bluuebunny/crossref_metadata_2025 huggingface dataset:
Ammonium fixation and availability in some cereal producing soils in Queensland.
Authors: Black AS , Waring SA
Published: April 2005

Native fixed ammonium nitrogen and fixation of added ammonium nitrogen were studied in 24 Queensland cereal producing soils. The availabiiity of both forms of fixed ammonium nitrogen to wheat was investigated using a montmorillonitic soil under pot culture. Fixation and release of fertilizer ammonium nitrogen were followed in the soil by sequential sampling during crop growth. All soils contained native fixed ammonium nitrogen (6-107 p.p.m. nitrogen, mean 39 p.p.m. nitrogen). Fixation of added ammonium nitrogen was only significant in high clay montmorillonitic soils. Under moist conditions an average of 5% (200 p.p.m. nitrogen added) and 1% (4000 p.p.m. nitrogen added) was fixed. Fixation increased threeto ten-fold following air drying. Intensive cropping only released small but non-significant amounts of native fixed ammonium nitrogen. Of the 15% of added ammonium nitrogen which was fixed, only 50% was released by a single low density cropping causing less nitrogen uptake by wheat tops from ammonium compared with nitrate nitrogen sources. Intensive or successive cropping released almost all recently fixed ammonium nitrogen.
Age and significance of slope deposits, Black Mountain, Canberra
Authors: Costin AB , Polach HA
Published: April 2005

Extensive slope deposits are described from Black Mountain, Canberra, with particular reference to a profile exposed in an excavation at 590 m on the lower eastern slopes of the mountain. Buried organomineral soil materials near the base of the slope deposits contain fragments of carbonized wood with an average age of 27,800 (+2500, - 1900) years B.P. This age is not significantly different from the mean age of 26,790 � 810 years B.P. for carbonized wood in slope deposits near Lake George, and is close to the mean age of 31,500 � 1000 years B.P. for slope deposits above 1000 m in the Snowy Mountains. A method for comparing the results of carbon-14 determinations is described. The Snowy Mountains deposits indicated a periglacial climate with mean annual temperatures at least 8-10�C lower than at present. On the basis of their similar appearance and age, it is suggested that the Black Mountain deposits were also formed under cold-climate conditions. If this were so, the synchronous slope deposits near Lake George (and river terraces and slope deposits in an upland tributary of the Shoalhaven River) must also have developed during a colder climate. The climatic and associated soil conditions considered necessary for the formation of periglacial deposits at Black Mountain are discussed. Estimates of the lowering in temperature (compared with present-day temperature) which would have been involved vary from a crude estimate of about 14�C (annual) with relatively high precipitations and prolonged snow cover, to a more conservative estimate of 9�C (winter), 11�C (summer), and 10�C (annual) if the winter precipitations and snow cover were light. Even under the latter conditions, tree cover would have been minimal or absent from the tableland environment.
Corrigenda - 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.
The effect of superphosphate on the cadmium content of soils and plants
Authors: Williams CH , David DJ
Published: April 2005

The cadmium content of phosphatic fertilizers manufactured in New South Wales ranged from 18 to 91 p.p.m. and was closely correlated with phosphorus content. Superphosphate contained 38-48 p.p.m. cadmium. The evidence suggests that the rock phosphate raw material was the sole source of the fertilizer cadmium. The cadmium in superphosphate was soluble in water and was associated with both the phosphate and sulphate components of the fertilizer. It appeared to be as readily. available to plants as the cadmium in cadmium chloride. Cadmium impurities in superphosphate accumulated in the soil, mostly in the surface 10 cm, principally in a cation exchangeable form, and this increased the supply of available cadmium to plants. This accumulated cadmium was extracted from the soil by hydrochloric acid. Increases of up to five-fold in total soil cadmium were found in soils which had been fertilized with superphosphate, and in one soil there was a 12-fold increase in hydrochloric acid-soluble cadmium. Plant uptake of cadmium from soil was generally small and ranged from 0.4 to 7% of that available. Uptake was greatly influenced by soil type, and addition of calcium carbonate reduced the uptake by subterranean clover from cadmium residues in soil. Plant species differed greatly in their ability to take up cadmium, and the concentration of cadmium varied widely within the plant. Generally only 12-18 % of the cadmium in cereal plant tops was translocated to the grain which had a lower cadmium content than any other part of the plant. The addition of cadmium to soil, either as cadmium chloride or in superphosphate, always increased the cadmium content of the grain of cereals or the edible portion of vegetables. Top-dressing of improved pastures with superphosphate brought about considerable increases in the cadmium content of pasture species, especially that of subterranean clover. Analyses of wheat grain and cereal breakfast foods indicated that, although Australian cereal growing soils have long histories of superphosphate usage, the cadmium content of the grain produced is low, the range found being 0.012 to 0.036 p.p.m. Low values, < 0.010 to 0.015 p.p.m., were also found in processed green peas.
A study of the mechanisms of aggregation in a krasnozem soil
Authors: Coughlan KJ , Fox WE , Hughes JD
Published: April 2005

