bluuebunny/crossref_metadata_2025 huggingface dataset:
The calibration, interpretation, and evaluation of tests for the phosphorus fertilizer requirements of wheat in Northern New South Wales
Authors: Colwell JD , Esdaile RJ
Published: April 2005

A general procedure is described for the estimation of fertilizer requirements from measurements on all factors that affect plant response to fertilizer. Tests for fertilizer requirement are defined as all measurements of factors that affect the fertilizer requirements of a crop, and the calibration procedure is based on the prediction of yield response functions for particular sites from test measurements representing the sites. Several tests can be used simultaneously for the prediction of fertilizer requirements, and this is demonstrated by the calibration of the soil tests, NaHCO3-soluble phosphorus, NaHC03-soluble potassium, and pH, against yield response of wheat to phosphorus fertilizer using data from 49 field experiments in northern New South Wales. The value of rainfall and clay content as tests was also investigated but their contributions to the calibration equations were non-significant. The application of economic principles for the estimation of optimal phosphorus fertilizer requirements is demonstrated. Fertilizer requirements decrease with increase in the value of NaHCO3-soluble phosphorus, with increase in pH, and with decrease in NaHCO3-soluble potassium. A statistical and economic evaluation of the tests is made on the basis of the regression surfaces established under the calibration procedure, and it is concluded that the value of testing for phosphorus fertilizer requirements is considerable.
Seasonal fluctuations in mineral sulphur under subterranean clover pasture in southern New South Wales
Authors: Williams CH
Published: April 2005

Seasonal changes in sulphate sulphur were studied in a soil under subterranean clover pasture. Fluctuations in sulphate content were found to be similar to those in nitrate. Both sulphate and nitrate accumulated in the surface soil during summer, immediately after senescence of the pasture. High concentrations were maintained throughout the summer-autumn period and these decreased to low values in winter and spring. The higher values in summer probably resulted from mineralization of soil organic matter under favourable moisture and temperature conditions, and lack of plant uptake. Minor fluctuations were associated with partial leaching by rainwater. The low values in winter and spring were probably brought about by leaching and plant uptake, together with low rates of mineralization at low soil temperatures.
Surface conductance related to electrolyte concentration in bentonite pastes
Authors: Blackmore AV
Published: April 2005

The present paper describes a method of obtaining experimentally the relationship between surface conductance and electrolyte concentration for a bentoniteJNaC1 system over a wide range of clay content. The method exploits the natural tendency of clay suspensions to form oriented films upon drying, in order to build up oriented pastes within a conductivity cell. Work previously reported in the literature has been concerned with disordered clay systems. In such systems, changes in salt concentration cause differences in internal structure of the paste which prevent a satisfactory approach to the required relationship. Surface conductance decreases with increasing electrolyte content at all interparticle spacings and it has a maximum value, in relation to paste porosity, for each electrolyte level. This maximum occurs at lower spacings as the salt content increases. The results are explained in terms of the dissociation and overlap of opposing counter-ion layers in the paste.
The annual pattern of potassium release from organic matter in sandy soils of south-west Australia
Authors: Roberts FJ
Published: April 2005

Regular field sampling of the 0-3 in. horizon of a sandy soil disclosed an annual pattern of potassium release from the organic matter fraction and retention by the microbial population. The exchangeable + soil-solution potassium content KE+S reached a maximum in autumn (March) at a time when microbial potassium KM and non-exchangeable potassium associated with organic matter KOM were at minimum levels. In soils containing 4% or more of organic matter the KM and KOM categories were important sources of supply of potassium entering the KE+S form. Release of potassium was rapid at temperatures of 40�C and above, but was much slower at lower temperatures. Temperatures in the surface horizon of soils in parts of south-west Australia often exceeded 40�C during the summer period; at these temperatures release occurred more readily in wet soils than in dry soils. Two slight peaks in microbial retention of potassium occurred during early winter (April-May) and spring (October-November). The significance of the observed fluctuations is discussed in relation to leaching and plant uptake of potassium.
The movement of water in swelling materials
Authors: Smiles DE , Rosenthal MJ
Published: April 2005

A theory is developed to describe the one-dimensional movement of electrolyte in clay-electrolyte systems that are free to swell in the direction of electrolyte movement. This theory develops from the observation that Darcy's law describes flow of fluid relative to the comparatively immobile particles of clay, and is based on a scale of length defined with reference to the distribution of mass of the clay rather than the more conventional fixed scale of length. It is shown, theoretically and experimentally, that in this scale of length the appropriate equation is the diffusion equation, for the use of which there exists a large body of information in soil physics and other literature.
Kinetics of sorption and volume change in clay-colloid pastes
Authors: Philip JR
Published: April 2005

