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  • 1
    Language: English
    In: Journal of agricultural and food chemistry, 13 June 2012, Vol.60(23), pp.6037-44
    Description: This study examined the effects of applied selenium (Se) species, time of application, method of application, and soil water management regimen on the accumulation of Se in rice plants. Plants were grown to maturity in a temperature- and humidity-controlled growth chamber using three water management methods: field capacity (FC), submerged until harvest, and submerged and drained 2 weeks before harvest. Two Se species, selenate (SeO4(2-)) and selenite (SeO3(2-)), were applied at a rate equivalent to 30 g ha(-1). Four application methods were employed as follows: (i) Se applied at soil preparation, (ii) Se-enriched urea granules applied to floodwater at heading; (iii) foliar Se applied at heading; and (iv) fluid fertilizer Se applied to soil or floodwater at heading. Total Se concentrations in rice grains, husks, leaves, culms, and roots were measured, as well as Se speciation in grains from the Se-enriched urea granule treatment. Highest Se concentrations in the grain occurred with SeO4(2-) and with fertilizer applied at heading stage; SeO4(2-)-enriched urea granules applied at heading increased grain Se concentrations 5-6-fold (by 450-600 μg kg(-1)) compared to the control (no fertilizer Se applied) in all water treatments. Under paddy conditions other Se fertilization strategies were much less effective. Drainage before harvesting caused Se to accumulate in/on rice roots, possibly through adsorption onto iron plaque on roots. Rice grains contained Se mainly in the organic form as selenomethionine (SeM), which comprised 〉90% of the total grain Se in treatments fertilized with SeO4(2-)-enriched urea granules. The results of this study clearly show that of the fertilizer strategies tested biofortification of Se in rice grains can best be achieved in lowland rice by broadcast application of SeO4(2-)-enriched urea granules to floodwater at heading stage.
    Keywords: Fertilizers -- Analysis ; Oryza -- Chemistry ; Selenic Acid -- Chemistry ; Selenium -- Analysis ; Urea -- Chemistry
    ISSN: 00218561
    E-ISSN: 1520-5118
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  • 2
    Language: English
    In: The Science of the Total Environment, Oct 1, 2012, Vol.435-436, p.337(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2012.07.009 Byline: Manpreet S. Mavi, Jonathan Sanderman, David J. Chittleborough, James W. Cox, Petra Marschner Keywords: Dissolved organic carbon; Salinity; Sodicity; Soil texture; Sorption Abstract: Loss of dissolved organic matter (DOM) from soils can have negative effects on soil fertility and water quality. It is known that sodicity increases DOM solubility, but the interactive effect of sodicity and salinity on DOM sorption and how this is affected by soil texture is not clear. We investigated the effect of salinity and sodicity on DOM sorption in soils with different clay contents. Four salt solutions with different EC and SAR were prepared using combinations of 1M NaCl and 1M CaCl.sub.2 stock solutions. The soils differing in texture (4, 13, 24 and 40% clay, termed S-4, S-13, S-24 and S-40) were repeatedly leached with these solutions until the desired combination of EC and SAR (EC.sub.1:5 1 and 5dSm.sup.-1 in combination with SAR 〈3 or 〉20) was reached. The sorption of DOC (derived from mature wheat straw) was more strongly affected by SAR than by EC. High SAR (〉20) at EC1 significantly decreased sorption in all soils. However, at EC5, high SAR did not significantly reduce DOC sorption most likely because of the high electrolyte concentration of the soil solution. DOC sorption was greatest in S-24 (which had the highest CEC) at all concentrations of DOC added whereas DOC sorption did not differ greatly between S-40 and S-4 or S-13 (which had higher concentrations of Fe/Al than S-40). DOC sorption in salt-affected soil is more strongly controlled by CEC and Fe/Al concentration than by clay concentration per se except in sodic soils where DOC sorption is low due to the high sodium saturation of the exchange complex. Article History: Received 5 February 2012; Revised 2 July 2012; Accepted 3 July 2012
    Keywords: Soils ; Soil Carbon ; Salinity
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Soil Biology and Biochemistry, 2011, Vol.43(9), pp.1908-1916