Dry sieving, wet sieving, and soil analytical techniques were used to study the levels of organization within dry aggregates of virgin and cultivated krasnozem soils. Three mechanisms of aggregation appeared to exist. In the c 0.5 mm size range, the mechanism was independent of cultivation and was connected with basic soil particle properties. In the 5.0-0.5 mm range the hydrophobic properties of organic matter are proposed as important in determining water stability. In the range > 5.0 mm, binding of roots in the virgin soil and clod formation by implements in the cultivated soils appeared to be operative. Reduction in clay crystal size and surface activity appeared to be connected with phosphate fertilizer application.
The comparative effects of exchangeable calcium, magnesium, and sodium on some physical properties of red-brown earth subsoils. II. The spontaneous dispersion of aggregates in water
Authors: Emerson WW , Bakker AC
Published: April 2005

Aggregates from the subsoils of four red-brown earths were brought into equilibrium with chloride solutions of known SAR, 1 mM in calcium or magnesium. The solutions were replaced by water and the amount of clay which subsequently dispersed from the aggregates measured. For the three soils from the same area, the ESP required to induce dispersion was about 3 for magnesium-sodium aggregates compared with 5 for calcium-sodium aggregates. For the other soil the respective ESP values had to be increased by a factor of 2. The increased resistance to dispersion of the latter was maintained even after sodium saturation. The results are used to show that differences in the dispersion of the natural aggregates in water are due primarily to the composition of the cations on the exchange sites, including aluminium. Shepparton aggregates of known ESP were wetted with water at 12 cm suction. Compared with calcium or magnesium aggregates, there was a marked further water uptake by magnesium-sodium aggregates for ESP > 3 and for calcium-sodium aggregates for ESP >9. The subsequent dispersion in water of such aggregates was much less than that of aggregates treated in the standard way. It is suggested that the spontaneous dispersion of clay from a wet aggregate of low ESP immersed in water depends on the gradient of the soluble salt concentration at the boundary of the intact portion of the aggregate, as well as the actual concentration.
Studies on soil potassium. III. The intensity of soil potassium following exhaustion by different plants
Authors: Martin AE , Fergus IF
Published: April 2005

Exhaustive cropping of four soils by four species revealed only small differences in the limiting intensity (expressed as the equilibrium activity ratio, ARo) of soil potassium, for which the mean value was 5.0 x 10-4 mole1/2 L 1/2. Replanting of depleted soils led to slightly lower values. With a fifth soil, which contained significant amounts of potassium felspar in both clay and sand fractions, grasses reduced the intensity to a lower level (3.8 x 10-4 mole1/2 L 1/2) than did legumes (21.0 x 10-4 mole1/2 L 1/2), and these values were substantially reproducible with replantings of the same species. It was suggested that the peculiar behaviour of this soil may have been associated with the differential ability of the various plants to use potassium from orthoclase. The intensity at which potassium was first absorbed from sources not initially in equilibrium with 0.001M calcium chloride varied from 8 to 29 x 10-4 depending on the soil, and, in the case of the felspathic soil, depending on the plant.
Measurement of aeration, respiration rate and oxygen diffusion in soil during the growth of cotton in a rhizotron
Authors: Melhuish FM , Huck MG , Klepper B
Published: April 2005

Gaseous diffusion experiments were conducted in soil below cotton plants in a rhizotron throughout a growing season. Buried oxygen transducers permitted the estimation of transient-state oxygen diffusion coefficients after soil sterilization with methyl bromide at the end of the season. This provided a relationship between soil air-filled porosity and oxygen diffusion coefficient which was applied in calculations of soil respiratory activity at steady state earlier in the season. These values varied with root density throughout the season. Transient-state values for respiratory activity were different from steady-state values at similar times, even when allowance was made for continual loss of water by transpiration during the transient state. Possible reasons for such differences are discussed, and the utility of the technique for field studies is outlined.
Factors influencing salt and water movement near crystalline salts in relatively dry soil
Authors: Scotter DR
Published: April 2005

Crystalline salts were placed at one end of sealed tubes of initially uniformly wet soil. The effect of soil texture, the initial soil water content, temperature, and the particular salt used on the resulting water and salt distributions in the soil was studied. In all experiments using relatively dry soil a zone of water accumulation adjacent to the salt, and a zone of water depletion further away from the salt, developed. Dissolved salt moved into the wetter zone next to the salt. The rate at which salt dissolved and moved out into the soil was found to depend very strongly on the solubility and saturated solution vapour pressure of the salt used, and the initial soil water content. Soil temperature and texture were less important factors. In some experiments quite large amounts of water accumulated in the crystalline salt, apparently when adequate contact was not maintained between the salt and the soil as the salt dissolved.
Relationship between pore size distributions and physical properties of clay soils
Authors: Sills ID , Aylmore LAG , Quirk JP
Published: April 2005

