Showing papers in "Soil Research in 1963"

Studies on soluble silica in soils. I. The sorption of silicic acid by soils and minerals

Abstract: Soils, representing a variety of great soil groups, were shaken with solutions containing monosilicic acid at concentrations not exceeding 135 p.p.m. The residual concentrations of monosilicic acid under near-equilibrium conditions depended on the nature of the soil, the level of added monosilicic acid, the solution : soil ratio and the pH of the soil suspension. The experimental results indicate that the residual concentration of monosilicic acid is controlled by an adsorption equilibrium which is dependent on pH; with acidification below pH 8-9 the residual concentration in soil suspensions steadily increases. Several samples of oxides and hydroxides of iron and aluminium were also shown to sorb monosilicic acid from solution. This sorption resembled that recorded for soils in its strong dependence on pH in the range 4-9. Sesquioxides appear to be responsible for much of the capacity of soils to sorb monosilicic acid. Wyoming bentonite and two kaolinite samples also sorbed monosilicic acid, at least from suspensions of pH above 7, and some natural and synthetic carbonates sorbed monosilicic acid at their natural pH values. Such minerals may contribute to the ability of some alkaline soils to sorb monosilicic acid. The avidity with which some soils sorb added monosilicic acid suggests that some native silica occurs in soils in the sorbed state. Some implications of this suggestion and of the other results are discussed in relation to some previous work on soils and natural waters, possible adsorption mechanisms, and some pedogenetic processes.

The chemical nature of soil organic phosphorus. I. Inositol phosphates

Abstract: Gradient elution chromatography, using a column of anion exchange resin, Dowex AG I-X8, has been used to separate and isolate constituents of the 'phytin' fraction of soil organic matter. In addition to the commonly occurring myoinositol hexaphosphate the presence of the corresponding derivatives of DL-inositol and scylloinositol was demonstrated. Of the lower inositol phosphates present pentaphosphates appeared to be the major constituents. The occurrence in nature of inositols, other than the myoinositol, as phosphorylated derivatives, has not previously been recorded. Present knowledge is insufficient to decide whether soil inositol phosphates are of plant origin or accumulated through the activities of soil microorganisms.

The rate of water entry into dry sand and calculation of the advancing contact angle

Abstract: For water entry into a vertical column of dry sand, the height of capillary rise, h, is defined for the present purposes as the maximum height of capillary rise in the sand, below which the moisture content is uniform. Previous experimental results on water entry into dry sand have been reviewed to show the validity and usefulness of this definition. The rise of the wetting front into a vertical column of sand was measured, the rate of rise of the wetting front was plotted against the reciprocal of the height of rise, and 1/h was found by extrapolating the line to zero rate of rise. For water-repellent sand a positive hydrostatic head was applied to the base of the sand to obtain an adequate number of points for the extrapolation. This pressure was adjusted so that the initial rate of advance of water into the sand was about equal to that of water into the ignited sand with no positive applied pressure. The advancing contact angle averaged over the wetted surface area of the sand was then calculated from the ratio of the values of h obtained with sand before and after ignition. The contact angle of a water-repellent sand has been shown to be higher than 90°. This explains the difficulty experienced in the field of wetting these sands. Two remedial measures are suggested: one is to cultivate and mix the soil to give a uniform average contact angle, the other is to cut slots so that a positive hydrostatic pressure can be applied to the deeper patches of high contact angle sand.

Activity of polyphenolic constituents of leaves of Eucalyptus and other species in complexing and dissolving iron oxide

Abstract: The polyphenolic constituents of aqueous extracts from the leaves of 11 Eucalyptus species and 7 other Western Australian tree and shrub species are examined in relation to their capacity to complex iron and dissolve iron oxides. The leaves of the Eucalyptus species contain mainly gallic acid, ellagic acid, hydrolysable tannins, leucoanthocyanins, and flavonol glycosides. Gallic acid forms soluble complexes with ferrous and ferric iron which are relatively less stable than ferrous aa'-dipyridyl. Tannic acid forms a soluble ferrous complex which is more stable than ferrous aa'-dipyridyl. The complexes formed on addition of ferric iron to the hydrolysable tannins, leucoanthocyanins, and flavonol glycosides are apparently insoluble, but can be solubilized by reduction to ferrous iron in the presence of sufficiently strong reducing agents. Ferrous complexes with flavonol glycosides and leucoanthocyanins are less stable than ferrous aa'-dipyridyl. No simple correlation could be established between the total quantity of polyphenols and iron oxide solubilized under aerobic conditions. This may be due to the contrasting effects of solution and precipitation of iron-polyphenol complexes which are shown by different classes of polyphenols and to the appreciable capacity shown by substances other than polyphenols to dissolve iron oxides.

