bluuebunny/crossref_metadata_2025 huggingface dataset:
Redistribution of soil water after infiltration
Authors: Peck AJ
Published: April 2005

The one-dimensional vertical redistribution of water is studied following infiltration into deep homogeneous soil with an initially uniform moisture content. There is assumed to be no loss of water by evaporation or transpiration during the redistribution. Assuming two factors to be constants, a first-order ordinary differential equation is derived which can be integrated numerically to compute the mean moisture content in the surface zone of draining soil as a function of the redistribution time. The depth of the draining zone increases with time, and this can be calculated too. That these factors are relatively constant is indicated by analysis of data for several soils and wetting depths over a wide range of redistribution times. Using mean values of the factors for several soils, and only wetting values of the diffusivity and conductivity functions, predicted redistribution behaviour agrees well with experimental data in four of six soils. In the remaining cases calculation of the factors for the particular soils, using an approximate method which includes hysteresis data, gives better results. The model is applied to predict the redistribution behaviour of different soils under identical treatments, and of a single soil for various infiltration quantities and initial moisture contents.
An examination of the wet aggregate analysis, the moisture characteristic, and infiltration-percolation methods of determining the stability of soil aggregates
Authors: Collis-George N , Laryea KB
Published: April 2005

Four methods of assessing structural stability of aggregates which employ different disruptive forces have been examined. Sorptivity (Philip 1957) has been demonstrated to be a useful method of assessing structural stability of soils during infiltration. The results obtained are consistent with those using either the high energy moisture characteristic method of Childs (1940, 1942), the wet aggregate analysis method of Quirk (1950), and the qualitative slaking-dispersion classification of aggregates proposed by Emerson (1967). Using these four methods, one soil was classified as stable, and two unstable to flood irrigation, whereas conventional chemical definitions did not distinguish unequivocally between them.
Water movement in unsaturated soils as influenced by gypsum
Authors: Sharma ML
Published: April 2005

Three soils varying in texture and exchangeable sodium were treated either with distilled water or with a gypsum solution of 10 or 30 m-equiv./l. concentration and their water-flow properties, diffusivity (D), capillary conductivity (K), and weighted mean diffusivity (D) determined. Invariably the treatment of soils with gypsum resulted in increased D and K, the increases being more pronounced near saturation and declining with desaturation. The soil with the highest clay content and exchangeable sodium percentage (ESP) responded most. For the three soils, at the end of the third wetting and draining cycle the highest increase in D and K varied from about 3 to 15 times while D increased by a factor of 2 to 7.5. Wetting and draining cycles resulted in decreased D for all soils when distilled water was used, but only for two soils when 10 or 30 m-equiv. solutions were used. In the soil most responding to gypsum D was slightly increased with increasing number of wetting and draining cycles when gypsum solutions were used. This was due probably to rebuilding of structure by cation exchange, which was lost by slaking and dispersion during the first wetting and draining cycle. The electrolyte concentration of flowing solution did not significantly affect the water flow properties provided that the slaking and dispersion were reduced by a solution of high concentration during the process of cation exchange. At the end of the third wetting and draining cycle, 30 m-equiv. solution gave about 1.7 times higher D compared to 10 m-equiv. for the high clay, high exchangeable sodium soil. This was probably because initial structural loss caused by the first wetting and draining with 10 m-equiv. was not fully regained during subsequent wetting and draining.
Mineralogy of soils from the holocene volcanic area of Southern Australia
Authors: Hamblin AP , Greenland DJ
Published: April 2005

The mineralogy and chemical composition of the soils developed on Holocene basaltic ash deposits in southern Australia have been examined. The bulk of the clay-sized material in all samples was made up of a morphologically continuous gel incorporating small amounts of crystalline primary minerals and layer silicates. Fibrous allophanes were present, but no imogolite. Weathering of the primary material is accompanied in all cases by an increase in the proportion of hydrous oxides (from about 15 to 18%) and a reduction in the Si/Al ratio, irrespective of the age of the deposit. A slight predominance in silicon occurred in the clay samples, but this decreased to a Si/Al ratio of around 1.0 with increasing age and depth of the samples. The variations in the composition of the ash appear to control the formation of subsequent clay types, and no single weathering sequence describes the mineral alterations in the soils of even so restricted a geological and climatic region.
Studies on soil potassium. II. The Q/I relation and other parameters compared with plant uptake of potassium
Authors: Fergus IF , Martin AE , Little IP , Haydock KP
Published: April 2005

