bluuebunny/crossref_metadata_2025 huggingface dataset:
The reaction of plant nutrients and pollutants with soil
Authors: Barrow NJ
Published: April 2005

The mechanism of reaction of most anions, and of the heavy metal cations, with soil has not been fully understood. However, the observations can be closely described if it is assumed that ions react with variable charge surfaces, that the surfaces are not uniform, and that an initial adsorption is followed by a diffusive penetration. With these assumptions, it is possible to describe the relation between the amount sorbed and the solution concentration; the effects of pH, of electrolyte concentration, of time and of temperature on sorption; the slowness of desorption; and the effects of previous additions on the reaction with further additions.
A dispersibility index for soils and its dependence on other soil properties tested with a group of soils from the Lockyer Valley Uplands, Qld, and the Lower Namoi Valley, NSW
Authors: Little IP
Published: April 2005

The ratio between the weight of a sample of the suspension of a soil given minimal dispersion treatment and a sample of a similar suspension where the particles were completely dispersed provides an index of dispersibility. The weight is proportional to the component elements. Values for K, Mg, Fe and A1 were obtained by HF/HClO4 digestion of a small portion of the suspension, and the ratio of the amount of any of these elements estimated before and after dispersion was found to provide a reproducible index of dispersibility. The relationships between this dispersibility index and exchangeable plus soluble cations replaced by Ag or Cu thiourea, pH and specific conductivity of a 1 : 5 soil/water suspension, and the K, Mg, Fe and A1 content of the suspension of dispersed soil sampled to provide the index were investigated for a set of 105 soil samples that included soloths and grey clays from the Lockyer Valley and grey clays from the Namoi region. It was found that, while the B horizons of soloths from the Lockyer Valley uplands were non-dispersive, the deep subsoils were often highly dispersible. With the grey clays of the Namoi region, surface soils assessed as being poorly structured were often non-dispersive, but such soils showed a rapid increase in dispersibility with increasing depth. A principal component analysis of the data showed that soils from the two sites were different in terms of the cations extractable with copper thiourea, clay content, pH and conductivity. The Mg content of the soil suspension was related to the dispersibility index, i.e. smectitic clays were more dispersible. However, the K, Fe and A1 contents were not related to dispersibility. A simple linear regression with soluble plus exchangeable Na, Ca and Mg, pH, clay content and conductivity accounted for 78-81% of the variation in the dispersibility index. When Na, Ca and Mg were expressed as a percentage of the cation exchange capacity, 76-84% of the variability in the dispersibility index was accounted for. A log-transformation of the data was not as successful overall, with 50% of the variability being accounted for, but with the Namoi soils, which were higher in Ca, 84% was accounted for. To explain the dispersibility observed in soils from a landslip in the southern Lockyer Valley, a separate regression equation was able to account for 88% of the variation. When the sequence of profiles from the landslip site was examined individually, there was a catenary trend in the attributes related to dispersibility. Similarly, regression equations on sub-groups of closely related soils showed that the control over dispersibility was site-specific.
A review of the USDA SCS curve number method
Authors: Boughton WC
Published: April 2005

The origin and evolution of the USDA SCS curve number method for estimating runoff from small ungauged rural catchments is traced, and the characteristics of the method are examined. When the method is expressed as an infiltration equation, the infiltration rate becomes dependent on both total storm rainfall and rainfall intensity. When expressed as a spatially varied saturation overland flow model, the method implies that some part of any catchment has infinite surface storage capacity. The lack of physical reality in the formulation of the method is an inherent limitation to any further development. A major weakness is the sensitivity of estimated runoff to errors in the selection of the curve number. Changes of about 15-20% in the curve number doubles or halves the total estimated runoff. The results of some Australian studies where curve numbers have been calibrated against actual runoff data are collated.
Rill erosion of a self-mulching black earth. I. Effects of tillage
Authors: Loch RJ , Donnollan TE
Published: April 2005

The effects of three tillage treatments-rough-, fine- and zero-tilled-on rill erosion of a bare, self-mulching black earth were tested to determine whether tillage practices could reduce susceptibility of such soils to entrainment and transport by overland flow. In contrast to reported results for a silt loam soil, rill erosion was greatest for zero-tilled soil, and similar for the two tilled treatments. Sediment size distributions were independent of initial dry aggregate size distributions. It seems that, for self-mulching soils, stubble retention is the only method available to increase resistance to erosion by overland flow.
Evaluation of the CREAMS model. I. Sensitivity analysis of the soil erosion sedimentation component for aggregated clay soils
Authors: Silburn DM , Loch RJ
Published: April 2005

