bluuebunny/crossref_metadata_2025 huggingface dataset:
Decomposition of plant material in Australian soils. III. Residual organic and microbial biomass C and N from isotope-labelled legume material and soil organic matter, decomposing under field conditions
Authors: Ladd JN , Amato M , Oades JM
Published: April 2005

After eight years decomposition of 14C, 15N-labelled legume (Medicago littoralis) material previously mixed into topsoils (0-10 cm) at four field sites in South Australia, residual organic 14C and 15N to 30 cm depth accounted for respectively 11-13% of input 14C, and 31-38% of input 15N. About 90% of the residual organic 14C and 70-80% of the residual l15N was recovered in topsoils. For sites in similar rainfall areas, soils of heavier texture retained slightly greater amounts of 14C and15N-labelled residues. Throughout the eight-year experimental period, the rates of decline of residual organic 14C and 15N exceeded those of native soil organic C and N. A comparison of the decline of organic 14C in topsoils, averaged for the four South Australian sites, with the average decline reported for 14C-labelled plant residues in soils at English and Nigerian field sites, suggests that net decomposition rates doubled approximately for an 8-9�C rise in mean annual air temperatures. Microbial biomass 14C and 15N of topsoils with time accounted for decreasing proportions of total biomass C and N, and of residual organic I4C and I5N. The relatively greater retention after eight years of biomass 14C and 15N in soils of heavier texture is consistent with the concept that the net decay of C and N in soils is dependent upon the turnover of biomass C and N, and that decay rates are decreased in soils which have the greater capacity to protect decomposer populations.
Properties of rainfall induced crusts in alluvial soils and their effect on modulus of rupture
Authors: Sharma D
Published: April 2005

Crust and bulk soil samples, collected from a semi-arid region, were analysed for different properties. Crust samples had higher clay, silt, water dispersible silt plus clay, bulk density and cation exchange capacity (CEC) than the soil below the crust. Modulus of rupture (MOR) as determined on distributed crust material, showed better correlations with textural parameters viz. clay (r = 0.70), silt (r = 0.68), silt + clay (r = 0.82) and fine sand (r = -0.81) than with other parameters like CEC (r = 0.53), ESP (r = 0.55), exchangeable magnesium percentage (r = 0.46) and exchangeable calcium percentage (r = -0.44). Multiple linear regressions between MOR and different crust parameters showed that clay, silt and ESP accounted for 84.1% variation in MOR in these soils.
A proposed new reagent for the measurement of cation exchange properties of carbonate soils
Authors: Tucker BM
Published: April 2005

A solution of choline chloride (1 mol L-1) in aqueous ethanol (65% by weight) is proposed as a reagent for extracting double-layer exchangeable cations from soils containing calcium carbonate, instead of the previously used solution of NH4Cl (1 mol L-1) at pH 8.5 in aqueous ethanol. This choline chloride reagent gives better estimates of double-layer exchangeable cations and of double-layer charge (exchange capacity) because it dissolves less CaCO3, and reacts less with specifically adsorbed forms of Ca, Mg and K than the NH4Cl reagent does. Because plants can use both adsorbed and exchangeable cations, the new reagent is not suitable for measuring nutrient cation availabilities. Cation exchange values for a range of Australian carbonate soils are presented to show the differences to be expected between analyses by the choline chloride and the NH4Cl reagents.
A study of soil erosion on vertisols of the eastern Darling Downs, Queensland .I. Effects of surface conditions on soil movement within Contour Bay catchments
Authors: Freebairn DM , Wockner GH
Published: April 2005

Effects of soil surface conditions on runoff and soil loss were studied on two major cracking clay soils of the Darling Downs, Queensland. Techniques used to measure soil loss between field contour bays under natural rainfall are described, and the results from 10 contour bay catchments (66 plot years) are presented. Soil movement was separated into rill, interrill, suspended sediment and channel deposition. Two slope lengths were considered (60 and 35 m), and interrill erosion appeared to be the major source of soil loss. Runoff and sediment concentration were both inversely related to surface cover and total soil movement was greatly reduced by surface cover. In an annual winter-wheat, summer-fallow system, removal of stubble resulted in soil movement of 29-62 t ha-1 year-1. Retention of stubble (stubble mulching) reduced soil movement to less than 5 t ha-1 year-1. Greater than 75% of the variance in soil movement from single events was explained by surface cover and peak runoff rate. Surface cover is a measure of the surface area protected from soil detachment and entrainment. Peak runoff rate describes the amount of energy or stream power available for detachment and entrainment.
Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. I. Overall changes in soil properties and trends in winter cereal yields
Authors: Dalal RC , Mayer RJ
Published: April 2005

