bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting lime-induced changes in soil-pH From exchangeable aluminum, soil-Ph, total exchangeable cations and organic-carbon values measured on unlimed soils
Authors: Hochman Z , Crocker GJ , Dettman EB
Published: April 2005

The 'Lime-it' model is a decision support system for graziers wanting to lime acid soils. In this study we used field experimental data to test, improve and validate the model's ability to predict changes in soil pH due to variable rates of lime. Data from 13 field experiments, in which soil parameters were measured 1 year after liming acid soils, were used to derive an index of pH responsiveness to lime (LRI) at each site. Multivariate analysis was used to derive a predictive model: LRI was found to be significantly correlated (P < 0.0001) with hydrogen ion concentration ([H+]x 105 ), exchangeable aluminium (Al), exchangeable cations (TEC) and percent organic carbon (C) data of the unlimed soils. The multivariate equation was then tested against an independent data set by comparing the predicted pH change with the measured pH change for eight soils. This evaluation, though generally acceptable, showed a small but significant deviation from the desired 1:1 ratio between observed and predicted pH change. We re-calibrated the model for the combined data to derive the model: LRI = 0.764 + 0.042 [H+] - 0.016 TEC - 0.097 Al - 0.016 C. When this model was tested over the whole data set for predicted v. measured pH changes, the following result was found: measured pH change = 1.01 (predicted pH change) - 0.05 (R2 = 0.85, n = 308). The implications of the predictive equation are considered with regard to the mechanisms that are thought to be associated with pH buffering.
Measurement of gaseous emissions from denitrification of applied N-15 .2. Effects of temperature and added straw
Authors: Avalakki UK , Strong WM , Saffigna PG
Published: April 2005

Gas emissions of applied 15N were measured beneath a soil cover daily following saturation of Vertisol and Alfisol soils repacked in pots to the original field bulk density and held at three temperatures (5, 15 or 30�C) with or without addition of wheat straw. Collective gas emissions over 57, 43 and 15 days at 5, 15 and 30 degrees C respectively were compared with the 15N loss determined by mass balance.
Loss measured by gas emissions (15N2 and 15N2O) ranged from 36% to 152% of the denitrification loss as determined by 15N mass balance. In the absence of added straw, measurement by gas emissions was consistently less than loss by 15N balance. Where straw was added, 15N loss by gas emissions was overestimated, probably because of a smaller headspace (0.3 L) than considered desirable (1-1.5 L) for emission measurements. Potential denitrification rates, in the presence of added straw, were similar for the Vertisol and Alfisol. Decreasing temperature slowed potential rates of denitrification from similar to 2.5 kg ha-1 day-1 at 30 �C to 0.8 kg ha-1 day-1 at 15 �C and 0.4-0.5 kg ha-1 day-1 at 5 �C. Decreasing temperature prolonged the period of waterlogging following a saturating event. Thus, collective loss of 15N was considerable even at the lower rates of denitrification at 5 �C (52-76% over 57 days) or 15 �C (87-92% over 43 days). Straw addition (10.5 t ha-1) to the Vertisol, which contained no visible plant residues from previous crops, more than doubled the losses of applied 15N. In the absence of straw, rates of denitrification and immobilization were similar in magnitude, 0.97, 0.26 and 0.16 kg ha-1 day-1 for 30, 15 and 5 �C respectively. Very rapid loss of appliedha-1 day-1N in the presence of added straw led to decreases in immobilization of applied ha-1 day-1N, highlighting the potential effects of the much higher maximum rates for denitrification than for immobilization. The N2O emissions generally represented the smaller fraction (<25%) of denitrification emissions, becoming smaller as temperature was increased. As a proportion of emissions due to denitrification, N2O emissions were very low (<0.5% Vertisol, <3% Alfisol) in the presence of added straw.
Measurement of gaseous emissions from denitrification of applied N-15 .3. Field-measurements
Authors: Avalakki UK , Strong WM , Saffigna PG
Published: April 2005

Field experiments were conducted during autumn and winter (April-July) at four locations on Vertisol or Alfisol soils on the Darling Downs of Queensland in 1988 and 1989 to determine 15N losses when soil was saturated after applications of 15N labelled nitrate-N prior to sowing winter cereal crops. Losses of applied 15N were quantified by either gas emission or mass balance measurements on microplots (0.043 m2) confined laterally to a depth of 110 or 260 mm. At each field location, two experiments were established, one on a soil containing little visible crop residue where winter cereal had been harvested the previous November and another site containing residues of a recently harvested sorghum crop. Because shallow (110 mm) confinement was found to be unsatisfactory for both gas emission and mass balance measurement of 15N losses, comparison of the two methods was not applicable at one of the four field locations. Loss estimates for the six field sites by accumulating daily gas emissions averaged 80.7 � 33.4% (range 43-132%) of that estimated by mass balance. Loss estimates from peak emission measurements were generally closer to that estimated by mass balance 100.8� 39.9% (range 56-169%). Loss of applied 15N (40 kg N ha-1) when soils were saturated in April was several-fold more (19-29 kg N ha-1)) than that lost when soils were saturated in July (3.9-6.4 kg N ha-1)). Loss of 15N following saturation during July 1988 was similar in magnitude to the quantity of 15N apparently immobilized into soil organic forms (5.8-6.0 kg N ha-1)). Sorghum residues returned in March, or wheat straw added in December prior to a long period of dry weather, promoted loss of 15N applied prior to soil saturation in April or July. Alternatively, where residues of a previous winter cereal had decomposed considerably, loss of applied 15N was much lower than where sorghum residues had been added prior to saturations in April (15.3 cf. 28.6 kg N ha-1)) or July (3.9 cf. 6.4 kg N ha-1)).
Soil modification by termites in the central wheat-belt of Western-Australia
Authors: Debruyn LAL , Conacher AJ
Published: April 2005

