bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrologic response of undisturbed soil cores to simulated rainfall
Authors: Smettem KRJ , Kirkby C , Chittleborough DJ
Published: April 2005

Experiments to characterize runoff and drainage from large undisturbed soil cores obtained from a site under volunteer pasture are presented. The objectives were to evaluate if a simple kinematic wave model could be used to characterize drainage under conditions of by-passing flow and to investigate the variability of runoff generation under wet and dry antecedent conditions in this well structured soil. Cores were taken to depths of 0.4 and 0.7 m, with six cores obtained from each depth. Results show that variations in soil structure between cores have a greater influence on the hydrologic response than variations in antecedent water content. It may be inferred that, in this soil, good structural continuity substantially enhances soil drainage and, in consequence, decreases surface runoff. During wetting, kinematic celerities ranged from 337 to 3200 mm h-1 in the short cores and from 357 to 1400 mm h-1 in the long cores. The corresponding estimated ranges of mobile or 'macropore' fractions were from 0.015 to 0.154 m3 m-3 in the short cores and 0.033 to 0.132 m3m-3 in the long cores. Both parameters were approximately log-normally distributed. Measured drainage hydrographs were reasonably well described by the kinematic model but the physical significance of the model parameters was unclear.
Transformations of sulfur in soil and subsequent uptake by subterranean clover
Authors: Blair GJ , Till AR , Shedley CD
Published: April 2005

For a soil test to be effective it must sample pools of sulfur (S) that are immediately available to the plant and organic pools that turn over rapidly and supply S in the longer term. An experiment was conducted in two phases, the first being over 96 days to study the incorporation of S from Na2 35SO4 into various soil components at two temperatures [18/11�C (day/night) and 27/22�C] and two S application rates (10 and 50 �g S g-1 soil) and its uptake by subclover grown in pots. At intervals the pots were destructively sampled and the components radioassayed. In the second phase, soil sulfate was removed from the soil used in the first phase and the soil was potted and replanted with subclover. Soil and plant samples were taken 70 days later and the plant uptake and recycling of S-35 from the labelled soil organic pools were measured. Within 14 days in phase 1, at least 40% of the applied 35S sulfate had been incorporated into the hydriodic acid-reducible (HI-S) fraction. Subsequently, the S in the newly formed H-S fraction was recycled with mean net release rates of 35S being 26% and 38% over the next 21 and 28 day periods respectively. The mean 35S content of the carbon bonded (C-S) fraction reached a peak of 22% after 63 days, indicating a very much slower recycling rate than the H-S fraction. These results show the importance of the HI-S fraction and stress that any reliable soil testing method must at least include some estimate of the potential contribution from the H-S fraction as well as the 'available' inorganic S.
Zinc buffer capacity of vertisols
Authors: Dang YP , Dalal RC , Edwards DG , Tiller KG
Published: April 2005

The soil Zn buffer capacity is an important factor that regulates the concentration of plant-available Zn in soil solution. It is measured variously as Zn buffer power, Zn sorption or Zn desorption capacity. This study was conducted to determine Zn buffer power, and Zn sorption capacity and Zn desorption capacity in Vertisols as influenced by soil properties. The Zn buffer power, defined as the slope of the line relating soil solution Zn concentration to DTPA-extractable Zn, varied from 217 to 790. Soil pH was found to be the major soil parameter responsible for the variation in Zn buffer power. The sorption of Zn by these Vertisols was satisfactorily described by the Freundlich equation. The calculated values of the Freundlich parameters were closely related to the soil pH and amorphous Al and Fe content. Desorption of Zn by a series of successive extractions with DTPA was described by the Mitscherlich equation. The calculated values of desorption capacity were negatively correlated with soil pH and positively correlated with the contents of Al and Fe oxides. Work published elsewhere showed that the parameters of both the Zn buffer power and Zn desorption capacity accounted for as much as 62% of the variation in relative yield of wheat from Zn application to Vertisols.
Clay dispersion as influenced by pH and net particle charge of sodic soils
Authors: Chorom M , Rengasamy P , Murray RS
Published: April 2005

The effect of changing pH on the dispersion of clay from sodic soils was investigated in relation to changes in net charge on clay particles. A positive relationship was obtained between pH and the percentage of dispersible clay for each soil clay. The percentage increase in net negative charge was also positively correlated with pH. However, the slopes of these relationships varied between soil clays. In general, the net negative charge was the primary factor in clay dispersion and the pH affected clay dispersion by changing the net charge on clay particles. In comparing the values for pure clay minerals quoted in the literature with soil clays having similar mineralogy, it was found that soil clays had higher flocculation values. This is shown to be due to higher net negative charge on soil clays than the corresponding values for pure clay minerals found in the literature. The effect of soil organic matter in enhancing the net negative charge probably contributes to the higher charge on soil clays. The critical dispersion concentration for clay dispersion from soil aggregates was lower than the flocculation values observed for the separated soil clays. The separated soil clays had high negative charge due to exposure of surfaces which were originally bonded in the aggregates. The dispersive potential of a number of Alfisols, Oxisols, Aridisols (calcareous soils) and Vertisols collected from different parts of Australia was highly correlated with soil pH. The relationship with CEC was poor because CEC was estimated at a pH different to the natural pH of the soil. This study has brought out the importance of pH in the management of dispersive soils.
Bioremediation of agricultural and forestry soils with symbiotic microorganisms
Authors: Jasper DA
Published: April 2005