Changes in fertility of some southern Queensland soils resulting from extended periods of cultivation are presented, together with trends in yields of winter cereals on these soils. Six major soils of the cereal-belt, cropped for maximum periods of 20-70 years were examined. These were: Black earths, Waco soil; grey, brown and red clays (brigalow), Langlands-Logie soil; grey, brown and red clays (poplar box), Cecilvale soil; grey, brown and red clays (belah), Billa Billa soil; grey, brown and red clays (coolibah), Thallon soil; red earths, Riverview soil. Organic matter and its constituents, especially total organic C, organic C in the light fraction, total N and mineralizable N, were affected most by cultivation, showing decreases of 19-67% overall. Other soil properties probably associated with organic matter, including bulk density and DTPA (diethylenetriaminepentaacetic acid) extractable manganese, were also significantly affected by cultivation in all soils. Soil properties affected least by cultivation were concentrations of inorganic phosphorus, total and exchangeable potassium, calcium carbonate, and dithionite extractable iron and aluminium. Most other soil properties studied (organic P, total sulfur, pH, exchangeable magnesium and sodium, exchangeable sodium percentage, and oxalate-extractable iron and aluminium) were affected by cultivation in at least four soils. Four factors accounted for 70% of the total variation among the 45 soil properties considered. They appeared to represent organic matter, clay colloids, iron and aluminium oxides, and soluble salts. Dry matter yield and/or N uptake of winter cereal crops (wheat and barley) measured in 1983 showed significant decreasing trends with period of cultivation in all soils.
The role of lateral stresses on soil water relations in swelling clays
Authors: Richards BG
Published: April 2005

The moisture characteristic of a swelling soil is the result of complex interaction between the soil water potential and imposed mechanical stresses. This can give rise to soil water profiles which cannot be interpreted by soil water theories for non-swelling soils. Agricultural soil physics has been concerned primarily with highly structured surface soils, and has developed simple theories for the effects of stress on soil water relations in swelling soils. These simple theories ignore the effect of lateral stress in the soil. Civil engineers, on the other hand, dealing mainly with less complex soils at depth, have developed more complex theories for the effect of three-dimensional stress states on soil water relations. This paper shows how the effect of three-dimensional stress can and should be included in soil water studies of swelling soils, and gives examples to demonstrate the possible magnitude of such effects.
Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland .VI. Loss of total nitrogen from different particle size and density fractions
Authors: Dalal RC , Mayer RJ
Published: April 2005

The dynamics of total N in particle-size and density fractions of six major soils which have been used for cereal cropping for 20-70 years were studied in order to identify the labile organic matter fractions in soil. For virgin soils, no single particle-size was consistently enriched in N as compared with the whole soil. The clay fraction contained the largest proportion (53% overall) of total N. Silt-size and sand-size N fractions accounted for 26% and 21% of total N, respectively. Upon cultivation, the sand-size fraction lost most of its N (as much as 89% in Langlands-Logie soil). However, N losses also occurred from silt-size and clay-size fractions in most soils. Changes in C : N ratios of different particle-size fractions upon cultivation were not consistent in all soils, possibly because of the transfer of organic C and N among these fractions. Therefore, the separation of labile organic matter fractions from the whole soil based upon particle-size may not be successful in all soils. On the other hand, the density fractionation of soil into a light fraction (<2 Mg m-3) containing relatively labile organic matter (76-96% lost upon cultivation) and a heavy fraction (>2 Mg m-3) containing less labile organic matter appears to be more successful in most soils. It is suggested that the cultural practices that enhance the amount of light fraction would increase the rate of nutrient cycling through microbial biomass and may increase the overall availability of nutrients in soil.
The grouping of soils with similar charge properties as a basis for agrotechnology transfer
Authors: Gillman GP , Sinclair DF
Published: April 2005

A set of 94 variable charge soils (Oxisols and Ultisols) from humid tropical Queensland has been formed into three groups on the basis of their surface charge characteristics. Mean curves of basic cation exchange capacity (CECB) against pH, total cation exchange capacity (CECT) against pH, and anion exchange capacity (AEC) against pH for each group at various soil depths were derived, to describe the essential features of each group, designated as Type 1, Type 2 and Type 3 soils. Type 1 soils have high CEC and low AEC, Type 2 soils have low CEC and low AEC, and Type 3 soils have low CEC and high AEC. A number of statistical devices were employed to illustrate the clear separation of the three groups. Additional Oxisol and Ultisol soils from southern China, Peru and the south-eastern United States were successfully allocated to our three groups, but this was not possible for some Andisols from Papua New Guinea. Aspects of possible different management requirements of each group are discussed.
Numerical classification of saline groundwater chemistry in the Murrumbidgee irrigation area
Authors: Williams BG , Ward JK , Belbin L
Published: April 2005

Numerical classification techniques were used to examine the chemical composition of 169 shallow groundwater samples in relation to their geographical distribution within the Murrumbidgee Irrigation Area. The ionic proportions are very similar throughout the whole area, but the total soluble salt concentrations are very variable. The classification was more coherent when primary variables were used rather than derived variables such as Saturation Indices.
Morphology, crystallography and origin of needle fiber calcite in quaternary pedogenic calcretes of South Australia
Authors: Phillips SE , Self PG
Published: April 2005