The sensitivity of the soil erosion component of the CREAMS model to changes in various input parameters was assessed in the range of parameter values suited to erosion from aggregated clay soils. Predictions of total sediment yield were sensitive to changes in a number of parameters, and interactions between parameter values were observed, e.g., for situations when either detachment of sediment or transport capacity of overland flow limited sediment yield. The CREAMS model was classified as: (i) sensitive to: specific gravity of sediment (Sgi), slope steepness; (ii) sensitive under some conditions, moderately sensitive under others to: total runoff (Vu); Universal Soil Loss Equation factors of erodibility (K), cover (C) and support practices (P); Manning-type available shear parameter (nbov); (iii) moderately sensitive to: peak runoff rate (�p), storm erosivity (EI30), slope length, sediment size distribution and kinematic viscosity. The model was judged to be 'sensitive' to a parameter when change in that parameter caused an equal or greater relative change in predicted sediment yield.
Evaluation of the CREAMS model. II. Use of rainulator data to derive soil erodibility parameters and prediction of field soil losses using derived parameters
Authors: Loch RJ , Silburn DM , Freebairn DM
Published: April 2005

The first paper of this series identified several parameters to which predictions of the CREAMS erosion model were sensitive. Two of these, soil erodibility parameters nbov and K, cannot be measured directly. Therefore, this paper reports procedures for deriving nbov and K for the CREAMS erosion model from rainulator data. The procedures identify confidence regions for best fit combinations of nbov and K. Fairly specific values of nbov were obtained, but a wide range of K values provided similar near-optimal predictions. Optimum regions of nbov and K for plots where rilling was the dominant erosion process were significantly different to those for plots dominated by rain-flow erosion for two of the three soils studied. The parameters derived from rainulator data were used to predict soil losses for field catchments on two clay soils, for conditions where surface cover by stubble was 110%. Measured rainfall and runoff were used as inputs to the model. For an Irving clay site, the model gave excellent prediction of field soil losses. For a Moola clay site, the larger soil losses were considerably underpredicted, because resistance to rilling on the rainulator plots resulted in lower K values than required for erosion events where rilling is fully developed. The need for parameters to be derived from data reflecting the erosion processes of importance to field soil loss is illustrated. Nonetheless, this study shows that parameters for the CREAMS model can be obtained satisfactorily from rainulator data, provided that the erosion processes studied are relevant, and that there is sufficient replication within the rainulator studies.
Contributions to the understanding of soil and landscape relationships
Authors: Walker PH
Published: April 2005

A new approach to pedology was developed in Australia in the 1950's. It was based on geomorphic and stratigraphic principles and recognized the cyclic or episodic nature of soil and landscape development. The research reviewed here represents a contribution to that approach and further developments of it in fluvial erosional and depositional landscapes of south-eastern Australia and in glaciated landscapes of midwestern U.S.A. This research features detailed studies of hillslope layers and their relationship to alluvial valley fills; soil chronosequences on flights of alluvial terraces; the stratigraphy of coastal flood plains and the development of acid sulfate soils; dust accession in soils and the resulting problems of interpreting pedogenesis; the erosional-depositional origin of soils in enclosed drainage basins on glacial deposits of Iowa, U.S.A.; the development of a raintower-tilting flume facility and its use in elucidating the processes of soil erosion by flowing water.
Podzol development in a holocene chronosequence .1. Moruya Heads, New South-Wales
Authors: Bowman GM
Published: April 2005

Calcareous sands (Fluvisols/Regosols) and Podzol soils of at least seven different ages (0, 2500, 3000, 5000, 5800, 6200 and 6500 calendar years) form a soil chronosequence in the prograded beach-ridge plain near Moruya Heads, on the south coast of New South Wales. Ages of the soils were determined by radiocarbon dating of marine shell deposited with the sediment. The soils range from undifferentiated quartz sand mixed with marine shell debris at the youngest site, to well developed podzols with pronounced AI, A2 and iron-humus B horizons at the oldest sites. Age trends are evident in a range of physical and chemical soil properties, the most significant of which are: an increase in the thickness of the A2 and B horizons with a concomitant decrease in C horizon thickness; a decrease in Munsell colour chroma in the A1 and A2 horizons and an increase in B horizon chroma; a fall in the pH of all horizons (particularly in the younger soils); an increase in depth to the leaching front of marine shell carbonate; the progressive leaching of HC1-extractable manganese, calcium, magnesium and sodium from the soil profiles; and the progressive development of the A2 and B horizons in terms of HC1-extractable iron and aluminium.
A field test method for soluble (0.02 M CaCl2 extractable) aluminum in soils
Authors: Close EA , Powell HKJ
Published: April 2005

A field test is described for determination of 0.02 M CaC12 extractable ('soluble') aluminium in soils. The method uses a 5 min extraction (2 min shaking followed by 3 min settling period). An aliquot of extract is then added to the metallochromic reagent chrome azurol S, CAS (amber). Aluminium reacts rapidly with CAS in hexamine buffer (pH 4.9) to form a 1 : 1 complex, Al(CAS) (purple). Intermediate colours arise in solutions where CAS is partly converted to the aluminium complex. The developed colour may be compared visually (or spectrophotometricaliy in the laboratory) with standards. Alternatively the CAS concentration may be selected to give the purple colour at a predetermined concentration of aluminium in the extractant solution, corresponding to the toxicity threshold for a specific crop and soil. CAS-reactive Al (5 min extraction) was correlated with total Al (1 h extraction; AAS) soluble in 0.02 M CaCl2, by Alt = 1.62[CAS-Al]+0.5 for soils with Alt < 60 mg kg-1 (n = 22; r2 = 0.99).
Changes with time in the availability of soil applied zinc to navy beans and in the chemical extraction of zinc from soils
Authors: Armour JD , Ritchie GSP , Robson AD
Published: April 2005

