bluuebunny/crossref_metadata_2025 huggingface dataset:
Interpretation of soil features produced by ancient and modern processes in degraded landscapes .1. A new method for constructing conceptual soil-water-landscape models
Authors: Fritsch E , Fitzpatrick RW
Published: April 2005

A pedo-hydrological method which involves interpreting features in soils that result from both ancient and modern processes along toposequences in a subcatchment of the Mt Lofty Ranges, South Australia, is used to construct conceptual soil-water-landscape models. This method links soil-landscape features to soil-water processes with strong emphasis on: (i) soil water-flow systems and (ii) soil-forming and soil-change processes. The conceptual model illustrates the interactions between soil processes acting in soil water-flow systems. This model is able to predict future modes of soil-landscape evolution under changing environmental conditions. As well, it may be used by land and water supply managers to develop more efficient management strategies under conditions of increasing land degradation (e.g. erosion and water pollution). A typical Palexeralf-Natraqualf hydro-toposequence of soils (i.e. catena consisting of red-yellow-grey duplex soils) is used as an example to illustrate this new approach. The landscape selected is undergoing severe soil degradation (i.e. waterlogging, dryland salinity, erosion and water pollution). The constructed conceptual soil-water-landscape model is the result of detailed pedo-hydrological investigations along toposequences in a representative subcatchment in the high rainfall zone (>600 mm) of the Mount Lofty Ranges, South Australia. The model illustrates in graphic form interactions between three soil water-flow systems (freely drained red soil system, hydromorphic topsoil system, hydromorphic subsoil system) and eight soil processes (saprolitization, ferralitization, glaebulization, redoximorphism, eluviation/illuviation, salinization/solonization, sulfidization/sulfuricization and water erosion). The study demonstrates that this whole ecosystem has been placed into disequilibrium thereby developing severe land degradation problems as a result of rising saline sulfatic ground watertables and perched watertables due to land-clearing since European settlement. The purpose of this paper is to provide a methodology framework and overall summary for other papers in a series dealing essentially with detailed field and laboratory investigations of individual soil-water processes.
A rapid method for estimating soil shrinkage
Authors: Mckenzie NJ , Jacquier DJ , Ringrose-Voase AJ
Published: April 2005

The Coefficient of linear extensibility (COLEstd) is often used by soil survey agencies to characterize the shrink-swell behaviour of soil. Undisturbed clods or cores are required but these are rarely collected during routine survey in Australia. The standard linear shrinkage test (LSstd) uses sieved soil and is often used as an alternative. However, the natural soil fabric is destroyed and the results can be difficult to relate to field behaviour. We have developed a modified linear shrinkage test (LSmod) in which disruption to the natural soil fabric is minimized. The LSmod was found to be a good predictor of COLEstd)(r2 = 0-88) with the slope of the regression line close to unity. LSstd was a weaker predictor of COLEstd. LSmod and LSstd were more precise measures than COLEstd. The modified method has been tested on a limited range of soils but a more comprehensive evaluation is required. This can be performed wherever COLEstd measurements have been made and sieved material is still available.
Carbon content and bulk-density of an irrigated natrixeralf in relation to tree root growth and orchard management
Authors: Emerson WW , Foster RC , Tisdall JM , Weissmann D
Published: April 2005

This paper investigates why there are usually very few feeder roots present in the surface soil of irrigated orchards in the Goulburn Valley, as this may be reducing fruit yields. Nine orchards were selected to cover the range of soil and water management. In each orchard, when the soil was near field capacity, root proliferation and earthworm activity were noted and a core taken. Where the C content of cores was 1% or less, few roots were present, the soil was severely compacted and inter-particle bonding was weak. Root proliferation, soil porosity and clay inter-particle bonding all reached a maximum at about 2.2% C. With 3-4% C present, few roots were seen, bonding remained strong, but the soil was again compacted. It is suggested that with increasing C content, carbohydrate gel progressively bonds portions of the mineral matrix together. Eventually, probably mainly as a result of earthworm activity, the mineral matrix becomes embedded in gel. Then, although the gel itself retains about 4.6 g H2O per g of C at 10 kPa suction, none is available for root growth, because of the high penetration resistance of the soil. Root growth is also inhibited at low C contents, because of the high bulk density. Maximum root proliferation occurred in permanent banks raised around mature trees, where the banks were wetted by capillarity every 2-3 weeks.
The effect of valence and Ionic-strength on the measurement of pH buffer capacity
Authors: Aitken RL , Moody PW
Published: April 2005