In several calcrete profiles from South Australia, needle-fibre calcite is concentrated in the channels and voids of nodules, hardpans, carbonate silt and platy calcrete. The morphology, spatial arrangements and crystallography of the needle-fibre calcite were determined using scanning and transmission electron microscopy. Needle-fibre calcite is composed of single crystals of calcite containing less than 0 5 wt % Mg. Two distinct morphological classes are evident: (1) small single rods or micro-rods, 1 �m in length and 0.1 �m or less in diameter and (2) larger needle-fibres 2-120 �m in length and 0.5-6 �m in diameter which display a variety of habits including multiple rods and serrated forms. The basic unit for the second group is that of a double rod which may be modified by cementation to other rods, and by epitaxial growth or dissolution. Spatial arrangements of needle-fibre calcite are determined by their association with organic matter. The large fibres form within mycelial strands. Lysis of the strand by rod-shaped bacteria releases the needle-fibres for redistribution in the profile. The micro-rods are calcified rod-shaped bacteria.
Wheat straw decomposition in subtropical Australia .I. A comparison of 14C labeling and two weight loss methods for measuring decomposition
Authors: Cogle AL , Saffigna PG , Strong WM , Ladd JN , Amato M
Published: April 2005

Three techniques for measuring straw decomposition in the field were compared. They were 14C labelling, weight loss from unconfined straw, and weight loss from straw held in mesh bags. The effect of these techniques on nitrogen transformations was also considered. The percent recovery by weight of straw held in mesh bags was greater than that which had been left unconfined in microplots, and also was greater than the percent recovery of 14C from 14C-labelled straw. This suggested that the mesh bag technique gave an underestimate of decomposition. Unconfined straw in microplots provided results in general agreement with 14C recoveries. Straw decomposition under the conditions of the different treatments had little effect on nitrogen transformations.
Wheat straw decomposition in subtropical Australia .II. Effect of straw placement on decomposition and recovery of added 15N urea
Authors: Cogle AL , Strong WM , Saffigna PG , Ladd JN , Amato M
Published: April 2005

Decomposition of 14C-labelled wheat straw and its effect on fertilizer 15N transformations was studied in a subtropical environment over a 2 year period. The effect of straw management was also studied. Wheat straw incorporated in topsoil initially decomposed at a faster rate than wheat straw placed on the soil surface. This was due to the greater positional availability of straw carbon to soil organisms in incorporated straw. Later decomposition rates were similar. After 1.5 months, 44% of applied 15N-urea was recovered from incorporated straw treatments and 55% from surface-retained straw treatments. Losses were attributed to biological denitrification. The greater loss in incorporated straw treatments was suggested to be due to a greater availability of carbon to the denitrifying population compared with treatments where straw was retained on the surface. After 2 years, the recovery of 15N decreased to between 12 and 15% of that applied.
Rainfall energy in eastern Australia - Intensity kinetic energy relationships for Canberra, ACT
Authors: Kinnell PI
Published: April 2005

Rainfall kinetic energy values measured with a Joss-Waldvogel rainfall distrometer near Canberra are reported and compared with other data obtained in Australia using the same measurement technique. Intensity-energy relationships for Canberra are similar to those previously obtained at Gunnedah, N.S.W. and should apply over a wide area of south-eastern Australia.
Neutron moisture meters - the minimum error in the derived water density
Authors: Wilson DJ
Published: April 2005

Wilson and Ritchie (Aust. J. Soil Res., 1986, 24, 11-23) derived the response of a moisture meter to the soil parameters matrix density, mass absorption coefficient and mass scattering coefficient. The empirical equations describing these dependences were partially differentiated and used to determine the error introduced by the inaccuracy in each soil parameter. The present paper quantifies the error introduced by a 1% error in each of the soil parameters; the accuracy to which the soil parameters can be measured is discussed and the overall accuracy in the final water density is determined for a typical soil.
Aggregate breakdown in clay soils under simulated rain and effects on infiltration
Authors: Glanville SF , Smith GD
Published: April 2005

Wet sieving was used to separate aggregate-size distributions of four clay soils after pre-treatments of simulated rainfall, tension wetting and immersion wetting. Infiltration rates of columns of the soils were also measured under simulated rainfall. During rainfall, samples for wet sieving and the infiltrating columns were either bare or covered with a cloth mesh designed to absorb raindrop impact without affecting rates of wetting. Two swelling clay soils, one non-swelling clay soil and one clay soil dominated by sesquioxides, were used. For the first three soils, rate of wetting was the major factor governing aggregate breakdown. Significant changes in Mean Weight Diameter (MWD) occurred during the first few minutes of rainfall whether the samples were covered or not. As the rain continued, further breakdown was detected only in the uncovered samples. MWD of the sesquioxide soil decreased slightly during immersion, but most aggregate breakdown resulted from the impact of raindrops. Infiltration into the soil columns was virtually unrestricted if the soils were covered. Slaking without drop impact did not interfere with water entry. On bare soils, positive correlations were found between cumulative rainfall and the per cent of soil particles <0.12 mm diameter. An inverse relationship was found between this particle size range and infiltration rates. It is suggested that 25% of the <0.12 mm fraction must be present before infiltration rates decline.
Mineralogical and textural discrimination of loess derived from a tephra near Rotorua, New Zealand
Authors: Benny LA , Kennedy NM , Kirkman JH , Stewart RB
Published: April 2005