The effect of the incubation of zinc (Zn) applied to the soil on Zn uptake and the Zn concentrations in chemical extractants was studied. In a glasshouse experiment using a Zn-deficient gravelly sandy loam, the effect of recently applied Zn was compared with that of Zn incubated with the soil for 15 days at 40�C on growth and Zn uptake by navy beans (Phaseolus vulgaris cv. Gallaroy). At the second harvest (33 days after sowing), the dry weight of shoots of recently applied Zn was consistently higher than that of incubated Zn, except at the highest rate of 1 �g Zn g-1 soil, where yields were similar. Comparisons of the slope of the linear regressions of Zn uptake as a function of rate of application showed that incubated Zn was approximately 80% as effective as recently applied Zn. A laboratory experiment measured the decrease in Zn concentration in HCl, EDTA, DTPA, and dilute CaCl2 with incubation for up to 8 days at 40�C in four contrasting soils from Western Australia and Queensland. An addition of 2.5 �g Zn g-1 soil increased the concentration of Zn in all extractants at all times of incubation compared with the untreated soil. The recovery of the added Zn was generally highest with HCl and lowest with 0.002 M CaCl2 and decreased exponentially in all extractants with increasing time of incubation in all soils. The order of the rate of decrease in Zn concentration for all extractants was krasnozem > gravelly sandy loam > sand > sandy clay loam. The model, Y = CtB, where C and B are constants, was used to describe the relationship between the recovery of added Zn and time of incubation.
Microbial activity in gradually dried or rewetted soils as governed by water and substrate availability
Authors: West AW , Sparling GP , Speir TW
Published: April 2005

Microbial respiration, mass and activity (respiration/mass) in three silt loam soils with different moisture regimes (1000-2700 mm annual rainfall) were measured as the field-moist soils were gradually air-dried at 25�C in the laboratory. Microbial CO2 and O2 respiration and mass (estimated from substrate-induced respiration), and oxidizable organic carbon, extractable in 0.5 M K2SO4, were monitored throughout the 60 h drying period and also in samples of these gradually dried soils which were rewetted with water (2 ml g-1 soil). Water availability was the major factor controlling microbial respiration and activity as the soils dried. Both respiration and activity declined continuously as gravimetric water content (W) decreased. Microbial mass also declined, but only after W fell below 0.1-0.3. The microbial mass of the lowest-rainfall soil resisted desiccation better than the higher-rainfall soils. Extractable carbon levels increased after considerable soil drying (when W < 0.1-0.2). This increase in extractable carbon could be accounted for by the carbon released from micro-organisms killed by drying. Microbial respiration and activity increased sharply within 30 min of rewetting gradually dried soils. These increases appeared to be largely due to the carbon released from micro-organisms, killed by drying, being metabolized by the surviving micro-organisms when water was present. The ability of the surviving micro-organisms to metabolize this (extractable) carbon was remarkably similar for all three soils, suggesting that the carbon released from killed cells is of a very similar qualitative nature, and/or that the surviving populations were also similar between the soils.
A comparison between modified splash-cup and flume techniques in differentiating between soil loss and detachability as a result of rainfall detachment and deposition
Authors: Proffitt APB , Rose CW , Lovell CJ
Published: April 2005

Temporal changes in soil loss rates as a result of rainfall detachment were measured in modified splash-cups (kc) for two contrasting soil types with 5 mm depth of surface water at two constant rainfall rates (56 and 100 mm h-1). Results were compared with those from a flume (kf) for the same rainfall duration, rainfall rates, soil types and water depth. Reasons are given why soil loss rate commonly measured from splash-cups is not a true measure of soil detachment by rainfall when surface water is present. In order to yield the true rate of soil detachment, the measured net rate of soil loss must be augmented by a correction accounting for the rate of deposition. Theory for the net outcome of rainfall detachment and sediment deposition was used to interpret net soil loss data at equilibrium from splash-cups to yield true soil detachment rates (eTc), and compared those from a flume (eTf ). The two soil types were a cracking clay (black earth or Vertisol) and a slightly dispersive sandy clay loam (solonchak or Aridisol). Splash-cup modification allowed the proportion of sediment lost as airsplash (and therefore not deposited within the splash-cup) to be quantified to allow calculation of true soil detachment rates, and hence true soil detachabilities. Under constant rainfall rates and water depth, kc decreased significantly (5% level) with time until an equilibrium detachment rate was reached. This decrease was attributed to the development of a deposited layer on the soil surface, coarser in texture than the original soil. Values of kc were higher for the solonchak than the black earth, and increased with rainfall rate. At equilibrium, eTc and qf were approximately three orders of magnitude greater than kcand kf, illustrating the importance of recognizing the deposition process in determining true rates of soil detachment and soil detachabilities. There was no significant difference (5% level) between kc and kf at equilibrium for the black earth, but values of kc were significantly higher (5% level) than kf for the solonchak. There were no significant differences (5% level) between qc and eTf for both soil types at the low rainfall rate, but eTc were significantly lower than eTf for both the black earth (5% level) and solonchak (0.1% level) at the high rate.
Reclamation of a scalded, red duplex soil by waterponding
Authors: Ringrose-Voase AJ , Rhodes DW , Hall GF
Published: April 2005