In a semi-arid region of Western Australia, in kwongan and open woodland, we examined the texture and selected chemical properties of two soil types, firstly in the mounds of two mound-building termite species (Drepanotermes tamminensis and Amitermes obeuntis) and secondly in the foraging galleries of D. tamminensis and A. neogermanus. The soil properties of the termite-modified soil were compared with soil unaffected by termite activity. It was found that both mounds and foraging galleries had significantly higher clay contents, increased organic carbon, and lower pH than the surface soil. The mean standing mass of D. tamminensis mounds was 5 Mg ha-1) on yellow sand (under kwongan vegetation) and 7 Mg ha-1) on grey sandy loam (under open woodland). However, this modified soil is predicted to be inaccessible for plant growth for a considerable period of time, since termite mound longevity could be as much as 70 years. In contrast, termite-modified soil from foraging galleries and chambers in the soil or soil sheetings covering food sources would be more readily accessible to the plant-soil ecosystem than modified soil materials in termite mounds.
A review of physical management for crusting control in Australian cropping systems - Research opportunities
Authors: Bresson LM
Published: April 2005

Soil surface crusting has severe agricultural and environmental effects. In Australian cropping areas, many studies have dealt with chemical treatments (as reviewed by Chartres 1992) but less emphasis has been focussed on physical management practices. The present review deals initially with 30 papers which involve reduced tillage, stubble retention and seedbed formation. Conservation practices have usually been analysed by their effects on soil properties, soil erosion and crop yield rather than by their specific impact on crust development. Moreover, the effects of reduced tillage and stubble retention on crusting have not been determined in most studies. Seedbed formation (e.g. the Tatura system), however, has been shown to be an effective physical management practice for crusting control. Many stability tests have been developed in Australia and used worldwide. Choice of the most relevant predictive test, as well as selection of the most suitable control technique, actually requires a good knowledge of the processes which can be involved in crust formation according to the soil, climatic and management conditions. The results of this review, which deals with 95 papers, suggest a few research opportunities, i.e. (i) furthering of knowledge about the different processes involved in crust formation under various cropping environments, (ii) monitoring soil strength according to crust development, (iii) development of field methods for the assessment of crust development, (iv) development of quantitative models consistent with recent qualitative crusting models, (v) development of methods for the determination of crust development at the field scale rather than small plot scale. Finally, this review recommends to integrate soil surface crusting studies and soil erosion studies.
Effect of reaction-rate on leaching of phosphate through sandy soils of Western-Australia
Authors: Gerritse RG
Published: April 2005

The effect of reaction rate on the mobility of phosphate in soils was measured from breakthrough curves in the leachate from small columns of soil, following step increases in the input concentration of phosphate. Average mobilities of phosphate in columns of soil, following a step increase in the input concentration, decrease with decreasing rate of flow and with increasing distance travelled and appear to be linearly correlated on a log-log scale with both flow rate and distance travelled. An empirical equation, describing these relationships, fits data from leaching experiments at flow rates between 30 and 600 cm/day in columns of soil ~10-30 cm in length. Two coefficients are required and are obtained by curve fitting breakthrough curves, calculated with a numerical computer simulation model, to experimental breakthrough curves. The fitted equation enables extrapolation to flow rates and distances travelled that are more relevant to a field situation.
Water-retention, organic-C and soil texture
Authors: Emerson WW
Published: April 2005

Samples taken from the two textural phases of the surface soil of an irrigated natrixeralf and its clay subsoil were dried at wilting point and in air. Water retention increased linearly with C content, with values extrapolated to zero C content proportional to clay content. Emerson et al. (1994) (Aust. J. Soil Res., 32, 939-51) had already shown that water held by the surface samples at 10 kPa suction increased approximately linearly with C content, independently of clay content. Similar linear relations were deduced for other soils using values of field capacity and wilting point reported in the literature. A constant amount of water is considered to be held by portions of the silt/clay matrix. As the C content of the soil is increased, polysaccharide gels gradually fill additional 1-3 �m wide pores within the portions. It was calculated that, after a long period in grass, gel present increases available water on a weight basis, by 34% and 125% in loamy sand and sandy clay A horizons respectively. Where farmyard manure (FYM) was incorporated, gel only formed from the added C. Nevertheless the large increase in field capacity of a sandy loam produced by rotavation was temporarily preserved by prior addition of FYM. It is suggested that the gel here was mainly on microbial filaments.
Studies on non-wetting sands .1. The role of intrinsic particulate organic-matter in the development of water-repellency in non-wetting sands
Authors: Franco CMM , Tate ME , Oades JM
Published: April 2005

