bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorus acquisition in the soil-root system of Eucalyptus pilularis Sm. seedlings. I. Characteristics of the soil system
Authors: Heinrich PA , Patrick JW
Published: April 2005

An ancient sand-dune system located in the Myall Lakes National Park, N.S.W. (32�28'S., 152�30' E.) supports an open eucalypt forest with Eucalyptus pilularis as one of the co-dominant tree species. Profile development of the sand mass is typical of a light humic podzol. The relative pool sizes of available nutrients contained by the acidic podzol were such that phosphorus was the most limiting for the growth of E. pilularis seedlings. The bulk of seedling phosphorus was assimilated from the A, horizon of this podzol. Soil from the A, horizon was characterized by a low total level of phosphorus (= 30 �g P g-1 soil). Approximately 90% of this phosphorus was 0.1 M H2SO4 insoluble and probably organic in nature. In addition, 30% of the total phosphorus was associated with compounds containing aluminium and iron. The concentration of soluble phosphorus in the soil solution (CaCl2, extractable) was 0.36 �g P g-1 soil. Although this value is comparable to those reported for fertile soils, the amount of readily exchangeable phosphorus was found to be very low (1.43 �g P g-1 soil). Anion exchange resin studies indicated that after this pool was exhausted, release of phosphorus from slowly available sources was extremely limited (0.013 �g P g-1 soil h-1). Studies showed that transfer of phosphorus to seedling roots in A, horizon soil was predominantly a diffusive process. Moreover, the effective diffusion coefficient for phosphate (10.81 x 10-8 cm2 s-1) indicated that this process was comparatively fast.
Detection of denitrification, by a 15N racer technique, of nitrogen released from azolla and blue-green algae in a flooded soil
Authors: Mian MH
Published: April 2005

Denitrification of nitrogen from applied NH4+ and NO3-, and nitrogen released from Azolla caroliniana, Anabaena variabilis and Nostoc muscorum, was studied in a flooded soil. Denitrification did not occur in Azolla-, Anabaena-, Nostoc- or ammonium sulfate-treated soil, incubated at 18� to 25�C, until after 30 days since time was required to develop a surface-oxidized layer where nitrification could first take place. About 32, 45 and 49% of the total nitrogen in Azolla, Anabaena and Nostoc was released as mineral-N in 60 days, with 96, 93 and 93% respectively of this being lost as N2. Thus potentially serious losses of nitrogen from Azolla and blue-green algae may be avoided if their incorporated residues in flooded soils are left no longer than 3 weeks before planting a rice crop. Denitrification started within 3 days of incubation in the sodium nitrate-treated soil. About 10 and 75% of the ISN applied as ammonium sulfate and sodium nitrate, respectively, was lost as N, in 60 days. In addition, a substantial amount of 15N+4- N was formed from the applied 15NO-3-N (about 9% of the total amount added) in 60 days, indicating that a dissimilatory pathway also existed in this soil.
Distribution of introduced earthworms in the norhtern jarrah forest of Western Australia
Authors: Abbott I
Published: April 2005

Five species of introduced earthworm were recorded in the northern jarrah forest of Western Australia during 1980-83. These are Aporrectodea trapezoides (Duges), A. caliginosa (Savigny), Eisenia fetida (Savigny), Octolasion cyaneum (Savigny) (all Lumbricidae) and Microscolex dubius (Fletcher) (Megascolecidae). A. trapezoides was recorded most frequently. These introduced species occur within the forest only where there has been major disturbance, especially where forest has been replaced by pasture, orchards or settlement. They have not been recorded in forest that has been logged or in plantations of exotic trees. Introduced species of earthworm were frequently found in association with indigenous species. Most individuals of A. trapezoides kept in jarrah forest soil in the laboratory lost weight over 30 days, in contrast to an indigenous species of earthworm. How and when earthworm species were introduced is discussed in terms of the early European history of the jarrah forest.
The effect of electrolyte solutions on the unsaturated hydraulic conductivity of a sodic clay soil
Authors: Scotter DR
Published: April 2005

A technique for measuring the effect of different electrolyte solutions on the unsaturated hydraulic conductivity of low permeability soil cores is described. The technique was used to assess the effect of infiltrating gypsum (CaS0,.2H20) solution, sodium chloride solution, and distilled water on the conductivity of a sodic heavy clay at matric potentials between -0.5 and -8 kPa. Percolation of one liquid-filled pore volume of gypsum solution (concentration 29 m.e./l.) induced an approximately fourfold increase in hydraulic conductivity, relative to the conductivity with distilled water. This enhanced conductivity did not change when the permeating solution was changed to sodium chloride solution (30 m.e./l.). But when distilled water was substituted for either the gypsum or sodium chloride solutions, the conductivity declined rapidly, but not to its pretreatment value. Possible mechanisms responsible for the conductivity changes are discussed.
Sodium accession in rainfall near Scone Mountain, N.S.W
Authors: Elliott GL , Holman GJ
Published: April 2005

