Soil and Land Systems

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https://hdl.handle.net/2440/12036
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, Angus MacCallum"

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    Arsenic in the soil environment: a review
    (Academic Press, 1998) Smith, Euan; Naidu, Ravendra; Alston, Angus MacCallum; School of Earth and Environmental Sciences : Soil and Land Systems
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    Chemistry of inorganic arsenic in soils: II. Effect of phosphorus, sodium, and calcium on arsenic sorption
    (American Society of Agronomy, 2002) Smith, Euan; Naidu, Ravendra; Alston, Angus MacCallum; School of Earth and Environmental Sciences : Soil and Land Systems
    Received for publication November 30, 1999. There are more than 10000 arsenic (As) contaminated sites in Australia. The ability of soils at these contaminated sites to sorb As is highly variable and appreciable amounts of As have been recorded in the subsurface soils. The potential risk of surface and ground water contamination by As at these sites is a major environmental concern. Factors that influence adsorption capacity of soils influence the bioavailability and subsequent mobility of As in soils. In the present study we investigated the effect of PO³⁻4 and Na⁺ and Ca²⁺ on the sorption of AsV and AsIII by an Oxisol, a Vertisol, and two Alfisols. The presence of P (0.16 mmol L⁻¹) greatly decreased AsV sorption by soils containing low amounts of Fe oxides (<100 mmol kg⁻¹), indicating competitive adsorption between P and AsV for sorption sites. In contrast, the presence of a similar amount of P had little effect on the amount of AsV adsorbed by soils with high Fe content (>800 mmol kg⁻¹). However, AsV sorption substantially decreased from 0.63 to 0.37 mmol kg⁻¹ as P concentration was increased from 0.16 to 3.2 mmol L⁻¹ in selected soils. This suggests increased competition between P and AsV for soil sorption sites, through either the higher affinity or the effect of mass action of the increasing concentration of P in solution. A similar effect of P on AsIII sorption was observed in the low sorbing Alfisol and high affinity Oxisol. However, the amount of AsIII sorbed by the Oxisol was much greater than the Alfisol for all treatments. The presence of Ca²⁺ increased the amount of AsV sorbed compared with that of Na+ and was manifested through changes in the surface charge characteristics of the soils. A similar trend in AsIII sorption was recorded with changes in index cation, although the effect was not as marked as recorded for AsV.
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    Effectiveness of liming to minimise uptake of cadmium by wheat and barley grain grown in the field
    (CSIRO, 1996) Oliver, Danielle Peta; Tiller, K. G.; Conyers, M. K.; Slattery, W. J.; Alston, Angus MacCallum; Merry, R. H.; School of Earth and Environmental Sciences : Soil and Land Systems
    The effects of soil pH on cadmium (Cd) concentration in wheat and barley grain were determined from 8 field experiments in the Rutherglen (Victoria) and Wagga Wagga (New South Wales) regions of south-eastern Australia. Generally, raising soil pHc, from 4.0 to 5.0 using lime decreased Cd concentration in the grain. However, the response was variable between sites and years, with the greatest variation occurring between years. At those sites where there were statistically significant decreases in Cd concentration with increasing pH, the rate of decrease was small. The Cd concentration exceeded the maximum permissible concentration (MPC) of 0.05 mg/kg in barley grain at 3 sites and in wheat at 1 site. In some cases, raising soil pHCa, to 6.0 was not sufficient to decrease Cd concentration in grain below the MPC and raising soil pH above this value would not be considered economically viable in many areas.
