of soil layers and concentration of salt in the rootzone. This will increase the possibility of dissolving toxic elements from soil minerals. The yields of crops can be far below the potential yields determined by climate. The cost of continued use of amendments and fertilizers to maintain normal yields will increase under saline-sodic irrigation. Most of the irrigated soils in Australia need reclamation of sodicity of soil layers at least in the rootzone. The management of these sodic soils involves the application of gypsum, suitable tillage and the maintenance of structure by the buildup of organic matter and biological activity aver time. Then artificial drainage, an essential component of the management of irrigated sodic soils, is possible. By following these soil management practices, irrigated agriculture in Australia will become sustainable with increased yields and high economic returns.
Prediction of evaporation with the CONSEVB simulation-model - an experimental evaluation
Authors: Cresswell HP , Painter DJ , Cameron KC
Published: April 2005

The CONSERVB simulation model was evaluated by comparing predictions of evaporation, net radiation, and water and temperature profiles with measured values from a bare, tilled soil in New Zealand conditions. No model calibration was used whatsoever. The assessment included tests of the sensitivity of output to variations (uncertainty) in input parameters. On 18 of the 24 days simulated, evaporation was within 0.5 mm day-1 of the measured means, although that represented less than 20% error on only 6 days. The mean difference between measured and simulated surface soil temperature for the two drying cycles was 1.2 and 1.3�C; most of this error occurred in warm conditions around noon each day. Simulated soil temperature at 0.05 m exceeded measured values during the warmest parts of the day and fell below them at night. Soil temperature prediction was sensitive to the air temperature and solar radiation climatic inputs. Evaporation prediction was sensitive to initial profile water contents, to the soil moisture characteristic and to the unsaturated hydraulic conductivity inputs. An increase in the water content at each matric potential step in the soil moisture characteristic input by a factor of 1.10 resulted in an increase in simulated cumulative evaporation of over 40%. For the prediction of evaporation and soil water content, field effort in the measurement of the soil hydraulic properties and initial water contents (where simulations are short) for model parameterization is likely to give the highest cost-benefit. Very accurate determinations of these input parameters and functions are required for model evaluation. Given the sensitivities, and the uncertainties associated with measurement and prediction of model input parameters, the predictions from CONSERVB have large uncertainties associated with them. Field-measured values of cumulative evaporation were within the range of variation in predicted values that resulted from uncertainty in determination of initial soil water contents alone. CONSERVB is more applicable to an operations research modelling approach than to prediction of evaporation and surface water contents in specific conditions.
A transfer function approach to modeling the leaching of solutes to subsurface drains .I. Nonreactive solutes
Authors: Magesan GN , Scotter DR , White RE
Published: April 2005

The leaching losses of indigenous chloride and autumn-applied solid sodium bromide were measured for a mole-pipe drainage system in a silt loam soil under pasture. About half the applied bromide was recovered in the 230 mm of drainage that occurred in the year following application. Soil sampling to 1 m depth in the following spring showed that 12% of the applied bromide had moved below the mole drain depth (450 mm) into the relatively impermeable subsoil. Chloride concentration in the drainage was about 50 g m-3 in autumn, decreasing to about 10 g m-3 by the end of the drainage season in spring. Assuming pasture uptake and animal returns of chloride were in approximate balance, chloride was treated as a conservative solute. The leaching of resident chloride in two consecutive years was successfully simulated using the simple net-applied-water form of the transfer function equation, with an exponential function for the probability density function (pdf) describing solute travel. To account for plant uptake of bromide, which was not balanced by animal returns, first order decay was incorporated into the transfer function equation for bromide. But the same travel pdf could only be used for bromide and chloride if it was assumed that the bromide entered the soil's transport volume gradually, rather than as an impulse at the time of application. When the transfer function model '''was tested against published data for the leaching of native and surface-applied chloride from the same site in two earlier years, it did not perform as well as expected. This was apparently due to exceptional hydrological events in each of those years, an unusually large and heavy rain storm in one, and an unusually long dry period during winter in the other. These events apparently affected leaching in a complex way, through either the travel pdf or the way solute entered the transport volume.
A review of sodicity and sodic soil behavior in Queensland
Authors: Shaw R , Brebber L , Ahern C , Weinand M
Published: April 2005