Contemporary sodium accessions in rainfall occurring near Scone Mountain were estimated to be 6.9 � 1.8 kg ha-1 year-1. The ratios of Ca/Na, Mg/Na and K/Na were consistent with the addition of soluble material to rain by aeolian processes, and the estimation of cyclic salt accessions could not be attempted.
Effects of sieving on estimations of microbial biomass, and carbon and nitrogen mineralization, in soil under pasture
Authors: Ross DJ , Speir TW , Tate KR , Orchard VA
Published: April 2005

Biochemical indices of microbial biomass and other biochemical properties of a Typic Haplaquoll, sampled under pasture over four seasons, were compared in intact cores and soil sieved through a 6 mm and a 2 mm mesh. Sieving had an inconsistent influence on biomass C estimates, which tended, however, to be higher in <2 mm-mesh than in <6 mm-mesh soil. Sieving had no deleterious effect on mineral-N flush values, and no significant effect on biomass P, and generally adenosine 5'-triphosphate (ATP), contents. Judged by the values of biomass C/ATP and biomass C/mineral-N flush ratios, the biomass C estimates of winter samples, collected under water-logged conditions, were unrealistically low, particularly in sieved soil. CO2 production by soil at a standardized water potential tended to be lowest in <2 mm-mesh samples. In contrast, net mineralization of N, in all except the winter <2 mm-mesh soil, was highest in sieved soil, as generally were extractable inorganic and organic P contents. Overall, sieving is considered preferable to the use of intact cores for measurements of these biochemical properties in soil under pasture.
The development of micromorphological features in relation to some mineralogical and chemical properties of volcanic ash soils in highland Papua New Guinea
Authors: Chartres CJ , Wood A , Pain CF
Published: April 2005

A sequence containing six soil profiles developed within a Late Quaternary, andesitic tephra at different altitudes (1000-2400 m) and under different climatic conditions is described. Allophane dominates the soils above 2000 m, gibbsite those between 1200 and 2000 m and halloysite those below 1200 m. All the soils have isotic plasmic fabrics within the A horizons. A combination of allophane and organic matter, and in the lowest altitude soils halloysite and organic matter, seems to lead to the development of isotic fabric. B horizon plasmic fabrics range from undulic to isotic-argillasepic-indeterminate, with the most sepic plasmic fabrics occurring at lowest altitudes, where halloysite content is highest and wetting-drying cycles are more frequent. Gibbsans formed due to the precipitation of aluminium are prominent features infilling channels within the soils between 1200 and 2000 m, where desilication is most active. Above 2000 m climatic and drainage factors appear to limit the desilication of the alluvial clay features. Below 1200 m, silica and aluminium released by weathering combine to form halloysite under a less intense leaching regime. Gibbsite also was observed to be forming as a pseudomorph of felspar grains in most profiles.
Corrigenda - A portable microcomputer-controlled drip infiltrometer. II. Field measurement of sorptivity, hydraulic conductivity and time to ponding
Authors: Bridge BJ , Ross PJ
Published: April 2005

The lightweight portable drip infiltrometer described in Part I was used to determine the infiltration characteristics of a sandy loam soil. Sorptivity was determined by varying the application rate to maintain surface ponding and by measuring the time to ponding at a constant application rate. Saturated hydraulic conductivity was equated to the long-time steady-state application rate needed to maintain surface ponding. This rate could be determined to a precision of 0.5 �m s-1 (2 mm h-1) and agreed well with core data from 0.5 to 1.0 m depth in the profile. The results obtained were compared with ponded ring infiltrometer measurements. Sorptivities calculated from the ring infiltrometers were greater than those from the variable rate drip infiltrometer which in turn were greater than those from the constant rate drip infiltrometer. This was attributed to the effect of the macropores under the ponded rings and to confining the depth over which sorptivity was measured under constant application rate to the wetter surface soil. In dry soil, the drip infiltrometer measured low initial infiltration rates caused by poor wetting of the soil, but these were not measured by the ponded ring infiltrometers, which had a 50 mm head. In moist soil, poor wettability did not occur. Five equations for calculating sorptivity from measurements of time to ponding under a constant application rate of 8.3 �m s-1 (30 mm h-1) were used and four of these equations agreed within 20%. This was less than the range of sorptivities arising from uncertainties in determining the time to ponding, and the differences between the equations were attributed to the assumptions used in their derivation. It was concluded that any measurement of sorptivity on this soil was difficult to interpret because of non-uniformity in the upper soil profile.
Fluoride sorption by soil components: calcium carbonate, humic acid, manganese dioxide and ailica
Authors: Farrah H , Slavek J , Pickering WF
Published: April 2005

The ability of individual soil components to adsorb fluoride ions from dilute solutions (1-12 mg L-1 F-), at different pH values, has been investigated. No significant uptake was detected using substrates such as calcite, hydrous manganese(1v) oxide, cryptomelane, �-MnO2, pyrolusite, silica or silica gel, over the pH range 3-8 (for calcite, 6-9). The sorption of F- by calcite and humic acids at higher solution levels (up to 200 mg L-1) was also examined. Uptake by CaCO3 was observed when [F-] was >7 x 10-4 mol L-1, with the moles retained (pH -8.5) being approximately 1.6[F-]2. The amount of F removed increased on lowering the pH or on adding Ca2+, and it is proposed that the overall reaction is described by the equation CaCO3(S) + 2F- <=>CaF2(S) + CO23-. Two humic acid samples adsorbed increasing amounts of F- as the pH was lowered below 6.5, and increasing amounts of A1 and fluorocomplexes were detected in solution. The amount sorbed (mol kg-', at pH 5.5-6) varied with ash content and equalled either 16[F-]0.64 or 60[F-1. The major interaction appears to be HF attack on aluminosilicates in the ash fraction, with lesser contributions from sorption on calcium compounds and interaction with the counter-ions associated with the humic acid functional groups (e.g. Ca2+, Al3+, Fe3+).
The effects of gypsum on macroporosity and crusting of two red duplex soils
Authors: Chartres CJ , Greene RSB , Ford GW , Rengasamy P
Published: April 2005