    Description: In salt-affected soils, soil organic carbon (SOC) levels are usually low as a result of poor plant growth; additionally, decomposition of soil organic matter (SOM) may be negatively affected. Soil organic carbon models, such as the Rothamsted Carbon Model (RothC), that are used to estimate carbon dioxide (CO ) emission and SOC stocks at various spatial scales, do not consider the effect of salinity on CO emissions and may therefore over-estimate CO release from saline soils. Two laboratory incubation experiments were conducted to assess the effect of soil texture on the response of CO release to salinity, and to calculate a rate modifier for salinity to be introduced into the RothC model. The soils used were a sandy loam (18.7% clay) and a sandy clay loam (22.5% clay) in one experiment and a loamy sand (6.3% clay) and a clay (42% clay) in another experiment. The water content was adjusted to 75%, 55%, 50% and 45% water holding capacity (WHC) for the loamy sand, sandy loam, sandy clay loam and the clay, respectively to ensure optimal soil moisture for decomposition. Sodium chloride (NaCl) was used to develop a range of salinities: electrical conductivity of the 1:5 soil: water extract (EC ) 1, 2, 3, 4 and 5 dS m . The soils were amended with 2% (w/w) wheat residues and CO emission was measured over 4 months. Carbon dioxide release was also measured from five salt-affected soils from the field for model evaluation. In all soils, cumulative CO –C g soil significantly decreased with increasing EC developed by addition of NaCl, but the relative decrease differed among the soils. In the salt-amended soils, the reduction in normalised cumulative respiration (in percentage for the control) at EC 〉 1.0 dS m was most pronounced in the loamy sand. This is due to the differential water content of the soils, at the same EC ; the salt concentration in the soil solution is higher in the coarser textured soils than in fine textured soils because in the former soils, the water content for optimal decomposition is lower. When salinity was expressed as osmotic potential, the decrease in normalised cumulative respiration with increasing salinity was less than with EC . The osmotic potential of the soil solution is a more appropriate parameter for estimating the salinity effect on microbial activity than the electrical conductivity (EC) because osmotic potential, unlike EC, takes account into salt concentration in the soil solution as a function of the water content. The decrease in particulate organic carbon (POC) was smaller in soils with low osmotic potential whereas total organic carbon, humus-C and charcoal-C did not change over time, and were not significantly affected by salinity. The modelling of cumulative respiration data using a two compartment model showed that the decomposition of labile carbon (C) pool is more sensitive to salinity than that of the slow C pool. The evaluation of RothC, modified to include the decomposition rate modifier for salinity developed from the salt-amended soils, against saline soils from the field, suggested that salinity had a greater effect on cumulative respiration in the salt-amended soils. The results of this study show (i) salinity needs to be taken into account when modelling CO release and SOC turnover in salt-affected soils, and (ii) a decomposition rate modifier developed from salt-amended soils may overestimate the effect of salinity on CO release. ► Effect of soil texture on the response of CO release to salinity was assessed in incubation studies. ► At a given EC, relative respiration was higher in fine textured soils than coarse textured soils. ► The decrease in CO release in response to osmotic potential was less than with EC. ► A decomposition rate-modifier, developed from the salt amended soils, was included in the RothC model. ► The model overestimated the salinity effect on respiration of field-collected saline soils.