The present paper analyses one-dimensional absorption (swelling) and desorption (shrinkage or consolidation) in two-component pastes of clay-colloid and electrolyte solution. The work deals specifically with the case where solution exchange with the paste column is possible only through its base. The extension to systems with 'top drainage' and 'double drainage' is trivial. The analysis combines Darcy's law applied to the flow of solution relative to the colloid particles with the continuity requirement. The hydraulic conductivity K and the moisture potential (i.e. minus the 'swelling pressure') � are taken to be arbitrary known functions of the volumetric solution content �. The fundamental flow equation which follows is basically a nonlinear partial integrodifferential equation. It can be restated as a Fokker-Planck equation with �-dependent 'diffusivity' and the 'drift velocity' spatially constant but unknown and time dependent. The dependent variable is conveniently taken as �, although it can be made � if this is desired. The specific problem is that of sorption consequent on a step-function change in applied load (i.e. of the value of � (or �) at the base of the column). The column is taken to be effectively semi-infinite, so that the solution applies only until swelling or shrinkage at the upper surface of the column first becomes significant. Under these conditions, the solution is of the similarity form x(�, t) = �(�)t1/2 where x is the space coordinate, t is time, and � is a function of � which is found by the solution of a nonlinear, ordinary, integrodifferential equation. With �(�) known, it is an elementary matter to deduce a great variety of properties of the sorption process: the instantaneous distribution of colloid content; the instantaneous rate of total volume change; the cumulative total volume change; the instantaneous local velocity and volume flux density of colloid; the instantaneous local mean velocity and volume flux density of solution relative to colloid; the instantaneous local absolute mean velocity and volume flux density of solution; the instantaneous local volume flux density of solution due to mass flow; and the displacement history of colloidal particles initially at various positions in the column.
Factors controlling the increase of cobalt in plants following the addition of a cobalt fertilizer
Authors: Adams SN , Honeysett JL , Tiller KG , Norrish K
Published: April 2005

The effect of applied cobalt on the cobalt content of pasture plants has been studied in pot, field, and laboratory experiments. The generally poor agreement between pot and field experiments may be partly due to the noted variation of cobalt status of pasture with season and the influence of waterlogging. Cobalt treatments were effective for at least 2 yr on the humus podzol soils, but there was only a residual effect for 1 yr on other soils. Alteration of the soil pH did not prove a satisfactory means of increasing cobalt status of pasture on soils where it was most required. The efficiency of cobalt fertilizers as a means of alleviating problems of cobalt deficiency depends on the manganese content of the soil. Plants grown on soils containing > 1000 p.p.m. of total manganese are unlikely to benefit from application of cobalt fertilizer to the soil, necessitating foliar application by sprays or the use of cobalt oxide pellets for stock.
Moisture equilibrium in the vertical in swelling soils. I. Basic theory
Authors: Philip JR
Published: April 2005

The classical methodology of the scalar potential is used to develop the theory of equilibrium moisture distribution in the vertical in swelling soils. In addition to the well-known moisture potential � and the gravitational potential -z (z being the vertical ordinate, taken positive downward), the total potential � includes a further component �, the overburden potential. It is shown that � = de/d� [P(Zo) + ?zzo] (A) where e is the void ratio, 6 is the moisture ratio, P(zJ is the load (if any) at the surface z = z,, and y is the apparent wet specific gravity. The equilibrium condition that � be constant in depth reduces to a first-order differential equation, the solutions of which represent equilibrium moisture profiles. The singular solution � = �pt for all z > zo (B) separates two distinct classes of non-singular solutions. �p, designated the pycnotatic point, is the moisture ratio at which � assumes its maximum value. Swelling soils satisfying certain conditions (which appear to be theoretically reasonable and agree with the data of soil physics and soil mechanics) possess one, and only one, pycnotatic point. In such soils, then, three distinct types of equilibrium profile occur: (i) Hydric profiles, for which the surface moisture ratio �o > �p. 6 decreases with increasing z, asymptotically approaching 8, at great depths. (ii) Pycnotaticprojiles, for which 8, = aP and equation (B) is satisfied. (iii) Xeric profiles, for which �o < �p. � increases with z, asymptotically approaching �p at great depths. The physical significance of this result is discussed with the aid of calculations for an illustrative example. The hydrology of swelling soils is entirely different in character from classical hydrological behaviour, which ignores the consequences of volume change. Contrary to a common notion, the effects of overburden potential manifest themselves right to the surface of the soil: it is not the magnitude of n, but that of d�/dz, which is important. The effect of swelling on the behaviour of the soil water may be crudely summarized as follows: Gravity operates completely in reverse to the expectations of classical theory in the 'normal' part of the hydric range; its effect diminishes to zero at the pycnotatic point; and it approaches classical behaviour at the dry end of the xeric range. Applications of the analysis to equilibrium states in hydrology and soil mechanics are treated in Part II. In later papers the concept of the overburden potential is applied to steady vertical flows and to infiltration in swelling soils.
Moisture equilibrium in the vertical in swelling soils. II. Applications
Authors: Philip JR
Published: April 2005

