Soil and Land Systems
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The Soil and Land Systems discipline was part of the School of Earth and Environmental Sciences until 2013. Since then Soil Science has become part of the School of Agriculture, Food and Wine.
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Browsing Soil and Land Systems by Author "Alston, A."
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Item Metadata only Application of VARLEACH and LEACHM models to experimental data on leaching of a non-reactive tracer and three sulfonylurea herbicides(C S I R O Publishing, 2001) Sarmah, A.; Kookana, R.; Alston, A.A chromatographic model (VARLEACH) and a process-based model (LEACHM) were evaluated under low and high water input regimes (‘rainfall’ and ‘rainfall + irrigation’, respectively) using experimental data for a non-reactive tracer (KBr), and 3 sulfonylurea herbicides: triasulfuron, metsulfuron-methyl, and chlorsulfuron. Both qualitative and quantitative comparisons of predicted and measured water contents revealed that both models performed well under ‘rainfall’, but prediction was less satisfactory under the treatment of ‘rainfall + irrigation’. Both models failed to simulate the bimodal distribution of Br⁻ and the herbicides observed under ‘rainfall + irrigation’ treatment. Distribution of Br - and the 3 herbicides in the profile was over- or under-estimated at certain depths and times, probably due to the limitations inherent to the models (e.g. inability to deal with the macropore flow), and to simplifications associated with some input data. Simulations for a dry (1 decile), median (5 decile), and wet year (9 decile) with LEACHM and VARLEACH models using long-term weather data for the site showed that leaching and persistence of the herbicides are highly dependent on the amount of rainfall the site receives. The results indicate that the risk of injury to herbicide-sensitive crops in the following year of application of herbicides is likely to be greater when the herbicides are applied in a drier rather than a wetter year.Item Metadata only Differences in sorption behaviour of carbaryl and phosalone in soils from Australia, Pakistan, and the United Kingdom(C S I R O Publishing, 2001) Ahmad, R.; Kookana, R.; Alston, A.; Bromilow, R.Sorption of 2 nonionic pesticides, carbaryl (1-naphthyl methylcarbamate) and phosalone (S-6-chloro-2,3-dihydro-2-oxobenzoxazol-3-ylmethyl O,O-diethyl phosphorodithioate), was investigated for 48 soils from Australia, Pakistan, and the United Kingdom. A wide variation in sorption affinities of the soils to carbaryl and phosalone was observed. The sorption coefficient (K d) values for carbaryl ranged from 0.19 to 23.0 L/kg in Australian soils, from 0.99 to 59.7 L/kg in Pakistani soils, and from 1.09 to 23.0 L/kg in the UK soils. The K d values for phosalone ranged from 4.8 to 443 L/kg in Australian soils, from 15.5 to 1182 L/kg in Pakistani soils, and from 18.1 to 205 L/kg in the UK soils. To eliminate the effect of variation in organic carbon content among the soils, the K d values were normalised to the fraction of soil organic carbon (K oc ). However, K oc values for both pesticides varied by about an order of magnitude across the soils, decreasing in the following order: Pakistani > Australian > UK soils. Correlation between K d and organic carbon content of the soils was poor (r 2 = 0.44 and 0.46). The particulate organic C (53 µm–2 mm) was only slightly better correlated with K d than the total organic C in the <2 mm fraction of the soils. Thus soil organic C content alone is not a good predictor of sorption even for nonionic pesticides such as carbaryl and phosalone. Caution is needed during extrapolation of overseas data to predict sorption under local conditions.Item Metadata only Effect of nitrogen fertiliser placement on grain protein concentration of wheat under different water regimes(CSIRO, 1997) Lotfollahi, M.; Alston, A.; McDonald, G.Two experiments were conducted in pots 105 cm deep and 11 cm in diameter to determine the effects of subsoil nitrogen (N) on grain yield and grain protein concentration (GPC) of wheat (Triticum aestivum L. cv. Molineux). In both experiments, KNO₃ was applied in solution at different times and depths in the profile. In the first experiment, in which a sandy soil low in available N was used, application of 150 mg N at 60 cm, 2 weeks after anthesis, significantly increased grain yield and GPC. The N was taken up gradually by the plant after N was applied. Adding N to the subsoil increased root growth and this resulted in increased water use and water use efficiency. Although there was an increase in the rate of N uptake by the roots, the main factor that influenced the utilisation of subsoil N was the root length density. In the second experiment, the effects of depth and time of N application, and of a reduction in post-anthesis water