Weathering and soil formation on dolerite in Tasmania with particular reference to several trace elements

Abstract: The mineralogy and chemistry of weathering and soil formation have been studied at 17 widely separated sites with contrasting climatic conditions on comparatively uniform dolerite in Tasmania. The clay and fine sand mineralogy of the soils has been related to their degree of weathering. These studies have shown large chemical and mineralogical changes accompanying the initial stages of weathering in some krasnozem soils. The reorganization of cobalt, zirconium, nickel, copper, molybdenum, manganese, and zinc during genesis of four soil groups has been considered in terms of the factors involved. Some of these results indicate that the clay horizon of the podzolic soils has probably been formed by weathering in situ. Seasonal waterlogging in certain horizons has strongly mfluenced the chemistry and mineralogy of weathering in many of these soils. This study has shown that the composition of the parent material has only influenced the geochemistry of trace elements in less weathered soils and that pedogenic factors assumed greater significance as the soils became more strongly weathered. Geomorphic processes had a marked influence on the geochemistry of some soils by the truncation of mature soil profiles.

Solubility of simple aluminium compounds expected in soils. I. Hydroxides and oxyhydroxides

Abstract: Results from dissolution equilibria with four aluminium hydroxide and oxyhydroxide compounds in M/100 K2SO4 over pH range 3.5-10, when examined by plotting the negative logarithm of the aluminium ion concentration against the pH, showed that AlOH2+, Al(OH)2+, and Al(OH)4-, hydrated and possibly polymeric, were formed. For pH>7, precipitated aluminium hydroxide (containing mostly boehmite) gave bayerite equilibria while gibbsite, diaspore, and bauxite gave gibbsite equilibria. For p H t 7 amorphous A1(OH)3 and corundum equilibria were observed. Using accepted free energy values, the following were estimated at 2.5°: KS1 = log [(AlOH2+)(OH-)2] = -23.31 and KS2 = log [(Al(OH)2+)(OH-)] = - 14.04 for amorphous Al(OH), and KS1 = -24.41 and KS2 = -15.14 for corundum and also AF° values of 164.9, -215.1, and -313.9 kcal for A10H2+, Al(OH)2+, and Al(0H)-4 respectively in aqueous solution.

Cracks, peds, and their surfaces in some soils of the Riverine Plain, New South Wales

Abstract: The nature and arrangement of cracks (planar voids) and peds in two redbrown earth profiles and two grey and brown soils of heavy texture profiles are described and their possible origin is discussed. The planar voids are classified and six patterns recognized. The vertical sequence of these patterns in each profile appears to be mainly controlled by the wetting and drying history, but in all profiles vertical cracking tends to predominate in the uppermost clay horizons and horizontal cracking becomes more significant with increasing depth. Specific modifications on natural surfaces (cutans) are not associated with particular kinds or patterning of planar voids, but are probably influenced to some extent by the swelling-shrinkage behaviour of the material. Peds have been redefined on the basis of recognizable natural surfaces as distinct from the occurrence of populations of units of similar size and shape; certain of the crack patterns separate peds of variable size and shape.

Isotopic studies on the uptake of nitrogen by pasture grasses. I. Recovery of fertilizer nitrogen from the soil : plant system using rhodes grass in pots

Abstract: Results are reported of the first of a series of studies on the fate of nitrogen applied to soil under pasture. Two series of pretreatments (nil and 200 lb/ac N) were imposed on Rhodes grass, Chloris gayana Kunth, grown on a light-textured soil in pots in a glasshouse. Subsequently the grass was cut 3.3 cm above the soil surface and labelled ammonium nitrate (15NH4NO3) was added in amounts up to the equivalent of 800 lb/ac N. The fate of this added nitrogen was determined at the end of the experiment by analyzing the total contents of each pot for nitrogen and for 15N. The quantity of total nitrogen found in the pots (which included both labelled and unlabelled forms), and that of labelled nitrogen, were each linearly related to the amount of ammonium nitrate added. Regression analysis showed that 93.6% of added total nitrogen, and 94.0% of added labelled nitrogen, was recovered from the soil : plant system. These recoveries did not differ significantly from one another, indicating that the loss fell equally on labelled ammonium nitrogen and some unlabelled form of nitrogen; it is possible that this loss took place from the added ammonium nitrate fertilizer. There was no evidence to indicate the stage at which this loss occurred. Nitrogen pretreatment had a marked effect on the weight of stubble and roots in the pots when the ammonium nitrate was applied, but had no effect on nitrogen loss. Errors encountered during chemical and mass spectrometric analysis of the soil and plant material are discussed.