The paper discusses, with the aid of calculated examples, applications in hydrology and soil mechanics of the analysis developed in Part I. Various classical concepts of groundwater hydrology fail completely for swelling soils. The distributions of saturation and of hydraulic conductivity relative to the water table differ entirely from the conventional picture. Variations in surface topography affect moisture distribution in swelling soils. The theory of this effect is developed for topographies that are not too steep and is illustrated by examples. The equilibrium distributions found would be classically interpreted as disequilibrium states persisting because of small hydraulic conductivity; but, in fact, the moisture differentials are maintained, not by a lack of conductivity, but by a lack of difference in total potential. The variation of specific yield with water table elevation and stratum thickness in swelling soils is basically different from that in non-swelling soils. The analysis of Part I is used to discuss the following topics in soil mechanics: the variation of equilibrium soil levels with water-table depth, and with water depth over the soil; the effect of surface loading on equilibrium moisture profiles and on soil levels. Extension of the analysis to two- and three-dimensional systems is treated briefly.
Allophanic material in Australian soils derived from Pleistocene basalt
Authors: Briner GP , Jackson ML
Published: April 2005

The clay fraction of four soils derived from Pleistocene basalt in Victoria, under a Mediterranean type climate, have been studied by X-ray diffraction, differential thermal, infrared, and electron microscopic techniques. Their chemical dissolution with alkali has shown that they contain about 25 % of allophane having a SiO2/Al2O3 molar ratio of about 4. This ratio is higher than that reported for sesquioxidic allophane and halloysitic allophane, and the name 'siliceous allophane' is proposed.
Early stages of infiltration in two- and three-dimensional systems
Authors: Philip JR
Published: April 2005

The paper establishes the series solution of problems of infiltration from cylindrical and spherical cavities. The leading term is the fundamental horizontal absorption solution. The second term, representing linearly additive interactions of gravity and m-dimensionality (m = 2, 3), follows at once from known solutions for one-dimensional infiltration and for m-dimensional absorption. The third term is evaluated by solution of an ordinary linear integrodifferential equation. Higher terms involve circumferential flow components, and partial equations must be solved to evaluate them. For small enough times these higher terms are negligible. Physically, this implies that flow is essentially radial at such times; mathematically, that, taken no further than the third term, the solution applies indifferently to infiltration from cavities and from semicircular furrows (m = 2) and hemispherical basins (m = 3). The relation between this solution and the linearized and delta-function approximations is explored. The practical implications for sorptivity determinations based on short-time infiltration from furrows and basins are examined.
Effect of extractant and molecular size on the optical and chemical properties of soil humic acids
Authors: Butler JHA , Ladd JN
Published: April 2005

Humic acids extracted from soil with sodium pyrophosphate have greater proportions of lower molecular weight material, less acid-hydrolysable amino acid nitrogen contents, but greater carboxyl contents and extinction values (260 and 450 nm) than humic acids extracted subsequently from the same sample with alkali. Humic acids extracted with alkali from fresh soil samples have intermediate values. Extinction values at 260 nm are directly correlated with carboxyl contents for a given soil. Different crop histories have no significant effect on the measured properties of the extracted humic acids. An alkali-extracted humic acid has been fractionated by gel filtration into seven fractions of different nominal molecular weight ranges. As the molecular weights of the fractions increase, both aliphatic C-H (based on infrared absorption at 2900 cm-1) and acid-hydrolysable amino acid contents increase, whereas extinction values at 260 nm and carboxyl contents decrease. The infrared spectra of the high molecular weight fractions have peaks at 1650 and 1510 cm-1 which correlate with acid-hydrolysable amino acid contents and which correspond to amide I and II bands of peptide bonds. Alkaline hydrolysis to split peptide bonds eliminates both these peaks. The spectra also have peaks at 1720 and 1210 cm-1 which correlate with the carboxyl content.
Inhibitory effect of soil humic compounds on the proteolytic enzyme pronase
Authors: Ladd JN , Butler JHA
Published: April 2005

Neutralized solutions of soil humic acids inhibit the proteolytic activity of the enzyme pronase when tested against a variety of substrates. Protein hydrolysis was less sensitive than hydrolysis of dipeptide derivatives; 50% inhibition of benzyloxycarbonylglycylleucine hydrolysis was achieved with concentrations of humic acids as low as 1-2 �g/ml or less than 10-5M, on a carboxyl group basis. Humic acids, extracted from soils with different crop histories, showed only slight differences in their effectiveness as inhibitors of pronase activity. Their inhibitory power was comparable with that of other high molecular weight polyanions, e.g. polyacrylic acid and polycondensates derived from p-benzoquinone and catechol. Alginic acid was a relatively poor inhibitor. Preincubation of humic acids for various periods with either pronase or substrate (albumin or benzyloxycarbonylglycylleucine) had little or no effect on the subsequent inhibition of enzymic activity. However, inhibition is decreased by increasing substrate concentrations, following preincubation of humic acids and pronase. Both observations are consistent with a reversible inhibitory mechanism. Kinetic studies demonstrate that humic acids inhibit pronase activity towards albumin and N-benzyloxycarbonyl dipeptides by effectively reducing the affinity of pronase for the substrate, i.e. by increasing the Km value for the reaction. With benzoylarginine amide and benzoylarginine ethyl ester as substrates, the reaction velocity is lowered due to a reduction of the maximum velocity of the system. Both effects may possibly be explained by a conformational change in the enzyme structure due to combination with the humic acid molecules.
Corrigenda - Inhibitory effect of soil humic compounds on the proteolytic enzyme pronase
Authors: Ladd JN , Butler JHA
Published: April 2005