The occurrence of sodic soils in Queensland is more related to soil genetic factors of the past than to the current rainfall pattern, with lower sodium accessions and smaller occurrence of saline lands than other areas of Australia. A soil sodicity map of Queensland is presented. On an area basis, 55% of soils in Queensland are non-sodic, 25% are strongly sodic and 20% are of variable sodicity. The map was prepared using exchangeable sodium percentage (ESP) values at 0.6 m depth from 2 009 soil profiles, as well as the soil boundaries of the 1:2000000 Atlas of Australian Soils maps (Northcote et al. 1960-68). There is general agreement with the earlier sodicity map of Northcote and Skene (1972). The relationships between exchangeable sodium and field-measured soil hydraulic properties and plant-available water capacity are discussed. Behaviour of sodic soils depends on the exchangeable sodium percentage, clay content, clay mineralogy and salt levels. The binary component particle packing theory has been used to explain soil behaviour and identify those soils most susceptible to sodium. Cracking clay soils with dominantly smectite mineralogy and high clay contents are less susceptible to a given ESP level, as determined by their hydrological behaviour, than soils of moderate clay content and mixed mineralogies. The sodicity and the salt content of an irrigation water are important in maintaining permeability of soils. The naturally occurring equilibrium salinity-sodicity relationships of a wide range of subsoils in Queensland is compared to the published relationships between stable permeability and decreasing permeability based on sodicity and salt content. Aspects of management of sodicity under dryland and irrigation are discussed.
Aggregate slaking and dispersion class, bulk properties of soil
Authors: Emerson WW
Published: April 2005

Diffuse double-layer swelling of soils with aggregates in dispersion classes 1 and 2 can cause piping failures in earthen structures. For saturated aggregates in classes 3 or 4 from clay soils, the matric suction at which shrinkage starts depends on the size of the clay particles. As a result, cracks form sooner in highly swelling soils and aggregates around the cracks do not slake. This makes the soils easy to irrigate. Non-cracking clay subsoils may be difficult to drain because porosity created by ripping is lost by slaking. Very few Na-ions are needed on exchange sites to move class 3a aggregates into class 2. The number required is increased in neutral to acid soils because of cationic forms of aluminium on exchange sites. Aggregates from the tops of columns of a natrustalf were found to be in class 3, the bases in class 2. It is deduced that it is unlikely that the tops move seasonally. The results axe also used to illustrate the difficulty of defining natric horizons by exchangeable cation composition. The main challenge to improving soil structure and crop yield is where surface soils with aggregates in class 3a overlie clay subsoils with aggregates in classes 1 or 2.
Changes in the forms of cadmium with time in some Western Australian soils
Authors: Mann SS , Ritchie GSP
Published: April 2005