Although the measurement of pH buffer capacity (pHBC) is used to determine lime requirement and acid addition rate in acidification studies, the experimental conditions under which pHBC is determined have not been studied. The effect of valence and ionic strength on the measurement of pHBC was investigated on a range of soils. The effect of the monovalent or divalent accompanying ion was examined by establishing separate titration curves for each of 100 soils by adding incremental amounts of either Ca(OH)2, NaOH, HCl or H2SO4 to soil suspended (1 : 5) in water. Linear regressions were fitted to the linear portion of each titration curve and the slopes of these lines were used as a measure of pHBC. For each soil, the pH buffer capacities were statistically compared. The pHBC determined with Ca(OH)2 was significantly (P = 0.05) greater than that determined with NaOH in 92 soils and, on average (all soils), was 2.2 times the pHBC in NaOH. The effect of ionic strength on pHBC was investigated in each of 20 soils by titrating with HCI in water and suspensions at nominal ionic strengths of 0.006, 0.03 and 0.3 m. In all soils there was a trend for increasing pHBC with increasing ionic strength (I) and, for I < 0.03 m, there was a marked increase in pHBC with increasing I. The results are discussed in relation to the effect of valence and ionic strength on pH buffer capacity mechanisms, and the implications with respect to calculating acidification rates and lime requirements.
The removal of magnetic materials from surface soils - a solid state 13C CP/MAS NMR study
Authors: Skjemstad JO , Clarke P , Taylor JA , Oades JM , Newman RH
Published: April 2005

Five surface soils of differing chemical and mineralogical compositions were subjected to either a sequence of dithionite/citrate extractions in which the soil: citrate ratio was varied or to a sequence of 1% or 2% HF extractions. The 2% HF treatment resulted in the removal of the highest Fe concentrations (79-95%) while the dithionite/citrate extractions were less effective in removing Fe from the same soils (18-75%). The Fe remaining after HF treatment appeared to be mostly associated with ilmenite crystals which were only slowly attacked by the dilute acid. During the 2% HF treatments, some organic carbon was lost (8-17%), but this loss had no significant effect on the organic chemistry of the samples as determined by CP/MAS 13C n.m.r. spectroscopy. The total 13C signal recovered after the various treatments was found to be correlated, in order of decreasing significance, with the mineral fraction present in the sample, the organic carbon/Fe ratio and the mass magnetic susceptibility. The expression (organic carbon/Fe) -0.147 (mineral fraction present in the sample) +0.043 (1/mass magnetic susceptibility), accounted for 85.3% of the variation in the relative visibility of the 13C signal. Prior to soil state CP/MAS 13C n.m.r. analysis, the recommended pretreatment for surface soils containing Fe involves a sequence of 2% HF extractions in the order 5 x 1 h, 2 x 16 h and 1 x 64 h. For soils high in Fe, this procedure allows CP/MAS 13C n.m.r. spectra to be acquired that would otherwise be difficult to obtain. It also results in a significant increase in sensitivity and in resolution of the 13C n.m.r. spectra of soils with moderate Fe contents.
Effect of cropping on the physical fertility of krasnozems
Authors: Bridge BJ , Bell MJ
Published: April 2005

The physical properties of krasnozems and euchrozems in Australia have received little attention due to the widespread perception that they are 'good' soils. We present data from three locations which are representative of these soil types in the South Burnett region of southern Queensland. At each location, paired sites were chosen where continuously cropped and uncropped land existed side by side. The effect of continuous cropping on physical fertility, relative to that of soil in virgin condition, is assessed and related to published data from other locations where available. Continuous cropping has reduced infiltration rates from 80 mm h-1 or more to values as low as 25 mm h-1. Originally low bulk densities ranging from 0.6 Mg m-3 at the surface to 1.3 Mg m-3 at 70 cm depth have been increased to corresponding values of 1.0 and 1.4 Mg m-3. Local maxima of 1.3 Mg m-3 occur between 15 and 30 cm depth. Penetration resistance has been increased markedly at low water contents as a result of increased cohesion, with an uncropped soil having values <2.5 MPa over the available water content range comapred with values of >6 MPa in the continuously cropped soil. Organic carbon in the surface soil has been reduced from 4-5% to 1% and aggregate stability under rain has been reduced, the % aggregates <0.125 mm diameter increasing from 10% to 20% or more. Soil water storage has been reduced together with crop water extraction, with these effects attributed to a loss of water storage pores in the top 30-50 cm of the profile and restricted root development. The problems of rehabilitating these soils are briefly discussed. Continuous cropping under dryland conditions has greatly reduced the physical fertility of krasnozem and euchrozem soils and made them more susceptible to variation in seasonal conditions. Available data suggest degradation is also occurring on krasnozems used for intensive vegetable production. Methods of rehabilitating physical fertility of degraded krasnozems are required, as are farming systems which are more sustainable in the long term.
Structural and dynamic properties of soil organic-matter as reflected by 13C natural-abundance, pyrolysis mass-spectrometry and solid-state 13C NMR-spectroscopy in density fractions of an oxisol under forest and pasture
Authors: Golchin A , Oades JM , Skjemstad JO , Clarke P
Published: April 2005