Setaria (Setaria sphacelata cv. Nandi) was grown in 10 surface soils, of contrasting properties, in pots until (after repeated harvesting of tops) plant growth virtually ceased. Uptake of potassium by tops and roots was correlated with change in exchangeable potassium during cropping, initial exchangeable potassium, and with quantities of potassium predicted from the immediate Q/I relations of the soils. Some initially non-exchangeable potassium was absorbed from seven of the soils by the plants, such that these soil quantity parameters (which were statistically equivalent) predicted two-thirds of the total potassium uptake averaged over all soils. Potassium uptake was also correlated with soil potassium soluble in constant-boiling hydrochloric acid, and with potassium extracted by a cation exchange resin (both of which predicted about twice the plant absorption). For six of the soils, uptake of initially non-exchangeable potassium was correlated with the quantity of total potassium present in each pot in the 1 0 . 1 pm clay fraction. The intensity of soil potassium (measured in dilute calcium chloride solution from the immediate Q/I relation) was reduced on all soils by exhaustive cropping to a mean value for the equilibrium activity ratio (AR0) of 4.7 10-4 mole1/2 L.-1/2 (�G = -4500 cal equiv.-1); it was suggested that the observed variations in this value were unlikely to prohibit its use for practical soil testing, except for the prediction of the quantity parameter for those soils for which the form of the isotherm is altered by cropping. A tentative value for the potential of soil potassium at which setaria has an adequate average potassium concentration in its tops was - 3600 cal equiv.-1 (AR0 2.1 x 10-4 mole1/2 L.-1/2).
Seasonal and stratigraphic controls in coastal floodplain soils
Authors: Walker PH
Published: April 2005

Soils of the Macleay River coastal floodplain are developed in a relatively thin veneer of alluvium which is underlain by extensive estuarine deposits representing the postglacial rise of sea level. Soil particle size, water table, salt, and pH distributions relate to catenary variations from levee to back swamp and acid aeration products derived from the underlying estuarine beds. Groundwater data from 50 swampland locations for the period 1962 to 1968 showed strong seasonal trends. At 39 sites, water-table level correlated closely and positively (P < 0.05) with rainfall summed for the 6 months (log R6) prior to the month of sampling. Groundwater salinity at 20 sites correlated negatively (P < 0.05) with water-table level. Surface soil salinity up to 7.8% and groundwater pH as low as 2 were recorded during the 7-year period. Aeration experiments showed that reserves of estuarine sediment occurred in certain swamplands which were capable of further acid production. Programmes of swamp drainage need to avoid exposure of these reserves. A system of shallow drains, set no deeper than the upper limit of the estuarine deposits, could be used both to remove excess flood water from back swamps and to remove salts produced by aeration of the estuarine materials.
Soil zinc and its uptake by plants. II. Soil chemistry in relation to prediction of availability
Authors: Tiller KG , Honeysett JL , De Vries MPC
Published: April 2005

Representatives of nine soil groups were extracted with reagents that have been used to predict zinc deficiency. The amounts of soil zinc removed were discussed in terms of specific and non-specific bonding in relation to the reagent used. The desorption of natural zinc was also described in terms of the quantity/intensity (Q/I) relation and an equilibrium zinc concentration (ZnQ) at natural pH. The ZnQ values varied from 1 to 4 �gI. for the alkaline soils and 8-190 pg/l. for the acidic soils. The Q/I ratio was derived by radioisotopic and chemical isotherm procedures. Log Q/I (I = total soluble zinc) approximated closely a linear relation of unit slope with pH. This was ascnbed to a common reation of zinc with all soils by specific sorption dominated by ZnOHA ions such that Q/I� = constant where I' = (ZnOH+aq). Deviations from this relation are discussed. The relations between soil and plant (clover and wheat) variables were studied by simple and multiple regression analysis. Single values of intensity variables, and, to a lesser extent, Q/I variables, correlated well with plant data but not the quantity variables. The improved correlations of Q variables when combined with Q/I variables accorded with published work. The problem of predicting zinc availability on alkaline soils which are dominated by very high Q/I values, is discussed.
Soil moisture distribution during two-dimensional absorption from a cylindrical source
Authors: Talsma T , Parlange J , Groenevelt PH
Published: April 2005

The moisture content distribution in a fine sand, during two-dimensional, horizontal, absorption from a cylindrical source, was analysed using a recently developed theory. Well-justified approximations yield the result that, for a particular rigid porous medium, the time course of the moisture profile depends only on two functions, each of which depends on the moisture diffusivity function. This permits the reduction to a common basis of experimental results on a single soil, using different source dimensions and sampling at different times. Moisture profiles, obtained experimentally after various absorption times and with two source radii, were in satisfactory agreement with the theory.
Contamination of soil with zinc, copper, lead, and cadmium in the Wollongong city area
Authors: Beavington F
Published: April 2005

From a grid sampling procedure over 56 km2 of the Wollongong city area, levels of acetic acid-extractable soil zinc, lead, and cadmium, and EDTA-extractable soil copper, have been investigated. Mean levels of these metals in four groups of urban grassland, namely, farm land, recreational land, industrial land, and roadsides, are up to 10 times greater than those in a rural control area. Highest levels of all four metals are found in the Port Kembla industrial area, where 21 samples within 1 km of the main heavy metals smelting complex have mean values of 82 p.p.m. zinc, 343 p.p.m. copper, 21 p.p.m. lead (15 samples), and 2.8 p.p.m. cadmium (11 samples); mean levels in the rural area are 2.7 p.p.m. zinc, 5.3 p.p.m. copper, <1 p.p.m. lead, < 1 p.p.m, cadmium. Profile samples show that all four contaminants were very largely concentrated in the top 15 cm soil, confirming an airborne origin.
Diurnal water stress in plants grown on a coarse soil
Authors: Carbon BA
Published: April 2005

