Showing papers in "Soil Research in 1978"

The use of environmental chloride and tritium to estimate total recharge to an unconfined aquifer

Abstract: A portion of the Gambier Plain underlain by an unconfined aquifer with readily definable hydrologic boundaries has been divided into a number of areas within which soil types have similar hydrologic properties. Mean annual recharge has been estimated for each area using both the tritium concentration and the chloride concentration of water within the soil profile. Good agreement was obtained between the two methods with local recharge varying between 50 and 250 mm year-1. Total mean annual recharge for the area has been estimated to be 2.4 ± 0.3 x 108 m3 year-1, and this compares favourably with an estimated discharge of 2.5 ± 0.3 x 108 m3 year-1.

Soil solution studies on weathered soils from tropical north Queensland

Abstract: Solutions obtained from six soils in tropical North Queensland after incubation at a moisture tension of 0.1 bar were analysed to obtain data on their ionic strengths. Soil extracts, at soil: solution ratios of 1:1, 1:2.5, 1:5, and 1:10 were also examined. Determinations on the aqueous phase included electrical conductivity, pH, ammonium, calcium, magnesium, potassium, sodium, bicarbonate, chloride, sulphate, and nitrate. Ionic concentrations of the soil solutions were found to be low when compared with many of the values reported in the literature. The upper limit for the ionic strength was about 0.005. Ionic strength was well correlated with the electrolytic conductivity of the soil solution itself, and also of the soil extracts. Relationships found between the soil solution and soil extracts in respect of total cation (and anion) content and also cation ratios, allow predictions about the soil solution to be made from soil extract data. Consideration of the ionic ratio of calcium to total cations in these soils suggests that the soils may have suboptimal levels of calcium for the growth of many plant species.

The stability of soil aggregates as affected by organic materials, microbial activity and physical disruption

Abstract: On moist incubation the equivalent of 50 t ha-1 or more of ground, readily decomposable organic materials greatly increased the proportion of stable aggregates of Shepparton fine sandy loam within 1-4 weeks; the aggregates remained stable for up to 32 weeks if left undisturbed. Severe restriction of microbial activity in aggregates of Shepparton fine sandy loam by sterilization or dryness increased the effect of physical disruption associated with intermittent wetting and drying, and simulated cultivation. The results suggest that microorganisms in non-sterile moist soil can produce bonding substances which compensate partially for those bonds broken physically.

Salinization of non-irrigated soils and associated streams: a review

Abstract: Saline seepage has reduced agricultural production and increased solute and sediment loads in streams and rivers in Australia and North America. The problem has developed where soils which contain substantial quantities of soluble salts have been developed for cultivation within the last 50-100 years. Salts may accumulate in surface soils by evaporation of saline surface water from poorly drained areas, or by seepage and capillary flow from unconfined or leaky confined aquifers. For some part of the year, water at atmospheric pressure is usually found within a few metres of the surface of a saline seep. In exceptional combinations of soils and weather, salts accumulate in the plant root zone because there is no net movement of water beyond this depth. The key to reclamation of a saline seep is appropriate management of water: either surface or subsurface drainage, or encouraging maximum use of water by plants, particularly in recharge areas. Another strategy is to plant salt-tolerant vegetation on the seep and await the result of natural leaching processes, but these are often very slow. Several reclamation techniques have been investigated, but they have found little application up to the present time.

Preferential solute movement through larger soil voids. I. Some computations using simple theory

Abstract: Viscous solution flow down vertical cylindrical channels and planar cracks, with simultaneous molecular diffusion of the solute into the surrounding soil, was modelled. Chloride and phosphate were chosen as representative of non-sorbed and adsorbed ions respectively. In channels at least 0.2 mm in diameter, and cracks at least 0.1 mm wide, almost instantaneous preferential movement of both chloride and phosphate was predicted. Little or no preferential movement was predicted in smaller channels or cracks. For example phosphate was predicted to move to a depth of 200 mm within 10 min in saturated soil containing 0.2 mm diameter continuous channels. However, it would take phosphate over 2 months to reach the same depth in similar soil with the same hydraulic conductivity, but containing only 0.05 mm diameter channels. Channels and cracks permitting preferential solute movement would be solution-filled only at pressure potentials above - 0 2 m, so such movement can only occur in near saturated soil. Although highly idealized soil-void geometries were assumed, the results have a number of practical implications related to the movement of nutrients and pollutants in field soils.