The effects of gypsum on the physical properties of two red duplex soils in northern Victoria were investigated by assessing the relative abundance of macropores (diameters greater than 75 �m) in the 0-30 mm zone of their cultivated layers. Samples were collected in October 1983 from both fallow cropped and stubble cropped plots. Changes in soil porosity between untreated and gypsum-treated plots were measured on photographic images of thin-sections using a Quantimet 720 image analyser. The soils differed in their clay mineralogy, one being dominated by illite, the other by randomly interstratified material. The results indicate only a minor improvement due to gypsum application in the area of macropores in the soils dominant in illite and kaolinite, whereas in the soil with the higher proportion of randomly interstratified clay minerals the area of macropores approximately doubled on the stubble cropped site and also considerably increased on the fallow cropped site. Micromorphological observations indicated that, in the presence of gypsum, crust formation was reduced because less clay was mobilized and redistributed in the surface soil layers.
Corrigenda - The effects of gypsum on macroporosity and crusting of two red duplex soils
Authors: Chartres CJ , Greene RSB , Ford GW , Rengasamy P
Published: April 2005

The effects of gypsum on the physical properties of two red duplex soils in northern Victoria were investigated by assessing the relative abundance of macropores (diameters greater than 75 �m) in the 0-30 mm zone of their cultivated layers. Samples were collected in October 1983 from both fallow cropped and stubble cropped plots. Changes in soil porosity between untreated and gypsum-treated plots were measured on photographic images of thin-sections using a Quantimet 720 image analyser. The soils differed in their clay mineralogy, one being dominated by illite, the other by randomly interstratified material. The results indicate only a minor improvement due to gypsum application in the area of macropores in the soils dominant in illite and kaolinite, whereas in the soil with the higher proportion of randomly interstratified clay minerals the area of macropores approximately doubled on the stubble cropped site and also considerably increased on the fallow cropped site. Micromorphological observations indicated that, in the presence of gypsum, crust formation was reduced because less clay was mobilized and redistributed in the surface soil layers.
The effects of gypsum-enriched slots on moisture movement and aeration in an irrigated swelling clay
Authors: Jayawardane NS , Blackwell J
Published: April 2005

The low yields of flood irrigated row crops on transitional red-brown earths have been attributed to low infiltration rates and poor aeration. A new method for soil amelioration using gypsum-enriched slots to overcome these limitations was investigated in a field experiment. Gypsum-enriched slots were formed by excavating 0.4 m deep and 0.15 m wide parallel slots, mixing the excavated soil with gypsum and loosely refilling the slots. Moisture and aeration profiles were regularly monitored using a neutron moisture meter during the cropping season on field plots with gypsum enriched slots, and on plots with surface gypsum application and without gypsum. A sorghum crop was grown on all plots. Owing to faster flow through the slots during irrigation, the slotted plots showed deeper wetting than the no gypsum and surface gypsum treatments. Consequently the surface soil layers between the slots were subjected to less wetting and better aeration than in the other plots. The slots, which except immediately after an irrigation, showed high air-filled porosity values due to faster redistribution rates, should provide pathways for oxygen flow to the soil between slots and to lower depths. Infiltration rates measured using infiltration rings showed a twofold increase with addition of surface gypsum and a further two- to three-fold increase through the gypsum-enriched slots. The implications of the changes in the moisture and air filled porosity profiles due to slotting with gypsum for irrigated and non-irrigated cropping on these soils are briefly discussed.
Soil temperature and the energy balance of vegetative mulch in the semi-arid tropics. I. Static analysis of the radiation balance
Authors: Ross PJ , Williams J , Mccown RL
Published: April 2005

Planting crops into chemically killed pasture protects seedlings from high soil temperature. In this paper the radiation balance and convective heat loss of such dead vegetative mulch canopies are analysed mathematically for windless conditions, and maximum soil temperatures are calculated, together with their sensitivities to mulch and soil parameters. An approximate expression for soil heat flux, and assumptions about rates of change of radiation and other inputs with time, allow calculations where actual data are unavailable. A simplified analysis regards the mulch as a radiation filter which acts independently of the soil surface. Agreement with experimental data is good. The results show that energy losses by reflection, conduction, convection, radiation and evaporative cooling are all important in balancing incoming radiation and determining soil surface temperature, so that quantitative analysis is essential for a proper understanding of the system. .Mulch can reduce soil surface temperature by up to 20�C by intercepting incoming radiation; it dissipates this intercepted energy quite efficiently by free convection without concomitant increase in the temperature of the underlying soil surface. Penetration of radiation through the mulch is its most important characteristic. Forward scattering of shortwave radiation from the mulch to the soil surface has a big effect on soil temperature, but backward scattering has little effect, hence lighter-coloured more reflective mulches may be less efficient than darker ones. Evaporation of soil water is very efficient in reducing soil temperature, and the mulch prolongs the process of slow evaporation from the soil surface. The resulting higher soil water content also decreases soil surface temperature through its effects on soil thermal properties.
An evaluation of eight soil phosphate extractants on acidic wheat growing soils
Authors: Holford ICR , Cullis BR
Published: April 2005