Symbiotic micro-organisms are important in alleviating the limitations of nitrogen and phosphorus deficiency on plant growth in Australian soils. Maximization of the contribution of these micro-organisms can give important benefits for plant production. In some cases, optimization of the infectivity of the target organisms will be achieved most effectively through changing soil management stratregies. In soils where the infective organisms are absent, or where the indigenous isolates are not effective, inoculation with selected isolates may be appropriate. Adoption of inoculation technology depends on a well defined benefit and a reliable source of high quality inoculum at a cost which is appropriate for the overall cost structure and returns of the industry. Further, inoculation should not require additional complex technology or machinery and should fit easily into existing processes of production. Inoculation with rhizobia in legume production meets these criteria and consequently is widely used. By contrast, inoculation with VA or ectomycorrhizal fungi still only occurs on a small scale, in part due to practical difficulties of inoculum production but also due to the limited number of situations where the benefits of inoculation can be clearly demonstrated.
Correction
Authors: Moody PW
Published: April 2005

Chemical Fertility of Krasnozems (Vol 32, Pg 1021, 1994)
The plastic limit of silty, surface soils in relation to their content of polysaccharide gel
Authors: Emerson WW
Published: April 2005

By using values reported in the literature, the plastic limits of mainly silty surface soils have been found to increase by 6-7 g H2O per g of C present. To explain this, it is suggested that at the plastic limit, particles of coarse silt are being rolled over each other with compacted portions of fine silt/clay matrix in between. The plastic limit is increased because of water sorbed by bonding polysaccharide gels in additional 1-3 �m sized pores between the compacted portions. The presence of such pores should have little effect on the matrix suction since this is determined by the size of the largest water-filled pores present. Water sorbed will then be proportional to C content as found, provided the composition of the polysaccharides present is constant and polysaccharide C forms a constant percentage of total C. This allows changes in the plastic limit of a soil to be used to indicate relative amounts of gel present. For example, several years after cropping was changed from grass to arable, more gel was present than in the same soils under continuous arable. Mild peroxidation of one soil did not alter the proportion of the total C present in gel form.
Drying and oxidation effects on the magnetic properties of sulfidic material during oxidation
Authors: Crockford RH , Willett IR
Published: April 2005

Laboratory experiments aimed at understanding the changes in magnetic properties of a sulfidic clay during its oxidation are described. Samples of a sulfidic clay from an acid sulfate soil were slowly oxidized and their magnetic susceptibility (χ) and remanence properties (ARM and SIRM) were measured over a 28 week period. Magnetic properties were measured for the undried material and for subsamples which had been dried by rapid air-drying or by extraction of water with dioxane. Magnetic susceptibility decreased during the first 12 weeks of oxidation and then increased. Samples dried in dioxane showed similar values to the undried material, but air drying caused decreases in χ in samples taken up to 7 weeks of oxidation. Thereafter, there was no effect of drying on χ. In contrast to susceptibility, the remanence properties decreased throughout the experiment, to 8% of their initial values. The results were interpreted in terms of rapid chemical oxidation of a labile magnetic compound (possibly greigite) during the early stages of oxidation and by air drying, and the biological oxidation of pyrite during later stages of oxidation. Associated with these reactions was the formation of a paramagnetic compound, probably ferrihydrite. The effects of changes in iron mineralogy during 28 weeks of oxidation on χ are shown schematically.
Krasnozems - organic-matter
Authors: Oades JM
Published: April 2005

Virgin krasnozems contain about 6% C from 0-15 cm and, while the C content is less at depth, the total C reserves may exceed 200 t ha(-1) to about Im depth. Highest organic matter contents occur where the annual rainfall is 1500 � 200 mm. At higher rainfalls, the C contents are less. There is a negative correlation between organic C and N content and mean annual temperature. Krasnozems contain more C than other soils in the same climate and are comparatively more fertile. Correlations of C contents with clay contents are confounded by the contents of free iron oxides. While data are fragmented, it is evident that the clearing of rainforests and replacement by pastures or other agricultural and horticultural pursuits have led to losses of up to 50% of the organic C over several decades. A simple model illustrates that this is caused by lower inputs of C to the soil in most situations except perhaps long term productive pastures where inputs may be greater than under rainforests. Studies using natural isotopes of C have shown the persistence of some C in krasnozems for hundreds of years. Some of this is particulate organic matter occluded in aggregates but most of it appears to be associated with clays, particularly at depth. The chemistry of organic matter in krasnozems appears similar to that of other soils, although solid state 13C nuclear magnetic resonance has shown more aliphatic materials in krasnozems than other soils, but the reason for this is not clear. There is little information on biota in krasnozems. The deep well structured soils are a good habitat for organisms and their high fertility guarantees a good supply of substrate for fauna and flora. It is important to maintain the organic matter contents of krasnozems to maintain cation exchange capacity, mineralization of N and other elements, to decrease phosphate sorption and to stabilize larger aggregates and thus macro porosity.
Measurement of gaseous emissions from denitrification of applied N-15 .I. Effect of cover duration
Authors: Avalakki UK , Strong WM , Saffigna PG
Published: April 2005