Soil studies at Swan Hill, Victoria, Australia. IV. Groundsurface history and its expression in the array of soils

Abstract: This paper traces the events associated with the development of aeolian and riverine landscapes at Swan Hill. These phenomena are characterized by a sequence of alternations between unstable phases featuring erosion and deposition and stable phases during which soil development occurred. Four groundsurfaces were studied in the aeolian landscape. The unstable phases involved were sufficiently arid to result in a depletion of protective vegetation and allow the destruction of the previous groundsurface by erosion and burial. Inception of more humid conditions allowed the re-establishment of the vegetation. Aridity also extended westward from Swan Hill, but it was probably more severe to the west during the three earlier unstable phases than during the more recent one. Three groundsurfaces on riverine material were studied and it was considered that one of these could be subdivided into two layers. The unstable phases were characterized by deposition resulting in the burial of the previous groundsurface and evidence suggests that it also occurred during the more arid conditions rather than the more humid. There is a waning in magnitudes (as indicated by the degree of profile development) of both the unstable and stable phases from the earlier to the more recent groundsurfaces.

Soil studies at Swan Hill, Victoria, Australia. II. Dune moulding and parna formation

Abstract: The study involving a granulometric examination of the sedimentary nature of layers of aeolian material at Swan Hill, Vic., shows that the wind erosion of soils leading to the sorting of the components can result in the formation of a dust or suspended component and a saltation or dune-sand component. The former material, parna, contains most of the clay and lime of the original soil material. This is considered to be composed of fine aggregates associated with a companion sand which, in the neighbourhood of the dunes, has a diameter range of 70 to 90 µ. This material is normally separated from the saltation sand by wind action. However, under conditions of accession of parna at a site where saltation sand is in motion the parna becomes mixed with the saltation sand in a graduated manner, least being deposited at the crest. The periodic moulding of the dunes by local erosion and deposition and accession of regional parna is discussed.

Unsaturated flow properties of soils

Abstract: Experiments to determine the unsaturated flow properties of soils are based either on the steady-state Darcy equation or on the transient diffusion equation. An apparatus has been designed to compare the steady-state and transient methods on the same sample. Results indicate that the transient outflow pattern at high moisture contents (using a coarse sand) differs considerably from that predicted by diffusion theory. The extended theory which takes into account the air as well as the water phase also does not agree with the observed transient behaviour at the high moisture contents. At low moisture contents the agreement between the two methods is considerably better. The transient outflow method was found to be inapplicable at the high moisture contents. Much of the difficulty is attributed to the inaccessibility of air to drainable pores under these conditions.

Soil studies at Swan Hill, Victoria, Australia. III. Some aspects of soil development on aeolian materials

Abstract: The progress of soil development at Swan Hill has been examined by the comparison of four successively older soil profiles which have all developed on aeolian materials at different times in history. The initial development is one of homogenization effected by biotic agencies that obliterates the depositional fabric and structure. There are found to be several other trends in profile differentiation which have advanced further in each older soil. These trends include the leaching of lime from the surface and its concentration into concretions, and the removal of clay from the surface and its deposition as coatings to grains, pores, and peds and as a dense matrix.

The measurement of chemical potential of phosphate in soil suspensions

Abstract: The dependence of Schofield's phosphate potential on the soil/solution ratio and the time of shaking of the suspensions was reaffirmed and studied in some detail. Some factors which could affect the measurement of potential were investigated, but the cause of the observed variations of potential was not resolved.

Soil history and debris avalanche deposits along the Illawarra scarpland

Abstract: Two major periods of avalanching have occurred along the Illawarra scarpland. The older, the Scarborough formation, is characterized by a very thick, acid, weathered zone, similar to the lower mottled horizons of laterite profiles. The younger, Keira formation, has relatively shallow red and yellow earth profiles developed in it. Although its profile of deep weathering has some features in common with laterite, the Scarborough formation is not part of the general laterite surface, but represents a separate period of prolonged stability and weathering. The debris-avalanches are thought to have been deposited during excessively wet climatic conditions in the past, and they represent an alternate form of instability compared with the dry phase instability proposed for the K-cycle history of milder hillslope terrain near Nowra.