Sorghums were grown on a coarse deep sand under various sprinkler irrigation regimes. Bulk soil water potentials under all treatments remained in the range of 0 to - 1000 cm throughout the experiment. Measurements of leaf water potential showed a rapid diurnal change from no plant water stress at dawn, to large negative potentials in mid-afternoon. It is concluded that, at least in part, this stress was a direct consequence of the unavailability of soil water to meet the potential demand of the plant. Theoretical and experimental evidence suggests that the rate of supply of soil water was limiting. Increased diurnal water stress reduced plant growth and tiller numbers in forage sorghum, and delayed time to flowering in grain sorghum. Less water was evaporated from the treatments showing the greatest levels of diurnal water stress.
Relationship between a soils ability to adsorb phosphate and the residual effectiveness of superphosphate
Authors: Barrow NJ
Published: April 2005

Twenty-two unfertilized soils from four localities in south-western Australia were used in a pot trial. In March powdered, single superphosphate was applied to the surface of eight of the pots at a range of levels. All the pots were kept moist until August when subterranean clover seed was sown and fresh superphosphate was applied to the previously unfertilized pots. Response curves were fitted to the yields and from the coefficients of the curves the relative effectiveness of the March and the August applications was calculated. For most of the soils, the March application was between 50 and 60% as effective as the August application. There was a small but significant trend for the relative effectiveness to increase as the soils' ability to adsorb phosphate from solution (�P) increased. There was a close relationship between the effectiveness of the August application and the inverse of �P. Since �P is a measure of the distribution of phosphorus between the solid and the solution phases in the soil, it was argued that the decreased effectiveness of the March application could be explained by a change in the distribution of phosphate. An incubation experiment showed that such a redistribution occurred and that the proportional change was little affected by �P. This seemed to explain the small effect of �P on decrease in effectiveness.
Aggregation of clay by the products of iron (III) hydrolysis
Authors: Blackmore AV
Published: April 2005

An attempt has been made to discover the mechanism of iron cementation in clays by comparing the aggregation effected in dispersed pure mineral clay by its exposure to different stages in the active hydrolysis of a ferric chloride solution. Contact of the clay with the early products of the hydrolysis is apparently necessary for the achievement of stable bonding; clay mixed with the gelatinous precipitate formed at the end of the hydrolysis is not stably aggregated, but a combination of these two phases produces aggregates which are particularly resistant to normal dispersion treatment. The results are discussed in terms of the kinetic steps in the hydrolysis of iron(III) solutions, and their implications for structure formation in soils are outlined.
The temperature profiles of soil columns during infiltration
Authors: Collis-George N , Lal R
Published: April 2005

Liquid front movement and temperature profile development during infiltration were determined for columns of aggregates of a non-swelling kraznozem and a swelling chernozemic soil at two initial moisture regimes. The temperature front can be divided into three zones: (a) A zone of vapour condensation and temperature rise; (b) a zone between (a) and (c) where temperature falls and heat is lost by conduction to the Liquid Wetting Front; (c) a zone starting at the liquid wetting front and with temperature decreasing to ambient. The mechanisms of vapour diffusion under a vapour pressure gradient, of liquid flow under a potential gradient, of heat conduction under a temperature gradient, and of transport of heat by convection by water and by vapour condensation occur simultaneously and qualitatively explain all the observed results, without recourse to other models. In one soil, there is also transfer of heat ahead of the condensation front as hot air. Heat balance procedures are used to show that the thermodynamic heat of wetting obtained from the adsorption isotherms is the dominant quantity in each experiment, if corrections are made for the radiant heat loss by the columns. The results are discussed in terms of infiltration into unstable soils. It is concluded that the multiple-transfer mechanisms first collectively discussed by Philip and de Vries can be applied directly to these systems.
Aggregation in swelling clay soils
Authors: Coughlan KJ , Fox WE , Hughes JD
Published: April 2005

Dry sieving, wet sieving, and aggregate bulk density measurements were used to study the mechanisms of dry aggregate formation in three swelling clay soils. These experiments showed that, for a given soil, a single probability function can be used for all dry aggregate fractions to predict their water stability and the distribution of water stable aggregates in their unstable portions. This result is explained in terms of the mode of formation of dry aggregates. Coarse aggregation in these soils was attributed to the binding action of dispersed clay. Soil disruption experiments showed that, above a certain moisture content, soil samples were susceptible to disruption by mechanical action. This moisture content is linearly related to the specific surface area of the soil, and agrees closely with the soil liquid limit. Aggregate disruption in the coarsely aggregated soil sample is explained in terms of soil mineralogy and electrolyte concentration. The effect of rate of reflocculation of disrupted clay on soil aggregation is considered.
The comparative effects of exchangeable calcium, magnesium, and sodium on some physical properties of red-brown earth subsoils. I. Exchange reactions and water contents for dispersion of Shepparton soil
Authors: Bakker AC , Emerson WW , Oades JM
Published: April 2005