Changes in the content and isotopic composition of organic carbon as a consequence of deforestation and pasture establishment were studied in three neighbouring areas on an Oxisol from Australia and used to measure the turnover of forest-derived carbon (C3) under pasture (C4) over 35 and 83 year time scales. The results indicated that the quantity of forest-derived carbon declined rapidly during the first 35 years under pasture but the content remained nearly stable thereafter, suggesting the presence of two pools of carbon with different turnover times. The calculated values for turnover time of labile and resistant fractions of forest-derived carbon were 35 and 144 years respectively. The soil samples were separated into five fractions with densities <1.6 (free and occluded), 1.6-1.8, 1.8-2.0 and >2.0 Mg m-3. Based on the spatial distribution of organic materials within the mineral matrix of soil, the soil organic matter contained in different density fractions was classified as free particulate organic matter (1.6 free), occluded particulate organic matter (<1.6 occluded, 1.6-1.8 and 1.8-2.0) and clay associated organic matter (>2.0 Mg m-3). The 13C natural abundance showed that the free particulate organic matter formed a significant pool for soil organic matter turnover when the forest was replaced by pasture. Compared with free particulate organic matter, the organic materials occluded within aggregates had slower turnover times. The occluded organic materials were in different stages of decomposition and had different chemical stabilities. Comparison of the chemistry and isotopic composition of occluded organic materials indicated that the O-alkyl C content of the occluded organic materials was inversely related to their stabilities whereas their aromatic C content was directly related to their stabilities. In soils under pasture, a considerable amount of forest-derived carbon was associated with clay particles in the fractions .2.0 Mg m-3. The rate of accumulation of pasture-derived carbon was also rapid in this fraction, indicating the presence of two different pools of carbon (C3 and C4) associated with clay particles. The forest-derived carbon had the highest stability in the fractions >2.0 Mg m-3, probably due to strong interaction with active aluminium or iron and aluminium oxides associated with clay surfaces.
Sulfur and phosphorus dynamics in an acid soil/crop system
Authors: Santoso D , Lefroy RDB , Blair GJ
Published: April 2005

The objective of this study was to evaluate different methods, forms, and times of sulfur fertilizer application on a highly weathered soil under different rates of added lime and phosphorus. A pot experiment was conducted using a medium phosphorus (P) and sulfur (S) sorbing red earth (Haplohumult) of pH (1:1 H2O) 4.9 soil. The experiment was carried out using an incomplete factorial combination of two rates of lime (0 and the equivalent of 1.5 x exchangeable Al), three rates of phosphorus (0, 10 and 30 �g P/g soil), two sources of sulfur fertilizer [elemental S (ES) and gypsum (GS)], two methods of placement of sulfur fertilizer (mixed with or separated from the P fertilizer), and two different times of sulfur application (ail treatments applied as a basal dressing and a split application, half applied as a basal and half applied 14 days after planting). Three treatments with P only (0, 10 and 30 �g P/g soil) were added as a check for S responses Liming had no effect on crop yield or S and P dynamics. The experiment demonstrated that movement and leaching losses of applied S fertilizers, and thus their efficiency, were not only determined by soil properties but also influenced by form, rate and time of application of the S fertilizers, and their placement relative to the placement of P fertilizer. In addition, the mobility and effectiveness of S fertilizers was affected by the S requirement of the plants and the fate of P fertilizer application. Gypsum provided available S immediately and thus was advantageous for rapidly growing corn. However, the immediate availability of sulfate-S from gypsum resulted in considerably higher amounts of S being lost by leaching, ranging from 2.2% to 15.7% of the applied S. On the other hand, the application of elemental S resulted in lower S losses by leaching (<1%), but the amounts of S taken up by the plant from the elemental S fertilizer were also lower, especially if the fertilizer was applied in a split application. The mixing of S and P fertilizers increased the effectiveness of gypsum and, more particularly, elemental S fertilizer. Mixing 30 �g P/g soil with a single application of elemental S increased fertilizer S uptake by the whole plant from 2.7% to 12.4%. The advantage of mixing S and P fertilizers has important agronomic implications, and suggests that combined S/P fertilizers should be investigated further on weathered soils.
A comparison of sulfur extractants for weathered acid soils
Authors: Santoso D , Lefroy RDB , Blair GJ
Published: April 2005

The increasing incidence of S deficiency throughout the world has focused attention on ways of assessing the S status of soils. An incubation experiment was conducted using three acid soils varying in S sorption capacity. The soils were a gleyed podzolic (Aquic Haplustalf), a red earth (Haplohumult) and krasnozem (Haplohumult) with a S sorption (at 5 �g S mL(-1)) of 13, 48 and 135 �g S g(-1)) soil, respectively. A factorial combination of S (0 and S applied to 5 �g S mL(-1)) in soil solution), P (0 and P applied to 0.2 �g P mL(-1)) and lime (0, 1.5 x exch. Al) was applied to the soils which were incubated at 70% of field capacity at 25�C for 3 weeks. At the end of the incubation period the soils were extracted with 0.01 M P as Ca(H2PO4)2 (MCP), water (water) and 0.01 M CaCl2 (CaCl2). The concentration of S extracted (�g S g-1) soil) varied between soils, treatments and extractants. In the krasnozem, the order was MCP > water > CaCl2. In the gleyed podzolic the amounts extracted by the three methods were similar and in the red earth the order was water > CaCl2 > MCP. The addition of P and lime affected the extractans in different ways. The use of 35S-labelled sulfate allowed a calculation of the recovery of added S and this differed between soils and extractants. The results indicate that on low S-sorbing soils the extractants used were not sensitive enough to account for differences brought about by P and liming and that care is needed in interpreting results from such experiments.
Emission of nitrous-oxide from some grazed pasture soils in New Zealand
Authors: Carran RA , Theobald PW , Evans JP
Published: April 2005