The bulk of the organic matter in sands from the south-east of South Australia is present as discrete particles which constitute 4-6% of the mass of the sand. Hydrophobic particulate organic matter was separated from non-wetting sand obtained from two sites in the south-east of South Australia and characterized with respect to size and ability to induce water-repellency. When heated with both a wettable acid washed sand and a natural sand (non-wetting sand washed free of particulate organic matter), the intrinsic particulate organic matter induced strong water-repellence. The degree of hydrophobicity created was higher with the natural-washed sand than the acid-washed sand which indicated that a precoated surface, even one with a low initial hydrophobicity, has a strong enhancing effect. Particulate organic matter, especially the larger size fractions, acted as a reservoir of waxes or hydrophobic materials which diffused onto the surfaces of sand grains during heating, and particularly during wetting/heating/drying cycles. Thus, intrinsic particulate organic matter plays a substantial role in the development of water-repellency in sandy soils. In addition to hydrophobic waxes which diffuse out under environmental conditions prevalent in the field, water-repellency increases significantly when these hydrophobic particles interact with the natural precoated hydrophobic surface of the sand.
Effects of modifying plant carbon inputs on nitrogen distribution in intact cores of a perennial grass pasture
Authors: Robertson FA , Myers RJK , Saffigna PG
Published: April 2005

Perennial pastures can accumulate large quantities of roots and surface litter of high C:N ratio, which may reduce N availability to the plant by stimulating microbial immobilization. We studied the effects of modifying carbon inputs from roots and litter on the distribution of nitrogen (N) in plant and soil fractions of an old N-deficient green panic (Panicum maximum var. trichoglume) pasture. Intact pasture cores were taken from the field to a glasshouse, and the surface litter was removed before applying the following treatments: (i) surface litter added, (ii) roots pruned to kill approximately 60% of roots, and (iii) plant shoots removed. A small pulse of 15N as ammonium sulfate was added to the soil surface, and the cores were destructively sampled on several occasions over the following 4 months. Litter addition had little effect on N uptake by uncut plants. When plant shoots were removed, litter markedly reduced plant N uptake. Litter increased N and 15N in microbial biomass and N and 15N stabilized in non-biomass soil organic matter, and reduced loss of N from the cores. Root pruning had little effect on N distribution, except for an initial reduction in plant uptake. Removal of pasture shoots markedly increased soil nitrate and loss of 15N, and decreased non-biomass organic N and 15N. Recovery of 15N in non-biomass organic matter was around three times greater than 15N in microbial biomass, and was closely associated with microbial CO2 production. There was evidence that 15N entered the non-biomass organic matter by both abiotic and microbially mediated processes. In these pastures, the non-biomass soil organic matter may be a more important sink for N than the microbial biomass.
Soil-phosphorus fractions under 5 tropical agroecosystems on a volcanic soil
Authors: Paniagua A , Mazzarino MJ , Kass D , Szott L , Fernandez C
Published: April 2005

The organic P pool is usually considered a major source of available P in high P-fixing soils of the tropics. Agricultural management practices which maintain or increase soil organic P(o) contents would, therefore, help maintain soil fertility over time. The effects of organic additions and P fertilization on soil P fractions and yield of maize were examined after a 10 years rotation involving beans and maize on a tropical volcanic soil. Five maize cropping systems were analysed: (1) monoculture, alley cropping with Erythrina poeppigiana, alley cropping with Gliricidia sepium and monoculture mulched with E. poeppigiana prunings, all treatments fertilized with 20 kg P ha-1 and 54 kg K ha-1; and (2) monoculture mulched with E. poeppigiana prunings without fertilization. Soil P fractions were determined by a sequential extraction procedure. Little differences were found in size and distribution of P pools among treatments fertilized with P regardless of whether they received organic amendments. Mulching without P fertilization showed the lowest values of NaOH-Po (16% v. 22% of total P) and labile Pi, (2.4% v. 4.8%). These results suggest that (1) organic P accretion and mineralization is strongly dependent on inorganic fertilization; and (2) organic additions without synthetic fertilizers may be decreasing the organic P pool, and consequently the soil P fertility. Nevertheless, absolute values of labile Pi (resin+NaHCO3-Pi were quite high (52 mg kg-1) in this treatment, and yields of maize were among the highest obtained during most of the 10 years of cultivation.
Retention of nitrate and phosphate in soils of the Darling plateau in Western-Australia - Implications for domestic septic-tank systems
Authors: Gerritse RG , Adeney JA , Dimmock GM , Oliver YM
Published: April 2005