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    Effects of soil pH and applied cadmium on cadmium concentration in wheat grain
    (CSIRO, 1998) Oliver, Danielle Peta; Tiller, K. G.; Alston, Angus MacCallum; Cozens, G. D.; Merry, R. H.; School of Earth and Environmental Sciences : Soil and Land Systems
    The effects of pH and soil-applied Cd on Cd concentration in wheat grain were determined using 4 soils in a glasshouse study. Grain Cd concentrations increased significantly (P < 0·001) with increasing applications of Cd for all soils. Generally, for the Alfisols the Cd concentration in grain decreased with increasing soil pH for all Cd treatments. The Cd concentrations in grain from plants grown on the Haploxerert showed variable responses to pH, depending on the Cd treatment. Smaller decreases in grain Cd concentration with increasing pH were seen on soils with native Cd compared with grain from soils to which Cd had been added. Generally, Cd uptake (mg/pot) by grain grown in the Alfisols showed the same trends with increasing pH as seen with grain Cd concentrations, indicating no yield dilution effect. On the Bordertown soil (a Palexeralf) the ratio of Cd in shoot material (excluding grain) to Cd concentration in grain was found to increase significantly (P < 0·001) with increasing Cd treatments and decrease significantly (P < 0·001) with increasing pH. The ratio on the Bordertown soil did not remain constant across Cd or pH treatments, which suggests that the use of soil tests to predict Cd concentration in grain may be problematical. The transfer coefficients for Kapinnie, Freeling, and Bordertown soils were dependent on pH, whereas that for the Inman Valley soil was independent of pH. The relationship between the reciprocal of the distribution coefficient (K¡ 1 d) and the transfer coefficients (Cd grain/Cd soil) was generally good for all soils except the Vertisol from Inman Valley.
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    Fate and behaviour of triasulfuron, metsulfuron-methyl, and chlorosulfuron in the Australian soil environment: a review
    (CSIRO, 1998) Sarmah, Ajit K.; Kookana, Rai S.; Alston, Angus MacCallum; School of Earth and Environmental Sciences : Soil and Land Systems
    The sulfonylurea herbicides comprise a group of compounds designed to control broad-leaved weeds and some grasses in a variety of crops. The herbicides have become popular because of their low application rates (10-40 g/ha), low mammalian toxicity, and unprecedented herbicidal activity. We present a review of the fate and behaviour of these herbicides in soils with particular reference to alkaline soils of Australia. The review shows that the low application rates of sulfonylurea herbicides continue to present an analytical challenge, although in recent years a number of new methods capable of detecting them at very low concentrations have been developed. A range of analytical methods is available, including high performance liquid chromatography, gas chromatography, immunoassay, and bioassay. However, analytical sensitivity required to detect trace levels of these herbicides continues to pose problems in routine detection of herbicide residues in soils. The review reveals that there are no reports of studies of the behaviour of sulfonylureas in soils with pH >8·2. This is of particular significance to Australian conditions because a number of Australian soils are even more alkaline, and the pH(water) in subsoils can be as high as 10· 2. Sorption of sulfonylureas is pH-dependent and has a strong negative correlation with pH. At pH >8·0 sorption is very low. In acid soils, however, sorption of chlorsulfuron, metsulfuron-methyl, and triasulfuron is strongly influenced by the soil temperature, clay content, and, particularly, organic matter content. The principal modes of degradation of the herbicides are acid hydrolysis and microbial degradation with the latter being the only major pathway in alkaline soils. Hydrolysis of the sulfonylureas is more rapid under acidic conditions (pH 4{7), and the data suggest that hydrolysis is likely to be very slow in alkaline soils. Data from other countries suggest that the half-life of chlorsulfur on increases exponentially with pH, and that it is also influenced by variations in the temperature and water content of the soil. Being acidic in nature, the herbicide molecules become anionic at high pH and can move to a considerable depth in the soil profile by leaching. Movement of the sulfonylureas in soil is largely influenced by organic matter content and soil pH and the reviewed data show that sulfonylureas have substantial leaching potential in the sandy alkaline soils of Australia. This is likely to result in increased persistence in alkaline subsoils lacking in organic matter and biological activity. Computer models to predict the persistence and movement of the sulfonylureas are available; however, additional input parameters are required to predict accurately the behaviour of specific herbicides in alkaline soils under Australian conditions. Since new herbicides with chemistry similar to existing sulfonylureas are increasingly likely to be available for use, there is a need to develop comprehensive understanding of their fate, behaviour, and impact on Australian cropping and ecological systems.