Nitrous oxide emissions from grazed pastures were measured at four sites for a 2 year period. Sites differed in drainage class and N cycle characteristics. At two intensively farmed sites on Kairanga silt loam, which is poorly drained, daily emissions ranged from 0 to 100 g N ha-1 day-1 and annual emission was in the range 3-5 kg N2O-N ha-1. Emissions occurred when the soil was near or above field capacity indicating denitrification is the probable source of N2O. Multiple regression analysis, using soil water content, NO3-, NH4+ and temperature, gave r2 = 0.44 and 0.57 at sites 1 and 2 respectively. Soil water content and NH4+ were significant variables. Emissions at a low fertility hillside site were very low and an annual emission of 0.5 kg N2O-N yr-1, or less, was indicated. The highly fertile hillside site also showed low emission values. It is suggested that grazing animals may have a large impact on emissions through hoof damage on wet soils.
A soil-landscape model for close-jointed mudstone, Gisborne-East Cape, North-Island, New Zealand
Authors: Mcleod M , Rijkse WC , Dymond JR
Published: April 2005

A soil-landscape model, comprising 12 land components at a scale of 1 : 5000, has been developed in Neogene close-jointed mudstone in the Gisborne-East Cape region of the North Island, New Zealand. In a validation, soil order was predicted correctly in 81% of observations, soil group in 80%, soil subgroup in 63% and soilform in 60% of observations. A simplified model based on 11 land components for use at a scale of 1 : 50 000 has also been validated. Here soil order was predicted correctly in 71% of observations, soil group in 73% and soil subgroup in 49% of observations. For application with a digital elevation model (1 : 50 000), the number of land components was amalgamated to five. Here the soil order and soil group were predicted correctly in 63% of observations and soil subgroup in 40% of observations during validation. In all trials, the percentage of correct observations increased if a second choice or subdominant soil class was allowed. It took 2 person-weeks to produce a soil map from the 1 :50 000 form of the model over 400 km2 of steep and hilly country by photo interpretation of stereo aerial photographs, compared with 1 day of applying computer algorithms on the digital elevation model (DEM). The soil-landscape model succinctly relates soil class to land component and it enables improved targeting of farm and planning inputs by empowering existing research into soil fertilizer requirements and soil physical properties.
Root-induced dissolution of phosphate rock in the rhizosphere of lupins grown in alkaline soil
Authors: Hinsinger P , Gilkes RJ
Published: April 2005

Dissolution of North Carolina phosphate rock (PR) in the rhizosphere of white lupin (Lupinus albus) and narrow leaf lupin (L. angustifolius) was measured in a growth chamber experiment. Plants were grown for 8-13 days in an artificial soil (pure alumina sand) at alkaline pH to eliminate dissolution of PR due to reaction with the soil. Phosphate rock was supplied as the sole source of P and Ca for the plants at two rates of application (0.1 and 1 mg P g-1 soil). Both species dissolved considerable amounts of PR (up to 70% of PR present within 3 mm from the roots). Phosphorus extracted from the soil with 0.5 M NaOH showed that up to 69% of dissolved P accumulated in the rhizosphere of both species due to sorption by the soil, particularly at the high rate of application. Only white lupin utilized significant amounts of Ca. Thus P and Ca uptake were not driving forces for the root-induced dissolution of PR which was probably due to proton excretion that occurred concurrently, as evidenced by a decrease of rhizosphere pH of about 2 pH units. White lupin dissolved up to twice as much PR than narrow leaf lupin. This may be related to either the larger root biomass of white lupin or the particular excretion activity of its proteoid roots.
An analysis of the fragmentation of remolded soils, with regard to self-mulching behavior
Authors: Grant CD , Watts CW , Dexter AR , Frahn BS
Published: April 2005

A power-law relation was used to analyse the (mass-derived) number-size distributions of fragments generated by wetting and drying remoulded soils. Various soils from Europe and Australia produced a range of values for the two fragmentation coefficients, d and k, generated by the power-law function. Both coefficients had physical significance with respect to self-mulching behaviour. Likened to a fractal dimension, the d coefficient varied directly with the tendency of the remoulded soil to fragment during wetting and drying. Assessment of the number of generated fragments >1 cm was made with the k coefficient. Consideration of both coefficients together in a plot of k v. d enabled similar soils to be grouped and falsely large values of d to be identified; k values were small for limited fragmentations even if the size distribution of the fragments that were produced gave large values of d. Most strongly self-mulching soils produced d values >1 . 5 after three wet/dry cycles, and k values that increased sharply after one cycle and declined with subsequent wetting and drying. Other soils with lesser abilities to self-mulch generally produced smaller d values and more variable k values. Reasonable correlations were found between these two coefficients and other measurements of self-mulching behaviour, particularly after three cycles of wetting/drying. Examination of the aggregate size distributions produced from remoulded soils in this way offers the potential to understand more clearly the dynamics of structure regeneration in soils exhibiting various degrees of self-mulching behaviour.
Characterization and analysis of soils using mid-infrared partial least-squares .2. Correlations with some laboratory data
Authors: Janik LJ , Skjemstad JO
Published: April 2005