Streams in mixed rural and residential areas on the Darling Plateau near metropolitan Perth in Western Australia were monitored for nitrate and phosphate. Concentrations of nitrate in streams are proportional to surveyed rates of inputs of nitrogen in water catchments dominated by agricultural land use. In catchments dominated by unsewered residential land use, stream concentrations of nitrate are much lower than expected from rates of input. A comparison of mass balances of inorganic nitrogen and bromide, added as a conservative tracer, indicates that at least 80% of nitrogen leaching from domestic septic tank systems into soils is lost within a distance of 10 m from the leach drain. Concentrations of dissolved phosphate in streams are low (mostly <5 �g/L P-PO4) and are not significantly related to type of land use. Adsorption of phosphate to soils was measured after batch equilibration of soil slurries for periods up to 12 months and the isotherms were described by a time-dependent Freundlich type adsorption equation. Adsorption capacities for phosphate are high and reflect high levels of iron and aluminium oxides in the soils. Soil adsorption data together with data from leaching experiments in small columns of soil were fitted to an empirical equation, describing the effect of flow rate and distance travelled on the mobility of phosphate in a saturated soil. A minimum travel time for a distance of 5 m in these soils of between 1 and 8 years is predicted with this equation for phosphate leaching from a septic tank. Monitoring of ground water near 6-7 year old domestic septic tank systems showed that phosphate had not yet moved beyond 5 m from the leach drain.
Comparison of the effects of latex and poly(DADMAC) on structural stability and strength of soil aggregates
Authors: Bernas SM , Oades JM , Churchman GJ , Grant CD
Published: April 2005

Two types of high molecular weight polymers having contrasting charge properties and molecular shapes [latex and poly(DADMAC)] were applied at different rates to three Alfisols and a Mollisol to examine the effects of these polymers on soil strength and structural stability, and to identify some of the mechanisms by which these polymers act to stabilize soils. Wet aggregate stability, mechanically dispersible clay, and soil friability tests were used to assess treatment effects, which were found to be greatest in soils having a poor structural condition. Each polymer acted differently. Latex, which acted like a coat of paint (because of its inability to penetrate beyond the surface of aggregates), dramatically increased the proportion of water stable aggregates >2 mm in all soils examined, and this was achieved without the traditional (expensive) use of aromatic oils and stabilizers. The latex coating produced a conglomeration of smaller soil aggregates, but did not extensively alter either the dispersibility of the aggregates in the face of mechanical action, or their strength and friability. Results indicate latex may be best suited to minimum tillage cropping systems. Poly(DADMAC), by contrast, was capable of entering most pores accessible to water. This enabled it to minimize clay dispersion, increase soil friability, and to modestly increase the size of water stable aggregates. In many ways, poly(DADMAC) would appear to be an ideal soil conditioner, although the economic suitability of this polymer and its effects on erosion control and plant growth have yet to be assessed.
The measured mobile-water content of an unsaturated soil as a function of hydraulic regime
Authors: Clothier BE , Heng L , Magesan GN , Vogeler I
Published: April 2005

To account for observations of preferential solute transport through soil, increasingly models are used in which the total water content of the soil (�, m3 m-3) is partitioned into an essentially mobile phase (8,) and an apparently immobile fraction (�im). However, few methods exist for measuring this separation in the field. Here we use the recently proposed, disc permeameter technique. Following infiltration with a tracer, measurements of the resident solute concentration directly under the disc are used to infer the �m-�im partitioning. For Manawatu fine sandy loam in situ, we applied this technique at the three pressure heads (ho) of -20, -40 and -150 mm, in order to deduce the influence of the hydraulic regime on the soil water fraction �m/� that appears to be actively involved in solute transport during infiltration. When a depth I of between 15 and 25 mm of KBr tracer was added to soil already wet by pure water to h,, the measured mobile fraction �m/� rose from 0.41 at -20 mm, through 0.50 at -40, to 0.64 at the most unsaturated head of -150 mm. Thus, less evidence of preferential solute transport was recorded with decreasing ho. The spatial distance between the preferential paths was observed to range from 20 to 150 mm, the separation increasing and the pathways becoming more diffuse with decreasing h,. Depthwise dispersion of the invading solute thus increased with ho. At the two higher heads, when I =80mm of KBr was allowed to infiltrate, the �m/�, inferred from the resident concentration observed directly under the disc, now also became 0.65. For ho = -40 mm, the measured rise in the resident concentration under the disc, with I, could be predicted using a dispersivity, �, of 20 mm in the approximation provided by the 1-D form of the convective dispersion equation. When 15-25 mm tracer was applied directly to initially dry soil (� = 0.3), capillary forces drew the invading solute from the disc with much less dispersion, such that the resident concentration under the disc rose more rapidly with I. Now �m/� was found to be virtually 0.65 at all the heads. In several experiments at h, = -40 mm, ethanol was used as the solvent for the tracer. No change in the measured �m/� was observed. Thus hydrophobicity was deemed not to be a factor in our measurement of 8,/B being consistently about 0.65. An attempt was made to parameterize the diffusive-exchange scheme that the Coats and Smith (1964) model, taken from petroleum engineering, proposes as the link between the mobile and immobile domains. However, our observations at ho = -20 mm suggest that no single mass-transfer coefficient 5 can describe this solute exchange. Over the first few days, a � value of 0.5 day-1 seemed reasonable, but over the next fortnight there appeared no further interdomain exchange of solute between the two domains.
Changes in soil chemistry associated with changes in soil-pH in Victorian pastures
Authors: Crawford DM , Baker TG , Maheswaran J
Published: April 2005