Pore size distributions using mercury injection and nitrogen sorption techniques were determined on a number of soils classified as clays on the basis of particle size analysis. Some of these soils exhibit markedly different consistencies during texturing and undergo changes in texture during prolonged manipulation, e.g. subplastic, superplastic and self-mulching soils. The pore size distributions for these soils do not differ significantly from those obtained for the normal labile clay soil in the pore size range 2 nm to 50 �m. The clay soils examined, with the exception of the krasnozem, have the majority of their pore volume within pores smaller than 10 nm with the predominant pore size centred around 3 nm plate separation. In the case of the krasnozem, the particle size analysis does not correspond to the texture assessment as a clay loam. Surface and subsoil samples of the krasnozem have high porosities and predominant plate separations of 6 nm. They consequently possess significantly different pore size distributions from the other clays. In the case of the surface sample, only a small proportion of its total pore volume is in pores smaller than 10 nm. These differences in pore structure observed between the krasnozem and the other soils examined may result from differences in mineralogy, and in particular from the high sesquioxide content of the krasnozem.
Studies on potassium. IV. Interspecific differences in the uptake of non-exchangeable potassium
Authors: Fergus IF , Martin AE
Published: April 2005

Five soils were cropped with four plant species in pot experiments in the glasshouse, without addition of potassium, until growth virtually ceased, after which the depleted soils were replanted with either the same species, or a different one, to test the reproducibility of the 'exhaustion' conditions imposed. Uptake of potassium by the plants exceeded the changes in exchangeable potassium in four soils; the excess amounts taken up differed markedly between species and these differences were reproducible on replanting. Uptake by setaria (Setaria anceps) and siratro (Macroptilium atropurpureum) exceeded that by Rhodes grass (Chloris gayana) and lucerne (Medicago sativa), except for one swelling clay soil from which uptake by lucerne equalled that by siratro. Most of the differences between species were attributed to the uptake of initially non-exchangeable potassium, which was removed in significant amounts from three of the soils. For these three soils, uptake from non-exchangeable sources was detected only after about 80% of the exchangeable potassium had been removed. It is postulated that the efficiency of plant removal of non-exchangeable potassium from soil is directly related to the degree to which plant roots can lower the concentration of potassium in the soil solution.
Numerical analysis of vertical water movement in a bounded profile
Authors: Watson KK , Curtis AA
Published: April 2005

The usual assumption made in soil water studies that the effect of the air phase on the flow process is negligible is discussed in relation to certain profile configurations where such an assumption is not valid. A computer-based numerical solution of the equation describing water movement in an unsaturated soil is then modified by the inclusion of a time-dependent boundary condition, thus allowing the modelling of the air compression effect during infiltration. This analysis also satisfactorily models the drainage along primary draining scanning curves which occurs in the upper part of the profile as the air pressure increases. The analysis is limited to the Darcy flow regime which, for the system considered, terminates when the excess air pressure equals the air entry value of the porous material. Detailed results are presented for a sand and a sandy loam. Profile depths of 200 cm and 1000 cm have been analysed, and comparisons made of the effect of the air compression on the shape of the wetting front. The effect on cumulative infiltration is also noted.
Redistribution of water following precipitation on previously dry sandy soils
Authors: Carbon BA
Published: April 2005

Theoretical and experimental evidence is provided to show that the redistribution of a given amount of water some days after infiltration into a previously dry soil can be predicted, provided that the relationship between soil water potential and soil water content is known. The capillary potential at the wetting front during infiltration into the dry soil is also required. In sandy soils an increase in amount of applied water leads to a decrease in the soil moisture content at the soil surface. This change in 'field capacity' as a function of applied water is shown to strongly influence seedling emergence.
Simulation of the water balance for plants growing on coarse textured soils
Authors: Carbon BA , Galbraith KA
Published: April 2005

A computer simulation model* of the water balance for plants growing on coarse soils was developed and tested against field measurements. The inputs for this model are measurable physical parameters. From the close agreement between simulated and observed results, it is suggested that evaporation, soil water storage and deep drainage may be satisfactorily predicted.
Leaching of copper and zinc from trace element superphosphate
Authors: Gilkes RJ , Young RC , Quirk JP
Published: April 2005

Leaching of surface applied trace element superphosphate through soil in a laboratory experiment showed that sulphur, phosphorus and calcium are mobile, whereas copper and zinc are relatively immobile. It is suggested that this immobility is responsible for the requirement for such large excesses of copper and zinc in fertilizers relative to plant uptake.
Isotopic studies of the nitrogen balance in a cracking clay. II. Recovery of nitrate 15N added to columns of packed soil and microplots growing wheat in the field
Authors: Craswell ET , Martin AE
Published: April 2005