In a study using earlier data from 44 wheat field experiments on acidic (pH < 5.6) soils in southern New South Wales, eight soil phosphate extractants (Bray,, Bray,, neutral fluoride, Mehlich, Truog, lactate, Olsen and Colwell) were evaluated and calibrated in terms of responsiveness (�) and response curvature (C) parameters derived from the Mitscherlich equation. All extraction procedures, except Colwell, had a standard shaking time of 30 min and so1ution:soil ratio of 50. The order of efficacy of the tests was different from that obtained on moderately acid to alkaline soils of central and northern New South Wales. Neutral fluoride and acidic sulfate (Truog) replaced lactate as the best extractant, followed by the double acid Mehlich extractant. The Colwell test was more effective on these very acid soils than on the more alkaline soils, being equal to Bray1 and greatly superior to Bray2 and Olsen. The critical values of the fluoride, Mehlich, Truog, lactate and Colwell tests were significantly lower than they were for more alkaline soils in central New South Wales. The changes in extraction procedures could explain the lower critical values of the lactate and Truog tests, but differences in the critical values of the other three tests were inconsistent with changes in extraction procedures. The results support the hypothesis that a different phosphate extractant is required on very acid soils from that required on moderately acid to alkaline soils.
Effect of irrigation method on the recovery of 15N fertilizer in a slowly permeable clay soil cropped with maize
Authors: Mosier AR , Meyer WS , Melhuish FM
Published: April 2005

A study using 15N~labelled fertilizer was initiated in a lysimeter facility to quantify the amount of N assimilated by maize plants and that which remained in the soil at the end of a cropping season. Maize was planted in 0.43 m2 by 1.35 m deep intact Marah clay loam soil cores removed from an improved pasture in mid-October 1983. Two irrigation treatments, flood-impounding water on the soil for up to 72 h, and control-applying enough water to prevent plant stress without ponding, were employed. The crop was harvested in early April 1984 and the amount of fertilizer- and soil-derived N in the plant and remaining in the soil was determined. Grain yields were reduced about 33% by flood irrigation. Although about 30 kg N ha-1 more fertilizer N was lost from the flood-irrigated system, the difference in N recovery between the flood- and control-irrigated soils was not sufficient to account for the reduced grain yield. Flood-irrigated plants were less efficient in transporting fertilizer N to the seed than were control irrigation plants. The data suggest that the reduced seed yield and total N content of maize plants grown under flood irrigation was metabolically controlled rather than being derived from a difference in soil mineral N content compared with control-irrigated soils.
Soil water extraction by a mixed eucalypt forest during a drought period
Authors: Talsma T , Gardner EA
Published: April 2005

Eucalypt trees growing on deep soils, with a water table at about 8 m depth, showed no apparent drought effects during the 1982-83 dry period in south-east Australia when gross precipitation was only 388 mm. At the end of the drought, soil water to 4 m depth was depleted to a soil water potential of -0.5 MPa and under these conditions unsaturated flow from the water table to the lower root zone was calculated to be 0.17 mm day-1. Water extraction over the depth interval from 0 to 6 m in the drought year was 533 mm, some 200 mm in excess of that used during a year of average rainfall. The contribution to tree water use from unsaturated flow from the water table was calculated to be small (15 mm) even in a drought year, and in most years water movement would be towards the water table to yield a deep drainage term estimated between 40 and 100 mm. Growth ring studies indicated that the lower water use, estimated at 2.6 mm day-1 during the spring-summer drought, did not affect the slowly growing E. radiata species, but reduced stem diameter growth of the faster growing E. dalrympleana and E. pauciflora species.
The effect of conventional cultivation, direct drilling and crop residues on soil temperatures during the early growth of wheat at Murrumbateman, New South Wales
Authors: Aston AR , Fischer RA
Published: April 2005

Soil temperatures were measured at different depths under wheat crops sown by three different methods in a dry (1982) and a wet season (1983). A conventionally cultivated treatment, which comprised a short cultivated fallow, was compared with one which was directly drilled with full disturbance of the soil surface after previous crop residues had been burned, and with another treatment which was directly drilled with minimum disturbance into soil carrying 2-4 t ha-' stubble. Generally the soil temperatures at any particular depth of the conventionally cultivated treatment were warmer during the day and cooler during the night than the soil temperatures at the same depth in the direct drilled treatments. These patterns persisted throughout both the growing seasons, but in the wet year (1983) there was little difference between temperatures under conventional cultivation and direct drill with stubble burning and full disturbance. Similar temperature patterns were measured when the same treatments were imposed on an adjacent area which had previously been growing fertilized ryegrass/clover pasture. It was found that wheat sown by conventional means had a larger shoot dry weight per plant at the 4 1/2 leaf stage of development than direct drilled wheat. The improved early vigour of wheat sown by conventional cultivation practices could at least partially have been due to the patterns in soil temperature.
Modification to the compulsive exchange method for measuring exchange characteristics of soils
Authors: Gillman GP , Sumpter EA
Published: April 2005