supply, were determined. A more fertile soil was used than the one in the first experiment. There were 5 KNO₃ treatments: nil N; 150 mg N applied to the topsoil at sowing; 75 mg N to the topsoil and 75 mg N to the subsoil (60 cm depth) at sowing; 150 mg N to the subsoil at sowing; 75 mg N to the topsoil at sowing and 75 mg N to the subsoil 1 week after anthesis. The effect of post-anthesis water stress was assessed by allowing the topsoil to dry and then supplying half the amount of water used by the well-watered control treatment at 60 cm in half of the pots. Adding N increased yield and GPC but there was no significant difference in yield and GPC between the different N treatments. When N was applied to the topsoil only, most of it was used by the wheat plants or leached to the subsoil by anthesis; post-anthesis uptake of N depended on the amount of N in the subsoil. Adding N, irrespective of the depth of placement or time of application, increased water use and water use efficiency. In both experiments, increasing the availability of N in the soil after anthesis reduced the amount of N that was remobilised from the roots and stem to the grain. The recovery of applied N in both experiments was high (about 80%). These experiments have shown that N available in the subsoil after anthesis can be used very efficiently and can contribute to both grain yield and GPC. A critical factor in the efficient use of this N appears to be root length density in the subsoil.Item Metadata only Effects of electrolyte composition on chromium desorption in soils contaminated by tannery waste(C S I R O Publishing, 2001) Avudainayagam, S.; Naidu, R.; Kookana, R.; Alston, A.; McClure, S.; Smith, L.We conducted batch studies to investigate the effect of phosphate and dominant cations present in tannery waste on desorption of chromium (Cr) from surface and subsurface soil horizons from a contaminated tannery waste site at Mount Barker, South Australia. The surface horizon (0–15 cm) of the soil profile was alkaline (pH 7.9) and the subsurface horizon (50–90 cm) was acidic (pH 3.9). Aqua-regia extractable Cr concentration ranged from 62 g/kg in the surface to 0.26 g/kg in the subsurface soils. X-ray diffraction and scanning electron microscopic studies revealed the predominance of carbonate and kaolin minerals in the surface soils, and highly weathered framboidal particles, with morphology similar to that of pyrites, in the subsurface soils. The amount of Cr desorbed from the contaminated soils varied considerably with both the electrolyte’s cationic charge and soil properties. The effect of cations, Ca²⁺ and Na⁺ (CaCl₂ , NaCl), and phosphate on desorption of Cr was investigated. While the ionic strength of the solutions was standardised at approximately 0.03 mol/L, the concentration of phosphate (as KH₂ PO₄) was varied from 0 to 3.2 mmol/L. On the basis of studies on solution to soil ratio and desorption kinetics we chose a 20: 1 solution to soil ratio and 2 h equilibration time. In the surface alkaline soil, the amount of Cr released decreased in the order Na⁺ (286 μg/L) ≥ water (256 μg/L) > Ca²⁺ (156 μg/L). In contrast subsurface acidic soil showed a reverse trend, i.e. Ca²⁺ (52 μg/L) > Na⁺ (29 μg/L) > water (20 μg/ L). Speciation of Cr in the extracts showed predominantly Cr(VI) in the alkaline surface soil and Cr(III) in the subsurface acidic soil. A strong effect of phosphate on the cumulative amount of chromate desorbed was observed. The study shows that the presence of high concentrations of Na⁺ (0.03 mol/L) and phosphate (3.2 mmol/L) in soil solution enhances Cr(VI) mobility. In contrast, Ca²⁺ may induce retention of Cr(VI) in Cr-contaminated alkaline soils.Item Metadata only Effects of soil compaction on phosphorus uptake and growth of Trifolium subterraneum colonized by four species of vesicular-arbuscular mycorrhizal fungi(CAMBRIDGE UNIV PRESS, 1998) Nadian, H.; Smith, S.; Alston, A.; Murray, R.; Siebert, B.The ability of four species of vesicular–arbuscular mycorrhizal (VAM) fungi to increase phosphorus uptake and growth of clover plants (Trifolium subterraneum L.) at different levels of soil compaction and P application was studied in a pot experiment. Dry matter in the shoots and roots of clover plants decreased with increasing soil compaction. Colonization by Glomus intraradices Schenck & Smith and Glomus sp. City Beach WUM16 increased plant growth and P uptake up to a bulk density of 1•60 Mg m⁻³, although the response was smaller as soil compaction was increased. Glomus etunicatum Becker & Gerdeman and Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe had no effect on the shoot d. wt and P uptake when the bulk density of the soil was ≥1•40 and ≥1•60 Mg m⁻³, respectively. Soil compaction to a bulk density of 1•60 Mg m⁻³ had no effect on the percentage of root length colonized by G. intraradices and Glomus sp. City Beach, but total root length colonized