    Keywords: Carbon Pools ; Osmotic Potential ; Respiration ; Rothc ; Salinity ; Water Content ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, Feb, 2012, Vol.45, p.8(6)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2011.10.003 Byline: Manpreet S. Mavi (a)(b), Petra Marschner (a), David J. Chittleborough (c), James W. Cox (c)(d), Jonathan Sanderman (e) Abstract: The individual effects of salinity and sodicity on organic matter dynamics are well known but less is known about their interactive effects. We conducted a laboratory incubation experiment to assess soil respiration and dissolved organic matter (DOM) dynamics in response to salinity and sodicity in two soils of different texture. Two non-saline non-sodic soils (a sand and a sandy clay loam) were leached 3-4 times with solutions containing different concentrations of NaCl and CaCl.sub.2 to reach almost identical electrical conductivity (EC.sub.1:5) in both soils (EC.sub.1:5 0.5, 1.3, 2.5 and 4.0 dS m.sup.-1 in the sand and EC.sub.1:5 0.7, 1.4, 2.5 and 4.0 dS m.sup.-1 in the sandy clay loam) combined with two sodium absorption ratios: SAR 〈 3 and 20. Finely ground wheat straw residue was added (20 g kg.sup.-1) as substrate to stimulate microbial activity. Cumulative respiration was more strongly affected by EC than by SAR. It decreased by 8% at EC 1.3 and by 60% at EC 4.0 in the sand, whereas EC had no effect on respiration in the sandy clay loam. The apparent differential sensitivity to EC in the two soils can be explained by their different water content and therefore, different osmotic potential at the same EC. At almost similar osmotic potential: -2.92 MPa in sand (at EC 1.3) and -2.76 MPa in the sandy clay loam (at EC 4.0) the relative decrease in respiration was similar (8-9%). Sodicity had little effect on cumulative respiration in the soils, but DOC, DON and specific ultra-violet absorbance (SUVA) were significantly higher at SAR 20 than at SAR 〈 3 in combination with low EC in both soils (EC 0.5 in the sand and EC 0.7 and 1.4 in the sandy clay loam). Therefore, high SAR in combination with low EC is likely to increase the risk of DOC and DON leaching in the salt-affected soils, which may lead to further soil degradation. Author Affiliation: (a) School of Agriculture, Food and Wine, Waite Research Institute, The University of Adelaide, SA 5000, Australia (b) Department of Soils, Punjab Agricultural University, Ludhiana 141004, India (c) School of Earth & Environmental Sciences, The University of Adelaide, SA 5000, Australia (d) South Australian Research and Development Institute (SARDI) Adelaide, SA 5000, Australia (e) Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water, Adelaide, SA 5000, Australia Article History: Received 31 May 2011; Revised 7 October 2011; Accepted 10 October 2011
    Keywords: Leaching ; Soils ; Electrical Conductivity ; Salinity
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Science of the Total Environment, 01 October 2012, Vol.435-436, pp.337-344
    Description: Loss of dissolved organic matter (DOM) from soils can have negative effects on soil fertility and water quality. It is known that sodicity increases DOM solubility, but the interactive effect of sodicity and salinity on DOM sorption and how this is affected by soil texture is not clear. We investigated the effect of salinity and sodicity on DOM sorption in soils with different clay contents. Four salt solutions with different EC and SAR were prepared using combinations of 1 M NaCl and 1 M CaCl stock solutions. The soils differing in texture (4, 13, 24 and 40% clay, termed S-4, S-13, S-24 and S-40) were repeatedly leached with these solutions until the desired combination of EC and SAR (EC 1 and 5 dS m in combination with SAR 〈 3 or 〉 20) was reached. The sorption of DOC (derived from mature wheat straw) was more strongly affected by SAR than by EC. High SAR (〉 20) at EC1 significantly decreased sorption in all soils. However, at EC5, high SAR did not significantly reduce DOC sorption most likely because of the high electrolyte concentration of the soil solution. DOC sorption was greatest in S-24 (which had the highest CEC) at all concentrations of DOC added whereas DOC sorption did not differ greatly between S-40 and S-4 or S-13 (which had higher concentrations of Fe/Al than S-40). DOC sorption in salt-affected soil is more strongly controlled by CEC and Fe/Al concentration than by clay concentration per se except in sodic soils where DOC sorption is low due to the high sodium saturation of the exchange complex. ► We studied the interactive effect of salinity and sodicity on DOC sorption in soils varying in texture. ► DOC losses from saline–sodic soils will be lower than sodic soils due to cation bridging at high electrolyte concentration. ► DOC sorption in salt-affected soils is more strongly controlled by CEC and Fe/Al concentration than by clay concentration.