Grain size parameters and clay mineralogical analyses were used to characterize and compare Okareka Ash and post-Okareka tephric loess sampled at eight sites on a transect in Rotorua district, North Island, New Zealand. Grain size distribution analyses show consistently lower mean size and better sorting of the tephric loess compared with the Okareka Ash. The mean grain size of the loess is strongly influenced by the mean grain size of the tephra. Trends in the distribution of biotite and halloysite support the grain size distribution analyses. Taken with field observations, the analytical evidence allows differentiation between Okareka Ash and overlying associated tephric loess.
Surface physical properties of a sandy loam soil under different tillage practices
Authors: Chan KY , Mead JA
Published: April 2005

The infiltration behaviour and physical properties of a hardsetting sandy loam soil at Cowra, N.S.W., following 2 years of different tillage treatments are reported. Soil that had not been cultivated for 25 years was also investigated at an adjacent pasture site. Infiltration of simulated rainfall at the end of the wheat-growing season gave moisture profiles that were quite different for cultivated, direct drilled and pasture soils. The moisture profile for the cultivated soil suggested the presence of an impeded layer which retarded the movement of infiltrated rain to the subsoil. Porosity measurements confirmed the presence of a layer with significantly fewer macropores (> 300 �m diameter) at the 50-100 mm depth in the cultivated soil, when compared with the direct drilled soil. The old pasture soil had significantly higher porosity (> 300 �m diameter) in the top 100 mm. Aggregate stabilities and organic carbon contents were measured in narrow increments to 150 mm depth for the three different soils, and revealed that a surface 25 mm layer of high organic carbon and highly stable macro-aggregates was present in the pasture and direct drilled soils but absent in the cultivated soil. The unstable surface layer in the conventionally cultivated soil was a consequence of the mixing and inverting action of cultivation and was not due to a net loss of organic carbon from the profile. The organic carbon content of the pasture soil was not significantly different from the direct drilled soil below 50 mm; however, it was significantly lower than the conventionally cultivated soil between 50 and 150 mm depth. These results indicate a need to adopt tillage practices that can preserve the top 25 mm layer of such fragile soils.
The use of a copper thiourea reagent for the determination of exchangeable basic cations in soils
Authors: Little IP
Published: April 2005

A procedure for the rapid determination of basic exchangeable cations in soils that uses the copper(1) complex with thiourea is described and tested. The results obtained compared favourably with values obtained by displacement of cations with pH 8.5, 1M NH4Cl and 0.01 M silver thiourea.
Water repellency and its measurement by using intrinsic sorptivity
Authors: Tillman RW , Scotter DR , Wallis MG , Clothier BE
Published: April 2005

Measurements of intrinsic sorptivity (S*) by using both ethanol and water were used to indicate the extent of water-repellency in soil. Experiments with initially dry, acid-purified sand verified that in a non-repellent, nonswelling porous medium S' was indeed intrinsic to the medium, and independent of the sorbing liquid. For initially water-moist, non-repellent sand, the measured S* was different when ethanol and water were the invading fluids. But a bound can be put on this difference. It was concluded that in structurally stable soils, the ratio of S* from ethanol to that for water may be used as an index of water-repellency. In the laboratory, disturbance of repellent soil by sieving or shaking effectively removed the repellency. Subsequent incubation restored it. Field measurements of sorptivity, at a scaled negative surface potential, into an initially moist, fine, sandy loam were made. While the soil appeared to absorb water normally, the sorptivity for water was an order of magnitude lower than expected from the ethanol data. This was due, we suggest, to repellency. Some possible implications of this unexpected result are discussed.
Incorporation of uniformly labeled 13C glucose carbon into the organic fraction of a soil - carbon balance and CP MAS 13C NMR Measurements
Authors: Baldock JA , Oades JM , Vassallo AM , Wilson MA
Published: April 2005

The incorporation of uniformly labelled 13C-giucose into soil organic matter was followed using mass spectrometry to make carbon balance measurements, and using solid state CP/MAS 13C NMR (cross polarization/magic angle spinning 13C nuclear magnetic resonance) spectroscopy to determine changes in the chemical structure of the added 13C with time. A fine sandy loam soil was incubated in the presence and absence of the labelled 13C-glucose for up to 34 days at 22�C and a soil water matric potential of -33 kPa. Carbon balance measurements indicated that no priming effect of glucose addition on decomposition of the native organic carbon occurred, and that 65% of the glucose 13C was mineralized during the incubation period. The ability of solid-state CP/MAS 13C NMR to quantitatively detect all of the substrate 13C present in the samples was assessed by comparing the residual substrate 13C contents of the samples analysed with the corresponding CP/MAS 13C NMR signal intensities. Incorporation of the glucose 13C into the soil organic matter resulted in the synthesis of alkyl (26%), O-alkyl (66%), and carboxyl (8%) carbon, but little if any aromatic carbon. The influence of decomposition processes on the chemical characteristics of the soil organic matter is discussed, and the chemical structure of the materials synthesized by the microbial biomass is compared with that of the native soil organic matter.
The introduction of earthworms to an ameliorated, irrigated duplex soil in south-eastern Australia and the influence on macropores
Authors: Blackwell PS , Blackwell J
Published: April 2005