Infrared partial least squares (PLS) analysis is shown to provide a simple, rapid chemometric technique for the simultaneous analysis of soil properties. The method is capable of extracting both qualitative and quantitative information from soil spectra. A number of the mineral and organic components which are responsible for certain soil properties have been identified and the prediction of these properties assessed. Diffuse reflectance infrared Fourier-transform (DRIFT) spectra of whole soils were recorded to form a large training data set. The spectral information from this set was compressed into a small number of subspectra (called weight loadings) which contained positive and negative peaks reflecting correlations between the soil mineral and organic components and corresponding analytical data. Positive peaks in the weight loadings corresponding to organic components including alkyl, carboxylic and amide species were highly correlated with OC and N. Likewise, smectite, kaolinite and gibbsite clay minerals, together with organic alkyl and carboxylic species, contributed either positively or negatively to pH, sum of cations and clay content. Positive peaks due to calcite were well resolved in the first carbonate weight loading. Quartz was identified as an 'interference' for all analyses, with a series of negative peaks in the weight loadings. Implications were that quartz exerted a strong spectral signal for the majority of soil spectra, although it was not directly related to particular analyses. The usual PLS method, in which there is assumed to be a linear relationship between the loading intensities and soil property values, was found to give nonlinear prediction regression. The nonlinearity was assumed to be due to the effects of nonlinear response of the DRIFT signal and to significant compositional variability between calibration samples with high and low analyte concentrations. An alternative strategy of using a locally linear PLS model was tested, where small subsets of the total span of analytical values were independently used for PLS analysis. This approach improved prediction linearity and precision improved significantly for most analyses. The PLS method was thus shown to provide a useful surrogate technique for the study of soils, with which the PLS analysis of a single spectrum could provide simultaneous qualitative and quantitative information on a number of widely different soil analyses.
Effect of banded fertilizers on soil solution composition and short-term root-growth .2. Mono-ammonium and di-ammonium phosphates
Authors: Moody PW , Edwards DG , Bell LC
Published: April 2005

A layer of mono- or di-ammonium phosphate (MAP and DAP, respectively) was placed in contact for 5 days with duplicate columns of soil at a water content equivalent to 10 kPa matric suction. This was designed to simulate the effects of banded fertilizer on soil solution composition. Five soils were used: 0-10 cm samples from a Kurosol, a Ferrosol, a Vertosol and a Kandosol, and a 50-60 cm sample from the Kandosol. After the contact period, soil sections were recovered at successive 5 mm intervals from the fertilizer layer, the last section being 45-60 mm from the layer. Soybean (Glycine max (L.) Merr.) seedlings were grown for 48 h in each section and relative root elongation was determined. Soil solution was then extracted from each section and analysed. The amount of inorganic P in the soil solution (P-i) was summed over all soil sections for each soil and each P source and was found to be correlated with distance of P movement from the simulated band (r = 0 . 792, P < 0.01). Of several soil chemical parameters of the control (unfertilized) soils regressed against Pi, the following showed significant (P = 0.05) negative correlations: Ca and Mg concentrations in the soil solution for Pi from both MAP and DAP, exchangeable Ca and Mg for DAP, and citrate-dithionite extractable Fe and Al for MAP. These results suggest that adsorption (and possibly precipitation) reactions with Fe and Al hydrous oxides contributed to the removal of P-i from solution in the presence of MAP. However, with DAP as the fertilizer source, precipitation reactions involving Ca and Mg were the predominant factors. Dissolved organic C in the soil solution increased adjacent to both DAP and MAP, with larger amounts in proximity to DAP being a consequence of the higher soil solution pH (~ 7). Soil solution Si increased in all soils adjacent to both DAP and MAP, with concentrations being higher in the MAP treatments. Dissolution of aluminosilicates in the acidic conditions near MAP (pH ~5) was the probable cause. Relative root elongation (RRE) of soybean was restricted in soil sections close to the fertilizer. When RRE was plotted against each of soil solution EC, NH3 activity, and calcium activity ratio (CAR), a single curvilinear function described the relationship between RRE and CAR for all soils and both P sources. It is concluded that a salt-induced Ca deficiency was the cause of restricted root growth in proximity to DAP and MAP, rather than an osmotic effect or NH3 toxicity.
Cadmium distribution in hill pastures as influenced by 20 years of phosphate fertilizer application and sheep grazing
Authors: Loganathan P , Mackay AD , Lee J , Hedley MJ
Published: April 2005