    Keywords: Dissolved Organic Carbon ; Salinity ; Sodicity ; Soil Texture ; Sorption ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 6
    Language: English
    In: Soil Biology and Biochemistry, March 2011, Vol.43(3), pp.667-674
    Description: Net carbon dioxide (CO ) emission from soils is controlled by the input rate of organic material and the rate of decomposition which in turn are affected by temperature, moisture and soil factors. While the relationships between CO emission and soil factors are well-studied in non-salt-affected soils, little is known about soil properties controlling CO emission from salt-affected soils. To close this knowledge gap, non-salt-affected and salt-affected soils (0–0.30 m) were collected from two agricultural regions: in India (irrigation induced salinity) and in Australia (salinity associated with ground water or non-ground water associated salinity). A subset (50 Indian and 70 Australian soils) covering the range of electrical conductivity (EC) and sodium adsorption ratio (SAR) in each region was used in a laboratory incubation experiment. The soils were left unamended or amended with mature wheat residues (2% w/w) and CO release was measured over 120 days at constant temperature and soil water content. Residues were added to overcome carbon limitation for soil respiration. For the unamended soils, separation in multidimensional scaling plots was a function of differences in soil texture (clay, sand), SOC pools (particulate organic carbon (POC) and humus-C) and also EC. Cumulative CO –C emission from unamended and amended soils was related to soil properties by stepwise regression models. Cumulative CO –C emission was negatively correlated with EC in saline soils (  = 0.50,  〈 0.05) from both regions. In the unamended non-salt-affected soils, cumulative CO –C emission was significantly positively related to the content of POC for the Indian soils and negatively related to clay content for the Australian soils. In the wheat residue amended soils, cumulative CO –C emission had positive relationship with POC and humus-C but a negative correlation with EC for both Indian and Australian soils. SAR was negatively related (  = −0.66,  〈 0.05) with cumulative CO –C emission only for the unamended saline-sodic soils of Australia. Cumulative CO –C emission was significantly negatively correlated with bulk density in amended soils from both regions. The study showed that in salt-affected soils, EC was the main factor influencing for soil respiration but the content of POC, humus-C and clay were also influential with the magnitude of influence depending on whether the soils were salt affected or not. ► Soil respiration was measured in 120 soils from two salt-affected landscapes. ► Salinity (EC) was the main factor influencing the soil respiration. ► Soil respiration was negatively correlated with EC and clay content. ► Soil respiration was positively correlated with particulate organic carbon content.
    Keywords: Carbon Dioxide ; Salt-Affected Soil ; Stepwise Regression ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 7
    Language: English
    In: Soil biology & biochemistry, 2011, Vol.43, pp.667-674
    Description: Net carbon dioxide (CO2) emission from soils is controlled by the input rate of organic material and the rate of decomposition which in turn are affected by temperature, moisture and soil factors. While the relationships between CO2 emission and soil factors are well-studied in non-salt-affected soils, little is known about soil properties controlling CO2 emission from salt-affected soils. To close this knowledge gap, non-salt-affected and salt-affected soils (0–0.30 m) were collected from two agricultural regions: in India (irrigation induced salinity) and in Australia (salinity associated with ground water or non-ground water associated salinity). A subset (50 Indian and 70 Australian soils) covering the range of electrical conductivity (EC) and sodium adsorption ratio (SAR) in each region was used in a laboratory incubation experiment. The soils were left unamended or amended with mature wheat residues (2% w/w) and CO2 release was measured over 120 days at constant temperature and soil water content. Residues were added to overcome carbon limitation for soil respiration. For the unamended soils, separation in multidimensional scaling plots was a function of differences in soil texture (clay, sand), SOC pools (particulate organic carbon (POC) and humus-C) and also EC. Cumulative CO2–C emission from unamended and amended soils was related to soil properties by stepwise regression models. Cumulative CO2–C emission was negatively correlated with EC in saline soils (R2 = 0.50, p 〈 0.05) from both regions. In the unamended non-salt-affected soils, cumulative CO2–C emission was significantly positively related to the content of POC for the Indian soils and negatively related to clay content for the Australian soils. In the wheat residue amended soils, cumulative CO2–C emission had positive relationship with POC and humus-C but a negative correlation with EC for both Indian and Australian soils. SAR was negatively related (β = −0.66, p 〈 0.05) with cumulative CO2–C emission only for the unamended saline-sodic soils of Australia. Cumulative CO2–C emission was significantly negatively correlated with bulk density in amended soils from both regions. The study showed that in salt-affected soils, EC was the main factor influencing for soil respiration but the content of POC, humus-C and clay were also influential with the magnitude of influence depending on whether the soils were salt affected or not. ; Includes references ; p. 667-674.
    ISSN: 0038-0717
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 8
    Language: English
    In: Journal of Hazardous Materials, 05 May 2016, Vol.308, pp.430-439
    Description: Dissolved organic matter (DOM) in surface waters used for drinking purposes can vary markedly in character dependent on their sources within catchments. The character of DOM further influences the formation of disinfection by products when precursor DOM present in drinking water reacts with chlorine during disinfection. Here we report the development of models that describe the formation potential of trihalomethanes (THMFP) dependent on the character of DOM in waters from discrete catchments with specific land-use and soil textures. DOM was characterized based on UV absorbance at 254 nm, apparent molecular weight and relative abundances of protein-like and humic-like compounds. DOM character and Br concentration (up to 0.5 mg/L) were used as variables in models ( 〉 0.93) of THMFP, which ranged from 19 to 649 μg/L. Chloroform concentration (12 − 594 μg/L) and relative abundance (27 − 99%) were first modeled ( 〉 0.85) and from these, the abundances of bromodichloromethane and chlorodibromomethane estimated using power and exponential functions, respectively ( 〉 0.98). From these, the abundance of bromoform is calculated. The proposed model may be used in risk assessment of catchment factors on formation of trihalomethanes in drinking water, in context of treatment efficiency for removal of organic matter.