Two species of lumbricid, Aporrectodea caliginosa and Aporrectodea longa and a megascolecid, Eukerria saltenis were introduced, during the winter, to a duplex soil (transitional red-brown earth) ameliorated by either gypsum-enriched slots or beds formed after deep ripping and gypsum application. Some were introduced to areas enclosed by mesh within the slots, others were released in adjacent unenclosed areas. The enclosed areas had the equivalent of 0, 5 or 10 t ha-l of wheat straw on the surface, the unenclosed areas had 5 t ha-1. The enclosed areas were excavated in the spring, 17 weeks after earthworms were introduced. Proportionally more Eukerria adults were recovered than Aporrectodea adults (4040% compared with 10-30%). At 20-45 cm depth, Eukerria adults were four times more common than Aporrectodea. Cocoons and immature forms of Aporrectodea were very common, especially near the surface. Nine months after the introduction, even after a drier than average summer fallow, earthworms were still present. More Eukerria than Aporrectodea adults were found in the sample from the unenclosed areas. The smaller species, Eukerria, (about 1 mm diameter and 30 mm long) may be better adapted to survive in these ameliorated clay soils, but further research is needed. In the enclosed areas, soil macroporosity was unaffected by the 17 weeks with earthworms, but air permeability through the macropores was significantly increased, probably due to the burrows increasing vertical pore connectivity within 0 . 3 m depth.
Thick iron oxide pans in soils of Taranaki, New Zealand
Authors: Childs CW , Palmer RWP , Ross CW
Published: April 2005

Thick iron oxide pans are a distinctive feature of some soils in Taranaki, New Zealand, which occur on the ringplain, or on terraces of valleys draining the ringplain of Mount Egmont. The pans tend to form in the boundary area between layers of differing texture within the zone of water table fluctuations. The pans are indurated, brittle, and vesicular, and have a black or reddish brown appearance with a shiny black fracture. They are up to 50 cm thick and form lenticular deposits sometimes several metres across at depths ranging from a few centimetres to about 1 m. Analysis of seven samples of pan gave 34-45% elemental Fe, 3-5% A1 and 4-10% Si, consistent with about 55-70% iron oxides, together with entrapped and adhering soil particles. V and Mo are enriched in the pan samples and probably occur as anionic species strongly adsorbed on the iron oxide surfaces. X-ray powder diffraction, Moessbauer spectroscopy and acid-oxalate dissolution indicate that the dominant iron oxides present are goethite and ferrihydrite. The relative proportion of these two minerals varies widely without any noticeable change in the nature of the pan materials. Microstructures in one sample were examined by scanning electron microscopy. The pans are considered to have formed from the aeration of groundwaters (rich in ferrous ions) moving laterally through the soils. Such groundwaters are formed on Mount Egmont from the reaction of meteoric water, sometimes containing dissolved volcanic carbon dioxide, with ferromagnesian minerals. Positive tests for ferrous ions (using �,�'-dipyridyl as indicator) were obtained from groundwaters presently associated with the pans.
Effects of eight year rotations of grain sorghum with lucerne, annual legume, wheat and long fallow on nitrogen and organic carbon in two contrasting soils
Authors: Holford ICR
Published: April 2005

Soil nitrogen and organic carbon levels during 8-year rotations of grain sorghum (4 years) with lucerne (4 years), annual legume (faba beans or cowpeas in alternate years), wheat (4 years) and long fallow (alternate years) were measured on a black earth and a red clay in northern New South Wales. Total soil nitrogen (0-15 cm) increased at about 100 kg ha-1 yr-1 in the lucerne leys, but it maximized after 2 years on the red clay and then declined at about the same rate, suggesting that nitrogen fixation had ceased in response to heavy grazing pressure and drought conditions. The positive effects of lucerne on total nitrogen and organic carbon were maintained during 4 years of subsequent sorghum growth on the black earth, but effects on the red clay were not significant. Sorghum, when its residues were incorporated, had a much larger effect than lucerne in raising soil organic carbon. Concentrations of soil nitrate were much higher immediately after the lucerne than after continuous cereal, and they remained higher in the lucerne rotations after 2 years of sorghum. Accumulation of nitrate during long fallows was much larger after sorghum, with incorporated residues, than after no-tilled wheat, and the magnitude of this difference suggested biological nitrogen fixation by free-living bacteria during the sorghum long fallows. Fluctuations in nitrate were generally larger in the red clay than in the black earth, but sorghum yields and nitrogen uptake were less responsive to high nitrate in the red clay, apparently because of its lower nitrate buffering capacity and poorer soil structure. In comparison with continuous cereal growing, the annual legume rotation had no significant effect on organic carbon or total nitrogen, but it sometimes increased nitrate during the sorghum rotation, probably by a nitrate sparing effect during the cowpea crop.
Reaction of zinc with soil affecting its availability to subterranean clover. 2. Effect of soil properties on the relative effectiveness of applied zinc
Authors: Brennan RF
Published: April 2005