The susceptibility to waterlogging of red-brown earth subsoils is discussed. One of these, Shepparton, has been leached with chloride solutions of given SAR, in the range 0-7, the last solution being 1 mM in calcium or magnesium. The soil was then extracted with neutral lM ammonium chloride and the displaced cations measured. The exchange of sodium for both calcium and magnesium was similar, following the Gapon equation except at very low SAR values. Some potassium and sodium was extracted from calcium and magnesium soils. Shepparton soil of known SAR was remoulded over a range of water contents and synthetic aggregates formed. The percentage of the clay fraction which dispersed from the aggregates was measured. The water content for perceptible dispersion of magnesium soil was only about half that of calcium soil, the water contents being near the 15 bar and 0.1 bar values respectively for unsheared soil. The water content for dispersion decreased sharply with increasing SAR of the soil. Calcium-sodium soil with an ESP of 3.5 dispersed at the same water content as magnesium soil. Possible reasons for the enhanced dispersion of sheared, wet magnesium soil compared with similar calcium soil are discussed.
The comparative effects of exchangeable calcium, magnesium, and sodium on some physical properties of red-brown earth subsoils. III. The permeability of Shepparton soil and comparison of methods
Authors: Bakker AC , Emerson WW
Published: April 2005

Beds of aggregates of Shepparton soil were leached with calcium chloride or magnesium chloride or with chloride solutions of given SAR with either calcium or magnesium as the complementary cation to bring the aggregates to a known ESP within the range 2.6-5.2. The last solution was 1 mM in the divalent cation. Water was then allowed to flow slowly through and the decrease in the flow rate measured. The permeability of aggregate beds washed with calcium or magnesium showed only a negligible decrease with time. With sodium present, the rate of decrease for a given ESP was faster the greater the initial flow rate of the water and also for smallersized aggregates. The ESP required to produce a given decrease in flow rate was reduced when magnesium was the complementary cation rather than calcium. The flow patterns are explained in terms of the rate of dispersion of clay from the aggregates in sympathy with the rate of loss of soluble salts, rather than detachment due to viscous drag. Four methods of measuring aggregate stability in water have been described in this series of papers. Their possible use to predict whether sodium in conjunction with magnesium will reduce water transmission through subsoils compared with similar calcium soils is discussed.
Evaluation of clay mineral equilibria in some clay soils (usterts) of the brigalow lands
Authors: Veen AWL
Published: April 2005

A model of the thermodynamic stability of the montmorillonite-kaolinitequartz system is constructed on the basis of published values of standard free energies of formation. The effect of differences in stability of montrnorillonite is estimated by considering different montmorillonites. Compositions of soil solutions from soil samples from the brigalow lands of south-east Queensland with a montmorillonite-kaolinite-quartz mineralology are plotted against equations for the montmorillonite-kaolinite, montmorillonite-quartz, and montmorillonite-kaolinite-quartz equilibria. The effect of different assumptions regarding the relation between the composition of saturation extracts and soil solutions is shown. A shallow surface zone is established with a chemical environment favourable to the formation of montmorillonite. In the deeper layers the soil solution is much closer to equilibrium with the mineral constituents, or quartz may be favoured instead of montmorillonite. Kaolinite cannot form in the present chemical environment. The high kaolinite content, therefore, is suggested to be a relict from an earlier phase of soil formation. It is further suggested that the strong gilgai, and the acidity of the deeper soil layers, may be explained by the hypothesis that montmorillonite has formed in originally kaolinitic materials, because the kaolinite to montmorillonite conversion is accompanied by volume increase, and release of H+ ions.
Sorption and precipitation of iron on koalinitie. V. Comparison between kaolinite and ion exchange materials
Authors: Fordham AW
Published: April 2005

The uptake of low concentrations of iron(III) by ion exchange materials was measured in the presence of relatively concentrated supporting electrolyte solutions. The results were compared with those obtained under the same conditions in the preceding study of kaolinite suspensions. Distinctive differences between kaolinite and strongly acidic polystyrene resin systems at 0.15M ionic strength were found in (a) the nature of the sorption-pH relationships, (b) the reversibility of the reaction with respect to both concentration and temperature, (c) the effects of competing ions, and (d) the extraction of iron after sorption. Such observations confirmed that the iron-kaolinite bond formed under these conditions was stronger than that normally produced by electrostatic attraction at ion exchange sites. When the electrolyte concentration was lowered to 0.01M , some of the above characteristics of ion exchange uptake appeared in kaolinite systems. A comparison of the effects of time, temperature, and ionic strength between iron sorption by kaolinite and by cellulosic ion exchange materials suggested that both ion exchange and specific sorption mechanisms were operating at the lower ionic strength.
A soil catena on weathered basalt in Queensland
Authors: Gunn RH
Published: April 2005