Phosphate sorption by reduced and reoxidized rice soils

Abstract: Intact cores of two rice soils of south-eastern Australia were flooded for 146 days to simulate part of a rice-upland crop rotation. The phosphorus sorptivity, and acetate (pH 4.8) and oxalate (pH 3.0) extractable iron levels were monitored for 210 days, before, during and after flooding. The effects of additional organic matter (rice straw) and the growing of rice plants were examined. In non-flooded soils phosphorus sorptivity was mainly influenced by clay content; there were no relationships between extractable iron and phosphorus sorbed. On flooding there were large increases in acetate and oxalate extractable iron and phosphorus sorptivity. Additional organic matter initially increased the rates of formation of extractable iron, and phosphorus sorptivity increased accordingly. However, with prolonged waterlogging, levels of oxalate iron and phosphorus sorptivity reached values dependent on the free iron oxide content of the soils. The growth of rice plants had no significant effects on phosphorus sorptivity or extractable iron at any time of sampling. During oxidation of previously flooded soils, levels of phosphorus sorptivity and oxalate iron decreased rapidly, but did not return to levels occurring before reduction. The results are consistent with domination of phosphorus sorption processes by ferrous hydrous oxides during the flooded (reduced) phase and by poorly crystalline ferric hydrous oxides during the post-flooding reoxidation phase. Agronomic implications of the results are mentioned.

The release of phosphorus from plant material added to soil

Abstract: An experiment was conducted to study the release of 32P from white clover plant residues in the presence and absence of growing oats plants in both low and high phosphorus status soils. Net reutilization of phosphorus from the added plant material after 48 days was highest in the high phosphorus system in the presence of plants (29.3 %) and least in the low phosphorus system in the absence of plants (0.6%). Watering to field capacity daily, every 3 days, or every 6 days, had no significant effect on reutilization rates. Evidence from the soil inorganic phosphorus data suggests that the addition of plant material resulted in a significant immobilization of soil phosphorus only in the low phosphorus soil in the absence of plants. The significance of these findings is discussed in relation to the large number of incubation studies conducted to study phosphorus turnover rates in soil.

Preferential solute movement through larger soil voids. Ii. Experiments with saturated soil

Abstract: Miscible displacement experiments, with chloride and phosphate ions in the displacing solution, were conducted on soil material manipulated to contain different void geometries. In packed 50 mm long columns of 0.2-0.5 mm aggregates the displacing solution moved fairly uniformly through the soil, with the relative chloride concentration in the effluent reaching 0.5 approximately 8 min after chloride was applied to the surface. The relative phosphate concentration reached 0.5 after approximately 7 h. In 50 mm long cast-columns of the same soil material containing a single cylindrical channel 0.5 mm in diameter, or a slit 12 mm by 0.2 mm, both chloride and phosphate moved almost instantaneously through the columns, reaching a relative concentration of 0.5 in less than a minute. The cast columns and packed aggregate columns all had similar hydraulic conductivities. These results are in general agreement with a previously developed theoretical model. An 'undisturbed' core of the same soil showed similar pronounced preferential movement of chloride and phosphate, indicating the presence of a continuous void greater than the critical minimum size. However, in contrast a duplicate core gave results more like those found for the columns of aggregates. Soil water retentivity curves are shown to be of very limited value for predicting preferential solute movement.

Interaction of monomeric and polymeric species of metal ions with clay surfaces. III. Aluminium(III) and chromium(III)

Abstract: Hydrolysis and polymerization in aluminium nitrate and chromic nitrate solutions with different metal/OH ratios were studied by gel filtration chromatography and ultrafiltration techniques. The characteristics of poly[Al(III)-OH] cations separated by ultrafiltration depended on the molecular weight which was controlled by the OH/Al ratio of the original solution. When the OH/Al ratio was 2.0 , the polycations had molecular weight > 100 000, low positive charge and rapidly condensed to gibbsite. Polymerization in chromic nitrate solutions was slow and the separated poly[Cr(III)-OH] cations had low molecular weight ( 100 000 could be explained if they consisted of planar sheets, formed from coalesced rings of aluminium octahedra, which crystallized into gibbsite.