The effect of moist incubation on the availability of applied zinc was examined on a range of Australian soils. Incubating soil with applied zinc decreased the uptake of zinc by subterranean clover and DTPA extractable zinc (ZnD) on all soils relative to freshly applied zinc. On soils where plant growth was increased by zinc application, prior incubation of the soil led to decreased plant growth responses to zinc. The relative effectiveness (RE) of zinc application for subterranean clover growth was measured by dry matter production, uptake of zinc by shoots and ZnD. Values obtained by all three methods of determining the RE were closely correlated. The extent of the decline in availability with incubation differed among soils being greater in alkaline soils, in soils with high clay contents, in soils with high levels of organic carbon , and in soils with free calcium carbonate. A multiple linear regression model was used to explain the relationship between the RE and the soil properties (r2 > 0.87).
Distribution and forms of phosphorus and aluminum in acidic topsoils under pastures in south-eastern Australia
Authors: Mclaughlin MJ , Baker TG , James TR , Rundle JA
Published: April 2005

The vertical distributions of pH, and forms of phosphorus (P) and aluminium (Al) in acidic topsoils (0-100 mm depth) under pastures were examined at 15 sites in New South Wales and Victoria. The soils were characterized by shallow surface strata of moderate pH, high P and low Al concentrations overlying more acidic, P-deficient and Al-rich subsurface strata. Significant amounts (35-65%) of the total P in acidic pasture topsoils were present in organic forms (Po). Some 20-40% of this Po was extractable using 0.5 M NaHCO3, and is regarded as easily mineralizable and a potential source of P for plant uptake. Substantial amounts of Al were present in crystalline and non-crystalline oxides (2000- 6000 mg kg-1) and complexed to organic matter (up to 400 mg kg-1). The amount of aluminium extracted using reagents commonly accepted to indicate Al toxicity in soils (1 M KCl and 0.01 M CaCl2) was not related to the amounts of those Al forms (extracted by ammonium oxalate, sodium citrate-dithionite) typically identified in pedological and mineralogical studies. Sampling and analysis of soils for determining P fertilizer requirements and diagnosing acidity and related problems (e.g. Al toxicity, Ca deficiency) should take into account the vertical heterogeneity in soil properties in the top 100 mm of the profile.
Remote sensing of change in components of the regional water balance of the Murray-Darling basin using satellite imaged and spatially registered environmental data
Authors: Jupp DLB , Walker J , Kalma J , Smith R
Published: April 2005

The project aims to develop a series of maps by remote sensing to monitor aspects of the regional hydrology of the Murray-Darling Basin as well as its properties as a hydrothermal (water/energy) system. The methods are based on the analysis of thermal and microwave data collected by satellites to extract information on surface temperature and emissivity and thereby to estimate the spatial and temporal variation of soil moisture, rate of evaporation, water balance and associated properties of the root zone at a regional scale.
Improvements in aggregation and infiltration characteristics of a krasnozem under maize with direct drill and stubble retention
Authors: Prove BG , Loch RJ , Foley JL , Anderson VJ , Younger DR
Published: April 2005

Maize was grown for 6 years in a 7-year trial at Kairi, on the Atherton Tableland, North Queensland. Conventional tillage, direct drilling and reduced tillage were compared and each tillage practice was imposed with and without stubble retention. Direct drilling and stubble retention were found to have significant positive effects on aggregate water stability, water-stable aggregation under rain, dry aggregate size distribution and resistance to abrasion. Effects on infiltration were not significant, although cumulative infiltration (using the rainfall simulator) was higher for direct drilling and reduced tillage with stubble retention. Significant differences were found between row and inter-row for all measurements that enabled this comparison.
Runoff and soil loss from bare fallow plots at Inverell, New-South-Wales
Authors: Armstrong JL
Published: April 2005

Three 41 m long bare fallow plots were established on a chocolate soil (Mollisol) at Inverell in late 1976 to determine the soil erodibility (K) factor for use in the Universal Soil Loss Equation (USLE). The K-factor was estimated as 0.018 tonne hectare hour per hectare megajoule millimetre, indicating a soil of low to moderate erodibility. This value was close to that predicted from the soil erodibility nomograph used in the USLE. The average annual soil loss over the eight year period was 51 t/ha, while the largest individual storm soil loss from the plots was 47 t/ha. The two largest soil losses in each year accounted for 60-99% of the annual soil loss. Various erosivity indices were examined for their ability to predict runoff and soil loss from individual erosive storms. Indices which had separate variables for soil particle detachment (energy component) and particle transport (runoff component) were superior, although a large proportion of the variation in runoff and soil loss remained unaccounted for, and the possible reasons for this are examined. The highest correlation was obtained between soil loss and runoff amount.
Soil compaction and cotton growth on a vertisol
Authors: Mcgarry D
Published: April 2005

Differences in growth, yield and root systems of two adjoining cotton crops on a Vertisol near Dalby, Queensland, were explained in terms of soil profile morphology and soil shrinkage indices. The soil beneath the strongly inferior crop had platy structure in the 0.05-0.28 m layer and significantly less air-filled specific pore volume in the 0.2-0.4 m layer. This soil structure degradation was caused by seedbed preparation of wet soil, prior to sowing the cotton crop.
Evaluation of radiant canopy temperature and soil water measurement for quantifying the contribution of shallow watertables to crop evaporation.
Authors: Mateos L , Meyer WS , Smith RCG , Sides R
Published: April 2005