Deep weathering in the upper layers of basalt flows in central Queensland led to the deveIopment of lateritic profiles with a surface cover of leached red clay soils overlying ferruginous and mottled zones. Subsequent erosion and bevelling of the weathered mantle left small residuals of the old surface and exposed the underlying weathered zones. In places the mantle was completely removed to uncover fresh rock. A soil catena comprising six zones with associated discrete plant communities developed in these landscapes. Soil differences are related to variations in the intensity of weathering of parent materials and the leaching, translocation, and precipitation of differentially soluble and mobile constituents of the parent rock. The sequence of clay minerals is kaolinite -->kaolinite + randomly interstratified material + montmorillonite --> montmorillonite. The distribution of the plant communities is closeIy associated with variations in soil properties, particularly those which affect water relationships.
The effect of initial moisture content and infiltration quantity on redistribution of soil water
Authors: Talsma T
Published: April 2005

The effects of initial moisture content and infiltration quantity on redistribution of water were studied in a loam, a fine sand, and a coarse sand. Moisture profiles during redistribution were obtained by gamma ray attenuation. Measured values of the hydraulic properties of these soils were used to calculate fluxes at the transition from drainage to wetting. The results were used to check a recent analysis of Peck. Gravity effects dominated in both sands, while in the loam capillary effects dominated at the smaller initial moisture contents and infiltration quantities. In all materials, increasing initial moisture content or infiltration quantity increased the contribution of gravity to the flux at the transition, and decreased the contribution due to capillary potential gradients. For a particular material, it depends on the magnitude of these fluxes whether mean moisture contents in the draining zone will be higher or lower at increasing values of initial moisture content or infiltration quantity.
Salt and water movement in relatively dry soil
Authors: Scotter DR
Published: April 2005

When dry crystalline salt is placed in contact with relatively dry soil, water is found to accumulate in the soil immediately adjacent to the salt, and dissolved salt moves into this wetter region. A recent paper by Parlange presents a theory modelling the salt and water movement in such situations. To allow this theory to be checked against experiment, basic data on water potentials and water and salt diffusivities as functions of water content for the particular soil used are necessary. Such data, as well as data showing salt and water movement in soil near crystalline salt, are reported and used to check the Parlange theory. The theory is shown to have some limited success in predicting the salt movement into the soil, but to inadequately explain the water distribution in the wetter region adjacent to the crystalline salt. It is suggested that this failure is due to significant water movement in the vapour phase into the wetter soil, which is not accounted for in the theory.
Influence of some soil properties on Wimmera wheat yields
Authors: Ford GW , Jessop RS , Martin JJ
Published: April 2005

In two experiments the growth and grain yield of wheat were compared on calcareous grey and brown clay soils, and related to seasonal changes in soil water, mineral nitrogen and labile (mineralizable) nitrogen. The soils occurred at the sites either as a mosaic (experiment 1) or as topographically distinct areas in the same paddock (experiment 2). Soil type did not affect grain yield in either experiment, although the more favourable seasonal conditions in 1971 (experiment 2) resulted in substantially higher yields. In experiment 2, grain protein content was highest on the grey clay, and was associated with a lower lability of organic nitrogen in the brown clay. In both experiments mineral nitrogen was predominantly nitrate. It declined during crop growth to very low levels by flowering; increases during grain ripening were small. The net decline in mineral nitrogen closely approximated plant uptake in both experiments. Losses due to leaching and denitrification appear to be small. Labile nitrogen increased during crop growth, probably as a result of the 'rhizosphere effect'. Soil type affected the depletion of soil water by the crop; consumption was higher in both grey clays, partly due to lower depletion from the subsoils of the brown clays. In experiment 2 this was associated with restricted root development in this zone. In both experiments the crops had depleted soil water to below the - 15 bar level by flowering; stress during grain filling was greatest in experiment 1, and higher on the brown clays.
Salt content of lateritic profiles in the Darling Range, Western Australia
Authors: Dimmock GM , Bettenay E , Mulcahy MJ
Published: April 2005

Soil cores from some 40 complete laterite profiles as deep as 40 m in the Darling Range, W.A., have been examined for salt content, and in some cases, pH. The sites cover a range of topographic situations from divides to valley floors, and of rainfall from 560 to 1350 mm per annum. Increases in surface soil salinity and in the salt concentration of water yields following clearing of the native hardwood forest are related to the amounts of soluble salts stored in the lateritic pallid zones. Storage increases as rainfall decreases in all slope situations. In low rainfall areas (<800 mm per annum) the salt stored under unit area of landscape in the profile down to bedrock is five times greater than in high rainfall areas (≫1000 mm per annum). One area with an annual rainfall of 600 mm has an estimated storage of nearly a million kg of total salts per ha and marked increases in surface soil salinity have occurred within 10 years of clearing. Although in the past, increasing soil salinity has mainly affected agricultural land, the present emphasis on bauxite mining in the forested areas of the Darling Range, particularly in the drier parts, poses new problems in revegetating the exposed saline and acid pallid zone clays after mining operations have ceased.
Moisture profiles in swelling soils
Authors: Talsma T
Published: April 2005