Measurement of gas emissions from denitrification of applied N has been restricted because of the lack of a convenient method. Recently a method using an electric are to measure 15N contents of dinitrogen (N2) and nitrous oxide (N2;O) in air has been developed. Gas emissions from denitrification of applied 15N were determined using this method for gas analysis of the 15N2 and 15N2O captured beneath an air-tight soil cover. Loss of 15N was calculated from gas emission measurements by two methods, accumulation of daily emissions and from the peak 15N emission value by assuming linear increase and decrease over the period of emissions. Losses estimated at low emissions with incomplete soil saturation were similar (1.9 - 5.6% 15N applied) for the two methods. Losses estimated at higher emissions with complete soil saturation were higher when calculated using peak emission values (14.8 - 28.5%) rather than accumulated daily emissions (9.5 - 18.7%). Losses estimated by emissions were compared with 15N loss estimated by mass balance at the completion of two successive soil saturations. As daily cover duration was shortened, gas emission estimates of loss more closely approximated total gaseous 15N as estimated from unaccounted for 15N in the15N balance. With shortest cover duration (15 min day-1) there was close agreement (94% estimated from peak emissions) with 15N loss estimated by 15N balance. A strategy for quantitatively estimating 15N loss by emission measurements is suggested.
Respiration from soil and litter in a sown perennial grass pasture
Authors: Robertson FA , Myers RJK , Saffigna PG
Published: April 2005

The severe nitrogen (N) deficiency which occurs in many sown grass pastures in Queensland is believed to be exacerbated by large and continuous inputs of carbon (C) from decomposing plant residues. In this study we attempted to quantify the importance of surface litter, roots and soil organic matter as sources of respiration in an established green panic (Panicum maximum var. trichoglume) pasture in south-east and Queensland. Intact pasture cores were taken from the field and the surface litter was removed before applying the following treatments: (i) surface litter added, (ii) roots pruned to kill approximately 60% of roots but not kill the plant, and (iii) plant shoots removed. Cores from bare soil between green panic plants were also included. The cores were kept in a glasshouse and CO2 evolution measured continuously for 117 days using an alkali absorption method. Respiration from the various components of the system was estimated. Evolution of CO2 from the cores was increased by litter addition and decreased by shoot removal. Root pruning stimulated CO2 evolution in litter-removed treatments but had no effect in litter-added treatments. Root respiration and microbial respiration of root-derived C accounted for an average of 53% of the total evolved CO2. Surface litter, soil organic matter and dead roots accounted for an average of 40%, 4% and 3% respectively. The importance of a particular C source to microorganisms varied depending on the availability of other C sources. Cores were destructively sampled on five occasions and the soils incubated at 25�C for 10 days to measure CO2 evolution with surface litter and roots removed. Evolution of CO2 in incubated soils was increased by litter and, to a lesser extent, by live roots, demonstrating that some of the labile C from these plant components was soluble or well incorporated into the soil.
Subsoil amelioration by plant-roots - the process and the evidence
Authors: Cresswell HP , Kirkegaard JA
Published: April 2005

Actively growing plant root systems have the potential to ameliorate subsoil in poor physical condition (biological drilling). Studies in which improved crop growth has been attributed to biological drilling by previous crops are reviewed. Whilst we might expect that plants are able to modify subsoil pore size distribution and that subsequent crops will benefit from the improved structure, this has yet to be demonstrated. Improvements in root growth, water extraction and grain yield do not, on their own, definitively establish the occurrence or benefits of biological drilling. Firstly, specific measurements of soil pores, their size, number and continuity are required to establish that soil structural change occurs through biological drilling. Secondly, the effects of biological drilling must be isolated from other confounding influences such as disease reduction and improvements in plant nutrition that might occur from crop rotation. The expected benefits from biological drilling might not eventuate where roots are unable to function efficiently in large pores or are unable to exit from them into the soil matrix. Model approaches can extend site and season specific observations and link soil structural changes to soil-plant-water processes, thus improving assessment of the consequences of biological drilling. Results are presented from an investigation into biological drilling by canola (Brassica napus L.) and the subsequent benefits to following wheat crops. Two seasons of canola did not create any measurable changes to soil structure at the top of the B horizon of a red brown earth (Natric Palexeralf) at Temora, N.S.W., even though grain yield and water extraction were greater for wheat following canola compared with wheat following wheat (probably due to reduced incidence of root disease). The canola appeared unable to create new pores due to the high strength of the soil matrix, and thus relied on the pre-existing pores. This, and other studies, tend to indicate that tap rooted annual crops such as lupins or canola are unlikely to be able to improve B-horizon porosity in dense, duplex soil. Perennial species (e.g. lucerne [Medicago sativa]) might be more effective at biological drilling because of the longer time and wider range of water content conditions in which to establish a deep root system. It remains to clearly demonstrate biological drilling as an effective process for ameliorating these dense subsoils.
Use of Time-Domain Reflectometry (TDR) to measure the water-content of sandy soils
Authors: Gregory PJ , Poss R , Eastham J , Micin S
Published: April 2005