The compulsive exchange method for the measurement of cation and anion exchange capacities of soil as described by Gillman and subsequently recommended by the American Society of Agronomy for acid soils has been modified to achieve greater simplicity. Though originally intended for the measurement of highly weathered soils, the method has be extended to saline and non-saline calcareous soils, and also to the measurement of the variation of exchange capacity with pH.
Exchange characteristics of some acid organic rich forest soils
Authors: Khanna PK , Raison RJ , Falkiner RA
Published: April 2005

The cation exchange characteristics were determined for several acid organic-rich soils formed under sub-alpine eucalypt forests growing in the Australian Capital Territory. Most of the exchange sites in the red and yellow earths studied are occupied by Al and are associated with soil organic matter. Unbuffered salt solutions extract more Al than could be associated with exchange sites, so that the sum of cations in the extracts is an overestimate of the effective cation exchange capacity (CECe). The CECe is not a unique property but depends upon pH and ionic strength (I) of the equilibrating solution. The exchange sites mainly carry negative charges of both permanent and variable nature. Higher carbon contents of the soils are correlated with increases in CECe due to increasing I, and with greater negative charge due to increasing pH. Some modifications to the compulsive exchange method of Gillman for determining CECe are proposed for its use with acid organic-rich soils.
Characteristics of soil and productivity of Pinus radiata (D Don) in New South Wales .II. Pedogenesis on a range of parent materials
Authors: Ryan PJ
Published: April 2005

Soil profile descriptions were made at a series of 11-year-old unfertilized Pinus radiata stands in the Lithgow district of New South Wales. Catenas within three soil parent materials were selected to compare variation in soil physical and morphological properties with growth of P. radiata. These parent materials were a Silurian siltstone, a Permian conglomerate and a Silurian-Devonian rhyolite. Basal area growth of the P. radiata stands increased down catenas on the Silurian siltstone as soil depth to a root impeding layer increased. Plateau soils on the Permian conglomerate had hardsetting surfaces and high gravel contents, and were associated with very poor pine growth. By way of contrast, lower slope, colluvial gradational earths were deep, fine-textured soils and supported more productive pine stands. The Silurian-Devonian rhyolite parent material produced highly leached soils, commonly with conspicuously bleached A2 horizons and poor sandy textures of surface soil. Both physical and chemical features of the rhyolite interacted with pedological processes to affect adversely soil physical conditions and trace element availability, in particular boron. The poorer P. radiata growth on lower or concave slope in comparison with upper slope position was a result of increased soil leaching and horizon differentiation. This pattern contrasted with improved pine growth on the deeper soils on lower slopes on the two sedimentary parent materials. These case studies emphasize the importance of geology and pedological processes when evaluating the applicability of specific soil physical factors to site classification for P. radiata plantations.
A study of soil erosion on vertisols of the eastern Darling Downs, Queensland .II. The effect of soil, rainfall, and flow conditions on suspended sediment losses
Authors: Freebairn DM , Wockner GH
Published: April 2005

Runoff water was sampled as it discharged through weirs installed at the outlet of 1 ha contour bay catchments. Cover, rainfall intensity, and soil tilth were important factors determining the concentration of suspended sediment in runoff. Mean delivery ratios for a grey clay, and a black earth, were 0.19 and 0.13 respectively. Contour banks reduced sediment loads reaching the bottom of slopes by at least six-fold. Three methods of calculation of total sediment loss were assessed. It was found that a flow-weighted mean of rising stage samples, and the arithmetic mean of sequential samples, were adequate in most cases for determining sediment losses. However, sequential samples weighted for discharge between samples were necessary for reliable measurements, especially during complex events.
Surface charge characteristics and lime requirements of soils derived from basaltic, granite and metamorphic rocks in high rainfall tropical Queensland
Authors: Gillman GP , Sumpter EA
Published: April 2005

The cation and anion exchange capacities of a large number of soils formed on basaltic, granitic, and metamorphic parent materials in the high rainfall area (approximately 4000 mm) of tropical north Queensland have been examined. Aspects studied included the changes in CEC and AEC between pH 4 and pH 6, the relative amounts of permanent and variable charge over this pH range, and the lime requirements of these highly weathered soils. A distinction is made between the Total Cation Exchange Capacity (CECT), defined as the Ca + Al adsorbed, and the Basic Cation Exchange Capacity (CECB), which is the Ca adsorbed. At low pH, CECB may be much less than CECT. The CEC, increase with pH in the highly oxidic basaltic soils is largely due to changes in surface charge, while in the granitic and metamorphic soils, increasing occupation of exchange sites by Al as pH decreases is the factor responsible for the increase in CECB. A good estimation of CECB at soil pH is obtained with a previously described compulsive exchange method, and there is high correlation between CECT at soil pH and the Effective Cation Exchange Capacity (= Ca + Mg + K + Na + Al). The amount of lime required to raise soil pH to pH 5.5 in the granitic and metamorphic soils was equivalent to the amount of exchangeable Al, but in the basaltic soils the lime requirement was two to three times greater than the amount of exchangeable Al.
The measurement of soil cation exchange properties using the single extraction, silver thiourea method - an evaluation using a range of New Zealand soils
Authors: Searle PL
Published: April 2005