Relationships between changes in soil pH and changes in other soil chemical properties were examined using data from a survey of 107 pasture sites from across Victoria. At each site, soil samples (0-5, 5-10, 10-15 and 15-20 cm depths) were taken from the pasture and an adjacent undisturbed (reference) area for chemical analysis. Changes in soil chemical properties were inferred from differences between pasture and reference soils. Increases in extractable Al and extractable Mn and decreases in the sum of exchangeable cations were associated with decreases in pH. Changes in soil organic C, total soil N and total soil P were not associated with changes in pH but were related to pasture composition at each site. Increases in total soil P and exchangeable Ca, and decreases in exchangeable Mg were partly attributed to the application of superphosphate. Decreases in electrical conductivity are discussed in relation to vegetation and salinization.
Mineralization of C and N in organic materials as affected by duration of composting
Authors: Robertson FA , Morgan WC
Published: April 2005

The effect of composting fowl manure, grass clippings and brown coal on the subsequent mineralization of C and N from these materials was studied in a glasshouse experiment. Columns of soil were amended with mixtures of these materials which had been composted for 0, 2, 4, 8, 12 or 16 weeks, or with each material alone. Periodically over the next 81 days, CO2 evolved from the soil surface was collected in alkali traps, and N released from the amendments was collected by leaching the columns with distilled water. With the mixtures of fowl manure, grass clippings and brown coal, mineralization of C and N decreased linearly with increasing duration of composting beyond 2 weeks, due to progressive depletion of labile C and N. Mineralization of C and N from the uncomposted mixture was similar to that from compost aged 4 weeks. Brown coal contributed neither C nor N in an available form. Around 70% of N in fowl manure and grass clippings and 11-34% of N in compost was potentially mineralizable during the 81 days of the experiment. Leachates collected from the columns contained N in NO-3 , NH+4 and organic forms. Mineralization of C and N was strongly positively correlated. All amendments except brown coal had a positive residual effect on total soil N. The increase was largest in compost treatments but was not related to compost age. All amendments had a similarly small positive residual effect on soil water-holding-capacity.
Nitrogen-cycle processes and acidification of soils in grazed pastures receiving or not receiving excreta for 23 years
Authors: Carran RA , Theobald PW
Published: April 2005

Soil acidification in agricultural systems can be related to production and consumption of protons during nutrient cycling processes. Carbon and nitrogen cycles are particularly important in this respect for grazed pastures. Rates of acidification were calculated for grazed pastures that had received animal exreta in the normal way and for areas that had been free from excreta for 23 years. Acidification rates were 3.59 and 0.86 kmol H+ ha-1 yr-1 respectively. Measurement indicated that the areas were not diverging in pH. Short term effects of excreta caused a significant increase in pH over much of the area receiving excreta. When these effects were eliminated, no indication of decreasing pH or titratable acidity in the areas receiving excreta was apparent; a decrease in buffer capacity in the 150-300 mm horizon was noted, however. The calculation of acidification rates is discussed and the possible need to account for movement of NH+4 and inputs of CO2-3 in faeces is identified.
Solute movement through two unsaturated soils
Authors: Magesan GN , Vogeler I , Scotter DR , Clothier BE , Tillman RW
Published: April 2005

Simple and inexpensive apparatus is described for studying the solute movement during unsaturated water flow through intact soil columns. A preset pressure head is maintained at the top and bottom of the soil. The applied solution is easily changed, and there is negligible 'dead volume' both above and beneath the soil. Columns 37-150 mm long, carved from the A horizons of a well structured silt loam and a weakly structured fine sandy loam, were used in the apparatus. After the soil was preleached with calcium sulfate solution, solid potassium nitrate was applied, followed by a solution of potassium chloride. Nitrate and chloride concentrations in the effluent, and in the soil after leaching, were measured. With the imposed pressure heads of between -40 and -150 mm, flow rates ranged from 0 . 5 to 9 mm/h. The convection dispersion equation (CDE) with the appropriate boundary conditions was found to adequately describe the flow of chloride and nitrate in both soils. The outflow concentration data indicated all the soil water participated in the solute transport, and the chloride breakthrough curves scaled with column length as predicted by the CDE rather than by stochastic-convective theory. The dispersivity values for the well structured silt loam were 15 and 19 mm. The values for the weakly structured fine sandy loam were 68 and 27 mm. The dispersivity may be a useful structure index, as well as being the key parameter needed to describe solute movement. The resident concentration data indicated all the water in the well structured soil was mobile, but about 15% of the water in the weakly structured soil was relatively immobile.
Characterization and analysis of soils using mid-infrared partial least-squares .1. Correlations with XRF-determined major-element composition
Authors: Janik LJ , Skjemstad JO , Raven MD
Published: April 2005