Hydraulic properties of a red-brown earth determined from in situ measurements

Abstract: Hydraulic conductivity characteristics are described for the soil profile of a red-brown earth exhibiting swelling properties. These were determined from in situ measurements of water content and suction during the redistribution of water following the irrigation of a non-vegetated field plot. Greater water contents were required for the same hydraulic conductivity in the subsoil than for the surface soil below cultivation depth. At a given suction, hydraulic conductivity was generally lower in the subsoil. In a field check on the theory of hydrostatics in swelling soils, values of the overburden potential (U) were derived from theory in terms of readily measurable parameters; these were shown to be in good agreement with values determined independently from the measured change in soil-water suction following the removal of overburden.

The effect of two manganese dioxides on the uptake of lead, cobalt, nickel, copper and zinc by subterranean clover

Abstract: The uptake of lead, cobalt and to a lesser extent nickel by subterranean clover grown in pots on lead-contaminated soils was reduced by the addition of two varieties of manganese dioxide, while there was little or no effect on the uptake of copper and zinc. The results were consistent with the previously determined distribution of these elements between the manganese and iron oxides in soils.

Solubility relationships of iron, manganese, copper and zinc in alkaline and calcareous soils

Abstract: The solubility relationships of the native forms of iron, manganese, copper, and zinc in alkaline and calcareous soils were determined by a modification of the chelate equiIibrium method proposed by Norvell. The experimentally determined activity product (Fe3+)(OH-)3 in soils was found to vary within the reported range of solubility products of amorphous hydrous ferric oxides. Soils which undergo alternate cycles of reversible, oxidation-reduction processes were found to maintain higher solubility of iron and manganese than other soils. Soil pH and organic matter content were found to significantly affect the solubilities of all the four micronutrient cations. The solubility relationships of manganese, copper, and zinc have been expressed as a function of soil solution pH. Probable mechanisms controlling the solubility of these metals in alkaline and calcareous soils are discussed.

A note on the effect of soil tillage on the frequency and vertical distribution of spores of vesicular-arbuscular endophytes

Abstract: Spores of vesicular-arbuscular endophytes resembling Acaulospora laezis and Glomus monospovus were common in the surface layers of a soil under wheat and pasture, declining in numbers down the profile until rare at 500 mm. Tillage had no effect on total spore numbers, but directly drilled wheat had more spores in the surface 80 mm and fewer from 80 mm to 150 mm than conventionally tilled plots. This is thought to be a consequence of mechanical inversion of the soil during cultivation.

Note on the role of a shallow aquifer in dryland salinity

Abstract: The depth of a saline water table which may affect salinity of non-irrigated surface soil is estimated by extrapolation of the criterion used in irrigation agriculture.

The oxidation of manganous ions under acid conditions by an acidophilous actinomycete from acid soil

Abstract: A Stveptomyces sp capable of oxidizing manganous ions in soil agar to manganese oxide over the pH range 5-65 was isolated from an acid (pH 50) soil The organism failed to grow on organic media above pH 65 and had a pH optimum for growth of 5-55 On acid media its growth was restricted by manganous ions, and these were deposited as the oxide some distance from the colonies It is suggested that the function of manganese oxidation is to protect the organism from inhibiting levels of manganous ions The organism produced, under acid conditions (pH 50) in the presence or absence of added manganous ions, a water-soluble extracellular substance that could rapidly oxidize manganous ions to manganese oxide These observations are discussed in relation to the manganese status of acid soils

Routine particle size analysis of soils using sodium hypochlorite and ultrasonic dispersion

Abstract: A simple and rapid method for ultimate particle size analysis of soils has been developed which replaces the methods first introduced by Piper. The method relies on the removal of organic matter by sodium hypochlorite and a dispersion in an ultrasonic bath. This method has now been used nearly 2 years in our laboratories, and has resulted in a substantially greater throughput of samples with the same staffing component. The method is recommended for all service laboratories.