In situ moisture profiles are examined, in two soils of clay texture and in a loam, for the condition of equilibrium about a water table. In addition, moisture profiles during periods of approximately steady upward flow are examined in one of the soils of clay texture. Equilibrium moisture profiles in the clay soils are typical of the 'hydric' profiles which have been predicted for swelling materials. Upward water movement occurs against the moisture gradient. The equilibrium profile in the loam is typical of those observed for non-swelling materials.
Recognition of gypsum-responsive soils
Authors: Loveday J
Published: April 2005

Gypsum response for 53 soils has been measured in terms of air-dry crust strength (resistance to penetrometer, Y1) and subterranean clover seedling emergence (Y2) in three glasshouse experiments. It was also measured in terms of hydraulic conductivity (Y3) of samples taken from the treated and untreated soils at the end of the experiments, and this proved to be the most sensitive response measure. Relationships between these response measures and a variety of soil properties have been examined by regression and canonical correlation analyses. A regression of Y3 on three properties, i.e. dispersion index, and percentage exchangeable sodium and magnesium, gives the greatest predictability (R2 86%). Regressions involving a pair of easily determined properties, dispersion index and pH, give reasonable predictability (R2 = 70, 73 and 77% respectively for Y1, Y2, and Y3). Limits to the values of Y1, Y2, and Y3 have been set to provide three categories of gypsum response, viz. strong, moderate and little or no response. It is argued from a general understanding of the ameliorative process that the predictive equations should be of value beyond the areas sampled in the present study.
The development of a typical red-brown earth
Authors: Oertel AC
Published: April 2005

Translocation of clay did not play a significant role in the development of the Urrbrae loam, a typical red-brown earth. This is shown by the manner of variation with depth of several features of the profile. Both A and B horizons apparently originated as distinct sedimentary deposits containing clay, any additional clay being formed in position.
Estimation of groundwater accession to and evaporation from a South Australian lake using environmental tritium
Authors: Allison GB
Published: April 2005

Groundwater throughflow in a small lake (volume = 9.6 x 104 m3) which penetrates a limestone aquifer in southern Australia, is estimated to be c. 3.0 x 104 m3/yr. To make this estimate, use was made of both a short-term and a long-term tritium balance for interpreting the environmental tritium concentration of lake water and surrounding groundwater. This value compares well with estimates made using groundwater isopotentials and lake and groundwater chemistry. Knowledge of the groundwater component of the water balance has enabled an estimate of lake evaporation to be made.
The association of phosphorus with iron in ferruginous soil concretions
Authors: Taylor RM , Schwertmann U
Published: April 2005

Ferruginous concretions from various Australian and German soils and samples of bog iron ore from various European localities were examined by X-ray diffraction and electron microprobe techniques. The association between phosphorus and iron in these samples was looked at from the point of view of differences in iron mineralogy and genesis. When surface area is considered it appears that hematite, goethite and possibly maghemite show phosphorus adsorption levels in the same order of magnitude as those obtained on synthetic preparations of these minerals. In most cases a high phosphorus content is associated with a high iron, but the converse is not true, so that although the iron minerals are definite sinks for the phosphorus in the environment a linear relation cannot be expected due to the variation in time and spatial distribution of these two elements. In the younger European soils the phosphorus/iron ratios are generally higher (average 0.015), reaching values as high as 0.05 in some bog iron ores formed in gleys, whereas in the older Australian soils the average ratio is 0.002.
Direct measurement of the composition of soil components which retain added arsenate
Authors: Fordham AW , Norrish K
Published: April 2005

The combined use of autoradiography, electron microscopy and electron probe microanalysis provided a direct method of defining the location of arsenate added to a soil and of identifying the soil component mainly responsible for its retention. In the soil examined, arsenate was retained by the goethite particles which also held the native phosphorus.
The influence of net charge on water dispersible clay and sorbed sulphate
Authors: Gillman G.P.
Published: April 2005

The variation of net electric charge with pH at four electrolyte concentrations has been determined on samples from four horizons of a krasnozem soil in north Queensland. A potentiometric titration technique was employed, which allowed the estimation of the zero point of charge (zpc) for each sample. Variation in zpc was related to organic matter content and clay mineralogical composition. The charge distribution characteristics explain the amounts of water dispersible clay and phosphate extractable sulphate in this soil.
Isotopic studies of the nitrogen balance in a cracking clay. I. Recovery of added nitrogen from soil and wheat in the glasshouse and gas lysimeter
Authors: Craswell ET , Martin AE
Published: April 2005