In a series of experiments, 15N-labelled nitrate fertilizer was used to study the nitrogen balance of a heavy clay soil. Two of the experiments employed 60-cm deep, 16-cm diameter columns of packed soil. In the first, no added 15N was lost until heavy rain saturated the soil in the undrained columns. Subsequently, fallow and planted columns lost 25% of the 15N added. While denitrification appeared primarily responsible for these losses, some of the 15N may have been lost by weathering of the plants during senescence. This experiment was repeated with precautions to prevent excessive rain saturating the soil. After 16 weeks, only 6 � 4.5% of the added 15N was not accounted for by soil and plant analysis. In the third experiment, I5N was added to 16-cm diameter confined microplots in situ. The microplots were fallow and were confined by 60-cm deep plastic pipe. After 16 weeks, during which 190 mm of rain fell, 97.7 � 2.4% of the added 15N was recovered.
The partition of basic exchangeable cations
Authors: Tucker BM
Published: April 2005

The sets of basic exchangeable cations in soil samples can be divided into subsets by changing the conditions under which their displacement takes place. Using a large cation (cholinium) in a nonaqueous solvent (alcohol), primary subsets of exchangeable calcium, magnesium and sodium are displaced. When ammonium ion in an aqueous solvent is used after this primary displacement, a conditionally exchangeable subset is obtained. Potassium is almost completely conditionally exchangeable in the soils studied. The conditional subsets may be further divided depending on whether the condition of using a smaller displacing cation (NH4+) or of having water present is met first. The concept of partition by exchange conditions is distinct from a partition based on exchange constants (under unchanged conditions) to which the epithets easily and difficultly exchangeable are appropriate.
Simulation of the rainfall runoff process using a hysteretic infiltration redistribution model
Authors: Watson KK , Lees SJ
Published: April 2005

The significance of the soil profile and its accompanying water status in deterministic catchment models is discussed in relation to the current use of the soil-store concept. An alternative numerical approach is described in which the movement of water into and through the soil profile (together with the determination of runoff volumes) is continuously monitored during any pattern of rainfall and non-rainfall events. A significant component in the approach is the use of a comprehensive domain-type hysteresis model for the analysis of infiltration-redistribution sequences. The simulation is illustrated by using a rainfall hyetograph of 7 h duration (including one non-rainfall period of 1 h) as the flux input into a homogeneous profile of a sandy loam of uniform initial water content. The time-dependent relationships of rate of surface flux, depression storage and runoff volume are calculated for the duration of the hyetograph period. Profiles of water content are also presented.
The base flow of the Glenelg river derived from tritium concentrations
Authors: Allison GB , Holmes JW , Hughes MW
Published: April 2005

Water samples collected during June 1966 from the Glenelg River, Vic., had tritium concentrations that decreased monotonically from 35 T.U. at the headwaters to 6 T.U. just above tidal influence. The dilution of tritium, by base flow, was interpreted to yield estimates of groundwater flow to the river from aquifers into which the river has cut its course. In a lower reach of the river approximately two-thirds of the total discharge of 2900 L sec-1 was made up by base flow additions. At a later collection in April 1970 the river was not in such a steady state as it was at the time of the earlier collection. The river was too perturbed for plausible interpretation of the observed tritium concentrations in other than three reaches of the river. Nevertheless the method and technique have general validity in humid and sub-humid regions where stream regimes are effluent.
Changes in soil sulphur fractions with fertilizer additions and cropping treatments
Authors: McLachlan KD , Marco DGD
Published: April 2005

Continued application of fertilizer to a pasture soil over a 4 year period, increased the phosphate extractable, the bicarbonate extractable, and the total sulphur contents. Where the same level of sulphur had been applied during this period, the phosphate extractable sulphur declined exponentially with time since the last fertilizer application. No such relation with bicarbonate extractable sulphur was established. Under a pasture regime, there was an increase in the carbon bonded sulphur fraction with increasing level of sulphur applied. Evidence from cropped soils showed that sulphur in the carbon bonded form was not a permanent sink for soil sulphur. On cropping, more sulphur was withdrawn from the carbon bonded than from the hydriodic acid reducible form. The similarity in composition between new additions to the soil sulphur and that already there, and the mobility of the element between the forms examined, will make it difficult to devise a satisfactory soil test for the sulphur status of a soil.
Chemistry of iron in soils. ferric hydrolysis products
Authors: Murphy PJ , Posner AM , Quirk JP
Published: April 2005

A method has been developed for dividing hydrolysed ferric species into unpolymerized, polymerized and precipitated species. The colour developed with 8-hydroxy-7-iodoquinoline-5-sulphonic acid measures the concentration of unploymerized species and centrifugation gives the precipitated species. Polymeric species are found by difference. The pH and polymeric species decreases, precipitate formation increases and unpolymerized species remain constant on aging a partially neutralized ferric solution. With increasing OH/Fe ratio at a given age, the pH, polymeric and precipitated species increase and the unpolymerized species decrease. The concentration of unpolymerized species was independent of the anion (NO3, ClO4 or Cl). Goethite, lepidocrocite and �-FeOOH were formed in the solutions under various conditions. The rate and amount of precipitate formation was dependent on the degree of anion penetration for the polycations and precipitates and the total anion concentration. The ferric hydroxy polycations had V= 0.286 and empirical compositions of [Fe(OH)x 3-x]n where 2.2 < x < 2.9.
Some properties of granulated superphosphate and its behaviour in the soil
Authors: Gilkes RJ
Published: April 2005