We investigated the potential sources of error when using time domain reflectometry (TDR) to measure the water content of sandy soils and evaluated the technique as a means of measuring evaporation from columns of soil and changes in soil water storage beneath crops. Inaccurate depth location of the transmission lines or the development of a hole at the tip of the transmission lines introduced an error about 10 times larger than the errors associated with hardware and software. Calibration in two sandy soils gave a curve of similar shape to that found by others except for values of dielectric constant < 6 when measured values of water content were less than those expected. Daily evaporation from soil columns measured by weighing and with TDR showed large differences between the two techniques (up to 32%) but compensating errors over time allowed cumulative evaporation to be estimated with TDR to within 6.6% of that determined by weighing over a 162 h period. Under field conditions, the agreement between TDR and neutron probe measures of changes in soil water storage in the upper 0.3 m was good and generally within 10% over both 14 day and longer periods.
Liming effects on soil exchangeable and soil solution cations of 4 soil types in north-eastern Victoria
Authors: Slattery WJ , Morrison GR , Coventry DR
Published: April 2005

The effects of lime additions on exchangeable and soil solution cations of four soil types in north-eastern Victoria are discussed. Liming significantly (P < 0.05) reduced the concentration of exchangeable (1 M KCl), extractable (0.01 M CaCl2), soil solution total and monomeric aluminium. Raising the soil pHCa to 4.8 decreased Ale, concentrations below 1 mg kg-1, Al saturation % of the effective cation exchange capacity below 5 and AlTot below 5 PM; and raising the soil pHCa to 5.8 decreased MnCa concentrations below 10 mg kg-1 and AlTot below 2�m on the four soil types used in this study. Grain yield responses were best described by the sum of the activities of the Al monomers. Where organic C was present, responses could also be attributed to the complexing of monomeric Al. Grain yield responses could not always be reliably predicted by the Al saturation % of the effective cation exchange capacity. Liming significantly (P < 0.05) increased the concentration of Ca in the ECEC, but the Ca activity was not well correlated with lime response for all sites. The In ratio of aCa2+/�aAl- mono shows promise in predicting negative responses to lime applications (with values > 6) where soil pHCa is less than 5. The combination of Ca activity and the sum of the activity of the Al monomers, together with organic C content, may provide a better description of the responsiveness of acid soils to lime applications.
Management-practices and soil biota
Authors: Roper MM , Gupta V
Published: April 2005

The soil biota consist of a large number and range of micro- and macro-organisms and are the living part of soils. They interact with each other and with plants, directly providing nutrition and other benefits. They regulate their own populations as well as those of incoming microorganisms by biological control mechanisms. Microorganisms are responsible for organic matter decomposition and for the transformations of organically bound nitrogen and minerals to forms that are available to plants. Their physical structure and products contribute significantly to soil structure. Management practices have a significant impact on micro- and macro-organism populations and activities. Stubble retention, an increasing trend in Australia, provides an energy source for growth and activity. Significant increases in the sizes and activities of microbial biomass, including heterotrophic microorganisms, cellulolytic microorganisms, nitrogen-fixing bacteria and nitrifying and denitrifying bacteria have been observed. In addition, increases in protozoa and meso- and macro-fauna have been seen. Stubble retention provides a means of maintaining or increasing organic matter levels in soils. The way in which stubbles are managed may impact further on the activities of the soil biota and may alter the population balance, e.g. bacterial:fungal ratios. In general, no-tillage results in a concentration of microorganisms closer to the soil surface and causes least disruption of soil structure compared with conventionally tilled soils. Some plant diseases increase with stubble retention and with no-tillage, particularly where the next crop is susceptible to the same disease as the previous crop. However, the general increase in microbial populations resulting from stubble retention can exclude pathogens through competitive inhibition and predatory and parasitic activity. Cropping sequences may be used to break disease cycles. Crop rotations that include legumes may provide additional nitrogen and stimulate mineralization processes. Coupled with no-tillage in stubble retention systems is an increased usage of herbicides to control weeds. Continued herbicide use has been shown to significantly depress some groups of microorganisms and some of their activities but, in Australia, little information is available about the effects of herbicides on microbial populations. Although we know that micro- and macro-organisms are vital in maintaining ecosystem function, our knowledge about them is still very limited. New techniques in molecular microbial ecology promise further advances. Much more detailed information about the effects of specific managements on the size and activities of populations is needed. Soils and their processes are extremely complex and, in order to develop appropriate management practices, integration of new and existing information is necessary. This is now being made possible through computer simulation modelling.
Field-based comparison of platinum and wax impregnated graphite redox electrodes
Authors: Biddle DL , Chittleborough DJ , Fitzpatrick RW
Published: April 2005