The measurement of soil cation exchange properties using a single extraction with 0.01 M silver thiourea (AgTU) was investigated using a range of New Zealand soils. There were no differences in the amounts of cations extracted by leaching or 16 h shaking and at least 90% recovery of calcium, magnesium, potassium and sodium was obtained after 1 h shaking. AgTU extracted similar amounts of aluminium to 1 M potassium chloride but approximately twice as much manganese. CEC values obtained by AgTU extraction agreed well with those obtained by Gillman's method. CEC determined by measuring the silver remaining in solution after AgTU extraction was found to be accurate and rapid.
Interaction of dilute fluoride solutions with hydrous iron oxides
Authors: Farrah H , Pickering WF
Published: April 2005

The amount of F- retained by hydrous iron oxide suspensions was found to be a function of F- concentration (2-100 mg L-1), pH, and structural form of the iron oxide. Uptake was minimal at pH >7, and increased with decreasing pH (e.g, with 10 mg L-1 NaF in solution, the amount sorbed by freshly precipitated hydrous iron oxide varied between 7 mg/g at pH 6 and 35.5 mg/g at pH 4.5). With fixed pH (between 4.5 and 6) the amount sorbed varied with concentration in accordance with a Langmuir isotherm relationship. The pH effect was countered at lower values by solid dissolution, hence each F- concentration studied exhibited a pH (between 3.5 and 4.5) where uptake was a maximum. Solid dissolution was accompanied by the formation of soluble iron(III) fluoro complexes. In acid media, the amount of F sorbed by hydrous iron oxide >> goethite > limonite >> hematite. In environmental systems, F interaction and retention should thus be most pronounced in acid media, containing recently precipitated hydrous oxides.
Influence of magnesium on aggregate stability in sodic red-brown earths
Authors: Rengasamy P , Greene RSB , Ford GW
Published: April 2005

Studies on sodium clay separated from a red-brown earth demonstrated that higher concentrations of magnesium salts than calcium salts were required for flocculation. Statistical analysis of the data from a range of red-brown earths showed that the dispersion of clays from soils with an SAR1:5 >3 increased as the Ca/Mg ratio of 1:5 soil-water extracts decreased below unity. The hydraulic conductivity of columns of <2 mm surface and subsurface samples from one red-brown earth was significantly reduced when Ca/Mg ratios in the percolating solutions were below unity only when the SAR was above 3 and the TCC (total cation concentration) values were less than the predicted flocculation values. When the TCC values of the percolating solution exceeded the flocculation values, hydraulic conductivity was not affected by either SAR or Ca/Mg ratio. If structural problems in sodic soils containing high levels of exchangeable magnesium (e.g. Ca/ Mg < 1) are to be minimized, it is necessary to maintain an electrolyte level above the threshold value for a particular soil. In red-brown earths the specific effect of magnesium is so small that for magnesium-dominant soils an additional gypsum application of 1 t ha-1 for the surface 10 cm of soil should be sufficient.
Long term effects of rice growing on some chemical properties of two soils of northern Australia
Authors: Willett IR , Malafant KWJ
Published: April 2005

Solodic soils (Natrustalfs) of the Lower Burdekin Valley, Qld, and grey-brown clays (Chromusterts) of the Ord Irrigation Area, W.A., of varying rice cropping histories, were analysed before and after a laboratory flooding experiment to determine whether any long-term changes in chemical fertility had occurred. In the solodic group changes in the extractability of iron and manganese in acetate and oxalate reagents indicated that oxides of these elements may be more easily reduced in soils that had grown nine or more rice crops than in soils which had not been used for rice growing. The flooding experiment showed that manganese and iron reduction and the mobilization of phosphorus were more rapid in the solodic soils which had been used for rice than those which had not. Iron reduction did not occur in the flooded grey-brown clays, and manganese reduction was apparent only in three soils, but was most rapid in those which had grown 15 rice crops. Extractable phosphorus levels decreased during flooding of the grey-brown clays, but this was not related to the cropping history. There were small increases in sodicity of the subsoil (40-50 cm) of the solodic soils which had been used for rice growing. It was concluded that for the solodic soils rice growing leads to soils more favourable for further rice growing but less favourable for non-flooded crops, whereas this effect was not shown for the grey-brown clay soils.
Effect of conversion from ryegrass pasture to wheat cropping on aggregation and bacterial populations in a silt loam soil in New Zealand
Authors: Ramsay AJ , Stannard RE , Churchman GJ
Published: April 2005