The composition and particle size distribution of granules in commercial granulated single superphosphate has been shown to be very variable, the distribution of micronutrients amongst granules being less uniform than the distribution of macronutrients. Under farming conditions, the amounts of fertilizer copper and zinc in granulated fertilizer applied to individual plants varied widely, although no correlation between amount applied and plant uptake was found. Most phosphate, copper and zinc moved into the soil through very small pores that developed within granules. A residual skeleton of anhydrite and poorly soluble phosphates remained in the soil. This granular residue persists in some soils for long periods and its properties may affect the residual value of the fertilizer.
Soil classification and survey studies at Ginninderra
Authors: Webster R , Butler BE
Published: April 2005

Studies were made of the interrelations of soil properties, their spatial variation, and the relations between sampling sites at Ginninderra Experiment Station near Canberra. Soil morphology was recorded at 0-10 cm, 15-25 cm (usually A2 horizon), 41-51 cm (usually B horizon) and 66-76 cm, and general profile features were noted. Samples from the 0-10 cm and 41-51 cm were analysed chemically, and bulk density and water held at 0.1 bar determined on 0-7.5 cm cores. Simple correlations between morphological and other properties of the topsoil were almost all negligible. Correlations in the B horizon were somewhat stronger, though few correlation coefficients exceeded 0.5 in absolute value. Ordination by principal coordinate analysis showed sample sites to be evenly spread in a single roughly spherical cluster in the three main dimensions of property space. Four classifications, two systematic, one a map, and the fourth a numerical classification, were unable to predict values of soil properties sufficiently well to be useful; the properties must be measured where they are of interest by a purpose-designed sampling scheme. Soluble potassium varies little between points 5 m apart, but very considerably over distances 56-180 m. Two-thirds of the variation in soil phosphorus at Ginninderra occur within 5 m and the remainder at more than 180 m. Variation in pH increases fairly steadily up to 56 m, and the rest at more than 180 m. Most variation in bulk density and water content occurs within 18 m, though the total variation is small. Variation in morphology occurs mainly within 5 m and at more than 180 m. Reasonable maps can be made of phosphorus and morphology by pooling data from samples from 5 m diameter circles, or by bulking samples from them, spaced on a grid of approximately 200 m mesh. For potassium a grid mesh of no more than 56 m is needed to map the variation, though pooling data from 5 m circles would give a small improvement.
The alpha activity of soils in relation to landscape development
Authors: Pepper RG , Quirk JP
Published: April 2005

The alpha activity of soils and the degree of the equilibrium of the thorium series has been related to the age of soils developed on a truncated laterite landscape in south-western Australia. The uplift of the old lateritic plateau has formed a sequence of erosional and depositional surfaces which form the parent materials of the present-day soils. These surfaces because of their different relative ages have been subjected to different degrees of weathering and leaching. The alpha activity of the soils formed on these different landscape surfaces is influenced firstly by the amount of weathering that the surface has undergone, and secondly by the degree of leaching that the soil has undergone as evidenced by profile development. It has been found that the younger soils have higher alpha activities with the thorium series tending more towards equilibrium when compared with older soils, where the alpha activity is lower due to the leaching of the daughter nuclides from the profile.
Exchangeable aluminium on kaolinite
Authors: Smith BH , Emerson WW
Published: April 2005

Three salt-free preparations of a ceramic kaolinite were made with different amounts and forms of (Al), where (Al) denotes aluminium ions balancing the isomorphous replacement charge of the clay. In two, (H) clay and (K/H) clay, prepared by washing with hydrochloric acid then water and potassium chloride/hydrochloric acid then water respectively, the (Al) was derived by decomposition of the clay itself. In the third, (Al/OH) clay, a known amount of aluminium together with sufficient alkali was added to give (Al) of the nominal form A1(OH)2.5. Electro-osmosis was used to determine the total charge carried by (Al). The moles of aluminium present as (Al) were estimated by series extraction of aluminium from the clay with potassium chloride/oxalate. Both the charge and the amount of (Al) were deduced from conductimetric titration curves of the clays with alkali. The isomorphous replacement charge of the clay was found to be 3.4 m-equiv./100 g. The average values deduced for the charge per (Al) ion were 3, 1.4 and 0.5 for the (H), (K/H) and (Al/OH) clays respectively. The potentiometric titration curves with alkali of the clays in 1N potassium chloride are discussed in terms of the form of (Al) present. The absorption of organic compounds by salt-free suspensions of kaolinite is also briefly discussed.
Coupled soil moisture, heat and water vapour transfers under simulated fire conditions
Authors: Aston AR , Gill AM
Published: April 2005

An approximate numerical method is presented coupling the transfer of water, heat and water vapour in a soil. The system is used to predict in time, soil temperature profiles under simulated surface fire conditions. Moisture profiles, ground heat flux and soil evaporation are also calculated. An experiment using a tube of moist sand heated by a radiant heater over a 30 min period to simulate fire conditions was used to test the model. A further test was imposed using experimental grass fire data from the literature. In all cases deviations between observed and calculated results were small.
The uptake of zinc-65 by oats in relation to soil water content and root growth
Authors: Nambiar EKS
Published: April 2005