An inert electrode was constructed using wax-impregnated graphite (WIG) as an alternative to Pt for permanent installation in the regolith. The performance of WIG electrodes has not previously been systematically evaluated by using data from field trials, although Pt and WIG measure similar Eh values in laboratory solutions. We compared the performance of the WIG electrode when installed adjacent to Pt redox electrodes in the A, B and C horizons of duplex soils in a X-eralf-Aqualf toposequence near Mount Crawford in the Mt Lofty Ranges, South Australia. Lower potentials, commonly in the order of 200 mV, were measured from WIG electrodes, relative to Pt electrodes. Measurements of potential from adjacently installed WIG and Pt electrodes did not show significant correlation. Generally oxidizing redox potentials were measured in all soils in which electrodes were installed due to below average rainfall during the sampling period. Further testing of WIG electrodes in reduced regolith is needed. Interpretation of Eh trends, measured using Pt electrodes, between the A, B and C horizon are presented.
Lime-slotting technique to ameliorate subsoil acidity in a clay soil .1. Effects on soil-pH and physical characteristics
Authors: Kirchhof G , Jayawardane NS , Blackwell J , Murray E
Published: April 2005

In soils with subsoil acidity, root growth of plants sensitive to acidity is restricted to surface layers resulting in reduced water and nutrient uptake and low yields of crops. In the present study, the use of the lime-slotting technique, with slots 0.15 m wide and 0.8 m deep, for providing long-term improvements of the adverse soil chemical and physical characteristics of an acid, clay soil was investigated. Lime-slotting using a rotary slotter resulted in a uniform increase in soil pH to the full depth of the slot (0.8 m), indicating a thorough mixing of the lime with the small soil fragments produced by slotting, as they are thrown up into the rotor shroud and redeposited in the slot. In contrast, ripping to 1.0 m depth and delve ploughing to 0.8 m depth only changed the soil pH close to the soil surface. The saturated hydraulic conductivity, total porosity and air-filled porosity at a potential of - 10 kPa measured on soil cores was significantly (P < 0.05) increased within the slot, compared to the undisturbed soil. Values of unsaturated hydraulic conductivities K(�) and diffusivities D(�), calcualted from the saturated conductivity and water potential-water content relationships, also showed increases in the slot, at high water contents. Although a polishing of sections of the slot wall due to rubbing of the rotors was observed in the field, the saturated conductivities of the cores taken across the slot walls did not show significant (P < 0.05) differences compared with the undisturbed soil adjacent to the slot. The extent of protection of the loosened soil in the slots from recompaction during subsequent farm trafficking was evaluated in a vineyard. Soil strength measurement showed distinct differences between field plots which were non-ameliorated, lime-slotted or deep ripped. Soil strength was estimated using penetrometer cone index measurements, which were made when the soils were at similar water contents. Zones of high soil strength observed in the non-ameliorated soils, were reduced in the ripped and slotted soil. However, the upper part of the ripped soil had soil strengths higher than the lower part, indicating repacking under trafficking. In contrast in the slotted soil, the slotted area had low soil strength to depth, indicating greater protection of the loosened soil during trafficking. This could be due to bridging of the tractor wheels and implements across the slot on to the stronger undisturbed soil on either side. Thus, lime-slotting is an effective technique for long-term amelioration of the adverse physical and chemical properties of dense clay soils with subsoil acidity. This should encourage root growth to depth within the slots, and use of the water stored in the subsoil.
Lime-slotting technique to ameliorate subsoil acidity in a clay soil II. Effects on medic root-growth, water extraction and yield
Authors: Jayawardane NS , Barrs HD , Muirhead WA , Blackwell J , Murray E , Kirchhof G
Published: April 2005