decreased as soil compaction was increased. Decreased P uptake and growth of clover plants colonized by G. intraradices and Glomus sp. City Beach, with increasing soil compaction up to a bulk density of 1•60 Mg m⁻³, was mainly attributed to a significant reduction in total root length colonized and in the hyphal biomass. Soil compaction, which increased bulk density from 1•20 to 1•75 Mg m⁻³, reduced the O₂ content of the soil atmosphere from 0•16 to 0•05 m3 m⁻³. The absence of any observable mycorrhizal growth response to any of the four species of VAM fungi in highly compacted soil (bulk density = 1•75 Mg m⁻³) was attributed to the significant decrease in the O₂ content of the soil atmosphere, change in soil pore size distribution and, presumably, to ethylene production.Item Metadata only Effects of soil compaction on plant growth, phosphorus uptake and morphological characteristics of vesicular-arbuscular mycorrhizal colonization of Trifolium subterraneum(WILEY, 1997) Nadian, H.; Smith, S.; Alston, A.; Murray, R.We investigated the effect of soil compaction and phosphorus (P) application on morphological characteristics of mycorrhizal colonization and growth responses, to determine the reasons for reduced responses observed in our previous work with compacted soil. Growth, phosphorus (P) uptake and intensity of vesicular–arbuscular (VA) mycorrhizal colonization were studied in clover plants (Trifolium subterraneum L.) with and without VA mycorrhizal colonization at two P applications and three levels of soil compaction. Phosphorus was supplied either at constant mass concentration (mg P kg⁻¹ soil) or at constant volume concentration (mg P dm−3 soil). Increasing bulk density of the soil from 1•1 to 1.6 Mg m⁻³ significantly decreased root length and shoot d. wt, but increased the diameter of both main axes and first order lateral roots regardless of P application. Total P uptake and shoot d. wt of clover plants colonized by Glomus intraradices (Schenck & Smith) were significantly greater than those of non-mycorrhizal plants at all levels of soil compaction and both P applications. However, soil compaction to a bulk density of 1.6 Mg m⁻³ (penetrometer resistance = 3.5 MPa at a matric potential of − 33 kPa) significantly decreased mycorrhizal growth response. There was no evidence that the increased volume concentration of P at high bulk densities was responsible for the reduced responses. Soil compaction had no significant effect on the fraction of root length containing arbuscules and vesicles, but total root length colonized by arbuscules, vesicles or by any combination of arbuscules, vesicles and intra-radical hyphae significantly decreased as soil compaction was increased. The air-filled porosity of highly compacted soil, which varied from 0.07 to 0.11 over the range of matric potentials encountered (− 33 and − 100 kPa), had no significant effect on the intensity of internal colonization.Item Metadata only Limitations of acid digestion techniques for the determination of fluoride in plant material(M. Dekker, 1995) Stevens, D.; McLaughlin, M.; Alston, A.Procedures for determination of fluoride (F) in plant material employing acid digestion and solution analysis by ion specific electrode (ISE) were compared to alkali fusion using a range of plant materials. The efficiency of the methods were assessed using standard reference plant material (SRM) not previously available for plant F analysis. All acid digestion procedures tested failed to obtain the certified value for F in the SRM. This was due to failure of the acids to liberate F bound strongly within silicate minerals found in the plant materials. Acid digestion is therefore not recommended for determination of total F, but could be used to determine labile F in plant materials. During investigation of the acid digestion procedures, it was also found that F concentrations determined in solution using the ISE are sensitive to solution pH, even at solution pH values where complexation of F with hydrogen ions (H⁺) can be discounted. It is therefore recommended that both ionic strength and pH of sample and standard solutions be matched when determining F concentrations in solution using the F-ISE.Item Metadata only Phytotoxicity of aluminium-fluoride complexes and their uptake from solution culture by Avena sativa and Lycopersicon esculentum(Springer Netherlands, 1997) Stevens, D.; McLaughlin, M.; Alston, A.Avena sativa (oats) and Lycopersicon esculentum (tomatoes) were grown in dilute nutrient solutions supplemented with Al only, F only or a combination of both. In solutions containing Al and F, shoot growth was limited when predicted Al(r). (Al3+, AlOH2+ and Al(OH)2/+) activities were < 0.1 μM, activities three orders of magnitude lower than the critical value determined with Al only. The data suggest that at the activities used in these experiments, Al(r) is most toxic, AlF2+ and AlF2/+ are toxic to a lesser extent, and AlF3, AlF4/- and F- are least toxic. Fluoride concentrations in shoots grown in solutions correlated best with positively charged AlF(x)/(3-x) species (i.e. AlF2+, AlF2+) and the molar ratio of F:Al in most plants shoots was about 3:2. However, when activities of positively charged AlF(x)/(3-x) species were low (< 50 μM) and the activity of AlF3 species high (500 μM) the molar ratio of F:Al in plant shoots suggested AlF3 was taken up. These findings are discussed in relation to plant uptake and toxicity. Measured concentrations of Al(r) and F- in solutions containing Al and F were compared with concentrations predicted by a computer model (GEOCHEM-PC). The method for measuring F- concentrations, using a non-complexing buffer and F ion-selective electrode, gave good agreement with predicted F- concentrations. The 8-hydroxyquinoline method for measuring Al(r) concentrations did not agree with predicted concentrations, highlighting the limitations of this method when measuring Al(r) in the presence of F in a multi-ligand system with high concentrations of F and Al.Item Metadata only Phytotoxicity of hydrogen fluoride and fluoroborate and their uptake from solution culture by Lycopersicon esculentum and Avena sativa(Springer Netherlands, 1998) Stevens, D.; McLaughlin, M.; Alston, A.The aims of this paper were to determine the phytoavailability and phytotoxicity of hydrogen fluoride (HF) and fluoroborate (BF₄⁻) in solution when exposed to the root of the plant. As fluoroborate undergoes a slow hydrolysis to F and borate ions, the stability of BF₄⁻ under solution culture conditions was determined. Fluoroborate was found to have a zero order rate constant of 0.0136 and took approximately 72 days to hydrolyse completely. Tomato (Lycopersicon esculentum) and oat (Avena sativa) plants were grown in dilute nutrient solutions which contained a range of activities of HF and BF₄⁻. Dry matter production of both tomato and oat plants grown in nutrient solutions were found to be restricted by increased activity of HF and BF₄⁻ in solution. Tomatoes were more sensitive to HF and BF₄⁻ than oats. Limitations to dry matter production coincided with increased uptake of F for F concentrations in tissue of both tomatoes and oats. Fluoride uptake of both HF and BF by tomatoes and oats was orders of magnitude higher compared to similar activities of other ionic species of F reported in previous studies. Possible mechanisms of uptake are discussed.Item Metadata only Phytotoxicity of the fluoride ion and its uptake from solution culture by Avena sativa and Lycopersicon esculentum(Springer Netherlands, 1998) Stevens, D.; McLaughlin, M.; Alston, A.Avena sativa (oats) and Lycopersicon esculentum (tomatoes) were grown in dilute nutrient solutions containing varying concentrations of fluoride (F). Shoot and root growth of tomatoes were limited when calculated F ion activities (F⁻) were greater than 1473 μM in solution. However, F⁻ activities up to 5130 μm had no effect on the dry weights of oat shoots or roots, suggesting that tomatoes are more sensitive to F toxicity. At low F activities in solution (<1684 μM) F concentrations in plant shoots increased almost linearly with activity, but then increased rapidly before reaching an upper asymptote. These findings are discussed in relation to plant uptake and toxicity of F. The complexation of Ca with F has been proposed as the mechanism of selectively altering membrane permeability to F, but further studies are required to confirm the role of Ca. Data recalculated from the literature and from this paper also suggest that growth solution ionic strength is positively related to uptake of F- by plants.Item Metadata only Sorption of ametryn and imazethapyr in twenty-five soils from Pakistan and Australia(Marcel Dekker Inc, 2001) Ahmad, R.; Kookana, R.; Alston, A.Changes in aerobic bacteria and autotrophic nitrifier numbers, and in respiration and nitrification in two soils treated with cinosulfuron at 42 (field rate) and 4200 μg/kg were studied after 1 and 4 weeks of incubation under laboratory conditions. Only nitrification at 1 week was slightly inhibited by the cinosulfuron treatment, even at the field rate. In vitro toxicity tests carried out in agar media on representative aerobic bacteria, fungi and Azotobacter strains isolated from the two soils, as well as on nine collection soil bacteria, showed that only a very high cinosulfuron concentration (100 mg/l) can have negative effects on the growth of a limited number of soil heterotrophic microorganisms, under conditions similar to those of soil environment. The absence of three branchedchain amino acids increased bacterial sensitivity, thus showing the importance of the chemical conditions and suggesting acetolactate synthase enzyme blockage as the toxicity mechanism. It is concluded that cinosulfuron has a negative effect on only a few