Cadmium (Cd) accumulating in the kidneys of older grazing animals threatens the continued access of New Zealand offal products to traditional markets. Phosphatic fertilizers represent the largest input of Cd into pastoral farming systems. Little research has been conducted on the cycling of Cd in grazed pastures. To estimate the distribution of Cd in grazed pastures, soil samples were collected from self-contained farmlets which had received either high superphosphate (HF) inputs (765 kg P ha-1), low superphosphate (LF) inputs (113 kg P ha-1) or no phosphate fertilizer (UF) inputs over the previous 20 years. The average total Cd concentration in the surface soil (0-30 mm; bulk density 0.64 g cm-3) of the farmlets which had received HF inputs was 0.40 mg kg-1 soil (range 0.18-0.60 mg kg-1), whereas farmlets which had received LF or no fertilizer inputs had an average Cd concentration of 0.10 mg kg-1 (range 0.02-0.19 mg kg-1). Cadmium concentration decreased with soil depth. The concentration of Cd in mixed herbage reflected the difference in soil Cd between the HF (mean � standard error = 0.321 � 0.033 mg Cd kg(-1) dry matter) and LF (0.063 � 0.004 mg Cd kg(-1) dry matter) farmlets. Soil Cd accumulation was highest on low slopes (0-12�) and lowest on high slopes (> 26�) in both LF and HF farmlets, whereas pasture Cd concentration in the HF farmlet increased with slope from 0.178 � 0.035 mg Cd kg-1 on low slopes to 0.487 � 0.053 mg Cd ha-1 on high dopes. A strong relationship was obtained between soil Cd and P in the 0-30 mm layer of the HF farmlet, demonstrating the link between phosphate fertilizer use and Cd accumulation. Zinc to Cd ratios were much lower in this layer compared with those in LF and UF sites, providing further evidence of the contribution of phosphate fertilizer to soil Cd. A model originally developed to explain the distribution of soil P in sheep-grazed fertilized hill pastures gave good predictions of present day soil Cd distribution in the HF farmlet. The model predicts Cd accumulation in soil by using the amounts of Cd applied in fertilizer per unit surface area of land and functions which calculate the redistribution of Cd by animal grazing and camping behaviour. The model on an average overpredicted the measured soil Cd by 17% in the high slope sites and by 10% in the low slope sites.
A review of bacterial-degradation of pesticides
Authors: Aislabie J , Lloyd-Jones G
Published: April 2005

Pesticide fate in the environment is affected by microbial activity. Some pesticides are readily degraded by microorganisms, others have proven to be recalcitrant. A diverse group of bacteria, including members of the genera Alcaligenes, Flavobacterium, Pseudomonas and Rhodococcus, metabolize pesticides. Microbial degradation depends not only on the presence of microbes with the appropriate degradative enzymes, but also on a wide range of environmental parameters. This review describes recent advances in biodegradation of pesticides by addressing the biology and molecular characterization of some pesticide degrading bacteria.
Review: the behaviour and environmental impact of contaminants in fertilizers
Authors: Mclaughlin MJ , Tiller KG , Naidu R , Stevens DP
Published: April 2005

The risks of contaminants accumulating in soils and crops due to inadvertent addition of impurities in agricultural fertilizers and soil amendments were assessed for Australian conditions. Elements considered of concern were arsenic (As), cadmium (Cd), fluorine (F), lead (Pb) and mercury (Hg). Consideration of background concentrations of these elements in Australian soils, inputs to soil in fertilizers and offtake in harvested crops indicates that Cd and F will accumulate in fertilized soils at a faster rate than As, Pb or Hg. The major factors affecting the accumulation of fertilizer-derived Cd, F, Hg and Pb in soils and their transfer to agricultural crops are reviewed in an Australian context where data are available. Cadmium is the element of most concern as its transfer from soils to the edible portions of agricultural food crops is significantly greater than for other elements. After consideration of the behaviour of F, Hg and Pb in the soil-plant system, we conclude that these elements pose negligible risk of accumulating to toxic concentrations in agricultural food crops. Proposed regulations governing maximum permitted concentrations (MPCs) of F in soils may need review and critical concentrations of F in agricultural soils need definition, given current F loadings to soil from fertilizers. Some agricultural produce currently exceeds Australian MPCs for Cd. However, the levels observed in crops and soils are in a range similar to those found internationally. While Cd concentrations in Australian phosphatic fertilizers have been historically high in comparison with fertilizers used in other countries, lower inputs of fertilizer per unit area and less atmospheric contamination of soils have resulted in similar or lower Cd loadings to agricultural land compared with Europe. In recent years the use of phosphatic fertilizers with lower Cd concentrations and the development of plant cultivars which restrict Cd uptake should assist in control of Cd accumulation by crops. However, acidification and salinization of soils in Australia poses a threat in terms of increasing Cd concentrations in agricultural produce. In comparison with other trace metals, Cd availability to plants appears to decline only slowly with time, if at all. More Cd is currently added to Australian soils than is removed in agricultural produce or by leaching. It is therefore important that the long-term behaviour of Cd in Australian soils be assessed, to determine if Cd concentrations in agricultural produce will slowly increase over time.
Subsoil hydraulic conductivity estimates for the Lower Macquarie Valley
Authors: Bird TL , Willis TM , Melville GJ
Published: April 2005

Field saturated hydraulic conductivity was measured in situ, at two depths in the B horizon, on irrigated soils in the Lower Macquarie Valley. Measurements were made with constant head well permeameters, using the single-head method, and water of moderate sodicity and high salinity. The hydraulic conductivity data were log-normally distributed for all soil groups and there were significant differences between some of these soil groups in mean hydraulic conductivity. Three soils exhibited significant differences in mean hydraulic conductivity between depths. Hydraulic conductivity measurements ranged up to 3 orders of magnitude within a soil. Variation in hydraulic conductivity estimates, both between and within soil groups, confirmed the variation observed in previous predictions of deep drainage, which were obtained using a semi-empirical model. A cluster analysis on hydraulic conductivity indicated that similar morphological soil properties did not necessarily reflect similar hydrologic properties. There was a strong relationship between hydraulic conductivity and exchangeable sodium percentage (ESP), hydraulic conductivity and clay content, and ESP and clay content. A model was developed to predict field saturated hydraulic conductivity from ESP and clay content data. Hydraulic conductivity measured in this study may not have been representative of percolation rates which would occur with low salinity irrigation water, but can be used to assess the risk of recharge from irrigation on different soils in the lower Macquarie Valley. Shallow watertables may potentially develop when the application of irrigation water greatly exceeds crop water requirements. Quantification of groundwater recharge will allow the likelihood of shallow watertable development in the Lower Macquarie Valley to be assessed.
Corrigendum — An urban soil study: heavy metals in Glebe, Australia
Authors: Markus JA , Mcbratney AB
Published: April 2005