In semi-arid New South Wales, waterponding is successfully used to reclaim red duplex soils which have been scalded by wind and water erosion exacerbated by overgrazing and drought. Reclamation was studied by comparing profiles under scald, 7 month old and 22 year old ponds, as well as under a sandy hummock and a naturally revegetated patch. The scalded soils were generally bare of vegetation, having crusted, silt loam A horizons over red, silty clay B horizons, which were saline and sodic with well developed structure. Infiltration was slow, causing rainfall to be lost by runoff and evaporation. Under recent ponds, there had been leaching of soluble salts but few other changes. Under older ponds and naturally reclaimed sites, besides leaching, the structure of the B horizon had become massive with the formation of large shrinkage cracks on drying which break open the crust. In thin section, the fabric showed more birefringent clay and there were some pore coatings of dispersed clay. These observations lead to the hypothesis that initial revegetation is a result of reduction in run-off and increased infiltration and possibly leaching of soluble salts. In the longer term, leaching causes reorganization of clay in the sodic B horizon and formation of a massive structure with shrinkage cracks which dramatically improve the infiltration rate. For waterponding to cause revegetation by this process, the soils should have a clay subsoil with shrink/swell potential and high sodicity so that restructuring takes place on leaching.
The role of termites and ants in soil modification - a review
Authors: de BRUYN LOBRY , Conacher AJ
Published: April 2005

The review examines the literature concerning the effects on soil profile development of ants (Hymenoptera: Formicidae) and termites (Isoptera), two prominent insect groups in the Australian environment. Their pedological influence is largely through the construction of nests, galleries, soil sheetings and mounds. Some of the pedological effects are manifested in the physical modification of the soil profile through selecting, transporting and rearranging soil particles. Within this group, findings in areas such as soil turnover, mound longevity, bioturbation, soil structure and water infiltration are discussed. Termites contribute actively to soil turnover, and the contribution of termite sheetings and ant mounds to soil turnover is also being recognized. Termite mounds may persist in the landscape for more than two decades, while ant mound longevity varies from weeks to decades. Information on the effects of ants and termites on soil structure and water infiltration is sparse; but ants and termites seem to either increase infiltration by improving soil structure and porosity, or to decrease infiltration by producing compact surfaces which assist runoff and erosion. Other effects involve the chemical alteration of the soil profile by ants and termites collecting and transporting live and dead animal and plant materials to their nest structures, and by the additions of secretions and excreta in nest construction. The majority of ants and termites probably increase carbon and nutrient levels, especially nitrogen, phosphorus and potassium, as well as exchangeable magnesium and calcium. The extent of the increases depends greatly on the type of mound construction and the degree to which organic material is incorporated. Problems with research techniques include the use of a variety of sampling techniques by different researchers, lack of detailed soil description or classification, and inadequate description of location of sampling points. These deficiencies make it difficult to draw valid comparisons between research projects. Many researchers also base their generalizations on ant or termite soil modifications on a small number of samples, although during the 1980s there has been an increase in sample sizes. Contradictory data often result from projects being undertaken on different species and in different environments. Future research directions need to include a greater concentration on the morphology of ant nests, more detailed assessment of the influence of ants and termites on soil structure and water infiltration, an increase in biopedological research in human-modified environments, a greater emphasis on termites and ants other than the most dominant or prominent species, and a focus on community as distinct from single-species effects.
Corrigenda - The role of termites and ants in soil modification - a review
Authors: de BRUYN LOBRY , Conacher AJ
Published: April 2005

The review examines the literature concerning the effects on soil profile development of ants (Hymenoptera: Formicidae) and termites (Isoptera), two prominent insect groups in the Australian environment. Their pedological influence is largely through the construction of nests, galleries, soil sheetings and mounds. Some of the pedological effects are manifested in the physical modification of the soil profile through selecting, transporting and rearranging soil particles. Within this group, findings in areas such as soil turnover, mound longevity, bioturbation, soil structure and water infiltration are discussed. Termites contribute actively to soil turnover, and the contribution of termite sheetings and ant mounds to soil turnover is also being recognized. Termite mounds may persist in the landscape for more than two decades, while ant mound longevity varies from weeks to decades. Information on the effects of ants and termites on soil structure and water infiltration is sparse; but ants and termites seem to either increase infiltration by improving soil structure and porosity, or to decrease infiltration by producing compact surfaces which assist runoff and erosion. Other effects involve the chemical alteration of the soil profile by ants and termites collecting and transporting live and dead animal and plant materials to their nest structures, and by the additions of secretions and excreta in nest construction. The majority of ants and termites probably increase carbon and nutrient levels, especially nitrogen, phosphorus and potassium, as well as exchangeable magnesium and calcium. The extent of the increases depends greatly on the type of mound construction and the degree to which organic material is incorporated. Problems with research techniques include the use of a variety of sampling techniques by different researchers, lack of detailed soil description or classification, and inadequate description of location of sampling points. These deficiencies make it difficult to draw valid comparisons between research projects. Many researchers also base their generalizations on ant or termite soil modifications on a small number of samples, although during the 1980s there has been an increase in sample sizes. Contradictory data often result from projects being undertaken on different species and in different environments. Future research directions need to include a greater concentration on the morphology of ant nests, more detailed assessment of the influence of ants and termites on soil structure and water infiltration, an increase in biopedological research in human-modified environments, a greater emphasis on termites and ants other than the most dominant or prominent species, and a focus on community as distinct from single-species effects.
Laboratory simulation of the surface morphology of self-mulching and non-self-mulching vertisols .1. Materials, methods and preliminary results
Authors: Pillai-McGarry UPP , Collis-George N
Published: April 2005