aspects of the microbial community in soil ecosystems, even at concentrations higher that those currently in use.Item Metadata only Surfactant-enhanced release of carbaryl and ethion from two long-term contaminated soils(Marcel Dekker Inc, 2004) Ahmad, R.; Kookana, R.; Alston, A.The potential of five nonionic surfactants, Triton X-100, Brij35, Ethylan GE08, Ethylan CD127, and Ethylan CPG660 for enhancing release of carbaryl and ethion from two long-term contaminated soils was evaluated using the batch method. Incorporation of the surfactants into soils enhanced the release of both pesticides to various extents, which could be related to the type of pesticides and type and the amount of surfactants added. Release of ethion was dramatically enhanced by aqueous concentrations of surfactants above their critical micelle concentration values. This was attributed to solubility enhancement through incorporation of the highly hydrophobic compound within surfactant micelles. A concentration of 10 g L-1 of various surfactants released >70% of the total ethion from the soil irrespective of the surfactant. For carbaryl, the surfactants were effective at low concentrations and dependence on concentration was lower than in the case of ethion. The ethylan surfactants (GE08, CD127, and CPG660) had a higher potential than Triton X-100 and Brij35 for releasing the pesticides. However, there was still a significant portion of carbaryl (11% of the total) and ethion (17% of the total) left in the soil. Our study also showed that there must be an optimal concentration of each surfactant to maximize the mass transfer of pesticides. At some threshold concentration level, additional surfactant started to inhibit the mass transfer of solute from the soil into the water. The results suggested that surfactants could help remediation of soils polluted by pesticides. The choice of surfactant should be made based on the properties of pesticides.Item Metadata only Syringe filtration as a source of error in pesticide residue analysis in environmental samples(Springer-Verlag, 2001) Ahmad, R.; Kookana, R.; Alston, A.Item Metadata only The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation(Springer Netherlands, 1996) Nadian, H.; Smith, S.; Alston, A.; Murray, R.The effects of vesicular-arbuscular mycorrhizal (VAM) colonisation on phosphorus (P) uptake and growth of clover (Trifolium subterraneum L.) in response to soil compaction were studied in three pot experiments. P uptake and growth of the plants decreased as the bulk density of the soil increased from 1.0 to 1.6 Mg m⁻³. The strongest effects of soil compaction on P uptake and plant growth were observed at the highest P application (60 mg kg⁻¹ soil). The main observation of this study was that at low P application (15 mg kg⁻¹ soil), P uptake and shoot dry weight of the plants colonised by Glomus intraradices were greater than those of non-mycorrhizal plants at similar levels of compaction of the soil. However, the mycorrhizal growth response decreased proportionately as soil compaction was increased. Decreased total P uptake and shoot dry weight of mycorrhizal clover in compacted soil were attributed to the reduction in the root length. Soil compaction had no significant effect on the percentage of root length colonised. However, total root length colonised was lower (6.6 m pot⁻¹) in highly compacted soil than in slightly compacted soil (27.8 m pot⁻¹). The oxygen content of the soil atmosphere measured shortly before the plants were harvested varied from 0.18 m³m⁻³ in slightly compacted soil (1.0 Mg m⁻³) to 0.10 m³m⁻³ in highly compacted soil (1.6 Mg m⁻³).Item Metadata only The nature of soil organic matter affects sorption of pesticides. 1. Relationships with carbon chemistry as determined by 13C CPMAS NMR spectroscopy(Amer Chemical Soc, 2001) Ahmad, R.; Kookana, R.; Alston, A.; Skjemstad, J.The structural composition of soil organic matter (SOM) was determined in twenty-seven soils with different vegetation from several ecological zones of Australia and Pakistan using solid-state CPMAS 13C NMR. The SOM was characterized using carbon types derived from the NMR spectra. Relationships were determined between Koc (sorption per unit organic C) of carbaryl(1-naphthylmethylcarbamate) and phosalone (S-6-chloro-2,3-dihydro-2-oxobenzoxazol-3-ylmethyl O,O-diethyl phosphorodithioate) and the nature of organic matter in the soils. Substantial variations were revealed in the structural composition of organic matter in the soils studied. The variations in Koc values of the pesticides observed for the soils could be explained only when variations in the aromatic components of SOM were taken into consideration. The highly significant positive correlations of aromaticity of SOM and Koc values of carbaryl and phosalone revealed that the aromatic component of SOM is a good predictor of a soil's ability to bind such nonionic pesticides.