Effects of water content of the topsoil on root growth and 65Zn absorption by oats were measured. Seminal roots of oats grew through a labelled uptake layer that had been initially wetted to various water contents. The uptake layer was separated from adjacent layers of wet sand or soil by a thin layer of wax. When the uptake layer was wetted initially and allowed to dry during the uptake period, water content affected root growth and 65Zn uptake similarly. 65Zn absorption by unbranched seminal roots decreased linearly as soil water suction increased from 0.3 to 5 bar. Nevertheless significant amounts of 65Zn were absorbed (40% of that from wet soil) even when the soil water suction exceeded 15 bar, with negligible concomitant uptake of water. Provided the roots had access to water in a subjacent layer, rates of 65Zn absorption from dry soil increased with the age of the plants. The exudation of mucilage from the root was enhanced locally where the soil was dry. The mucilage may facilitate the transfer of zinc to the root in dry soil.
Isotopic studies of the nitrogen balance in a cracking clay. III. Nitrogen recovery in plant and soil in relation to the depth of fertilizer addition and rainfall
Authors: Craswell ET , Strong WM
Published: April 2005

15N-labelled nitrate nitrogen was added at either 15 cm or 45 cm depth to 10-cm diameter undisturbed cores of black earth soil. Cores were either fallowed or planted to wheat and received either 444 mm or 255 mm of simulated and natural rain during a 17-week growing season under field conditions. Between 92 and 98 % of added 15N could be accounted for in planted or fallow cores receiving the lower rainfall, while those receiving the higher rainfall contained 75-94 %. The loss was larger where fertilizer was added at 15 cm than at 45 cm depth. Fallow cores lost more 15N than planted cores. These losses are ascribed mainly to denitrification and are discussed in relation to the results of earlier work with this particular soil-plant system. Plants yielded more, and recovered more of the fertilizer nitrogen, in those cores which received the higher rainfall. Plants recovered more applied nitrogen from 45 cm depth than from 15 cm depth. At harvest, over 40% of the applied nitrogen remained as nitrate in the planted cores which received the lower rainfall. In these cores, only 38-47 % of the fertilizer was recovered in plant tops. The significance of these results for fertilizer efficiency is discussed.
A note on the use of the Philip infiltration equation
Authors: Smiles DE , Knight JH
Published: April 2005

It is suggested that, as a matter of course, data from infiltration experiments should be graphed with (it-1/2) as a function of t1/2 Early-time linearity of this curve confirms the appropriateness during this/ time of the two-parameter equation of Philip. The two parameters emerge as the intercept and slope of the line. If subsequently infiltration is described by the equation di/dt = K0, then this part also will emerge as the asymptote of i = K0t.
Salt sieving within clay soil aggregates
Authors: Blackmore AV
Published: April 2005

The rates at which salt diffuses from the stable non-swelling aggregates of a heavy clay soil are studied in relation to both exchangeable cation type and free electrolyte content. Although the material is completely stable, it exposes a large clay surface of normal 'activity'. The results support a hypothesis that salt is constrained in some pores by salt-sieving within the aggregate; regions of anion exclusion, associated with surfaces in the narrower pores, restrict the cross section for diffusion from larger interior pores. It is shown that, when circumstances favour negative adsorption, that is with sodium cations and salt of relatively low concentration, salt is trapped within the microfabric; with calcium ions and salt of high concentration anion exclusion is suppressed and salt moves out of the aggregates much more easily. When the aggregates are in a saline sodic condition salt diffuses from them into saturated gypsum solution much more rapidly than it does into distilled water. This is in accord with the suggested model and implies that the ameliorative use of gypsum may involve a mechanism additional to those associated with swelling and flocculation. Application of the concept to soil in the field is briefly discussed.
Nitrate leaching and adsorption in a krasnozem from Redland Bay, QLD. III. Effect of nitrate concentration on adsorption and movement in soil columns
Authors: Black AS , Waring SA
Published: April 2005

Nitrate adsorption and movement was studied in soil from depths of 0-15, 40-90 and 160-300 cm. Adsorption was determined at concentrations ranging from 0.5 x 10-3 to 0.5M potassium nitrate and movement by adding 0, 3, 12 and 120 mg nitrogen15 ml of a potassium nitrate solution to packed columns and leaching with deionized water or 0.2M potassium sulphate. In the 0-15 cm soil, nitrate exclusion was evident in both the adsorption and movement studies at low concentrations, but no effect was measured at high concentrations. In the two subsoils, adsorption increased with concentration to 1.9 m-equiv./100 g when equilibrated with 0.5M potassium nitrate. In the subsoils the depth of leaching of nitrate increased with nitrate concentration; the nitrate distribution was skewed; and the rate of nitrate movement was less than that of water. Addition of sulphate to the subsoils resulted in nitrate movement being similar to that of water. The results are discussed in terms of nitrate adsorption. Comparisons with field observations provide further evidence that adsorption is a major process influencing leaching in these soils.
Subplasticity in Australian soils. V. Factors involved and techniques of dispersion
Authors: Norrish K , Tiller KG
Published: April 2005