Solubility of simple aluminium compounds expected in soils. II. Hydrolysis and conductance of Al3

Abstract: The results of conductimetric measurements on dilute aluminium chloride solutions at 25° were found to be best fitted by the limiting equivalent conductances A01/3Al3 + = A01/2AlOH2+ = 58.2 with the parameter for ionic diameter 6.0A and by *K1 = log [(AlOH2+)(H+)/(Al3+)] = - 5.05 when it was assumed that AlOH2+ and H+ concentrations produced by hydrolysis were equal in the measured solutions. Potentiometric measurements and calculations from solubility work gave *K1 = -5.00 and -4.97 respectively. After small changes, e.g. by aging, dilute aluminium salt solutions conform to the solubility expression for aluminium hydroxide, log [(AlOH2+) (OH-)2] = -23.31.

A study of some aspects of the hydrology of some irrigated soils of western New South Wales

Abstract: In an investigation of soil degeneration in an irrigation area adjacent to a channel, piezometric techniques were used to establish that seepage from the channel was the main source of water contributing to an abnormally high water-table, and by graphical integration methods it was possible to establish a rate of seepage which was verified using a numerical solution of the approximate equation az/at = KH/f . a2z/ax2 The two-well method of Childs, Collis-George, and Holmes (1957) was used to establish that there was little or no difference in horizontal permeability between various sites but that the areas with no or degenerate vegetation were isotropic, while the normal areas in terms of plant behaviour and soil surface stability were anisotropic with a value for the horizontal component of permeability greater than that of the vertical component. These observations, together with observations of a high water-table and high rate of potential evaporation, are used to propose a consistent theory to explain the incidence of and the increase in size of degenerate areas predisposed to become saline.

Solubility of simple aluminium compounds expected in soils. III. Aluminium ions in soil solutions and aluminium phosphates in soils

Abstract: Many published values for the aluminium contents of displaced solutions and extracts from soils at varying pH values have been examined and found to be quite compatible with recent findings that A1OH2+, Al(OH)2+, or their polymers are dissolution products from aluminium hydroxide. Variation of phosphate content has also been considered and no case can be made for the presence of variscite in the systems examined. As far as aluminium compounds are concerned, the evidence is in favour of sorption of phosphate by the aluminium oxyhydroxide surfaces in the soil.

The swelling of Na-montmorillonite due to water absorption

Abstract: Orientated flakes of dry Na-montmorillonite were brought into equilibrium successively with relative vapour pressures of 0.92 and 0.985 and the moisture contents, (001) spacings, and swelling measured, the latter with a travelling microscope. Over saturated water vapour the clay continued to swell with time, in contrast to Ca-montmorillonite. Hysteresis in swelling was only observed at values of p/po > 0.985. The further expansion of flakes when immersed in solutions, N in Na+, of sodium chloride with dilute buffer added (from pH 4.4 to 10) or sodium hydroxide or chloride plus neutral sodium pyrophosphate was determined. The Na+ concentration was then reduced and the corresponding swelling measured, until the flake dispersed. Similar experiments were made on orientated flakes prepared from Na-montmorillonite to which 1.5% cetyltrimethylarnmonium bromide (CTAB) had been added, as well as from Na-montmorillonite which had been washed with lithium chloride and heated before reconversion to the Na form. The expansion of Li-vermiculite crystals in lithium chloride solutions was also determined. In solutions N in Na+ the swelling of Na-montmorillonite flakes was independent of pH, but for Na+ < N/2 the swelling increased sharply above pH 8.0. The swelling of Na-clay + CTAB was much less than untreated clay and was independent of pH. Na-montmorillonite which had been lithium-treated at 95°C gave a swelling pattern at pH 4.4 similar to that of Na-clay + CTAB, whereas in sodium hydroxide the pattern was similar to that of untreated clay. The specific effect of the pyrophosphate anion on the swelling of the CTAB-treated clay was slight. There was marked hysteresis in the swelling of Na-montmorillonite with respect to salt concentration, whereas the swelling of Li-vermiculite was almost reversible. Adding CTAB inhibited the intercrystalline swelling of Na-montmorillonite, the CTA+ ions forming Stern layers on the external surfaces of the crystals. A similar effect was apparently produced in the acetate buffer by aluminium ions released during the lithium treatment. The increase in the swelling of the untreated clay with pH is consistent with the removal of aluminium ions from the external surfaces of the crystals. There must be residual attractive forces between the crystal at high pH to account for the stability of the clay in dilute salt solutions. The edge to face forces linking the silicate sheets together appear to be constant above pH 4.0. Neutral sodium pyrophosphate disperses the clay at Na+ concentrations of < N Na+ by removing aluminium ions and neutralizing positive edge charges. The montmorillonite crystals are considered to be linked mainly edge to edge in a tactoid. The bands observed in thin sections of expanded gels, using polarized light, may be due to a periodicity in the stacking of the silicate sheets forming the crystals.