This study investigated the occurrence of Pb, Zn, Cu, and Cd in the topsoil of an inner-city suburb of Sydney, Australia. The total heavy metal concentrations in the topsoil of Glebe were determined along with their spatial distribution. These concentrations were compared with environmental investigation limits. Stratified random sampling was conducted within 1-ha square areas taking 2 samples at 1 m separation from each stratum as a means to investigating spatial variation. Total metal concentrations were determined on an aqua regia extract analysed using atomic absorption spectroscopy. Fifty percent of total Pb, Zn, and Cu concentrations and 2.5% of Cd concentrations were above the ANZECC and NH&MRC (Australia & New Zealand Environment Conservation Council and National Health & Medical Research Council) guidelines of 300, 200, 60, and 3 mg/kg, respectively. Some spatial clustering was evident and a geostatistical analysis showed some large high-risk areas. Fuzzy clustering showed 5 groups of increasing contamination. Soil disturbance and distance from road explained 24% of the variation in total Pb concentration, 15% in total Zn and Cu concentrations, and 13% in total Cd concentration.
Oxygen isotope abundance in the quartz fraction of aeolian dust: implications for soil and ocean sediment formation in the Australasian region
Authors: Kiefert L , Mctainsh GH
Published: April 2005

Oxygen isotope ratios of quartz in soils and ocean sediments in the Australasian region have been used to infer aeolian dust contributions; however, few oxygen isotope data are available for Australian dusts. Dust isotope ratios are in the range 13.17–15.1‰, which correlate well with dust-derived soils (13.6–14.5‰) and dust-affected soils (11.6–11.7‰) in Australia, and New Zealand (12.9–13.9‰), and Pacific Ocean sediments of dust origin (12.6–15.8‰). These results provide support for the hypothesis that dust deposition has played an important role in soil and ocean deposit formation in the Australasian region.
Water retention in Australian soils. 2.* Prediction using particle size, bulk density, and other properties
Authors: Paydar Z , Cresswell HP
Published: April 2005

Different approaches were investigated for estimating the parameters in the Campbell soil water characteristic (SWC) equation from soil attributes such as particle size distribution (PSD), bulk density, and organic matter content. Predicted soil water characteristics were compared with measured values for soils of the wheatbelt of south-eastern Australia. A method of prediction is proposed incorporating an empirical relationship for estimating the slope of the SWC from the slope of the cumulative PSD. A power-law form is assumed for both the SWC and PSD functions. One measured SWC point is then used to locate and thus define the SWC curve. When SWC points predicted with this 'one-point' method were compared with measured values, the mean absolute value of the difference between each measured and predicted SWC point was 0.016 m3/m3 for the Geeves data and 0.027 m3/m3 for the Forrest data. Eight sets of predictive equations, previously developed using multiple regression analysis, were also evaluated. Whilst the equations predicted the slope of the SWC curves reasonably well, predictions of the air entry potential were poor. Although less accurate, the equations developed by multiple regression are less demanding in data requirement compared with alternative SWC prediction methods. The one-point method gave better predictions than the multiple regression approach but was less accurate than the 'two-point' method proposed in the first paper in this series. The one-point method should be considered where PSD data and 1 measured SWC point are available. In most other circumstances it will be more accurate and cost-effective to measure 2 SWC points to define the soil water characteristic function (the two-point method).* Part I, Aust. J. Soil Res., 1996, 34, 195–212.
Development and verification of a quick test for the diagnosis of aluminium toxicity on the deep yellow earths of Western Australia
Authors: Barton L , Carr SJ
Published: April 2005

A quick test for estimating phytotoxic aluminium (Al) has been developed for the deep yellow earths of Western Australia. The method is based on a visual assessment of Al extracted by 0.005 M potassium chloride, using pyrocatechol violet as a colorimetric reagent, combined with a measure of electrical conductivity (EC). Quick test measurements were compared with wheat yields from 52 sites to determine if the method could distinguish between Al toxic and Al non-toxic subsoils. A ratio of [Al]:EC was a better predictor of grain yield than [Al] alone.
Irrigation increases groundwater recharge in the Macquarie Valley
Authors: Willis TM , Black AS
Published: April 2005