Accurate estimation of the contribution of shallow watertables to crop water consumption is of major importance for improved irrigation practice and watertable management. A water balance model based on radiant canopy temperature estimations of crop evaporation and measurements of the change in the soil water content with a neutron probe was used to estimate the net upward flux from the watertable. The model was tested against measurements made by using two weighing lysimeters containing loam and clay loam soils, and the estimation of errors involved was analysed. The watertable in the lysimeters was maintained 1 m below the ground surface. Evaporation from a soybean crop was estimated by using an energy balance model with measured values of net radiant energy and soil heat flux. Sensible heat flux was calculated from the difference between the radiant canopy temperature and air temperature, together with an estimated aerodynamic resistance of the crop. Two sources of error were associated with the model, one due to the estimation of crop evaporation and the other due to the measurement of the change in soil water content. Errors of 0.7 and 5.1 mm per day were estimated for the first and second sources respectively. The accuracy of the method was determined by the length of the period considered and by the contribution of the watertable itself. An error of 20% was estimated when periods of 20 and 80 days were considered in the loam and clay loam soils respectively. Shorter time periods will result in larger uncertainty. The implications of the these results for watertable management are discussed.
Effects of fire intensity on soil chemistry in a eucalypt forest
Authors: Tomkins IB , Kellas JD , Tolhurst KG , Oswin DA
Published: April 2005

Soil samples taken in the Wombat State Forest in Victoria, at depths of 0-2, 2-5, and 5-10 cm before and after burning fuel loads of 0 (unburnt control), 15, 50, 150, and 300 t ha-1 were analysed for pH, exchangeable cations and cation exchange capacity, available and total P, organic carbon and soil moisture, over a 2-year, 2000 mm rainfall period. Short term responses (up to 6 months) occurred in levels of exchangeable NH4+, K+, and Mg2+, and long term changes (2 years or longer) over the period of the study were observed for pH, available and total P and exchangeable ca2+ at the 0-2 cm soil depth for the burnt treatments. Following burning (and 108 mm of rain), changes in soil chemical parameters were strongly correlated with fuel load and the quantity of fuel burnt. Changes through the 0-10 cm profile for the various chemical parameters are described, together with seasonal variations. For similar yellow podzolic soils, measurement of soil pH may be a useful criterion for monitoring soil chemical changes following slash and fuel reduction burning, provided that accurate estimates of fuel loads, composition and amount burnt can be established.
Activation energy of the slow reaction between phosphate and goethites of different morphology
Authors: Torrent J
Published: April 2005

Relatively little is known about the nature of the slow reactions between phosphate and iron oxides. For this reason, the sorptive behaviour of 15 goethites, ranging widely in specific surface area, aluminium substitution, morphology and other properties, was examined in detail. The slow sorption could be described by a modified Freundlich equation including time and activation energy (E) terms. The value of E ranged from 38 to 80 kJ mol-1, suggesting that a mechanism common to all samples, such as a simple penetration into the crystalline matrix, was unlikely. Multidomainic goethites showed higher E values than the monodomainic goethites. It is hypothesized that the wedge-shaped interdomainic grooves of the multidomainic crystals have sorption sites posing a more energetic barrier to phosphate than sites on the smooth surface of the mondomainic crystals. Sites in interparticle pores and bridging of particles by phosphate might explain why E values are relatively high, even for monodomainic crystals.
Subsoil macropore space of a transitional red-brown earth after either deep tillage, gypsum or both .I. Physical effects and short term changes
Authors: Blackwell PS , Jayawardane NS , Green TW , Wood JT , Blackwell J , Beatty HJ
Published: April 2005

This research aimed to improve understanding of the processes which cause deterioration of macropore space (volume and permeability of air-filled pores at -10 kPa matric potential), as well as providing some guidelines for improving management. This paper reports the effects of amelioration treatments on soil fragment sizes and horizon-of-origin, as well as the distribution of solid gypsum in the profile immediately after deep cultivation. The macropore space of the subsoil after initial winter cropping is described from measurements on soil cores collected from the experiment. The finer fragments from slotting at low speed resulted in smaller macroporosity than in the ripped soil. Macroporosity, permeability and organization of pore space generally increase with the amount of gypsum initially mixed with the soil. In spite of the smaller volume of soil disturbed by slotting than by ripping, the reduction in runoff was similar to the ripped soil when the gypsum application rate to the slotting was twice that applied to the ripped soil. Where no gypsum was applied to the slotted soil, slumping and swelling led to considerable loss of macroporosity formed by the initial deep tillage, as well as surface sealing by dispersed clay. Hence runoff from this treatment was similar to the unameliorated soil.
Availability and uptake of boron in a group of pedogenetically related Canterbury, New Zealand soils
Authors: Adams JA , Hamzah Z , Swift RS
Published: April 2005