Water-stable aggregates and soil bacteria were studied from May to January in a field trial comparing soil structure under three treatments: wheat sown in ploughed soil, direct-drilled wheat and long-term grass. During the trial, both the proportion and size of macroaggregates (> 250 �m) tended to increase. These increases were accompanied by decreases in the proportions of particles in all smaller size ranges, including <2 �m, in the early part of the growing season, but, over summer, larger macroaggregates (> 2000 �m) increased at the expense of particles between 2000 and 63 �m. The highest proportion of larger macroaggregates occurred under grass, in all except the spring sampling, while the lowest proportion occurred in the ploughed soils. Numbers of bacteria, obtained by direct microscopy, were higher in the ploughed soil soon after ploughing than in the direct-drilled soil, but no other treatment effect was detected. In all plots, numbers of bacteria were lowest in November when the soil was the driest. There were up to twice as many bacteria per g of < 20 �m diameter fraction soil compared with the rest of the soil. Seasonal changes in the bacterial population of the <20 �m diameter fraction did not follow the changes in the whole soil.
Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. IV. Loss of organic carbon from different density functions
Authors: Dalal RC , Mayer RJ
Published: April 2005

Six southern Queensland soils used for cereal cropping for cultivation periods ranging from 20 to 70 years were subjected to density fractionation. The soils were separated into fractions with densities of <2, 2.0-2.2, 2.2-2.4 and >2.4 Mg m-3 using bromoform-ethanol mixture. The < 2 Mg m-3 fraction (light fraction) contained only 1.8-3.2% of the total soil weight, but accounted for 15-32% of total soil organic C. In five clay soils the rate of loss of organic C from the light fraction was 2-11 times greater than that from the heavy fraction (>2 Mg m-3). The higher the clay content the larger was the difference between these two fractions in rate of loss of organic C. It is inferred that the heavy fraction was closely associated with clay in these soils. In a sandy soil, rate of loss of organic C from the heavy fraction was similar to that from the whole soil.
On the definition and identification of aquic soil moisture regimes
Authors: Childs CW , Clayden B
Published: April 2005

The definition of an aquic soil moisture regime given in Soil Taxonomy is difficult to understand and, in places, ambiguous. The essence of the definition as written, however, is the requirement for reducing conditions. A soil which is saturated with groundwater or with capillary fringe water may, or may not, have an aquic moisture regime. Reducing conditions are defined in Soil Taxonomy in relation to the virtual absence of dissolved oxygen, though morphological criteria for the differentiation of soil classes are based on the reduction and segregation of iron. The absence of requirements relating to duration of reducing conditions, or to the thickness of reduced soil, suggests that the definition was intended to apply to soil material rather than to a pedon. The aquic moisture regime has a particular depth connotation only when it is applied to the differentiation of soil classes. A simple field test, based on the complexing agent �,�-dipyridyl, is useful for the identification of ferrous ions in soil solutions and hence is potentially useful in the recognition of aquic moisture regimes. The sensitivity of this test limits its usefulness to those soils which contain more than about 0.5% free iron (i.e. iron which can be solubilised as iron(II) under reducing conditions as measured by extraction with dithionite reagent).
The Talsma-Hallam well permeameter - Modifications
Authors: Nash DM , Willatt ST , Uren NC
Published: April 2005

The Talsma-Hallam well permeameter has been modified in such a way as to increase its reliability, and thus allow the measurement of field hydraulic conductivities of less than 10-7 m s-1.
Corrigenda - Effects of exchangeable sodium on crusting behavior of a sandy loam soil
Authors: Painuli DK , Abrol IP
Published: April 2005

Field and greenhouse studies were conducted at the Central Soil Salinity Research Institute, Karnal, India, to evaluate the effect of exchangeable sodium (ES), amount of water applied, and evaporation and temperature conditions at drying on the crusting behaviour of a sandy loam soil. The exchangeable sodium percentage (ESP) ranged from 5.8 to 30.7 in the field and from 6 to 60 in the greenhouse studies. Soil crusting behaviour was evaluated in terms of crust strength measured by a simulated seedling emergence technique. Water was applied as natural or simulated rainfall. Crust strength increased with ESP, amount of water applied, and temperature, but decreased with increasing evaporation demand. This change in crust strength was steep above ESP 30. Although drying of the crust increased its strength, beyond a certain degree of dryness the disappearance of water films surrounding the soil particles reduced strength for low ESP soils.
The nitrogen status of red and yellow earths in the semiarid tropics as influenced by Caribbean stylo (Stylosanthes hamata) grown at various rates of applied phosphorus
Authors: Probert ME , Williams J
Published: April 2005

Changes in the nitrogen status of a red and a yellow earth in the semi-arid tropics of central north Queensland were examined following five years' growth of Stylosanthes hamata pasture under a range of phosphorus inputs. The results highlight the importance of leaching of nitrate-N in these environments. This could be accounted for satisfactorily by a simple water and solute exchange model. Small increases in organic carbon and total nitrogen in soil were restricted to the early years of the pasture phase but were not significantly related to the phosphorus treatments. The nitrogen supply to a test crop of millet, both in the field and for surface 0-10 cm samples cropped in the glasshouse, was enhanced by previous growth of legume, and the magnitude of the effect depended upon the yields of legume grown as influenced by its phosphorus nutrition. In terms of freshly applied ammonium nitrate, the contribution from the legume measured in the field was equivalent to 33 kg N ha-1 for an annual production of 1 t ha-1 of legume dry matter on the red earth, and similarly 38 kg N ha-1 on the yellow earth. Of several methods of soil analysis studied, mineral-N extracted with 1 M KCl, either at room temperature or at boiling point, were the best single predictors of the nitrogen supply as measured by the nitrogen uptake of millet. Evidence is provided to show that forms other than mineral-N also contributed to the nitrogen supply, but none of the methods of soil analysis used was able to quantify this nitrogen arising from mineralisation.
Effect of fire intensity on solution chemistry of surface soil under a Eucalyptus pauciflora forest
Authors: Khanna PK , Raison RJ
Published: April 2005