The stable isotope 15N was used to study the fate of nitrogen fertilizers applied to a black earth growing wheat. In a glasshouse experiment using soil packed at 56 % moisture (pF 2) into pots, added nitrate was almost completely recovered (mean, 98.8 � 2.3 %) by soil and plant analysis. This experiment was repeated using 15N-labelled ammonium as well as nitrate; mean recoveries at 15 weeks were 96.8 and 97% respectively (� 2.2% at P < 0.05). A series of pots with soil wetter than pF 2 (at 63% moisture) was also included in an attempt to favour denitrification. Again, virtually complete recovery of added 15N was measured, 97 and 96.8% at 56 and 63% moisture respectively. Fallow and planted systems were then studied in a gas lysimeter. During experiments lasting up to 14 weeks, gaseous losses as 15N-labelled denitrification products were less than the equivalent of 0.2 �g nitrogen/g soil (the lower limit of detection with a mass spectrometer). Although analysis of plant and soil from the lysimeter in two experiments showed virtually quantitative recovery (99.7 and 97.05%), small (0.16%) losses of labelled ammonia into the lysimeter atmosphere were detected. The significance of these results is discussed in relation to the common finding of large deficits in nitrogen balance studies.
Chemical form of inorganic phosphate in sheep faeces
Authors: Barrow NJ
Published: April 2005

A sample of sheep faeces was shaken with solutions which differed in initial concentration, of acid, of phosphate or of calcium. Measurements of calcium and of phosphate concentration and of pH were then made and used to construct a solubility diagram. This indicated that the phosphate was present as dicalcium phosphate and that calcium carbonate was also present. This appears to be consistent with published observations on the availability of faecal phosphate to plants.
Changes in extractable sulpher and potassium levels in soil due to oven drying and storage
Authors: Peverill KI , Briner GP , Douglas LA
Published: April 2005

Appreciable increases in 'available' sulphur were noted for six soils from South Gippsland after oven drying at 40�C. Oven dried soils stored at room temperature or 3�C for periods of up to 12 months showed significant increases in sulphur extractable with calcium phosphate but not in sulphur levels extractable with charcoal plus calcium phosphate. Application of toluene as a bacteriostatic agent failed to stop increases in levels of sulphur extractable with calcium phosphate, although the magnitude of the increases was reduced. No significant increase of 'available' potassium due to oven drying was noted, and the period of storage had no noticeable effects on 'available' potassium levels. Therefore soil samples may be stored for periods of at least 12 months prior to analysis.
Primary and conditional basic exchangeable cations in Australian soil profiles
Authors: Tucker BM
Published: April 2005

The examination of a range of soil profiles showed that both primary and conditional exchangeable calcium, magnesium and sodium are present in all the soils, but the proportions of these subsets vary widely. There are some general correlations with profile form, and it is likely that the partition of these exchangeable cations will prove useful in studying the properties and behaviour of soils. Potassium differs from the other three cations in its exchange reactions-it is present almost entirely in the conditional subset-and it requires an additional exchange reagent to partition it successfully.
Micromorphology and mineralogy of a layered red-brown earth profile
Authors: Sleeman JR
Published: April 2005

The micromorphology and non-clay mineralogy of a red-brown earth profile from Pyramid Hill, Vic., have been examined in order to test Butler's postulated genesis based on field criteria. The profile includes four separate parent material layers. The lowest layer appears to have been derived mainly from in situ weathering of granite. The upper three layers have been derived mainly from a source other than the local granite and have microscopic characteristics comparable to those of altered parna, viz. a non-clay fraction which shows a marked peak in the 30-60 �m range, which consists of quartz and felspar with magnetite, ilmenite, leucoxene and titanite and which has a zircon/tourmaline ratio of about 0.5. As well as a solum developed in the upper two parna layers, there appears to be a buried truncated soil associated with the third parna layer. In both soils there has been significant translocation and deposition of carbonates, iron oxides and hydroxides, manganese oxides and hydroxides and clay, with somewhat more material segregated in the lower solum. Weathering and water-table effects at some depth below a prior surface appear to have been responsible for segregations within the lower layer derived from granite. The data support the concepts of Butler, and in addition indicate contamination of the surface layer by reasonably fresh minerals.
Classification of carbonate layers in highland soils of the northern Murray Mallee, S.A., and their use in stratigraphic and land use studies
Authors: Wetherby KG , Oades JM
Published: April 2005

The various carbonate layers which occur in the Northern Murray Mallee in South Australia have been allocated to four classes and three subclasses based on field characteristics. The layers represent accumulations of carbonate in three pedoderms of different ages, some of which have been developed in different Cainozoic sediments. The four classes and three subclasses separated by observation in the field were shown to be significantly different from each other with respect to several chemical properties. A code is proposed to describe sections. This includes the solum, the carbonate layers and the relevant geologic strata. The use of such a code in detailed land-use surveys is described.
An electron microprobe study of the relationships between heavy metals and manganese and iron in soils and ocean floor nodules
Authors: McKenzie RM
Published: April 2005