The subplastic soils studied were two from the Riverina area of New South Wales, two montmorillonite rich clays formed on basalt, from South Australia and Queensland, and a krasnozem from New South Wales. To assess the effectiveness of physical and chemical methods of dispersion, theoretical clay contents were calculated from the ratio of the CEC of the soil to that of separated clay. The composition of the clay from the soils showed little or no change with degree of dispersion. To disperse the soils without chemical pretreatment, a method of disaggregation was devised that involved vigorous shaking of a soil paste. Following this technique the Riverina soils and the krasnozem yielded almost all their clay. Lithium saturation was the only chemical treatment that aided dispersion of the montmorillonite clays, and this, together with the high tetrahedral lattice charge, suggests that aggregate stability is mainly due to a large electrostatic interaction between clay sheets. Any pretreatments involving the use of sodium hydroxide improved clay yields for the Riverina soils. The data indicated that the loss of subplasticity was accompanied by the solution of clay, suggesting that aggregate stability was due to non-ionic bonds between clay particles, possibly as the result of intergrowth of clay mineral crystals. Organic matter and/or free iron oxide was responsible for cementation of the krasnozem.
Soil trends in two valley fill sequences
Authors: Walker PH , Green P
Published: April 2005

A sequence of profiles in alluvium from the South Coast of New South Wales and another from the Southern Tablelands are described and compared. Each sequence displays profiles of essentially sedimentary nature on low, narrow alluvial benches, cumulic soils on the more general flood-plain landscapes, soils with A and minimal texture B horizons on low terraces, and soils with strongly differentiated A and texture B horizons on high alluvial terraces. Profile development for each sequence is represented as depth functions and from these data indices of profile anisotropy (IPA) are derived. The step-wise changes in biotic and mineral profile organization from stratigraphically young to old soils are similar at both locations. Comparable profile sequences on ,alluvium have been observed in many other locations in humid south-eastern Australia. Available stratigraphic information at these locations is insufficient for estimates of rate of soil development to be made.
Surface charge characteristics of six weathered soils from tropical north Queensland
Authors: Gillman GP , Bell LC
Published: April 2005

Electrochemical studies on 18 samples from six weathered soils from tropical north Queensland showed that they contain colloids of largely the 'constant surface potential' type, i.e, their surface charge is controlled by the pH and ionic strength of the ambient medium. The point of zero charge (PZC), as well as the net charge at the soil pH and pH 7.0 at two electrolyte concentrations, were established. The implications with respect to cation exchange capacity, base saturation, buffer capacity, and water dispersible clay, and the importance of these properties to soil classification and agricultural management, are discussed.
The extraction and definition of non-exchangeable or fixed ammonium in some soils from southern New South Wales
Authors: Osborne GJ
Published: April 2005

The amounts of non-exchangeable or fixed NH4+ in six soils from southern New South Wales were determined by using three methods. Using a potassium hydroxide pretreatment 2-13 % of the total nitrogen in the surface soils was fixed and between 16 and 33 % in the subsoils. Different methods showed up to a threefold difference in the amount on some soils and non-significant differences in others. The interpretation of the part played by this fraction of soil nitrogen in the chemical and biological equilibrium of soil must be qualified according to the extraction method used. The use of soil samples having a larger particle size (< 2 mm) than previously used (<0.147 mm) was found to be adequate with the soils studied. As the present definition of non-exchangeable or fixed NH4+ is misleading, it is proposed that this fraction of soil nitrogen be called intercalary ammonium (NH4+). Intercalary NH4+ is defined as that nitrogen recovered from within clay minerals by hydrofluoric-hydrochloric acid treatment, subsequent to a potassium hydroxide or potassium hypobromite/potassium hydroxide pretreatment and 0 . 5N potassium chloride leaching to remove exchangeable NH4+ and organic nitrogen from the outside of the clay particles.
The significance of intercalary ammonium in representative surface and subsoils from southern New South Wales
Authors: Osborne GJ
Published: April 2005

Six surface and subsoils known to contain native intercalary ammonium were examined to assess the importance of ammonium fixation when nitrogen fertilizers were applied, the availability of native and recently fixed intercalary ammonium to plants, and the effect of potassium on fixation. Only one soil, a grey soil of heavy texture (Ug 5.4), fixed significant amounts of added ammonium sulphate, the level of intercalary ammonium being increased by 55 % in the surface and 100% in the subsoil. The native level of intercalary ammonium was reduced by 8 and 17% by the growth of plants in the red-brown earth (Dr 2.23) and the grey soil of heavy texture, respectively, but was unchanged in the other soils. The addition of small amounts of potassium prior to the ammonium did not affect fixation; however, additions of 500 ppm reduced the fixation of a 200 ppm solution of ammonium by 80 %. Intercalary ammonium is not considered to be important in the nitrogen economy of five of the six major farming soils of the slopes and plains area of southern New South Wales. The sixth, the grey soil of heavy texture, is an alluvium associated with the Murrumbidgee River and its tributaries, and as such is used extensively for irrigated agriculture. Because this soil can fix large amounts of ammonium, the use of ammonium or ammonium forming fertilizers is not recommended.
Gravity drainage of a sand profile under a time-dependent surface flux
Authors: Webb SN , Watson KK
Published: April 2005