Subsoil acidity causes low crop production, which is often associated with shallow root development and restricted soil water extraction. In part I of this series, lime-slotting of an acid soil was shown to improve the soil physical and chemical characteristics for root growth. In a lysimeter study on an acid soil, the effects of several soil ameliorative treatments on root growth, water extraction and yields of a medic crop were evaluated. Large lysimeter cores of 0.75 m diameter and 1.35 m deep were used. The soil treatments included a non-ameliorated acid soil, lime-slotting with a 0.15 m wide and 0.8 m deep slot containing 20 t ha-1 of lime, lime-slotting combined with surface phospho-gypsum application at 10 t ha-1, and complete amelioration of the entire soil volume by mixing lime at 133 t ha-1 and repacking to a low bulk density of 1.1 t m-3. In the non-ameliorated acid soil, medic roots were confined to the surface (0.1 m) layer, resulting in limited water extraction of 32 mm during a prolonged drying cycle, and a low dry matter yield of 70 g m-2. In the lime slotted soil, roots grew within the slot to its full depth, although penetration into the undisturbed soil was restricted to the soil immediately adjacent to the slot. Consequently, the root length per unit surface area (La) at depths below 0.1 m depth was increased to 9.9 km m-2. During a drying cycle, water extraction increased to 58 mm. The increased water extraction came from both the slotted soil and the undisturbed soil between slots. This led to an increase in dry matter yields to 270 g m2. In lime-slotted soils with surface gypsum applications, the root growth and crop water extraction patterns were similar to the lime-slotted soil. Repacking limed soil resulted in similar root lengths (L(a) 10.0 km m-2) as lime-slotted soil. However, owing to more uniform distribution of roots in the repacked soil, water extraction was increased to 100 mm and yields increased to 590 g m-2. Yields of non-ameliorated soil were only 12% of the repacked, limed soil. However, lime-slotting which involves loosening only 25% of the soil surface area and addition of only one-sixth of the amount of lime required for complete soil amelioration, led to marked increases in yield (46% of the yield of repacked soil). Future field studies are required to evaluate the optimum limed-slot configurations required for different soils, crops and climatic regimes.
Interaction effects of solution pH and calcium-concentration on Lupin (Lupinus-Angustifolius L) growth
Authors: Birchall C , Jessop RS , Sale PWG
Published: April 2005

The effects of sand solution calcium (Ca) concentration and pH on the growth of narrow-leafed lupin (Lupinus angustifolius L.) were examined in an attempt to assess the relative importance of these two soil factors. Two pH (6.5, 8.5) and three Ca concentration treatments (0.625, 6.25, 16.25 mM) were applied by growing lupin in columns of sand which were flushed regularly with otherwise complete nutrient solutions. Root and shoot weights 63 days after sowing were reduced by both increasing pH and increasing Ca concentration. The pH x Ca interaction effect on shoot weight suggested increasing Ca played an important role (which was greatest at pH 6.5) in reducing lupin growth. It was unlikely that growth was reduced by either disrupted iron (Fe) nutrition or poor nodulation of the lupins.
The cropping systems-model PERFECT as a quantitative tool in land evaluation - an example for wheat cropping in the Maranoa area of Queensland
Authors: Thomas EC , Gardner EA , Littleboy M , Shields P
Published: April 2005

The mechanistic cropping systems model PERFECT was validated for six different soils and used as a tool to evalute land suitability of wheat cropping in the Maranoa, a marginal cropping area of Queensland. Using 100 years of historic climate data from the area, and crop, soil and management parameters, simulations provided an objective insight into the key interactions of the cropping system. Current methods of land suitability evaluation are qualitative and rely on the experience of the land resource surveyor and local precedent. Consequently, where local precedent is lacking, as in marginal areas, current methods are considered less reliable and quantiative data from simulation studies will be useful. Using this process, the significance of key components of the systems (climate, plant available water capacity, soil nitrate and soil loss hazard) were quantified. These quantitative data were used to establish critical values for diagnostic attributes for land suitability evaluation in the Maranoa. The role for this approach as a tool in quantitative land evaluation is discussed.
Effect of sewage effluent on soil fauna in a Pinus-radiata plantation
Authors: Yeates GW
Published: April 2005

Water and nutrients in effluent applied to land may influence soil processes. This study uses late summer and autumn samples to assess changes in litter and soil fauna under a 17-year-old Pinus radiata plantation on dune sands of the Waitarere-Hokio association after 7 years of spray irrigation of sewage effluent. Populations estimated included 12 groups of litter arthoropods, earthworms, enchytraeids, tardigrades, rotifers and nematodes. Three groups of litter arthropods (adult diptera, spiders and aphids) were significantly less abundant in the effluent-treated area than in the unirrigated control. Increased moisture content was apparently responsible for greatly increased populations of earthworms and nematodes in the effluent-treated area. Bacterial-feeding and predatory nematodes showed marked increases, while fungal-feeding nematodes declined significantly. The nematode maturity index (MI) was lower in all treated plots. After effluent had been withheld for 52 days, there were significant increases in isopods and Collembola. Rotifers were most abundant in the control area. It appears that effluent enhanced physical breakdown of the P. radiata litter. Movement of the decayed fragments into the upper layers of sand may have produced conditions unfavourable for enchytraeids and rotifers.
Microtrenches and microridges on the accretive structural surfaces of some clayey soils
Authors: Sullivan LA
Published: April 2005