Neutralized solutions of soil humic acids inhibit the proteolytic activity of the enzyme pronase when tested against a variety of substrates. Protein hydrolysis was less sensitive than hydrolysis of dipeptide derivatives; 50% inhibition of benzyloxycarbonylglycylleucine hydrolysis was achieved with concentrations of humic acids as low as 1-2 �g/ml or less than 10-5M, on a carboxyl group basis. Humic acids, extracted from soils with different crop histories, showed only slight differences in their effectiveness as inhibitors of pronase activity. Their inhibitory power was comparable with that of other high molecular weight polyanions, e.g. polyacrylic acid and polycondensates derived from p-benzoquinone and catechol. Alginic acid was a relatively poor inhibitor. Preincubation of humic acids for various periods with either pronase or substrate (albumin or benzyloxycarbonylglycylleucine) had little or no effect on the subsequent inhibition of enzymic activity. However, inhibition is decreased by increasing substrate concentrations, following preincubation of humic acids and pronase. Both observations are consistent with a reversible inhibitory mechanism. Kinetic studies demonstrate that humic acids inhibit pronase activity towards albumin and N-benzyloxycarbonyl dipeptides by effectively reducing the affinity of pronase for the substrate, i.e. by increasing the Km value for the reaction. With benzoylarginine amide and benzoylarginine ethyl ester as substrates, the reaction velocity is lowered due to a reduction of the maximum velocity of the system. Both effects may possibly be explained by a conformational change in the enzyme structure due to combination with the humic acid molecules.
The effect of methylation of humic acids on their influence on proteolytic enzyme activity
Authors: Butler JHA , Ladd JN
Published: April 2005

Humic acids, methylated with diazomethane, no longer inhibit or stimulate proteolytic enzymes. If an exhaustively methylated humic acid sample is hydrolysed to different degrees, there is a direct relationship between the number of carboxyl groups freed and the effect of the sample on the activities of four proteolytic enzymes. When fully hydrolysed the humic acid sample has essentially the same effect as the untreated humic acid, although the phenolic groups are still methylated. These results suggest that carboxyl groups, not phenolic groups, are responsible for the influence of humic acids on enzyme activity.
The one-dimensional consolidation of columns of soil of finite length
Authors: Smiles DE , Poulos HG
Published: April 2005

An analysis of the one-dimensional consolidation of a saturated column of soil of finite length is presented. This analysis, which is based on the theory of water movement in one-dimensional swelling systems, makes no assumptions of constancy with regard to variation of the flow parameters with variation in void ratio, and is not restricted in its application by the magnitude of the strains involved. An explanation of secondary consolidation is a consequence of the procedure.
Effects of soil temperature on root growth and on phosphate uptake along Pinus radiata roots
Authors: Bowen GD
Published: April 2005

At 3 weeks, uptake of phosphate along roots of seedlings grown in soil at 25�C was greatest in the apical centimetre and decreased sharply along the roots. By contrast uptake was markedly more sustained along the roots of seedlings grown in soil at 14�C and here the greatest uptake occurred several centimetres behind the apex. No one pattern of ion uptake along roots can be assumed to hold for all conditions of growth when constructing mathematical models of ion uptake from soil. Increasing soil temperature from 15�C to 25�C approximately doubled total root length of 3-week seedlings of Pinus radiata; primary root length was increased but the main effect was due toa marked increase in the number and length of lateral roots. Lateral root growth of the 3-week seedlings was almost completely suppressed in the soil at 11�C. Roots of 3-week sterile seedlings growing in phosphate-deficient nutrient solution were considerably smaller than those of pine grown in complete nutrient solution at 15�C but not at 25�C. This interaction of temperature and phosphate deficiency did not occur with soil grown seedlings. The sustained phosphate uptake along roots grown at the low soil temperature did not compensate for greater root growth (and therefore soil exploration) at higher temperatures, for P content of 3-week seedlings grown in soil at 25�C was considerably greater than that of seedlings grown in soil at 15�C. In phosphate poor soils low temperature depression of root growth will seriously restrict phosphate uptake. A modification of the scanning method for uptake sites along roots showed translocation to occur from all parts of the root with rather less translocation from the apical centimetre than from other parts.
Numerical classification of soil profiles on the basis of field morphological properties
Authors: Campbell NA , Mulcahy MJ , Mcarthur WM
Published: April 2005