Chemical analysis is an important but often expensive and time-consuming step in the characterization of soils. Methods used for soil analysis ideally need to be rapid, accurate and relatively simple and infrared partial least squares (PLS) analysis is potentially one such method. Mid-infrared diffuse reflectance Fourier transform (DRIFT) spectra of powdered soils present the major mineralogical and organic components within each soil, relative to their concentrations. The theory indicates that experimentally derived soil properties may be correlated with the infrared spectra of some of these components, and the covariance between soil properties and spectra can then be modelled by PLS loadings and scores. Factors and scores can be derived independently for each Soil property using PLS-1, an extension of the more general PLS-2 method. This study evaluates the use of PLS-1 for the qualitative and quantitative study of soils, and in particular to classify the soil spectra and their associated major element chemistry by their PLS loadings and Scores. A subset of 100 soils, selected from a complete set of 298 samples from throughout eastern and southern Australia, was analysed by X-ray fluorescence (XRF) for major oxides as a calibration or training set to model the PLS loadings, scores and linear regression coefficients. Linear regressions resulted with R(2) values of 0 . 973-0 . 917 for XRF versus PLS predicted values for SiO2, Al2O3 and Fe2O3. Regressions for the other oxides, e.g. TiO2, MgO and CaO, were generally curved with a linear calibration giving severe underestimations at high concentrations. The PLS loadings and regression coefficients were then used to model the complete soil set to produce scores and concentration predictions for all the samples. The samples were plotted in bivariate score maps to give a visual representation of the spectral variability within the entire soil set. Samples were selected from the boundaries of the groups of soils in these maps for mineralogical characterization using X-ray diffraction (XRD) analysis. The XRD results confirmed the mineralogy obtained from the infrared spectra and PLS weight loadings. For this study, the depiction of the samples in the score maps was found to be of particular importance for demonstrating similarities in composition of the samples.
Occurrence of Enchytraeid worms and some properties of their casts in an Australian soil under cropping
Authors: Chan KY , Heenan DP
Published: April 2005

The population density of enchytraeid worms (Oligochaeta) was monitored on a red earth (Oxic Paleustalf) under cropping in Wagga Wagga, N.S.W. Physical and chemical properties of their casts were compared with those of the bulk soil and soil sampled adjacent to the permanent fenceline. In the autumn and winter period, the worm population was active close to the surface and the highest population (2037 per m(2)) was detected in the direct drilled/stubble burnt treatment. However, this was considerably lower than those reported elsewhere in temperate regions. Worm casts were composite in nature, predominately of 210-500 �m in diameter which were comprised of smaller spherical subunits (50-100 �m). The casts were found to be significantly more water stable and higher in total nitrogen than aggregates of the same size range separated from the bulk soil. Porosity of the casts was dominated by spaces between the subunits which were composed of very densely packed clay/silt size particles. Evidence from SEM (scanning electron microscope) suggests that the high stability was due to the presence of cements.
Multidisciplinary teams to conduct integrated research on farming systems - a challenge
Authors: French RJ
Published: April 2005

This paper reviews changes in farming practices that helped farmers to reduce soil erosion, and increase water-use efficiency and yield on their specific soils and climate. The program initially involved working with Soil Conservation Boards and conducting research on farmers' properties and on research stations. This work then extended from evaluating single factor effects to assessing the combined factors limiting yield in specific crop and pasture rotations. Benchmarks were established for different soils and climates as guides for farmers to measure their success. These included yield and water use efficiency, adequate and lower limit levels of soil organic nitrogen, and the need to maintain a nutrient input-output balance to provide a sustainable agriculture. The paper highlights the need for future research to adopt an integrated systems approach to overcome the major limitations to growth. This will require a cooperative effort between farmer groups and teams of soil scientists and agronomists to conduct multifactor research in farmers' paddocks.
Effect of banded fertilizers on soil solution composition and short-term root-growth .1. Ammonium-sulfate, ammonium-nitrate, potassium-nitrate and calcium nitrate
Authors: Moody PW , Aitken RL , Yo SA , Edwards DG , Bell LC
Published: April 2005

To simulate the effects of banded fertilizer on soil solution composition, layers of KNO3, NH4NO3, Ca(NO3)2.4H2O or (NH4)2SO4 were placed in contact with soil columns and allowed to equilibrate for 5 days at a moisture content equivalent to 10 kPa matric suction. Five soils were used in the columns: 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 increments from the fertilizer layer, the last section being 45-50 mm from the layer. Soybean seedlings (Glycine max (L.) Merr. cv. Forrest) were grown for 48 h in each section and relative root elongation (RRE) was determined. Soil solution was then extracted from each section and analysed. Nitrate salts moved 50 mm in all soils (measured as a change in the electrical conductivity of the soil solution), but the movement of the sulfate salt was dependent on soil type and was least in the Ferrosol. As distance from the fertilizer band decreased, concentrations of cations in the soil solution increased, often reaching a plateau value. In all soils, solution Ca concentrations near the (NH4)2SO4 fertilizer band were lower than those further away, indicating precipitation of CaSO4.2H2O had occurred. This effect was particularly evident in the Vertosol and Ferrosol. The relationship between electrical conductivity of the soil solution (ECss) and Ca activity ratio (CAR) was dependent on soil type and fertilizer source. For the sulfate source, all soils exhibited a common curvilinear relationship in which CAR decreased with increasing ECss. However, for the nitrate salts, the Ferrosol and Vertosol had a higher CAR for a given ECss than the other soils because of the higher Ca2+ activities in their soil solutions. Relative root elongation decreased curvilinearly with increasing ECss, and a common curve was obtained for all soils and fertilizer sources. Although CAR decreased with increasing ECss, there was no common curve relating RRE to CAR for all soils and fertilizer sources. Osmotic effects, and not a salt-induced Ca deficiency, were therefore considered responsible for the decrease in RRE as distance from the fertilizer source decreased. A 10% reduction in RRE occurred at an ECss of 4.1 mS cm-1.
An examination of the relationship between erodibility parameters and soil strength
Authors: Misra RK , Rose CW
Published: April 2005