Amounts of soil boron extracted from six Canterbury, New Zealand soils by hot water (HWS), hot 0.02 M CaCl2, 0.01 M CaCl2 + 0.05 M mannitol, and a boron specific resin were significantly (P < 0.01) correlated with each other. The soils are all formed from greywacke alluvium and/or loess but cover a range of organic matter and clay contents. Hot water and hot 0.02 M CaCl2 yielded higher levels of extractable boron than did 0.01 M CaCl2 + 0.05 M mannitol and the resin. Amounts of boron extracted by all four reagents were significantly correlated with soil organic carbon contents (and to a lesser extent clay contents), but not with soil pH. Dry matter yield and boron uptake by radishes (Raphanussativus L.) over two harvests increased with increasing extractable soil boron for all four extractants showing that all were suitable for assessing the boron available to radishes. Decreased yields occurred in soils with HWS or hot 0.02 M CaCl2 extractable boron levels less than 1.1 �g g-1 and were associated with a progressively lower allocation of dry matter to roots. For analytical purposes, the hot 0.02 M CaCl2 reagent provided the most convenient measure of available soil boron.
Rain energy and soil amendments effects on infiltration and erosion of three different soil types
Authors: Levin J , Ben-Hur M , Gal M , Levy GJ
Published: April 2005

The effect of rain kinetic energy and soil amendments on infiltration and erosion from three Israeli soils was studied using a drip-type simulator. The soil samples were from the top layer (0-250 mm depth) of cultivated fields differing in their texture, specific surface area and lime content. Three kinetic energies of raindrops were obtained by varying heights of fall (h = 0.4, 1-0 and 1.6 m) of 3 mm diameter drops. The soil types studied were Typic Chromoxerert, Typic Rhodoxeralf and Calcic Haploxeralf. Soil amendments were phosphogypsum (PG) and a combined application of an anionic polyacrylamide (PAM) with PG. An increase in the impact energy of the raindrops reduced depth of rain before ponding, final infiltration rate (FIR), cumulative infiltration (i.e. infiltration parameters) and increased soil erosion. The addition of PAM+PG to the soil surface significantly increased the infiltration parameters and reduced erosion compared with the PG and control treatments. The Typic Chromoxerert was the least susceptible of the three soils to sealing, probably because of its high smectitic clay content, high specific surface area and high CaCO3 content which stabilize soil structure. The Typic Rhodoxeralf with the lowest specific surface area was the most susceptible to clay dispersion, and seal formation. Relative to the Typic Chromoxerert and the Typic Rhodoxeralf, the Calcic Haploxeralf was intermediate in its susceptibility to seal formation.
Interrelations between soil pH measurements in various electrolytes and soil solution pH in acidic soils
Authors: Aitken RL , Moody PW
Published: April 2005

Ninety soil samples (81 surface, 9 subsurface) were collected from eastern Queensland and soil pH (1:5 soi1:solution) was measured in each of deionized water (pH,), 0.01 M CaCl2, 0-002 M CaCl2 and 1 M KCl. Soil solution was extracted from each soil after incubation for 4 days at the 10 kPa matric suction moisture content, and pH (pHss) and electrical conductivity were measured. The objectives of this work were to investigate interrelationships between soil pH measurements in various electrolytes and soil solution pH in a suite of predominantly acidic soils. Although the relationships between pHw and pH measured in the other electrolytes could be described by linear regression, the fitting of quadratic equations improved the coefficients of determination, indicating the relationships were curvilinear. The majority of soils exhibited variable charge characteristics (CEC increases with soil pH) and the curvilinear trend is explained on this basis. At low pH, the difference between pH, and pH measured in an electrolyte will be small compared with the difference at higher pH values because, in general, at low pH, soils will be closer to their respective PZSE (pH at which electrolyte strength has no effect). Of the electrolytes used, pH measured in 0.002 M CaCl2 gave the closest approximation to pHs,. However, when soils with ionic strengths greater than 0.018 M were selected (predominantly cultivated surface soils), pH in 0.01 M CaCl2 gave the best approximation to pHss. For predicting pHss, the ionic strength of the electrolyte will need to be matched to that of the soils studied. For a suite of soils with a large range in soil solution ionic strength (as in this study), it is preferable to measure pHss directly.
The effects of dispersants, stabilizer and slope length on runoff and water harvesting farming
Authors: Ben-Hur M
Published: April 2005

development in arid regions. The objectives of this study were to (i) study the effect of sodium polymetaphosphate (NaPMP), sodium tripolyphosphate (STP), phosphogypsum (PG) and slope length on seal formation, infiltration rate (IR) and runoff amount; and (ii) determine the efficiency of use of PG, STP and NaPMP in runoff farming for wheat production, whereby the PG spread over the collector area is used to diminish runoff, and STP and NaPMP spread over the contributing area is geared to increase runoff. Field experiments were conducted in the northern Negev, Israel, where the average annual precipitation is 209 mm. Runoff from Calcic Haploxeralf was measured by small plots (400 m2) under conditions of simulated and natural rainfall. In the stabilization of soil surface structure, and prevention of a sharp drop in the IR, 5 t ha-1 PG was found effective. The NaPMP and STP increased clay dispersion, and enhanced seal formation and runoff. This effect increased as the amount of the dispersant agents approached 150 kg ha-1. The NaPMP was more efficient than STP in increasing the runoff amount. The NaPMP and STP weakened the stability of soil aggregates, and increased clay dispersion, and enhanced seal formation. An increase in plot length decreased the runoff depth (amount area). However, plot rolling-which decreased surface storage-eliminated this reduction in runoff depth. The wheat yields for the seeded area in the runoff farming system which was treated with STP and PG, were significantly higher than with the ordinary system.