Six soils, six manganese nodules derived from soils and two ocean floor nodules were analysed by electron microprobe techniques to determine inter-element relationships. Cobalt was related to manganese in all samples, and a considerable fraction of the total cobalt in the soils was associated with the manganese oxides. Nickel was related to manganese in all of the nodules and some of the soils. In the soils, although the concentrations of nickel were highest in the manganese oxides, a large proportion of the total nickel was actually associated with the iron oxides. Copper and particularly zinc accumulated in the iron oxides in the soils, but in the nodules these elements were associated with either manganese or iron, and in some cases with neither.
Rates of growth, potassium uptake, and changes in the potassium properties of four Queensland soils during intensive cropping by buffel grass, Cenchrus ciliaris
Authors: MacKay DC , Russell JS
Published: April 2005

Four Queensland soils were intensively cropped by buffel grass, Cenchrus ciliaris, in controlled environment growth rooms at three temperatures. Rates of growth (dry matter production) of tops and roots, of potassium uptake, and of changes in soil potassium properties were examined. With adequate potassium applied, growth rates for 31 weeks were nearly constant at 2.7, 2.6, 2.0, and 2.0 t/ha/week on a brigalow, grey clay, podzolic, and solodic soil, respectively. Without potassium, exchangeable potassium decreased quickly to a nearly common level on all soils, corresponding decreases occurred in the potassium content of tops and roots, and severe deficiencies with restricted yields soon resulted. Without applied potassium, moderate release of non-exchangeable potassium occurred on all soils during the first 4 weeks of cropping (0.10-0.18 m-equiv./100 g). Apparent fixation of potassium resulted in the succeeding 6-9 weeks, and, on the fine-textured soils (brigalow and grey clay) only, further slow release took place during the period of potassium deficiency when growth was slow. The overall release of non-exchangeable potassium by all four soils was small (0.02-0.16 m-equiv.1 100 g). Higher temperatures significantly increased yields of tops and roots, decreased the potassium concentration in the plants, increased the rate of depletion of exchangeable potassium, and had no effect on the release of non-exchangeable potassium. It is concluded that on these soils, particularly the solodic and podzolic, potassium deficiency will occur under intensive cropping.
Liquid and vapour phase transport in soil
Authors: Scotter DR
Published: April 2005

Measurements of the desorption soil water diffusivities for vapour and liquid phase flow in a loamy sand and a clay at water contents covering the range between air dry and permanent wilting point are reported. The liquid and vapour components were separated using soil columns maintained at various air pressures. Vapour diffusivities were also calculated from desorption isotherms. At some water contents the measured vapour diffusivities were up to an order of magnitude greater than the calculated values. Liquid phase flow was detected in soils nearly air dry, suggesting some solute transport can occur under such conditions. The liquid and vapour diffusivities were found to be of comparable magnitude over a range of water contents, rather than each cutting off sharply as has been suggested in the literature. The measured component diffusivities at 298 K were used to calculate the total diffusivities at other temperatures, using the temperature coefficients of the basic physical parameters governing liquid and vapour flow, and good agreement was found between measured and calculated values.
Effects of pasture improvement with subterranean clover and superphosphate on the availability of trace metals to plants
Authors: Williams CH , David DJ
Published: April 2005

The effect of pasture improvement by the use of superphosphate and subterranean clover on the availability of trace metals to plants was studied in pot culture. Increased availability of manganese, zinc, copper, iron and aluminium was found in soils that had been under continuous improved pasture for 30 or more years, but no change in the availability of molybdenum could be determined. The effects of these availability changes on plant growth differed according to the plant species grown. Oats was little affected but substantial increases in the uptake of metal cations, especially of manganese, occurred with subterranean clover and lucerne, leading to severe manganese toxicity in lucerne. No significant differences could be measured between the amounts of manganese and copper extracted from virgin and fertilized soils using several reagents, but increases in zinc extracted by hydrochloric acid, EDTA and ammonium chloride, in iron extracted by EDTA, and in aluminium extracted by EDTA and ammonium chloride were found in the fertilized soils. It is concluded that the increased metal uptake was largely due to the lower pH of the fertilized soils. However, in the case of zinc, additions of fertilizer impurities could also have contributed. The increase in EDTA extractable iron appeared to be associated with the increased organic matter content of the fertilized soils.
The deposition of manganese oxide by an alga on acid soil
Authors: Bromfield SM
Published: April 2005

Deposits of manganese oxide were formed during the growing season on the surface of a cultivated acid soil (pH 5.0). A manganous ion oxidizing alga, Chlorococcum humicolum, was isolated from this soil. In liquid media, the alga deposited some oxide at pH 4.5, but oxidation was greater at pH 6.0. The pure alga formed a sparse deposit of oxide on the surface of soil agar at pH 5.0; however, the alga when mixed with certain bacteria deposited a dark brown oxide uniformly over the surface of this medium. The presence of bacteria caused the pH of the medium to increase to about 6.0. The pure alga also formed a dark brown deposit of oxide on soil agar adjusted to pH 6. It is suggested that the alga, in association with bacteria, formed the oxide deposit observed in the field and that the presence of manganese oxide on the surface of soils could indicate field situations which develop significant and perhaps toxic levels of soluble manganese.