To date, the definitions of 'self-mulching' in Vertisols describe the phenomenon only in the air-dry state with no details of the dynamics of the system. A laboratory study was carried out to simulate the field morphological features of the soil surface of three Vertisols, one self-mulching and two non self-mulching. The soils differed in shear strength in the field, clay type, ESP and exchangeable Ca/Mg ratio. The laboratory simulation involved both repeated wetting/drying cycles with 6 mm of water every 48 h, and a continuous drying phase. These were imposed on ponded and puddled samples of the soils. With repeated wetting and drying the self-mulching soil developed a surface with a more complex organization of structural features than either of the non self-mulching soils. The self-mulching soil generated a granular structure and developed the widest cracks. Most elements of the surface morphology observed in the field were achieved in the laboratory simulation.
Aerodynamics of a portable wind erosion tunnel for measuring soil erodibility by wind
Authors: Raupach MR , Leys JF
Published: April 2005

Portable wind erosion tunnels must satisfy several aerodynamic criteria to ensure that the flow within them acceptably reproduces the atmospheric flow causing natural wind erosion. We define these criteria and use them to assess the flow and turbulence in two alternative designs of portable wind erosion tunnel: the first has a working section with an approximately triangular, 'tent-shaped' cross section, while the second has a conventional, rectangular working section. The measurements were made with Pitot-static tubes and X-configuration hot-wire anemometers, over stable (non-eroding) rough surfaces, mainly mowed grass of height 1 cm. We found that, with careful attention to flow conditioning elements such as honeycombs and tripping fences, an acceptable flow can be achieved in the rectangular tunnel. The flow in the tent-shaped tunnel is less satisfactory, exhibiting departures from the logarithmic wind profile law which depend on the surface roughness.
Extractable Fe in the surface horizons of a range of soils from Queensland
Authors: Skjemstad JO , Bushby HVA , Hansen RW
Published: April 2005

The levels of iron and aluminium extracted from 36 surface soils by pyrophosphate, oxalate and dithionite are compared with a number of other soil properties. Correlations suggest that aluminium released by these extraction procedures is largely associated with organic matter while only a small fraction of the iron released is in this form. Significant correlations between soil pH and the negative logarithms of both oxalate (r = 0.715) and pyrophosphate (r = 0.959) extractable iron in soils with >20% clay content indicate that pH is the most significant factor in determining the level of ferrihydrite and iron/organic matter complexes in surface soils. The significance of these relationships in terms of soil weathering processes is discussed. Further, the data suggest that pyrophosphate extractable iron is a useful indicator of the most active, mobile component of iron in surface soils.
Reaction of zinc with soil affecting its availability to subterranean clover. 1. The relationship between critical concentrations of extractable zinc and properties of Australian soils responsive to applied zinc
Authors: Brennan RF , Gartrell JW
Published: April 2005

A number of glasshouse experiments were conducted in which subterranean clover cv. Nungarin was grown in pots of a wide range of Australian soils to which zinc was added. Levels of zinc extractable in DTPA and in ammonium oxalate were determined and related to the growth of clover. DPTA extractable zinc (ZnD) was found to be a reliable predictor of the response of subclover to zinc added to the soils. The critical levels of ZnD, determined for the maximum growth of subterranean clover were found to vary markedly among the soil types. No simple linear relationship between the critical ZnD levels and any one soil property were found. The ZnD critical levels were found to be related to the clay content (%) and pH (1 : 5 water). The selected model in a stepwise linear regression was: Y (DTPA critical level) = -0.087 + 0.039 pH, + 0.005 clay (%). For the non-responsive soils, ZnD was found to be above the calculated critical ZnD level.
Influence of soil mineral nitrogen content on soil respiratory activity and measurements of microbial carbon and nitrogen by fumigation-incubation procedures
Authors: Ross DJ
Published: April 2005