The influence of organic matter extracted from humified clover on the properties of amorphous aluminosilicates.II. Phosphate retention

Abstract: Freshly formed water soluble organic matter extracted from humified clover leaves was used to treat a range of amorphous aluminosilicates and hydrous alumina. Phosphate retention isotherms were determined on the resulting organomineral complexes. These isotherms revealed the influence of the organic matter on phosphate retention by amorphous aluminosilicates. The organic treatment was found to reduce phosphate retention by hydrous alumina and amorphous synthetic aluminosilicates with high and low Al/(Al+Si) mole ratios. There was no depression of phosphate retention with amorphous aluminosilicates of intermediate composition. Similarly, the phosphate retention capacity of an allophanic soil clay of intermediate Al/(Al+Si) mole ratio was not reduced by organic treatment. These results appear to be related to the degree of polymerization of charge balancing hydroxy-aluminium in the aluminosilicates.

Properties of biologically formed manganese oxide in relation to soil manganese

Abstract: Manganese oxide, produced from the oxidation of manganous ions by bacteria at pH 6.5, was extracted with solutions commonly used to estimate the availability of soil manganese to plants. Reducing agents at pH 7.0 completely dissolved the manganese oxide as did sodium ethylene diaminetetra-acetate (EDTA) solutions more acid than pH 6.0. Other acidic solutions extracted part of the manganese in amounts in proportion to the amount of oxide present. Neutral salts extracted only traces of manganese; however, the addition of copper or zinc salts to neutral M ammonium acetate resulted in the release of appreciable amounts of manganese from the oxide. The fact that sodium EDTA solutions and solutions containing copper and zinc released manganese from the bacterial manganese oxide indicates that the practice of extracting soils with these solutions to estimate of organically bound manganese is unsound. The oxide, when pre-heated from 50 to 108°C, became progressively more soluble in neutral M ammonium acetate. Manganese was also rapidly released when the pH of the oxide in suspension was lowered from pH 7 to pH 4. Conversely the oxide rapidly adsorbed manganous ions as the pH was raised from pH 4 to 7. These changes in manganese solubility parallel those reported for soils receiving similar treatments, and it is postulated that the active manganese oxides in soil are similar to bacterial manganese oxide. It is also suggested that the acid-replaceable manganese associated with the oxide plays an important part in the availability of manganese in soils.

A comparison of evapotranspiration measurements of crop communities using lysimeters and assimilation chambers

Abstract: A sensitive weighing lysimeter which can be constructed largely of common materials is described. The mechanical structure of the balance is similar to that of McIlroy, but it has a different sensing system. It is suitable for short or long term measurements of evapotranspiration (E(t)). Measurements of E(t) for a wheat crop growing on the lysimeters were compared with E(t) measured with air-conditioned field assimilation chambers (enclosures) placed over the lysimeters and on other plots. The results indicate that the enclosure method is reasonable for comparative measurements of water use by plots with different treatments, particularly where water use cannot be determined with other methods. The enclosure technique is not affected by advection and is therefore useful for small plot work.

Halloysite in late pleistocene rhyolitic tephra beds near Opotiki, coastal Bay of Plenty, North Island, New Zealand

Abstract: Investigation of the clay mineralogy of 14 rhyolitic tephra beds with a suggested age of 125000 to 220000 years revealed that the squat cylindrical form of halloysite is the dominant crystalline mineral. This mineral has probably crystallized from allophane over a long time period, excess silica being precipitated as a weakly hydrated phase. The squat cylindrical crystals perhaps characterize halloysite formation in rhyolitic tephras.

Arylsulphatase clay interactions. II. The effect of kaolinite and montmorillonite on arylsulphatase activity

Abstract: The reduction in arylsulphatase activity in the presence of kaolinite and montmorillonite was shown to be related to the total surface area of clay available for adsorption. Adsorption of arylsulphatase by kaolinite was confined to external surfaces, but with montmorillonite, interlattice sites were also involved. Evidence was presented that arylsulphatase held as a monolayer on exterior surfaces (‘primary surface’ adsorption), as well as that intercalated by montmorillonite, lost its activity. The remainder (‘secondary surface’ adsorption) retained its activity and could be removed from the clay-enzyme complex by elution.