The replenishment of groundwater supplies from recharge trenches often involves the use of water containing quantities of suspended solids which eventually become deposited on the sides and bottom of the trench with a consequent decrease in intake rate. This process is simulated numerically in one dimension by using a finite difference solution of the flow equation with a time-dependent surface flux boundary condition. Three algebraic functions are used to represent the flux change so that different physical characteristics of the system can be studied. The numerical results indicate that for a reasonably slow rate of flux reduction water content and pressure head profiles of a steady state configuration, appropriate to the flux at that time, are obtained. However, with a more rapid flux change unsteady state conditions remain established through the profile and predictions of water content and pressure head can only be made using an unsteady state analysis.
Seepage from small earth dams
Authors: Pepper RG
Published: April 2005

Tensiometers were installed to study seepage from an excavated earth tank used for farm water supplies near Badgingarra, W.A. Seepage was limited by a layer of soil about 0.2 m thick with hydraulic conductivity about one-tenth of that of soil deeper in the profile. The seepage limiting layer bounds the excavated tank. Water balances of several earth tanks were used to estimate hydraulic conductivities of soils in situ. Most of the variation of hydraulic conductivity could be accounted for by sand content, exchangeable magnesium percentage, exchangeable sodium percentage, and dithionite extractable iron in the soils. Laboratory measurements of the hydraulic conductivities of disturbed samples had no relevance to the field situation.
Some effects of the distribution of cadium and phosphate in the root zone on the cadmium content of plants
Authors: Williams CH , David DJ
Published: April 2005

Effects of the distribution of cadmium and phosphate in the root zone on the cadmium content of subterranean clover were examined in pot culture. Addition of cadmium, un~formly mixed throughout the soil, increased the cadmium content of plants at all levels of added cadmium. Plant yield was depressed and toxicity symptoms were evident when cadmium equivalent to 5 ppm, or more, was added to the soil, and yield of roots was depressed by the addition of 1 ppm. When the same amounts of cadmium were added only to the surface 2 cm of soil, plant yield was unaffected except at the highest level (40 mg per pot or 100 ppm in the treated layer) when slight cadmium toxicity was evident. The cadmium content of the plant material was increased, but to a smaller extent than when the cadmium was mixed throughout the soil. At the highest levels of cadmium addition (10-40 mg per pot) the plant cadmium content reached a maximum value of 44 ppm compared with 109-362 ppm for the fully mixed treatments. Root yield below the cadmium treated layer was unaffected, and immobilization of cadmium in the roots growing in the high cadmium layer of soil may have led to the reduced transfer of cadmium to the plant tops. Uptake of cadmium was also affected by the distribution of phosphate in the root zone. Addition of phosphate to the surface of phosphorus deficient soils led to the proliferation of roots in the phosphate-treated layer, which resulted in enhanced cadmium uptake from it, especially at low levels of phosphate application. When cadmium was concentrated in the same layer, increased uptake of the added cadmium occurred. This effect was less evident in soil of high phosphorus status. The cadmium content of plants was also affected by the amount of phosphate applied to soil The effects of phosphate addition varied from soil to soil, and both increases and decreases in plant cadmium content were recorded following the application of phosphate. On some soils decreases in cadmium content appeared to result partially from effects of phosphorus on plant growth.
Heavy metal contamination of soils around a lead smelter at Port Pirie, South Australia
Authors: Cartwright B , Merry RH , Tiller KG
Published: April 2005

A survey was made of the concentrations of EDTA-extractable lead, zinc, cadmium, and copper in surface soils at 472 sites surrounding an isolated lead smelter at Port Pirie, S.A. Contamination declined exponentially with distance near the smelter, but was detectable up to 40-65 km from the source depending upon direction. Close to the smelter, the fallout pattern was consistent with the direction of surface winds (NNW-SSE), but major contamination on hills 20 km due E was related to topography and rainfall and was independent of mean surface wind direction at the source. It is probable that most of the soil contamination occurred prior to 1940. The dispersion of heavy metals was ranked in the order cadmium > lead >> zinc. No contamination with copper was detected. The ratios lead/cadmium and zinc/cadmium for soils were high close to the smelter, but declined with distance to constant values. It was concluded that over short distances soil contamination resulted from the fallout of particulate emissions of variable composition, but beyond about 15 km the heavy metals are probably dispersed mainly as aerosols. The soils of the surveyed region were mostly of pH above 7.5, and vertical movement of heavy metals in soil profiles was negligible. Some implications of the results for human and animal health are discussed.