Changes in the forms of Cd with time could affect its uptake by plants and hence potential toxicity to animals and humans. The effect of time on the forms of native and added Cd was studied in four West Australian soils which differed in their clay, hydrous oxide and organic matter content. Sequential extraction of soluble (KCl), exchangeable (BaCl2), bound to organic matter (NaOCl), bound to oxides/clays (ammonium oxalate) and residual (concentrated acids) forms of Cd was carried out at different time intervals after the addition of Cd. The Cd that was added to the soils transformed with time to less soluble forms; the extent depending upon the type of soil. In addition, the rate of transformation in a particular type of soil was affected by both pH and rate of Cd addition. Soluble cadmium in the sandy soil decreased with time whereas the exchangeable form increased. The extent of the changes increased with increase in pH. In the peaty sand at pH < 5, exchangeable Cd increased apparently at the expense of soluble Cd. At higher pH values, however, Cd bound to organic matter increased with time as exchangeable Cd decreased. In the lateritic podzolic soil (dominated by kaolinite), there was no effect of time on the forms of Cd at pH values <. At pH > 6, the exchangeable form of Cd decreased whereas Cd bound to organic matter and residual Cd increased with time. In the yellow earth (dominated mainly by goethite), soluble Cd decreased with time at pH values < 5 and became a negligible fraction at pH 6. Exchangeable Cd decreased with time at pH values > 5 whereas Cd bound to oxides and residual Cd increased with time at all the pH values.
Exchange and solution phase chemistry of acid, highly weathered soils .I. Investigation of mechanisms controlling Al release into solution
Authors: Menzies NW , Bell LC , Edwards DG
Published: April 2005

Soil solid phase and soil solution characteristics were evaluated on surface and subsoil horizons of 60 acid, highly weathered soils in the unamended state, and on a subset of 39 surface horizons following the addition of CaSO4.2H2O. The activity of Al3+ Was found to be strongly correlated with the soil solution pH, with Al3+ activity increasing as pH decreased. For surface soils in the unamended state, and for the majority of subsoils, the Al3+ activity calculated was comparable to the theoretical activity supported by the dissolution of gibbsite (Al2O3.3H2O). The Al3+ activity in CaSO4.2H2O-amended samples tended to fall below that maintained by gibbsite dissolution and was more closely correlated with the Al3+ activity supported by the dissolution of jurbanite (AlSO4 (OH).5H2O).
Effects of ants on sandy soils in semi-arid eastern Australia .2. Relocation of nest entrances and consequences for bioturbation
Authors: Eldridge DJ , Pickard J
Published: April 2005

The rate of bioturbation by funnel ants (Aphaenogaster barbigula) was studied on an aeolian soil in western N.S.W. Nest entrances were tagged and monitored on permanent quadrats between May 1991 and May 1993. Nest entrances remained active for approximately 9 months and, on average, changed their location twice per year. Annual bioturbation was 336 g m-2 yr-1 which was equivalent to the annual development of a layer 0.28 mm thick. Bioturbation activity was poorly correlated with environmental variables. We estimate that 92% of the total volume of the soil would be removed from the profile during the construction of nest entrances within 100 years, and 100% within 200 years. This provides strong evidence that development of these soils is principally biogenic and may explain why there is little or no horizon development, or changes in particle size distribution with depth. Bioturbation is substantially greater than estimates of water erosion in these soils, suggesting that over time soil brought to the surface will lead to the development of a new layer. This deposition and subsequent incorporation of organic matter in the surface soils around the nest entrance may have consequences for enhanced nutrient development on a micro scale.
Mobility of radium and heavy metals from uranium mine tailings in acid sulfate soils
Authors: Willett IR , Noller BN , Beech TA
Published: April 2005

This study was aimed at determining whether heavy metals in tailings from Ranger Uranium Mine (N.T.) change in chemical form in such a way that they will become more mobile, or bioavailable, after they are mixed with extremely acidic soils from downstream of the mine. Four soils were studied: two samples were acid sulfate (jarositic or pyritic) materials and two were acidic materials overlying acid sulfate horizons. Copper, iron, manganese, lead, uranium and zinc fractions were determined in soils to which uranium mill tailings had been added. Total and exchangeable 226Ra were also determined in selected samples. The tailings-soil mixtures were incubated for up to 4 months and included a comparison of reactions under continuously moist conditions and when subjected to a saturation and drying cycle. The tailings had considerably greater concentrations of total Mn, Pb, U and 226Ra than the soils. The heavy metals in the tailings occurred as relatively immobile forms. In the non-pyritic soils, the distribution of the metals between the fractions did not change much during 4 months of reaction. In the pyritic soil, which underwent oxidation and acidification during incubation, there were 2- to 3-fold increases in the exchangeable fractions of Fe, Mn, Cu and U. The metals in the tailings and soil behaved similarly. There appeared to be more likelihood of increased mobility of metals from oxidation of pyritic materials than from addition of tailings. The fraction of total 226Ra that was exchangeable decreased from 11% in the original tailings to 2-7% after reaction with three of the soils but increased to 44% in one soil. At estimated long-term erosion rates, the tailings are not likely to be a source of heavy metal pollution, but addition of 226Rato soils presents a possible radiological hazard.
Sodic soils in Western Australia
Authors: Cochrane HR , Scholz G , Vanvreswyk AME
Published: April 2005