Binary packing theory and the physical properties of aggregates

Abstract: The objective of this study was to examine variations in the physical properties of non-compacted soil-sand aggregates in terms of binary packing theory. Two soils were used, a swelling black earth and a krasnozem with low swelling capacity, and aggregates with varying clay percentage were prepared by dispersing the soil, mixing with 100-50 µm sand, and wetting and drying. At lower clay percentages, void ratio with increasing clay was greater than that predicted from theory. This was attributed to clay entering between sand junctions and increasing porosity by expanding the coarse matrix. From water retention and swelling data, the transition from coarse to fine matrix occurs in both soils at about 40 % clay. In the fine particle matrix, variation of void ratio in the krasnozem aggregates was as expected from theory. In the black earth, no significant variation in void ratio occurs at clay percentages > 40%. This was attributed to porosity created around the sand particles owing to differential swelling and shrinkage. Results obtained by other workers are explained in terms of binary packing theory and the concepts developed in this paper.

The influence of organic matter extracted from humified clover on the properties of amorphous aluminosilicates. I. Surface charge

Abstract: A series of synthetic amorphous aluminosilicates, hydrous oxides and allophanic soil clays were treated with aqueous extracts of humified clover. The resulting changes in surface charge due to organic treatment were determined by comparing the charge characteristics of these organic treated samples and samples treated with a synthetic mixture of the inorganic components of the humified clover extract. Organic treatment caused a change of net surface charge to more negative values. The change in surface charge varied with the mole ratio Al/(Al+Si) of the aluminosilicate, being largest at low values of Al/(Al+Si). Where the aluminosilicates contain positive charges these are reduced by the organic treatment. This is a major contributor to the alteration of net surface charge in the more aluminous samples. The effect of organic treatment on the charge characteristics of allophanic soil clays was similar to that for the synthetic aluminosilicates of intermediate composition. The inorganic treatments also caused an increase in negative charge, and this is attributed to the neutralization of positive charge by the adsorption of phosphate and the removal of charge-balancing aluminium-hydroxy material. The effect of the organic and inorganic treatments on the positive and negative charge components of amorphous aluminosilicates is discussed in terms of the degree of polymerization of chargebalancing hydroxy-aluminium as envisaged in current models of the structure of amorphous aluminosilicates.

Accretion of organic carbon, nitrogen and phosphorus in sand and silt fractions of a red-brown earth under pasture

Abstract: Organic carbon, nitrogen and phosphorus were determined in particle size and density fractions of a red-brown earth under a wheat-fallow rotation and an old pasture. In the soil under pasture organic carbon, nitrogen and phosphorus had accumulated particularly in sand fractions in the form of plant fragments and in particles 1-20 µm diameter as microbial debris.

Soil-tree relationships in a forest of Pinus radiata with micronutrient deficiencies

Abstract: Multiple regressions of tree height and diameter on foliar nutrient contents of a second rotation 9-yearold Pinus radiata forest in an area with a history of micronutrient problems at Clover Hill (S.A.), showed low levels of copper and manganese and high chloride in trees with less height and larger diameter than normal. Areas which were swampy and had failed in the first rotation were better stocked than their surroundings in the second. Such areas were, however, more subject to disorder symptoms. The soils of the forest integraded and were: yellow podzolic, podzol, solodized solonetz and terra rossa. Swampy phases were observed in the podzol and particularly the solodized solonetz soils. Trees on the various soils had different foliar levels of copper, zinc, manganese, potassium, phosphorus, nitrogen, sodium and chloride. On increasingly swampy phases of the podzol, foliar copper and manganese decreased but nitrogen and sodium increased. The multiple regressions differed for the various soils; tree height increased and diameter decreased with higher foliar copper, manganese and nitrogen, whereas both increased with higher foliar zinc and sodium. On some soils the multiple regressions contained quadratic terms, enabling an estimate to be made for a 20% reduction in height (less than 1.5 ppm copper) or a similar increase in diameter due to tree malformation (less than 1.8 ppm copper). A similar reduction in height was also indicated when the foliar chloride was greater than 0.68 to 0.8%. Foliar phosphorus was unusually high at about 2.5 times the levels found in healthy trees in other forests. Statistical interactions between foliar nutrients did not contribute to the multiple regressions. Soil surveys to delineate saline and previously swampy areas should be part of future forestry investigations in the south-east of South Australia.