The use of numerical taxonomy to classify soils avoids classification schemes based on logical subdivision or keys by the application of objective numerical procedures to assess the similarity, and the subsequent identification, of soil groups. It was found that a combination of a hierarchical sorting strategy and a coordinate strategy avoided distortion of relationships and subjectivity in group recognition. The results of the numerical classification agreed closely with the original field grouping. Examination of the resulting soil groups indicated that texture profile was an important diagnostic property.
Mechanisms of clay stabilization with inorganic acids and alkalis
Authors: Ingles OG
Published: April 2005

A series of mono- and di-valent cation hydroxides, and certain strong acids, were allowed to react with a two- and a three-layer clay mineral (kaolin and montmorillonite) under conditions simulating those for normal soil stabilization in field practice, i.e. mixed, remoulded, and moist-cured at a moisture content and density approximating optimum compaction conditions. The progress of reaction was followed over extended periods of time, up to two years. Changes in strength and volume were correlated with chemical and mineralogical changes in order to identify those bonding mechanisms which contribute to inorganic soil stabilization. For an additive level of 10% by weight dry clay basis (9.1% total dry solids basis) it was shown that several distinct stabilization mechanisms exist. One major mechanism is the surface coating of fabric units, and another the reinforcement of the soil by product formation in crevices, angularities, pore constrictions, and similar defects which influence the mechanical properties of the whole sample. The importance of these reactions to practical soil stabilization is thus demonstrated.
The reaction of cobalt with manganese dioxide minerals
Authors: McKenzie RM
Published: April 2005

The adsorption of cobalt, copper, and nickel from solution by a number of synthetic manganese dioxides has been studied, and compared with the release of ions during the reaction. It was found that the initial rapid uptake of all three ions was followed by a period of slow uptake which continued for the duration of the experiment. During the slow phase of the reactions the uptake of cobalt was greater than that of copper or nickel, and cobalt released more manganese into solution. It is suggested that cobalt is able to replace Mn3+ in the crystal lattice, and this theory is supported by arguments based on crystal field theory.
The effect of column diameter on the infiltration behaviour of a swelling soil
Authors: Lal R , Bridge BJ , Collis-George N
Published: April 2005

The interaction between soil particles and the retaining wall of a column on the infiltration behaviour of a swelling soil was studied for six column diameters and three crumb sizes. The infiltration rate, rate of advance of the wetting front, and relative swelling, were found to be significantly affected by the column diameter, such that the smaller the diameter, the slower the infiltration rate and the rate of advance of the front and the smaller the swelling. In addition, an effect due to the soil fraction size was significant but much less important than column diameter. This secondary effect is attributed to the differential slaking of soil crumbs, greater slaking depth being associated with larger size fractions for a given column diameter. The surface layer during infiltration has a structure quite different from that associated with original crumb structure and the layers below the surface. This layer, in which both swelling and slaking have occurred, controls infiltration, and the entry of water into the profile is similar to that observed for a two-layered stratified system. It is concluded that the minimum column diameter for studies concerning water movement through swelling materials should be no less than 10 cm.
A statistical-chemical characterization of four great soil groups in Southern New South Wales based on orthogonal polynomials
Authors: Colwell JD
Published: April 2005

Statistical procedures are described for the characterization and comparison of profiles within soil classification units. Profile trends in a measured characteristic are represented by the coefficients of orthogonal polynomials in depth, and these coefficients are used as observations for standard statistical procedures. The mean of the respective coefficients provides estimates of the mean profiles for the classification units, and the variance-covariance matrix of the coefficients can be used to calculate the confidence intervals of these means. Differences between the mean profiles can be tested by analyses of variance. The variability of a range of chemical properties in the profiles of four Great Soil Groups, viz. yellow podzolic, red earth, red-brown earth, and grey clay, is described. The characterization is based on the analysis of profiles sampled from areas of about 0.4 ha chosen to represent cultivated examples of the groups in southern New South Wales. Variability of most soil properties is greater between these areas than within them, notable exceptions being exchangeable calcium and magnesium within the grey clay Group. This high localized variability is attributed to the gilgaied nature of this group in this region. Also variation between the soil groups is generally greater than within the groups. The differences seem, however, of limited importance from the point of view of soil fertility.
Atmospheric dust accession in South-Eastern Australia.
Authors: Walker PH , Costin AB
Published: April 2005

Reddish dust, transported by strong winds from the dry central regions of Australia, is periodically deposited in the humid eastern part of the continent. Dust sampled in snow on the Australian alps during 1968 is comparable in amount with accession reported earlier in the 1900's in New Zealand and Melbourne. The dust reported here has a median diameter of 4 pm, relatively high organic content, and mineralogy in the less than 2 pm fraction dominated by illite and kaolin. The rate of dust accession during the past was probably sufficient to have modified alpine soils. In particular, snow patch soils have a particle size and mineralogy consistent with dust enrichment. A much lower rate of dust accession seems to occur at present in Canberra on the Southern Tablelands.
Dissolution of gypsum, monocalcium phosphate, and superphosphate fertilizers in relation to particle size and porous structure
Authors: Aylmore LAG , Karim M , Quirk JP
Published: April 2005