Microtrenches (trenches up to 8 �m wide) and microridges (ridges up to 20 �m wide) have been observed during scanning electron microscopic studies of accretive structural pore surfaces in clayey soils. Microtrenches may form by the partial burial of hyphae during clay deposition followed by the lysis or removal of the hyphae, whereas microridges may be formed by complete burial of hyphae during clay deposition.
Magnetic-properties of two soils during reduction, drying and re-oxidation
Authors: Crockford RH , Willett IR
Published: April 2005

As part of a study of the use of magnetic properties to identify sources of sediments in water bodies for erosion studies, changes in the magnetic properties of two soils were determined during extended periods of reduction by saturation and during subsequent drying and oxidation. Mass magnetic properties rose during reduction and declined on re-oxidation. The results showed that a new magnetic compound was formed during reduction and then destroyed upon oxidation. These changes occurred in a soil which did not produce sulfides during reduction and the effects were little affected by amending the soil so that sulfides were formed. It was concluded that the compounds responsible for changes in magnetic properties were complex iron oxides rather than sulfides. Differences between the magnetic properties of wet and air dried samples were considered to be mainly due to physical rather than chemical changes. Therefore, when using magnetic properties as a tool for the identification of sediment sources, diagenesis and the effects of drying need to be taken into account.
Soil-landscape models and soils of Eastern Highlands, Papua-New-Guinea
Authors: Rijkse WC , Trangmar BB
Published: April 2005

Soil-landscape models of three landscapes representative of the Eastern Highlands, Papua New Guinea, have been developed and validated in a study area east of Kainantu. Soils were classified according to Soil Taxonomy. Validation of a model in a strongly dissected landscape predicted soils 88% correctly at Order level, 94% at Suborder and 88% at Great Group and Subgroup level. Soils in weakly dissected landscapes were predicted 96% correctly at Order level, 92% at Suborder and Great Group level, and 88% at Subgroup level. Soils on a simple alluvial terrace system were predicted 100% correctly at Order and Suborder level and 89% correctly at Great Group and Subgroup level. Soils of the strongly dissected landscape are formed from an irregular cover of weathered tephra overlying weathered schist. They are mostly well drained Hapludolls or Argiudolls on steep slopes with Troporthents on slipped slopes. Soils of the weakly dissected landscape are formed from thick weathered tephra. Broad ridges and sideslopes are dominated by Argiaquolls, Argiudolls, Hapludalfs, Hapludolls and Humitropepts with dense concretionary layers of iron and manganese. Soils of the terrace landscape are formed from alluvium and vary from Fluvaquents and Endoaquolls to Hapludolls. General nutrient trends of the soils of the strongly and weakly dissected landscapes show low levels of exchangeable cations, plant available phosphorus and zinc. Profile readily available water is low and clay mineralogy is dominated by kaolinite. Volcanic glass occurs in upper horizons of stable sites. Alluvial soils of the terrace landscape have higher nutrient values, particularly exchangeable magnesium.
Soil aggregates as mass fractals
Authors: Anderson AN , Mcbratney AB
Published: April 2005

Soil aggregates have a fractal mass. That is, they are porous and, as they are studied in greater detail, more pores may be observed. Mass fractals have scale-dependent bulk density. Larger objects, or soil aggregates, have a smaller bulk density. Bulk density in soil studies is sometimes assumed to be constant. If this was the case, soil aggregates would not be mass fractals, and their porosity would not change with scale. The fact that soil aggregates are mass fractals places restrictions on the estimation of the fragmentation fractal dimension (Df) of soil. The mass fractal dimension of soil (Dm) may be calculated from bulk density-aggregate size data. Linear and nonlinear methods of estimating Dm were compared and were shown to give similar results. The Dm is shown to influence porosity and the saturated water content. Fractal theory, in particular Dm, has implications for the calculation of the pore-size distribution and the moisture characteristic. By equating Campbell's (1985) Version of the Brooks-Corey water retention function, � Proportional �(-1 / b)and an equivalent form to the Brooks-Corey relation given by Crawford (1994), � Proportional �(Dm - d) it is suggested that D-m = d - 1/b, where d is the embedding dimension.
Surface erosion assessment in the South-Canterbury downlands, New Zealand using 137Cs distribution
Authors: Basher LR , Matthews KM , Zhi L
Published: April 2005