Sodic soils are common throughout Western Australia, particularly in the south-west agricultural area where they occur mainly as duplex or gradational profiles. Soils with sodic properties are dominant in 26% of the state; saline-sodic sediments and soils in intermittent streams, lakes and estuarine plains occupy a further 5%. Sodic soils are moderately common throughout the south and western portion of the rangeland areas (38% of the state). The south-west coastal sands and the desert and rangeland soils to the north and east of the state are rarely sodic. Although sodicity has been recognized as a discrete problem in W.A. soils since the 1920s, the extent and severity of sodicity has been satisfactorily described only for small areas of the state and most land managers are unaware of the role sodicity plays in limiting the productivity of their soils. Sodicity is implicated in a diversity of problems for both agricultural and non-agricultural uses of Western Australian soils. Subsoil impermeability is probably the most widespread of these, but no comprehensive, quantitative assessment of the influence of exchangeable sodium on subsoil properties has been undertaken. Topsoil sodicity is much less extensive but can severely restrict land productivity, particularly on sandy loam and finer textured soils which set hard when dry. The physical behaviour of Western Australian topsoils cannot usefully be predicted from measurements of exchangeable sodium alone because soils differ so greatly in their response to changing exchangeable sodium. Some remain structurally stable at ESP values >15 while others are so 'sodium-sensitive' that they exhibit highly dispersive behaviour at ESP values as low as 2%. Land values over much of the dryland farming and pastoral areas of W.A. do not justify sustained use of amendments which would reduce soil exchangeable sodium contents. Efficient management of sodic soils in these areas must rely on the prevention of degradation and the use of biological and physical means to maintain adequate soil physical properties. Effective restoration of degraded sodic soils, however, often does require application of inorganic amendments in combination with tillage to initiate structural recovery. Sodicity is currently not considered to be a problem at any of the three main irrigation areas in W.A., but all have sodic soil within their potentially irrigable lands, which may limit their future expansion.
Floodwater recharge processes in the Chowilla Anabranch system, South Australia
Authors: Jolly ID , Walker GR , Narayan KA
Published: April 2005

We report the results of a study into the interaction between floodwaters and an unconfined alluvial aquifer in the Chowilla anabranch system of the River Murray during a large flood. Data on watertable elevation, groundwater chemistry and unsaturated zone salt storage were collected before, during and after a flood in 1990 which inundated all but the very highest points of the floodplain. These data, combined with analytical modelling of the watertable behaviour throughout the flood, led us to conclude that diffuse vertical recharge of floodwater to the unsaturated zone is of little importance. As a consequence, only limited teaching of salt from this zone to the groundwater occurs. This appears to be due to a reduction in the infiltration capacity of the sodic clay surface soils of the floodplain which disperse and swell when wetted with the low salinity floodwater. This suggests that the unsaturated zone is not the major source of salt which enters the River Murray following floods. However, from previous studies it is clear that the floodplain is an important source of saline groundwater which is added to the river following floods. An alternative hypothesis to explain the observed salt accessions is that areas of the floodplain where the Coonambidgal Clay is thin or absent are zones of localized recharge which cause displacement of in situ groundwater into the floodplain streams. This hypothesis should be tested in further work.
Clay dispersivity and crusting of soils determined by Buchner funnel extractions
Authors: Singer A , Kirsten WFA , Buhmann C
Published: April 2005