The effect of variations in physical form such as particle size and mixing with other materials, on the rate of dissolution of sulphate and phosphate from solid fertilizers, has been investigated. It is apparent from these results that the degree of subdivision of a solid fertilizer is particularly important in determining its susceptibility to leaching. It has been demonstrated that leaching of sulphate is appreciably restricted when the granule size is 2 mm or greater in diameter. Except when leached immediately after application, the retention of phosphate is determined largely by 'reversion' to the relatively insoluble dicalcium phosphate form. combination of sulphate with phosphate in superphosphate or the addition of various additives to gypsum markedly reduces the rate of sulphate leaching in comparison to pure gypsum. A comparison of pore size distribution suggests that pores within the intermediate range from approximately 500 A to 105 A play a significant part in the dissolution process.
Effect of periodate and pyrophosphate on the seasonal changes in aggregate stabilization
Authors: Stefanson RC
Published: April 2005

Aggregates taken from sequential samplings of a range of red-brown earths showed a definite seasonal trend in relative stability. Maximum stability of the aggregates occurred in the summer, followed by a gradual decline during the autumn and early winter and an increase in the spring and early summer. In all phases of the crop-pasture rotation on all the red-brown earths, this trend was minimized by a combination of chemical treatments, designed to oxidize polysaccharides and polyuronides and to break the organic matter-polyvalent cation-clay bridge. The residual aggregate stability after the combined chemical treatment increased with the proportion of pasture phase in the rotation. Individually, the chemical treatments reduced the aggregate stability by a constant amount throughout all the seasons. The aggregate stabilizing mechanisms broken by the individual treatments make a constant contribution to stability throughout the year. This contribution increases with increasing cultivation in the rotation. In contrast, the aggregates taken from the solonized brown soil were stabilized by calcium carbonate. No seasonal trend or rotational effect was evident in these aggregates.
The influence of cobalt on the reactivity of manganese dioxide
Authors: McKenzie RM
Published: April 2005

The presence of cobalt in manganese dioxides is shown to reduce the reactivity when the amount of cobalt is sufficient to cover an appreciable fraction of the surface.
Physical and physico-chemical changes in the profile of sodic soil treated with gypsum
Authors: Sharma ML
Published: April 2005

Detailed examination of the profile of a brown sodic soil, 40 months after gypsum application, revealed that the effects of gypsum have extended down to a depth of 30 cm compared to 15-20 cm observed about seven months after the treatment. Comparisons also suggested that processes such as leaching and reaction with CO2 created by plant roots have been in operation as evidenced by reduced electrical conductivity (EC) down to 45 cm depth and pH in the 15-30 cm layer of the treated plots. Although the pH was significantly reduced in the surface layer (0-7.5 cm) of the control plots, the EC was increased. Probable reasons for this are discussed. Soil physical improvements in the profile were measured in terms of water penetration and storage, water desorption, aggregate stability, and relative hydraulic conductivity. Field measurements suggested that gypsum did not affect the bulk density in the profile, but increased water penetration and storage. In the laboratory, increased hydraulic conductivity (K), aggregate stability (ASI), and air-filled porosity were obtained for the samples collected from gypsum treated plots down to 30 cm depth. Highly significant negative correlations between the physical parameters (K, ASI) and the corresponding exchangeable sodium percentage (ESP) values supported the conclusion that physical improvements were consequences of gypsum treatment.
Reaction of surface-applied superphosphate with soil. I. The fertilizer solution and its initial reaction with soil
Authors: Williams CH
Published: April 2005

The phosphorus and calcium contents of the fertilizer solution from surfaceapplied superphosphate in contact with moist soil were shown to be similar to those of the metastable triple-point solution (MTPS) produced when an excess of monocalcium phosphate is shaken with water. The average phosphorus, calcium, and sulphur concentrations of saturated aqueous extracts of superphosphate at 20�C were 4.0M, 1.5M , and 0.023M respectively. The pH of these extracts ranged from 1.60 to 1.92 (0.15-0.47 units higher than that of MTPS). The sulphur content of the fertilizer solution was generally one-fiftieth to one-hundredth of the phosphorus content. In the absence of leaching both diffusion and capillarity were involved in the movement of phosphate from superphosphate particles into moist soil. The fertilizer solutes entered the soil mainly by diffusion but on soils of low moisture content the increase in pore size of the fertilizer particles, which resulted from the dissolution of monocalcium phosphate, led to a reversal of the suction gradient between soil and particle which caused movement of some of the fertilizer solution into the soil by capillarity. Leaching of superphosphate applied to dry soils by rainwater is likely to yield fertilizer solutions which have higher pH, lower phosphorus and calcium contents, and higher sulphur contents than the saturated solutions arising from superphosphate particles in contact with moist soil. When synthetic fertilizer solution reacted with acid soils the rate of removal of phosphate and calcium from solution depended upon the phosphate sorption capacity of the soil. In calcareous soil the calcium carbonate played a major part in phosphate precipitation. Appreciable amounts of iron and particularly aluminium were dissolved from each of the soils studied by the synthetic fertilizer solution to give solutions which, on standing, readily formed precipitates of phosphate. Both sulphate and organic sulphur compounds were displaced from the acid soils by the fertilizer solution but, in the calcareous soil, sulphate was coprecipitated with the phosphate.
Reaction of surface-applied superphosphate with soil. II. Movement of the phosphorus and sulphur into the soil
Authors: Williams CH
Published: April 2005