The chemical composition of soil solutions (field percolates collected in situ and laboratory saturation extracts) was measured at three sites subjected to widely varying fire intensity in subalpine Eucalyptus paucfiora forest near Canberra. The sites were unburnt forest, areas prescribed burnt resulting in almost complete canopy scorch, and ashbeds (intensely heated soil). Saturation extracts were obtained 1, 58, 375, 745 and 1095 days after the fire, and soil percolates were collected on 17 occasions during the initial year after burning. Large quantities of cations (Ca2+, Mg2+, K+ , NH+4) and anions (Cl-, SO24-) and soluble silica were mobilized by burning, especially under ashbeds. Mobilization resulted from deposition of water-soluble elements in ash, immediate effects of soil heating, and enhanced rates of mineralisation of soil organic matter indicated by high concentrations of NH+4 which persisted for more than one year in surface soils under the ashbeds. After burning Ca2+ became the dominant cation in saturation extracts of surface (0-5 cm) soils for the entire 3-year study period. In the 5-15 cm soil layer, firstly NH+4 and later K+ replaced some of the Na+ in the solution phase. Most of the Cl- deposited in ash was leached below 15 cm depth within one year and was probably accompanied by transport of K+, Mg2+, Na+ and NH+4, but very little transfer of Ca2+ occurred. Concentrations of NO-3 and phosphate were always low in saturation extracts and soil percolates, and levels were unaffected by burning, despite the presence of large amounts of exchangeable NH+4 in the soil and the deposition of significant amounts of phosphate in ash. Burning increased the concentrations of soluble silica and SO24- in saturation extracts for at least 3 years after the fire. Most of the changes in soil solution chemistry measured would increase nutrient availability to the vegetation during the initial year after burning, but these changes must be balanced against losses of organic matter and nutrients during and after fires.
Influence of soil water content on the supply of phosphate to plants
Authors: Mouat MCH , Nes P
Published: April 2005

Ryegrass (Lolium perenne L.) was grown in a pot trial in soil of high phosphate adsorption capacity at 10 levels of P-supply and at two water regimes, one regularly adjusted to the water-holding capacity of the pots corresponding to a water potential of -2 to -3 kPa, and the other at 20% less water volume corresponding to - 20 kPa. P uptake was lower in the lower water treatment at all P-supply levels, even when the P-supply was severely limiting P uptake. This reduction in P uptake at all P levels was equivalent to the reduction in water volume between the two water treatments, and is apparently a result of a lower supply of solution phosphate in the lower water treatment in the highly buffered soil.
WARIS - a computer based storage and retrieval system for soils and related data
Authors: Rosenthal KM , Ahern CR , Cormack RS
Published: April 2005

An interactive computer system for the storage, retrieval and manipulation of soil profile data is described. The input data to the system can be in any format designated by the user provided it satisfies a few simple guidelines. The system is flexible enough to answer a wide range of user enquiries. Over the years it has developed into a general-purpose resource information system for processing 'point and profile' data which is economical and easy to use. It is particularly suitable for soil, vegetation and land resource surveys, as it can easily handle data for a number of depths per site. The programs can be used to retrieve, sort, manipulate and decode morphological data recorded according to the Australian Soil and Land Survey Field Handbook. These profile data can be linked to laboratory data and displayed either as a complete decoded description for each site, or as tables, graphs, and frequency distributions of selected characteristics by soil groups or mapping units. All programs are written in Fortran-77 and hence are reasonably easy to port to other computers.
Effect of slaughterhouse effluent and water irrigation upon aggregation in seasonally dry New Zealand soil under pasture
Authors: Churchman GJ , Tate KR
Published: April 2005

Studies of the long-term (>25 years) treatment of a silt loam soil under pasture with slaughterhouse effluent showed that effluent did not affect macroaggregate stabilities as measured by wet-sieving, but increased the stability of clay aggregation as measured after selective disaggregation treatments. Highly humified organic matter was associated with the soil clays as a result of slaughterhouse effluent treatment. Studies of the similarly long-term irrigation of the same soil type with water showed that water decreased the stabilities of macroaggregates as long as they were kept wet, but increased their stabilities after air-drying. Scanning electron microscopy showed a web that became firmly bound to soils only after drying. Stabilities of aggregated clays were largely unchanged by water irrigation, though their sensitivity to the removal of polysaccharides and organically bound cations was increased by this treatment. Changes in stabilities could not be related to earthworm numbers or to the extent of mycorrhizal infection. Macroaggregate stabilities did not reflect obvious visual changes that occurred to the soil structure upon a major change in composition of the effluent. The effects of seasonal drying processes were very likely obscured by the stabilising effects of air-drying prior to wet sieving analyses for macroaggregate stabilities.