An investigation of recharge to the Namoi Valley aquifers using environmental isotopes

Abstract: Environmental tritium and radiocarbon were used to study aspects of groundwater origin, transport and mixing in the complex aquifer system underlying the Namoi Valley, N.S.W. A substantial proportion of the water in the upper aquifer (depth less than 25 m) percolated underground in the post-nuclear period (after 1955). The observed relationship between a13C value and distance is evidence for riverwater recharge in the upper aquifer. There is evidence that water in the middle aquifer system (depth 50-75 m) percolated underground about 600 years ago. Finally, it is suggested that water from the Great Artesian Basin leaks into the deeper water of the lower aquifer system.

Interpretation of electrical conductivity in a clay soil containing salts

Abstract: The use of directly measured electrical conductivity of soil to provide an index of soil salinity is discussed. It is suggested that if an anion exclusion mechanism within the microfabric of a wet clay soil can lead to a non-uniform, but stable, range of salt concentrations, then the validity of such an index would be jeopardized. Experiments involved the monitoring of soil electrical conductivity during leaching and diffusion of salts from stable clay-soil aggregates packed in columns and cells. The equilibrium values of conductivity are inversely related to exchangeable cation valence, but are not affected by the type of anion involved. The soil conductivity was often much smaller than the value inferred from the amount of salts actually extracted from the columns or contained in the small isolated electrical conductivity cells. The results are consistent with the operation of a salt exclusion mechanism in the smaller pores of the soil fabric. With monovalent cations and relatively low electrolyte concentrations, the trapping of salts within the microfabric is maximized, while in contrast, with aluminium and aged hydrogen clays the exclusion effect is almost completely suppressed, in accord with double-layer theory. If salts are retained against concentration gradients within the fine structure units of the soil, current-transmitting regions between the units are of correspondingly high resistance, and this is reflected in a soil electrical conductivity value that is low relative to the amount of electrolyte between the electrodes. The observed soil conductivity may, however, bear a simple relationship to the salt fraction of the soil actually 'available' to plant roots.

Humic substances in swamps of the Myall Lakes region, N.S.W

Abstract: Fulvic and humic acids have been extracted from swamp water and soil taken from the Myall Lakes area of New South Wales. Average molecular weights were estimated by gel permeation chromatography. Infrared spectra are presented.

Water absorption by swelling seeds. II. Surface condensation boundary condition

Abstract: The previously developed model of water absorption by a swelling seed has been applied to imbibition and germination of wheat seed with the limiting supply condition of purely water vapour transport both with and without the presence of a porous medium. Experimental imbibition and germination data show that with vapour transport, the rate of imbibition and germination of wheat decreases with increasing distance from the supply source and that competition for water vapour occurs between seed. This competition effect was verified by values of the flow pathway shape factor for vapour transport to seed, measured in a three-dimensional electrical analogue. After accounting for heat production and losses with vapour absorption and using appropriate values of the flow pathway shape factors, the equilibrium seed absorption isotherms were used to derive surface condensation boundary conditions for several imbibition situations. These calculations suggest that in the absence of porous media a significant temperature rise of the seed retards the rate of imbibition. By comparison, with a close-packed porous medium around the seed, the large thermal conductivity of the medium should maintain nearly isothermal conditions. Using a finite difference approximation, the swelling seed model and condensation boundary conditions are analysed to give predicted imbibition data which can be compared with experimental data. These results show good agreement between predicted and experimental imbibition in the absence of a porous medium. For seed embedded in a porous medium, the predicted imbibition rate significantly exceeds the experimental rate, but no account could be taken for restriction of seed swelling by the porous medium. The results are discussed in terms of their relevance to the sowing of seed in 'dry' seed bed conditions.

The Availability to Wheat of Copper from Various Sources including Copper Superphosphate

Abstract: This study compared the availability to wheat of copper supplied as CuOSP (copper ordinary superphosphate), CuSO4.5H2O, CuO, CUEDTA and a synthetic copper phosphate similar to that occurring in commercial CuOSP. The various sources were finely ground, thoroughly mixed with the soil, and compared with an OSP treatment. Plants were harvested after 40 days and at maturity. All copper sources produced a major response relative to the OSP treatment, with copper uptake by plant tops increasing with increasing rates of application. A 12-fold difference in the water solubility of the copper sources had no effect on dry weight of plant tops and copper uptake.