Phosphate moving into moist soil from particles of surface-applied superphosphate penetrated a hemispherical zone beneath the particle. The size of this zone and the distribution of phosphate through it were governed by the phosphate sorption capacity of the soil, the size of the particle, and the soil moisture. In calcareous soils the calcium carbonate content was important in determining phosphate penetration. Phosphate from superphosphate particles penetrated rapidly into moist (100 cm tension) soil during the first 5 or 6 days after contact and continued to move through the soil at a decreasing rate throughout the whole of an 8-week period. Movement of sulphate from surface-applied superphosphate into soil was governed by the particle size of the fertilizer and the soil moisture, both of which influenced the rate of solution of the calcium sulphate. The distribution of the sulphate through the soil was influenced by the sulphate sorption capacity of the soil. The rate of penetration of sulphate from surface-applied superphosphate into calcareous soil was considerably less than when the superphosphate was applied to acid soils. Leaching influenced the movement of both phosphorus and sulphur into the soil. It caused distortion of the hemispherical distribution of phosphate beneath superphosphate particles, resulting in deeper penetration of phosphate below the particles and smaller horizontal movement away from them. It also greatly enhanced the solution of sulphate, especially from small particles. The results indicate that the optimum particle size of superphosphate will vary from soil to soil, but a 2.5 mm diameter particle is likely to satisfy a wide range of soil and environmental conditions.
Infiltration and structural changes as influenced by initial moisture content
Authors: Collis-George N , Lal R
Published: April 2005

The variation of infiltration behaviour, in columns of aggregates of a structurally stable and an unstable soil, caused by pre-equilibrating the aggregates with a range of relative humidities from 0 to 98%, was measured in terms of advance of the front, cumulative infiltration, slaking, and swelling. In this range, the effect of initial moisture condition on the stable soil (krasnozem) was slight compared with that on the unstable soil (black earth); the wetter the soil initially, the greater was the infiltration rate, and the smaller the slaking and swelling. The change in the behaviour of infiltration into systems of stable aggregates is reflected as (1) an increase in the importance of the sorptivity, and (2) a reduction in the importance of the hydraulic conductivity contribution to the steady-state infiltration process. (The aggregates of 1/2-1 mm are of such a size that the sorptivity contribution should not normally be detectable in stable soils.) It is suggested that in the unstable soil, the heat of wetting is associated with aggregate collapse. The degraded structure of the surface layers prevents fast entry of water into the lower layers. The collapse of structure dominates the infiltration process so that the analysis in terms of sorptivity carried out for stable aggregates cannot be made. The effect of entrapped air on slaking of aggregates of these soils is shown to be negligible compared with the effect of initial moisture content. The application of the results to flood irrigation of unstable soils under field conditions is briefly considered.
Landforms and soils on an uplifted peneplain in the Darling Range Western Australia
Authors: Mulcahy MJ , Churchward HM , Dimmock GM
Published: April 2005

Landforms and soils of part of the Darling Range, Western Australia, are described. A controlling factor is rejuvenation of drainage following Tertiary (?) uplift of the Western Australian Shield, and the extent and effects of this are assessed. Broad divides carry remnants of old landscapes extensively preserved further inland, while sequential changes in valley forms and soils suggest stages in uplift. Upstream, valleys are broad and shallow, with low gradients, and deep weathering and old soils are widespread. Downstream, stages of progressively increasing sharpness and depth of incision of valleys are observable, and while deep weathering and old soils are preserved on the uplands, the steeper valley sides carry younger and fresher soil materials. Consideration of long and cross sections and soil patterns permit some separation of the effects of structure, uplift, and climate in landscape development.
Water repellence in sandy soils of South-Western Australia. II. Some chemical characteristics of the hydrophobic skins
Authors: Roberts FJ , Carbon BA
Published: April 2005

The hydrophobic organic skins on sand grains were resistant to removal by solvents such as cold water, concentrated acid, diethyl ether, ethanol, benzene, chloroform, and acetone. Prolonged treatment with hot diethyl ether, ethanol, and benzene removed part of the coating. Treatment with dilute solutions of alkali removed the skin as suspended particles. Compounds within the very stable humic fraction of the soil organic matter appeared to be mainly responsible for water repellence in soils. Deposits of fresh organic materials could also produce water repellent properties.
Flooded rice soils of Northern Australia. 1. Changes in salinity
Authors: Williams BG
Published: April 2005