The influence of soil mineral-N (min-N) content on rates of respiratory activity (CO2 production), and measurements of microbial biomass carbon and nitrogen by fumigation-incubation procedures, was investigated with three fertile soils and one low-fertility soil. These soils were sampled at each of the four seasons from pastures in which intensive grazing can result in high levels of min-N. Values of CO2-C flush and thin-N flush [the difference between CO2-C and min-N produced by fumigated samples and an unfumigated contl ol (or, for CO2-C only, fumigated control)] were used as indices of biomass C and N. Soil min-N content was adjusted by the addition of ammonium sulfate (approx. 50 �g NH4+-Ng-1 soil). In the low fertility soil and two of the fertile soils, added min-N had no significant effect on CO2 production or CO2-C flush values. In the other soil (Castlepoint), the added min-N usually lowered CO2 production in unfumigated samples, and increased CO2-C flush values when an unfumigated control was used; CO2-C flush values were not affected when a fumigated control was used. Use of a fumigated control for estimating biomass C in these grassland soils is recommended. Added min-N had few significant effects on the min-N flush values of the three fertile soils. In the low-fertility soil (Pomare), the min-N flush values of summer and autumn samples were appreciably higher in the presence of added min-N, with the results suggesting that the min-N flush values of the samples without added min-N were erroneously low because of N immobilization. Overall, min-N flush measurements appear to provide a satisfactory index of microbial biomass in fertile soils under pasture, but care in the interpretation of min-N flush values from low-fertility grassland soils seems advisable.
Wind erosion in eastern Australia
Authors: Mctainsh GH , Lynch AW , Burgess RC
Published: April 2005

Land degradation surveys in Australia may not have fully delineated the nature and extent of wind erosion, owing perhaps, to a shortage of quantitative data on wind erosion rates and to the subtle and transient nature of field evidence. The Ew Index of wind erosion demonstrates that regional climatic factors (i.e. effective soil moisture and wind erosivity) have a significant influence upon wind erosion rates (measured by dust storm frequencies). Also, a map of wind erosion classes shows areas where wind erosion is increased or decreased by local conditions of soil/sediment erodibility and/or agricultural and pastoral activities.
Air entrapment and differential swelling as factors in the mellowing of molded soil during rapid wetting
Authors: Grant CD , Dexter AR
Published: April 2005

The two principal mechanisms thought to be responsible for the mellowing (or weakening) of moulded soils during rapid wetting are air entrapment and differential swelling. These were investigated in order to obtain a quantitative estimate of the effect each mechanism has on the tensile strength of soils. Rapid wetting experiments were conducted on dry soil discs which had been prepared from moulded moist soil. The discs were wetted on sintered-glass funnels using two different wetting fluids at three different ambient air pressures. Discs were dried again and crushed between flat parallel plates to determine their tensile strengths. For the two soils used in this study, it was found that air entrapment on its own did not generate sufficient stress to induce mellowing, and furthermore that differential swelling on its own also had a limited effect. When the two processes acted simultaneously, however, a marked reduction in the tensile strength of between 35% and 47% resulted.
Extractable zinc in particle size fractions of soils from Western-Australia and Queensland
Authors: Armour JD , Ritchie GSP , Robson AD
Published: April 2005

The zinc (Zn) content of particle size fractions of 12 mainly Zn deficient soils was measured by extraction with three contrasting extractants. The soils, which ranged from sands to a black earth, were from Western Australia and Queensland and particle size fractions (clay, silt, fine sand, coarse sand) were obtained by sieving and sedimentation after ultrasonification of soil suspended in deionized water. The extractants were concentrated HNO3/H2SO4/HClO4 (acid extractable or AE-Zn), DTPA and 0.002 M CaCl2. For each extractant, Zn contents of the fractions and whole soils were correlated with organic carbon and ammonium oxalate extractable Fe and Al. The AE-Zn concentrations in whole soils were 0.6-132 mg kg-1 and high clay soils had higher concentrations (mean 54 mg kg-1) than low clay soils (mean 2 mg kg-1). After fractionation, lowest AE- and DTPA-Zn were found in coarse sand fractions and concentrations increased with decreasing particle size. Clay plus silt fractions contained 60-99% of the whole soil AE-Zn and 76-93% of the whole soil DTPA-Zn. The CaCl2-Zn concentrations were very low (<5.0 �g kg-1) for all soils. In whole soils, DTPA-Zn was only a small proportion, 3.2% and 1.8%, of the AE-Zn in the low clay and high clay soils, respectively. The CaCl2-Zn was generally less than 2% of the DTPA-Zn in whole soils. In whole soils, AE-Zn was correlated with oxalate extractable Fe and with oxalate A1 (r = 0.72 and 0.71, respectively; P <0.01), whereas DTPA-Zn was correlated with oxalate extractable Fe (r = 0.82; P < 0.01). The AE- and DTPA-Zn were correlated with organic carbon only in some fractions. The DTPA- and CaCl2-Zn were not correlated with AE-Zn content, nor was DPTA-Zn correlated with CaCl2-Zn in whole soils or fractions (P<0.05). Dispersion of the soils with ultrasonification in the absence of dispersing agents was not as effective as dispersion with conventional mechanical/chemical dispersion. The percentage of the soil recovered in the clay fraction after sonification was 23-78% of that recovered by the conventional method. Fine and coarse sand contents were similar for either method, indicating that incomplete dispersion of clay by ultrasonification resulted in higher silt contents.
Corrigenda - Predicting yield responsiveness and phosphorus fertilizer requirements of soybeans from soil tests
Authors: Moody PW , Dickson T , Dwyer JC , Compton BL
Published: April 2005