Erosion rate of soil by the impact of raindrops and overland flow of water is often considered to be affected by the shear strength of surface soil. Physically based erosion models indicate a link between defined erodibility parameters and soil strength. The objectives of this paper are to determine erodibility parameters with the process-based erosion model GUEST for a. krasnozem soil of two contrasting strengths, and to examine the influence of soil strength on erodibility parameters. Soil beds of width 1 m and length 5.8 m, with and without compaction, were exposed to simulated, constant rate rainfall. A range of slopes was used. Detachment trays of width 300 mm and downslope length 200 mm containing soils of identical strength were placed at the same slope and exposed to the same rain in order to determine the effects of rainfall-driven processes alone on erosion. Soil strength was measured with a hand vane tester and a pocket penetrometer to determine whether compaction was effective in modifying soil strength. Temporal variation in sediment concentrations (c) for the large soil beds and detachment trays was measured for each slope and soil strength. The settling velocity characteristic of soil, with and without exposure to rain, was determined with the modified bottom withdrawal tube technique. Values of c decreased with increase in soil strength. The relationship between c and slope was influenced by soil strength in a manner consistent with the theoretical expectation of the role of soil strength in controlling erosion. Rilling during erosion was absent only when the soil was compacted. The average settling velocity of the soil exposed to rain (i.e. its depositability) was significantly lower than for the same soil not subjected to rain, indicating a breakdown of soil aggregates as a result of raindrop impact. Rainfall detachability parameters (estimated with GUEST) Were lower when soil strength was high. Runoff-driven erodibility parameters, namely the specific energy of entrainment (J), increased and the approximate erodibility parameter (�) decreased with increase in soil strength. The Variation in these erodibility parameters with soil strength was consistent with the theory implemented in GUEST. Detailed analysis of the relative contribution of rainfall- and runoff-driven processes to c at varying stream powers and soil strengths indicated that, at high soil strength, uncertainty in the values of J and � is high because of the higher contribution to c of rainfall-driven rather than runoff-driven processes. The adequacy of in situ measurement of soil strength as an indicator of soil erodibility is discussed in relation to the results presented.
Correction
Authors: Walker SR , Blacklow WM
Published: April 2005

Adsorption and Degradation of Triazine Herbicides in Soils Used for Lupin Production in Western-Australia - Laboratory Studies and a Simulation-Model (Vol 32, Pg 1189, 1994)
Movement and persistence of triazine herbicides in soils used for lupin production in Western-Australia - Field-measurements and interpretations with the aid of a simulation-model
Authors: Walker SR , Blacklow WM
Published: April 2005

Movement and persistence of simazine and atrazine in an acid sand were measured in 1989 at a field site that received 76-105 mm of rainfall during 100 days after herbicide application. Three environments were created: (i) warm and wet (early herbicide application of 100 mg m-2 on 28 May); (ii) cool and dry (later herbicide application of 100 mg m-2 on 24 June); (iii) cool, dry and high pH (the later herbicide application after the surface pH had been raised from 4 . 8 to 6 . 4 by the application of 150 g m-2 CaCO3 42 days earlier). The soil profile was sampled for herbicide residues and soil water at six depths on five occasions during 100 days after herbicide application. Rainfall, pan evaporation, and soil and air temperatures were measured throughout the experiment. Soil temperatures at 13 mm ranged from 11 to 41�C (daily minimum and maximum). Most of the herbicide remained in the surface 25 mm of soil and after 100 days about 25% of that applied remained in the soil profile in the acid soils and about 40% remained in the soils treated with CaCO3. Despite eight, or nine, leaching rains that a simulation model estimated would have wetted the profile to 300 mm, residues < 2 mg m-2 were found in the 150-200 mm layer and in the high pH treatment only. A simulation model gave good agreement with observed losses of simazine residues in soil maintained at field capacity and buried within the soil profile. However, the simulation model underestimated residue losses in the soil profile and indicated that processes other than chemical hydrolysis were involved in the degradation of herbicide in the surface 25 mm of soil. Weed control reliant on persistent residues would be prolonged if the herbicide is applied near the sowing date of the lupin crop and incorporated below the surface 25 mm of soil by the method of sowing.
Effects of latex and poly-DADMAC on erosion, hydrophobicity and water-retention on two different soils
Authors: Bernas SM , Oades JM , Churchman GJ
Published: April 2005