    Keywords: Catchment Runoff ; DOM Character ; Thmfp ; Engineering ; Law
    ISSN: 0304-3894
    E-ISSN: 1873-3336
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  • 9
    Language: English
    In: Soil Biology and Biochemistry, February 2012, Vol.45, pp.8-13
    Description: The individual effects of salinity and sodicity on organic matter dynamics are well known but less is known about their interactive effects. We conducted a laboratory incubation experiment to assess soil respiration and dissolved organic matter (DOM) dynamics in response to salinity and sodicity in two soils of different texture. Two non-saline non-sodic soils (a sand and a sandy clay loam) were leached 3–4 times with solutions containing different concentrations of NaCl and CaCl to reach almost identical electrical conductivity (EC ) in both soils (EC 0.5, 1.3, 2.5 and 4.0 dS m in the sand and EC 0.7, 1.4, 2.5 and 4.0 dS m in the sandy clay loam) combined with two sodium absorption ratios: SAR 〈 3 and 20. Finely ground wheat straw residue was added (20 g kg ) as substrate to stimulate microbial activity. Cumulative respiration was more strongly affected by EC than by SAR. It decreased by 8% at EC 1.3 and by 60% at EC 4.0 in the sand, whereas EC had no effect on respiration in the sandy clay loam. The apparent differential sensitivity to EC in the two soils can be explained by their different water content and therefore, different osmotic potential at the same EC. At almost similar osmotic potential: −2.92 MPa in sand (at EC 1.3) and −2.76 MPa in the sandy clay loam (at EC 4.0) the relative decrease in respiration was similar (8–9%). Sodicity had little effect on cumulative respiration in the soils, but DOC, DON and specific ultra-violet absorbance (SUVA) were significantly higher at SAR 20 than at SAR 〈 3 in combination with low EC in both soils (EC 0.5 in the sand and EC 0.7 and 1.4 in the sandy clay loam). Therefore, high SAR in combination with low EC is likely to increase the risk of DOC and DON leaching in the salt-affected soils, which may lead to further soil degradation. ► We studied the interactive effect of sodicity and salinity on soil respiration and DOM. ► Low EC combined with high SAR increases the risk of DOC and DON leaching in the soil. ► Soil texture and water content play an important role in determining the response of microbes to salt.
    Keywords: Dissolved Organic Matter ; Salinity ; Sodicity ; Soil Respiration ; Soil Texture ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 10
    Language: English
    In: Soil Research, 2012, Vol.50(5), p.424-435
    Description: Soils with strong texture-contrast between A and B horizons dominate the agricultural zones of the west and south of Australia. The B horizon is often sodic and of much finer texture than the A (or E) horizon above, and can have a bulk density as high as 2 g cm. When dry, these B horizons may severely impede the root growth of annual cereal crops. The objective of this study was to characterise the mineralogy and chemistry of fine pores at the interface of an E and a sodic B horizon of an Alfisol (Sodosol). Micro-X-ray fluorescence spectroscopy (μ-XRF) was used to locate the distribution of calcium (Ca), manganese (Mn), iron (Fe), zinc (Zn), and copper (Cu), and μ-X-ray absorption near edge structure (μ-XANES) spectroscopy or μ-X-ray absorption fine structure (μ-XAFS) spectroscopy to investigate speciation of Fe, Mn, Zn, and Cu around a pore. Both natural aggregates and thin sections were employed but measurements from thin sections were more useful because of the smaller thickness of the sample. The distribution maps showed that Ca was present in the pores but the other elements were not. Copper, Mn, and Zn were concentrated around the micropore. Manganese was always well correlated with Fe.
    Keywords: Fluorescence – Methods ; Fluorescence – Chemical Properties ; Phosphates – Methods ; Phosphates – Chemical Properties ; Sulfates – Methods ; Sulfates – Chemical Properties;
    ISSN: 1838-675X
    E-ISSN: 1838-6768
    E-ISSN: 1446568X
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