Field experiments with rain-fed Bragg soybeans (Glycine max) were carried out at 30 sites in central south-eastern Queensland over six years. The sites covered a wide range of soil types and P buffer capacities. Several rates of P fertilizer were band-applied in 0.9 m rows at planting. Relative grain yield at each site was correlated with 0.5 M NaHC03 extractable (PB) and 0.01 M CaCl2 extractable (PC) phosphorus. Mitscherlich equations of best fit indicated that PC was better correlated (r2 = 0.85) with relative grain yield than PB (r2 = 0.59). At 90% maximum grain yield, the 'critical' PC value was 43 �g P kg-1. The Mitscherlich curvature coefficient, c, was correlated (r2 = 0.49, P < 0.001) with the amount of P fertilizer required for 90% maximum grain yield, but not with soil P buffer capacity, as measured by a single point sorption index (r2 = 0.06). Factors other than the P sorbing ability of the soil were affecting the curvature coefficient, but could not be identified in this work. PC was sufficiently well correlated (r2 = 0.66, P < 0.001) with P fertilizer requirements to have use as a predictor of these requirements. The findings are compared with those obtained for other crops and P fertilizer application methods.
Some spectral considerations for remote sensing of soil salinity
Authors: Hick PT , Russell WGR
Published: April 2005

The National Soil Conservation Program (NSCP) and CSIRO funded a research project titled Remote Sensing of Agricultural Salinity, which gathered field and airborne reflectance data for study sites in areas of dryland agricultural salinity in Western Australia. Multivariate techniques are employed to analyse these data gathered over a 3-year period to determine optimum, spectral and temporal considerations for maximizing information content. This report concentrates on some of the spectral aspects and concludes that: spectral bands, existing in currently available remote sensing systems, may not be optimal for the delineation of salinity; that volunteer vegetation indicated the impact of increasing salinity; and that minor amounts of soluble salts in surface soils will modify spectra. The usefulness of portable field spectroradiometers and airborne scanning systems are also assessed for the discrimination of areas of land in the early stages of the effects of salinization.
Determining ECa-depth profiles from electromagnetic induction measurements
Authors: Slavich PG
Published: April 2005

The response of the EM-38 instrument to a wide range of simulated apparent electrical conductivity (ECa) profiles of different shape and mean ECa was modelled using depth response functions derived for uniform ECa profiles. Relationships between the calculated EM-38 readings and average profile ECa for depths to 1 m were determined using linear regression. These relationships were used to predict ECa profiles measured in the field using a 4-electrode probe. The mean profile ECa of the simulated profiles was strongly correlated with simple linear combinations of the calculated vertical (EM,) and horizontal (EMh) dipole measurements. The model calculations indicated that the depth to which the EM-38 measures may vary from 1.65 to 5 m, depending on the ECa of these layers and the instrument range setting. Apparent electrical conductivity profiles measured with a 4-electrode probe were more closely predicted from EM-38 measurements using this approach than the established coefficient approach of D. L. Corwin and J. D. Rhoades. The results indicate that the depth response functions, derived for homogeneous profiles, also apply to heterogeneous profiles.
Estimating average rootzone salinity from electromagnetic induction (EM-38) measurements
Authors: Slavich PG , Petterson GH
Published: April 2005

Calibration relationships are required to convert electromagnetic induction (EM-38) measurements (EM, and EMh) to average rootzone salinity (EC(0-0.6m)) in order to estimate likely production losses from salinity. This paper compares two calibration approaches and discusses factors which affect the form of the calibration relationship. Also, coefficients to adjust EM readings from field temperature to 25�C are estimated by modelling the EM response to expected temperature profiles. Calibration relationships determined using multiple linear regression, (ECe(0-0.6m) = bv EM,+ bh EMh +C) have similar prediction errors as those determined by applying the modelled coefficients procedure (Slavich 1990) to estimate average rootzone ECa (ECa(o-o.~m)) from EM, and EMh (ECe(0-0.6m) = SECa(0-0.6m) + I). However, the coefficients of the ECe(0-0.6m) V S ECa(0-0.6m) equation were more readily interpreted in terms of soil texture than those of the multiple regression approach. Using temperature-corrected EM data, the relationship between the slope (S)and the mean profile saturation percentage was similar to published relationships determined using four electrode measurements on defined soil volumes and textures. The intercept term (I) appears to be influenced by field variation in water content, texture and salinity levels below 0.6 m, the depth of interest in this paper. In heavy clay soils with high water-table salinity, the calibration relationship became nonlinear at high salinity.
Thermoluminescence dating of coastal sand dunes at Cooloola and North Stradbroke Island, Australia
Authors: Tejan-Kella MS , Chittleborough DJ , Fitzpatrick RW , Thompson CH , Prescott JR , Hutton JT
Published: April 2005