Redistribution of the radionuclide tracer 137Cs was used to examine the pattern of erosion and deposition at two sites with contrasting long-term land uses (pasture and cropping) in the South Canterbury downlands, New Zealand. There were clear differences between the two land use types in variation in 137Cs concentrations and areal activity, erosion rates and topsoil depth variability. Erosion and deposition have resulted in greater variability and lower mean levels of 137Cs areal activity under cropping (46.3 mBq cm-2) than pasture (55.0 mBq cm-2). At the cropping site, erosion and deposition roughly balanced with the mean value over all sampling sites, suggesting no net soil loss, but considerable redistribution of soil within paddocks. At the pasture site results suggested slight net deposition. There was evidence for both sheet/rill and wind erosion being important in soil redistribution. While there was no difference in mean topsoil depth between pasture and cropping, there were significant differences with slope position. At the pasture site, there was little variation of topsoil depth with slope position, except for swales which tended to be deeper, whereas at the cropping site there was considerable variation in topsoil depth with slope position. Topsoil depth was a poor indicator of erosion status.
Effect of management practice on properties of a Victorian red-brown earth .1. Soil physical-properties
Authors: Lorimer MS , Douglas LA
Published: April 2005

The effects of five management practices (native forest, native pasture, Phalaris pasture, crop-pasture rotation, continuous cropping), that had been in place for 18 years, on some soil physical properties of a red-brown earth near Bendigo, Victoria, were studied. Particle size distribution, bulk density and hydraulic conductivity of soil in the A and B horizons at different, management sites were measured. Where cultivation had occurred, soil in the A horizon contained less silt and clay, and more fine sand and coarse sand. The bulk density of the A horizon of soil that had produced at least six wheat crops since 1969 was greater than that of soil used for pasture or forest, while the hydraulic conductivity of soil cropped every year since 1969 was much less than that of soil under native forest. Particle size distributions for soil from the B horizons at the five management sites were found to be similar. Where pastures and crops had been established, the hydraulic conductivity of the upper B horizon was lower, and the bulk density was higher, than that of soil in the native forest (Eucalyptus spp).
The effect of sulfate and fluoride on the mobility of aluminum in soil
Authors: Bond WJ , Smith CJ , Gibson JAE , Willett IR
Published: April 2005

The effect of the coordinating anions sulfate and fluoride on the soil pH and Al concentration, and on the transport of Al, was studied during unsaturated how in columns of an Oxisol. The soil was infiltrated with 0.1M NaCl, 1 or 10 mM SO2-4 , 1 mM F-, 1 mM Al, 1 mM Al with 1 or 10 mM SO2-4 , and 1 mM Al with 1 or 10 mM F- in a background of 0.1 M NaCl. The pH of the infiltrating solution was adjusted to 3.0. The inflowing solutions all caused a decrease in pH (relative to the initial value) near the column inlet and an increase further away from the inlet. The distance over which the change near the inlet occurred was greatly increased when Al was included in the inflow solutions. The magnitude of the pH change was affected by the accompanying anion; both SO2-4 and F- resulted in a higher pH, with 10 mM F- causing the greatest effect. Total solution Al concentration and the level of exchangeable (KCl-extractable) Al showed similar, but inverted, patterns compared with pH. Again, F- caused the greatest effect and resulted in large decreases of Al in both the solution and exchange phases. A consistent relationship between pH and pAl was observed which was in part related to that determined in earlier batch experiments, but it was apparently not at equilibrium. The relationship between solution and exchangeable Al measured in the columns agreed closely with the Al adsorption isotherm determined previously for this soil. The effect of SO2-4 on pH, concentrations of Al species, and Al transport was as predicted from earlier batch studies, the addition of SO2-4 resulting in enhanced retardation of Al transport caused by a steepening of the Al adsorption isotherm. The effect of F- was not totally in accord with earlier findings, which predicted an increase in the proportion of total Al in solution upon addition of F- and an enhancement of transport; in fact the opposite occurred. It is argued that the increased importance of the formation of Al-F minerals at the low solution to soil ratios in the column experiments caused this shift, in the distribution of Al between solution, KCl-extractable, and solid phases. It was therefore concluded that batch measurements have limited application to the prediction of Al chemistry at realistic soil water contents. It was further concluded that, while F- formed very strong complexes with Al, neither SO2-4 nor F- enhanced the transport of Al through soil.
Soil solution chemistry at a Westland-petrel breeding colony, New Zealand - Paleoecological implications
Authors: Hawke DJ , Powell HKJ
Published: April 2005

Surface soil samples from two sites in a breeding colony of Westland Petrels were compared with those from a control with no seabird breeding. Soil solution (-0.025 �m) analyses established significant differences in Al, P and natural organic matter (NOM) chemistry. At the breeding colony sites, low concentrations of total Al in soil solution, combined with high extractable phosphate, indicated formation of insoluble humic-Al-(Fe)-P complexes. NOM in soil solution was estimated from absorbances at 250 nn. NOM was at lower concentrations at the breeding colony and had a lower percentage of Al bound in non-labile complexes (38-86% compared with >97%). Gel filtration experiments showed that soil solution from the breeding area had an NOM size distribution weighted toward smaller size fractions. This is consistent with NOM having different properties at the two sites and could contribute to different processes in pedogenesis. The results reported in this paper support a hypothesis that localized extinction of breeding seabirds following Polynesian settlement has affected soil chemistry in the well leached soils on the West Coast of New Zealand's South Island.