Soil salinity, pH, and Eh were determined in two soil types on the Adelaide River plains (Northern Territory) throughout the growing period of a rice crop. Both the total salinity, as indicated by specific conductivity values of the soil solution, and individual ion species were followed at 30 sites in each soil. The results demonstrated the existence of salt gradients within the soil profiles and these gradients, together with the total salt concentration and ion ratios, remained relatively constant throughout the growing season. The results are discussed in terms of experimental methods commonly employed for determining the effects of soil solution properties on rice culture.
Studies on soil polysaccharides. III. Composition of polysaccharides in some Australian soils
Authors: Oades JM
Published: April 2005

Aldoses released by acid hydrolysis from soils, light fractions, soil extracts, and gel chromatographic fractions of the extracts were determined by gas-liquid chromatography. The results show that different soils contain different amounts of aldoses and these represent from 5 to 17% of the organic matter. Eight to 26% of the aldoses in soils was extracted by a pretreatment with 1N HCl; 25-55% by a subsequent shake in 0.5N NaOH, and a further 4-24% by a second treatment with 0.5N NaOH (ultrasonic dispersion). A final treatment of the soil with acetic anhydride containing H2SO4 extracted a further 8-29 % of the aldoses. From 4 to 35 % of the soil polysaccharides was not extracted by the four sequential chemical treatments. In the acid extracts of the soils, mannose dominated high molecular weight fractions, but glucose was dominant in smaller molecules. The sugar compositions of the NaOH extracts from different soils were similar, glucose representing about a third of the sugars present. The non-extracted polysaccharides and those extracted by the acetylation procedure were rich in glucose and considered to be from plant remnants not previously removed in the light fraction. It was concluded that the monosaccharide composition of different soils is very similar and that most of the differences in relative amounts of monosaccharides are associated with glucose, arabinose, and xylose which are probably present in plant fragments. These three sugars tend to be dominant in soils rich in plant remnants.
One dimensional vertical infiltration
Authors: Talsma T , Parlange J
Published: April 2005

Various concise equations have been proposed, and used, to describe the dynamics of one-dimensional, vertical, infiltration into uniform soils. Such equations, even when initial and boundary conditions are satisfied, do not describe infiltration with equal accuracy for all materials, especially when applied over a large time interval. Recently proposed equations appear more reliable and require only two, easily measurable, soil properties, viz., sorptivity and hydraulic conductivity, for application in most practical situations. Numerical, laboratory, and field data are presented. These adequately support the reliability of the solutions. The applicability of the solutions to field soils with systematically varying conductivity is more restricted than the two- or three-dimensional solutions.
Soil zinc and its uptake by plants. I. Isotopic exchange equilibria and the application of tracer techniques. II. Soil chemistry in relation to prediction of availability
Authors: Tiller KG , Honeysett JL , De Vries MPC
Published: April 2005

Isotopic exchange studies were applied to the laboratory and glasshouse measurement of labile zinc in 25 soils from nine Great Soil Groups. The laboratory equilibration procedures worked well with acidic and most near neutral soils, but may overestimate labile zinc values for the lateritic podzolic soils. The values for some acidic soils were also compromised because of lack of isotopic equilibrium. The laboratory method gave erratic and unrealistic data when applied to alkaline soils due to fixation of the added zinc. The procedures based on the specific activity of zinc absorbed by plants from soils equilibrated with carrier-free 65Zn gave reproducible values of the total amount of plant available zinc for all soils. These values agree well with the corresponding laboratory data for acidic soils. Furthermore, the specific activity data showed that magnesium chloride and EDTA extractions had equilibrated with the same chemical form or forms of zinc as that absorbed by the plants.
Effect of plant growth and form of nitrogen fertilizer on denitrification from four South Australian soils
Authors: Stefanson RC
Published: April 2005

In measuring losses of volatile nitrogen in sealed growth chambers, four major wheat-growing soils were used, namely, a mallisol, a red-brown earth, a calcareous sand, and a grey-brown soil of heavy texture. The rate of loss varied from 1 to 15 mg nitrogen/(kg soil/week) when nitrate nitrogen was applied to the soil; when ammonium nitrogen was used, losses were 1-4 mg nitrogen/(kg soil/week) over a 6-week period. The major component of these losses was nitrogen gas with lesser quantities of nitrous oxide. Both gases were produced by biological denitrification of soil nitrate. This was confirmed with an incubation experiment which used a portion of the same samples of soil. When nitrate nitrogen was applied to the soil, denitrification was increased by increasing soil water content and plant growth. These effects were greatest in the heavy textured soils. The application of ammonium nitrogen to the red-brown earth, mallisol, and grey-brown soil of heavy texture reduced the losses of soil nitrogen as nitrogen gas and nitrous oxide. Considerable losses of soil nitrogen were recorded for the calcareous sand when ammonium nitrogen was applied. Plant growth did not affect the losses of soil nitrogen from those soils receiving ammonium nitrogen.