Latex (natural polymer) and poly-DADMAC (synthetic polymer) were applied to a red brown earth (Alfisol) and a Wiesenboden (Mollisol). Run-off, infiltration, sediment loss and water stable aggregates were measured after subjecting the soils to simulated rainfall. Water retention of latex and poly-DADMAC amended soils was determined. The MED test for hydrophobicity was also carried out for the latex-treated soil. Latex decreased run-off and erosion, and increased infiltration on both soils. Poly-DADMAC minimized run-off and erosion, and increased infiltration on the Wiesenboden. It increased run-off and decreased infiltration on the red-brown earth; however, it still decreased erosion. Latex increased the percentage of water-stable aggregates > 2 mm on the red-brown earth, but it had less effect on the Wiesenboden. Poly-DADMAC decreased the percentage of water-stable aggregates < 0.125 mm on both soils after simulated rainfall. Both latex and poly-DADMAC had little effect on water retention of the red-brown earth and the Wiesenboden. Application of 1.5 g kg-1 of latex increased MED values of both soils, to give values that indicate moderate water-repellence but should not affect plant growth. Generally, latex was more effective on the red-brown earth and poly-DADMAC was more effective on the Wiesenboden. It seems that latex can be effective on all soil types, but poly-DADMAC will have more effect on clay soils.
Soil deformation observations in a vertisol under field traffic
Authors: Bakker DM , Davis RJ
Published: April 2005

A procedure based on the point grid method has been used to measure and visualize soil deformation resulting from tyre loads in a controlled traffic system. Several tests were performed in an irrigated heavy clay soil under various moisture conditions and two different geometries of the wheel tracks, recessed and elevated. This represented normal working conditions and illustrated that significant deformations were occurring. Deformations increased with moisture content and the number of passes. From the point grid displacements, bulk density changes were calculated which corresponded with the measured increases in density obtained from cores. Large displacements were observed when the soil was trafficked at high moisture content with little corresponding increase in bulk density. Soil structural degradation resulting from trafficking this soil at high moisture content should therefore be seen as a different process, such as a change in the orientation of clay particles or porosity of natural aggregates, rather than an increase in bulk density. Significant differences between vertical and horizontal displacements were found for the various tests. Increases in horizontal displacements were contributed to an increase in the degree of saturation. The recessed wheel tracks increased horizontal displacements due to the geometry of the wheel tracks.
The effect of furrow length on rain and irrigation-induced erosion on a vertisol in Australia
Authors: Carroll C , Halpin M , Bell K , Mollison J
Published: April 2005

Runoff and sediment movement were measured from irrigated furrows of different lengths on a Vertisol in central Queensland. Two farm properties (Denaro's and Roberts') were used to compare a short furrow length (SFL) and a long furrow length (LFL). At Denaro's farm, furrows were 241 and 482 m long, and at Roberts' farm they were 151 and 298 m long, with gradients of 1.0% and 1.3% respectively. Runoff and soil loss were measured from six furrows. At Denaro's farm, soil movement off the farm was measured at a taildrain outlet. Sediment concentration from both rainfall and irrigation declined when cultivation had ceased, soil in the furrows had consolidated and when the cotton canopy provided surface cover. Total soil loss from rainfall and irrigation was approximately 4-5 t ha-1. Rainstorms caused most of the seasonal soil loss, typically 3-4 t ha-1. The critical soil erosion period was between pre-plant irrigation and canopy closure. Soil surface cover, peak runoff rate and furrow length explained 97% of variance in soil loss caused by rainfall. Furrow length was not significant in the soil loss model for irrigation (r2 0.59).
The effect of hydroxide solutions on dissolution of organic-carbon in some New Zealand soils
Authors: Lieffering RE , Mclay CDA
Published: April 2005

The disposal of high pH, hydroxide-based, liquid wastes using land treatment systems is becoming increasingly common in New Zealand. For effective disposal of high pH liquid wastes to land, it is necessary to understand the effects of different hydroxide-based solutions on organic carbon dissolution to ensure soil physical properties are not adversely affected. Single-step and multi-step extraction experiments were designed to investigate the effect of high pH solutions on organic carbon dissolution in four New Zealand soils. In the single-step extraction experiments, soil was shaken with varying concentrations of NaOH and KOH (0.003, 0.01, 0.03, 0.1 and 0.3 M) at a 1:5 soil to solution ratio for 18 h. Organic carbon dissolution occurred at very low concentrations and increased linearly with hydroxide concentration, with up to 45% of the total initial organic carbon dissolved when 0.3 M NaOH was used. KOH dissolved slightly less organic carbon than NaOH, indicating that a cation difference occurred. When the anion was changed to chloride, the amount of organic carbon dissolved was very small (<2% of total initial organic carbon) for all concentrations, indicating that the hydroxide anion was most important in causing organic carbon dissolution. Multi-step experiments involved repeatedly shaking soil with fresh hydroxide extracting solutions, and showed that the difference between NaOH and KOH in dissolving organic carbon decreased as the number of extractions increased. The cumulative amount of organic carbon dissolved increased from about 45% after a single-step extraction to about 75% after five extractions. Organic carbon dissolution with different solutions tended to be higher in an allophanic soil, but similar in soils dominated by phyllosilicate clay minerals. The results indicate that factors such as the chemical composition of the liquid waste and soil type need to be considered prior to land disposal to prevent adverse effects on soil physical properties.