Soil dispersivity tests strongly disturb soils and therefore only remotely reproduce conditions in the field. A quick and inexpensive laboratory method for the assessment of clay dispersivity of soils is proposed that involves a much milder soil treatment. The method is based on the observation that, during the separation of the soil solution from soil pastes, the separated soil solution in some soils contains suspended fine matter. The method involves the consecutive extraction of wetted and only mildly disturbed soil packed in a Buchner funnel, under standardized conditions. The time needed for the completion of the extraction of 20 mL of solution, and the extracted mineral load, are monitored. After drying, the micromorphology of the soil cake can be observed by scanning electron microscopy. By this method, the results obtained from six South African soils compared well with spontaneous dispersion test data (after Rengasamy et al., Aust. J. Soil Res., 1984, 22, 413-31) obtained independently.
Effect of drying of soils on the adsorption and leaching of phosphate and 2,4-dichlorophenoxyacetic acid
Authors: Baskaran S , Bolan NS , Rahman A , Tillman RW , MacGregor AN
Published: April 2005

Surface samples of an allophanic (Patua silt loam) and a non-allophanic (Tokomaru silt loam) soil were used to examine the effects of drying on the adsorption and leaching of phosphate and 2,4-dichlorophenoxyacetic acid (2,4-D). Phosphate and 2,4-D adsorption isotherms and adsorption kinetics were determined for field-moist, air-dried and oven-dried soil samples using KH2PO4 and 14C labelled 2,4-D. In a separate experiment, the leaching of a pulse of phosphate or 2,4-D was examined using soil columns. The Patua silt loam adsorbed 4-7 times more phosphate and 2,4-D than the Tokomaru silt loam. Compared with field-moist soil, both air-dried and oven-dried soil increased (2-5 times) the adsorption of phosphate, and oven-dried soil decreased the adsorption of 2,4-D. The adsorption kinetics indicated that there was no effect of drying on the rate of adsorption of either phosphate or 2,4-D. In column experiments, there was less leaching of phosphate and 2,4-D from the Patua soil than from the Tokomaru soil. In both soils, there was no effect of drying on the leaching of phosphate, whereas oven-drying increased the leaching of 2,4-D. Solubilization of organic matter during drying increased the accessibility of P to adsorption sites on the mineral surface and thereby increased the adsorption, whereas the water-soluble organic matter bound 2,4-D and thereby decreased the apparent adsorption onto soil and increased leaching
Effect of P-buffer capacity and P-retention index of soils on soil test-P, soil test P-calibrations and yield response curvature
Authors: Bolland MDA , Wilson IR , Allen DG
Published: April 2005

Twenty-three virgin Western Australian soils of different buffer capacities (BC) for phosphorus (P) were collected. The effects of BC on the relationships between Colwell soil test P and the level of P applied, yield and soil test P, and yield and the level of P applied were studied. Wheat (Triticum aestivum cv. Reeves), grown for 27 days in a glasshouse, was used. Two methods of measuring P sorption of soils, P buffer capacity (PBC) and P retention index (PRI), were used. The PBC is determined from a multi-point sorption curve. The PRI is a new, diagnostic, one-point, sorption method now widely used for commercial soil P testing in Western Australia. Both PBC and PRI produced similar results. The relationship between soil test P and the level of P applied was adequately described by a linear equation. When the slope coefficient of the linear equations was related to PBC or PRI, there was no relationship. The other two relationships were adequately described by a Mitscherlich equation. When the curvature coefficient of the Mitscherlich equation was related to PBC or PRI, the trend was for the value of the coefficient to decrease with increasing PBC or PRI. Consequently, as the capacity of the soil to sorb P increased the trend was for larger soil test P or higher levels of P application to produce the same yield.