Trace element contents of some Queensland soils

Abstract: The weighted mean concentrations of cobalt, copper, gallium, manganese, molybdenum, nickel, vanadium, zinc, and zirconium (and also of iron) are given for 28 soil profiles from Queensland. The concentrations of the same elements in 118 surface soils are presented as histograms. Soils of any one taxonomic group have characteristic, but not unique, trace element properties. The concentrations in surface soils of most of the elements have well-defined frequency distributions.

Solubility of simple aluminium compounds expected in soils. IV. Reactions of aluminium hydroxide under acid conditions

Abstract: Solubility constants for aluminium hydroxides and oxyhydroxides previously obtained (Raupach 1963a) were supported by further studies at 20° and 50°. Polymeric aluminium ions were not present in systems obeying Ks1 = -log [ AlOH2+) (OH-) 2] = 23.31 at 25°C When 5 < -log [AlOH2+] < 3 no Al3+ ions are found in solution because the aluminium hydroxide surface readily binds Al3' ions, produced slowly in solution, and releases AlOH2+ ions. This also happens in soil solutions.

The uptake of calcium and strontium by plants from some Australian soils

Abstract: Calcium and strontium in eastern Australian soils and their uptake by plants have been examined in pot culture and under field conditions. The ratio of calcium to strontium in the plant material was closely related to the ratio of exchangeable calcium to exchangeable strontium in the soil, although the plants always contained a higher proportion of calcium. This was probably due to the difference in the adsorption of calcium and strontium by the soil colloids, and to small differences in the relative movement of calcium and strontium from the roots to the plant tops. The proportion of calcium to strontium in the plant material was similar to that in a water extract of the soil; this suggests that the two ions are taken up through the soil solution without any marked discrimination between them. While the proportion of calcium to strontium in the plant roots of oats and cocksfoot was generally similar to that in the plant tops, the roots of subterranean clover and Erodium botrys contained an appreciably higher proportion of strontium. However, since less than 20% of the total calcium and strontium uptake by these two species remained in the roots the effect of this on the proportions in the plant tops was small. Decreases in exchangeable calcium and strontium in soils following the growth of subterranean clover plants in pots were sufficient to account for almost 80 % of their total uptake by the plants. The amounts of calcium and strontium taken up by the clover in pots were related to the amounts of the exchangeable ions in the soil but the smaller uptake of calcium by oats was more closely related to the water-soluble calcium. When soluble calcium and strontium were added to soils in pot culture the ratio Ca/Sr (plant tops) in oats was closely related to the ratio Ca/Sr (exchangeable + added). The addition of calcium carbonate to the surface of three soils in pots markedly increased the ratio of calcium to strontium in the plant tops of subterranean clover in each case. Under field conditions the uptake of calcium and strontium by subterranean clover appeared to be related to the exchangeable forms in the surface 4 in. of soil. With wheat, however, other factors seemed to Influence their uptake including the soil calcium and strontium at depths below 4 in. The accumulation of calcium from superphosphate in the exchangeable form under subterranean clover pastures increased the ratio Ca/Sr (exchangeable) in the surface soil.

The distribution and pedology of soil mosaics, Barossa District, South Australia

Abstract: Black earths and Australian brown earths occur in ways contrary to normal expectation in the red brown earth zone of southern Australia. The soil pattern is an intimate fine-grained mosaic of the three great soil groups changing within a few yards from one to another in an erosional landscape and quite out of accord with the underlying Precambrian metamorphic rocks. Field studies reported here ascribe the black earths to thin intermittent remnants of a lacustrine Tertiary clay as parent material, and the brown earths to a mixture of the clay with the normal weathering products of the underlying rocks. A substantial part of the evidence for this is derived from their distribution as a horizontal lamina tracing out a contour band in the mid and upper mid slope topography. There is a nice accordance between the elevations of this band and of an adjacent, elevated, dissected black clay plain. The three soils are everywhere found in places which are consistent with the postulate that their parent materials were put there by processes of erosion, dissection, and redistribution of distinctly separate hill and high plain landscapes.