Thermoluminescence (TL) of quartz grains has been used to date a soil horizon at each of four sites in a chronosequence of freely drained podzols at Cooloola and North Stradbroke Island. The chronological order of the TL dates is in agreement with the sequence of inferred ages based on stratigraphic, geomorphic, denudational and pedological evidence, but at least one of the TL dates is of considerably greater age than the field evidence implies. Possible explanations of this anomaly are discussed. Differences in the nature of the quartz grains and the various pre-treatments used in TL dating were also examined by using a combination of thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM) methods. The DTA showed no dissimilarity among the quartz samples from the different sites, but the TGA results showed significant weight losses for some samples and pretreatments. The SEM method further showed that weight loss is associated with water-sorbing substances (allophanic materials) present as coatings on grain surfaces and/or in cracks within grains.
Micromorphology and genesis of some calcite pseudomorphs after lenticular gypsum
Authors: Sullivan LA
Published: April 2005

A micromorphological examination of some calcite pseudomorphs after lenticular gypsum in a deeply buried layer of an arid soil indicated that these features were formed by direct alteration. The likely changes in pedogenic environment that led to their formation are briefly discussed.
The mechanics of raindrop induced flow transport
Authors: Kinnell PIA
Published: April 2005

The process by which soil particles detached by drop impact move downstream within a flow under the stimulus of subsequent drop impacts is considered in terms of the horizontal movement of particles during their fall after being lifted from the soil surface. Available data are used to determine the variations in some of the variables in a mathematical model of raindrop-induced flow transport developed from the resulting theory. The analyses indicate that effects of variations in drop size and flow depth on the detachment of particles by drop impact can be masked by flow depth constraining the downstream movement of particles when flows shallower than about 3 drop diameters are impacted by medium-to-large raindrops.
Soil acidity in New-South-Wales - Current pH values and estimates of acidification rates
Authors: Helyar KR , Cregan PD , Godyn DL
Published: April 2005

An estimate has been made of the mean pH of the surface soils (0-10 or 0-15 cm) of New South Wales by mapping the soil pH (1:2, soil: 0.01 M CaCl2) values of soil samples analysed by the NSW Agriculture & Fisheries soil testing service. Within mapped classes the soil pH values vary around the mean by about 20.4 units for low pH soils (3.8-5.0) to about 20.9 units for high pH soils (>6.0). It is estimated that the areas of surface soils within agricultural holdings in NSW in the pH classes <4.5, 4.51-5 0, 5.01-5 5 and 5.5 1-6.0, are 5 3, 8.4, 5 7 and 5.1 million ha respectively. In general, pH values in the higher rainfall coastal and tablelands areas in the east are below 5.0, with the most acid areas being below 4.25. The latter are usually in the high rainfall zones (>1000 mm) and on low pH buffer capacity soils (sand to sandy loam texture). In the south of the state the area of low pH soils is broader, and extends into lower rainfall zones. Within the mapped pH classes the higher pH buffer capacity clay soils had pH values 0.83 (s.e. 0.6) units higher than the mean, whilst sands and sandy loams had pH values 0.34 (s.e. 0.1) units lower than the mean. Data on the acid addition rates for a number of agricultural systems in NSW and adjacent areas were collated and show net rates of acid addition to the soil profile from near zero to rates of 3-5 kmoles H+ ha-l year-1 over extensive areas. High acid addition rates, of 10-20 kmoles H+ ha-1 year-1, have been measured in some exploitative systems. These acid addition rate values can be used in association with soil pH buffer capacity data to estimate the rate of pH change in the future. At an acid addition rate of 4 kmol H+ ha-1 year-1, the soil pH can decline by one unit, in the surface 30 cm within 30 years for sandy loam soils, and within 120 years for clay soils.
Simultaneous adsorption of zinc and phosphate on synthetic lepidocrocite
Authors: Diaz-Barrientos E , Madrid L , Contreras MC , Morillo E
Published: April 2005

The joint adsorption of zinc and phosphate on an iron oxide is studied as a function of concentration of each adsorbate and pH. For a given P concentration, the amount of Zn adsorbed increases with pH and, at pH values above 6, more than 99% of total Zn in solution is taken up by the oxide. For a given pH value, increasing levels of P adsorbed cause strong increases in Zn adsorption, but precipitation of Zn phosphate can be ruled out, as the solution compositions invariably correspond to systems that are undersaturated with respect to that compound. From the plot of log(Zn2+) against pH, it is concluded that equilibria between soil solutions and what has been termed 'soil Zn' can be accounted for by the presence of oxide surfaces with phosphate adsorbed. Indirect estimations of the variations of the net charge conveyed to the surface by the adsorbed species suggest that Zn is adsorbed as ZnOH+.
The influence of centrifuging on phosphorus (Olsen P) soil test values
Authors: Poile GJ , Ring SM , Conyers MK , Slattery WJ
Published: April 2005

Variation in soil Olsen P tests can arise from the method of separation of the solution extract from the soil. With increasing centrifugation of the NaHC03 extract solution, we observed a decline in solution P values and these approached the P values obtained on soil-filtered extracts. The decline in solution P with increasing centrifugation was associated with a decline in organic carbon in the NaHC03 solution. We caution against unpublished modifications to methods and recommend that for consistency, simplicity, speed and cheapness, the NaHCO3 extract be soil-filtered as in the original method.