Rising groundwater, and the potential for development of shallow watertables, were recognised in the Lower Macquarie Valley of New South Wales in the late 1980s. Irrigated agriculture was proposed as a possible source of the recharge causing the problem. This paper reports the increase in deep percolation rates resulting from cotton irrigation on 4 soils in the Lower Macquarie Valley, New South Wales. Changes in deep percolation rates were measured on these soils over the long-term, using temporally separated chloride profiles and mass balance modelling. These changes in long-term deep percolation rates were integrated over all years since irrigation commenced. Irrigation affected deep percolation on all soils, with an increase in long-term mean rates ranging from 17 to 202 mm/year. This equated to increased leaching rates ranging from 3 to 25%. Deep percolation appeared to be related to the clay content of the B horizon. The potential groundwater rise varied from 37 to 524 mm/year. The largest increases in deep percolation rates corresponded to sites where the watertable was closest to the soil surface. This suggests that the development of shallow watertables is related to recharge resulting from irrigated agriculture. Detailed studies of deep percolation under irrigated agriculture are required in the Macquarie Valley.
In a paperless world a new role for academic libraries: providing open access
Authors: Bosc Hélène , Harnad Stevan
Published: April 2005

Academic libraries should be considered research tools, co‐evolving with technology. The Internet has changed the way science is communicated and hence also the role of libraries. It has made it possible for researchers to provide open access (OA) (i.e. toll‐free, full‐text, online access, web‐wide) to their peer‐reviewed journal articles in two different ways: (i) by publishing in them in OA journals, and (ii) by publishing them in non‐OA journals but also self‐archiving them in their institutional OA archives. Librarians are researchers' best allies in both of these strategies. Examples of these strategies are described. We conclude that an official mandate for OA provision is necessary to accelerate its growth and thereby the growth of research usage and impact worldwide.
Amplification of individual preferences in a social context: the case of wall-following in ants
Authors: Dussutour Audrey , Deneubourg Jean-Louis , Fourcassié Vincent
Published: April 2005

Amplification processes are an essential component of the collective phenomena observed in social and gregarious species. In this paper, we tested the hypothesis that a weak individual wall-following tendency in ants can be amplified by communication through chemical trails, leading to a response to the spatial heterogeneities at the collective level. In our experiments, ants had to cross a diamond-shaped bridge along either of two branches of equal length to get from their nest to a food source. Two types of bridge were used: control bridges without a wall, and experimental bridges equipped with a wall along the inner edge of one of their branches. On the control bridges, ants collectively chose either branch of the bridge in most experiments, whereas on the experimental bridges, the branch with the wall was selected almost systematically. A mathematical model is proposed to assess, in various conditions, the importance of the amplification effect of the chemical trail on the wall-following tendency observed at the individual level. The model highlights the fact that the amplification process can lead to an overestimation of individual capabilities and, thus, that the results of experiments investigating individual preferences at group level in animals must be interpreted with caution.
Structural basis of biological nitrogen fixation
Authors: Rees Douglas C , Akif Tezcan F , Haynes Chad A , Walton Mika Y , Andrade Susana , Einsle Oliver , Howard James B
Published: April 2005

Biological nitrogen fixation is mediated by the nitrogenase enzyme system that catalyses the ATP dependent reduction of atmospheric dinitrogen to ammonia. Nitrogenase consists of two component metalloproteins, the MoFe-protein with the FeMo-cofactor that provides the active site for substrate reduction, and the Fe-protein that couples ATP hydrolysis to electron transfer. An overview of the nitrogenase system is presented that emphasizes the structural organization of the proteins and associated metalloclusters that have the remarkable ability to catalyse nitrogen fixation under ambient conditions. Although the mechanism of ammonia formation by nitrogenase remains enigmatic, mechanistic inferences motivated by recent developments in the areas of nitrogenase biochemistry, spectroscopy, model chemistry and computational studies are discussed within this structural framework.
Comparative ecology of catfishes of the Upper Zambezi River floodplain
Authors: Winemiller K. O. , Kelso‐Winemiller L. C.
Published: April 2005

An 8‐month survey of the Upper Zambezi River, its associated floodplain and marginal upland habitats yielded 16 catfish (Siluriformes) species, among which Schilbe intermedius comprised over half of the 3534 specimens. Generally catfishes were most abundant in floodplain and river channel habitats, but three species (Clariallabes platyprosopos, Synodontis macrostoma, S. nigromaculatus) were most abundant in the river channel, and three species (Amphilius uranoscopus, Chiloglanis neumanni, Leptoglanis rotundiceps) were most abundant or restricted within small tributary streams. Diet analysis revealed low pairwise dietary overlaps, but there was no statistically significant pattern of community‐wide niche segregation based on prey type. The 16 catfishes fell into four size/trophic guilds: large carnivores (Clarias gariepinus, C. ngamensis), medium‐sized carnivores (C. stappersii, C. theodorae, Parauchenoglanis ngamensis, Clariallabes platyprosopos, Schilbe intermedius), medium‐sized omnivores (Synodontis leopardinus, S. nigromaculatus, S. woosnami, S. sp. cf. woosnami), and small omnivores (S. macrostigma, S. macrostoma, Amphilius uranoscopus, Chiloglanis neumanni, Leptoglanis rotundiceps). No evidence of reproductive activity was detected in any of the catfishes during the survey period of falling and low water conditions. Although catfishes are not as highly valued for food as cichlid fishes, three species are significant components of local commercial and subsistence fisheries: the two large Clarias by virtue of their size, and Schilbe by virtue of its great abundance. Abundances of the heavily exploited Clarias gariepinus and C. ngamensis stocks appear to be lower in the Upper Zambezi compared with the Okavango floodplain system.