Selenium Dynamics in Cereal Biofortification: Optimising Fertiliser Strategies and Assessing Residual Fate

Selenium (Se) is an essential micronutrient for humans and animals and hence, a low intake of Se in the diet can lead to health problems. The application of Se fertilisers to staple crops, a process called agronomic biofortification, can effectively improve humans’ Se intake levels. The overarching aim of this study was to develop improved strategies for Se biofortification through an enhanced understanding of Se dynamics in arable systems. A pot trial was set up to investigate whether the application of 3.33 μg kg⁻¹ of Se (equivalent to 10 g ha⁻¹) to wheat can be made more efficient by its co-application with macronutrient carriers, either to the soil or to the leaves. In the soil, Se was applied either on its own (selenate only) or as a granular, Se-enriched macronutrient fertiliser supplying nitrogen, phosphorus, potassium or sulphur. Selenium was also applied to leaves at head emergence with, or without, 2% w/v N fertilisers. With grain Se concentrations varying from 0.13–0.84 mg kg⁻¹, soil application of selenate-only was 2–15 times more effective than granular Se-enriched macronutrient fertilisers in raising grain Se concentrations. Foliar Se application was superior to soil-applied Se treatments in increasing grain Se levels, especially when foliar Se was co-applied with an N carrier. Under foliar Se+N treatments, grains accumulated twice as much Se as those fertilised with foliar Se only, the majority of which was highly bioavailable (selenomethionine). This study was perhaps the first to show the efficiency of co-applying foliar Se with N in improving Se uptake and recovery in wheat. Such findings support the hypothesis that the efficacy of existing agronomic practices for Se biofortification can be improved through the use of macronutrient carriers, which could potentially reduce costs associated with fertiliser application and management. The second experiment shed light on the residual fate of Se in different soils over a 300-day period, using both chemical and biological assays to estimate Se availability. Eight soils varying in physicochemical properties were spiked with 0.5 mg kg⁻¹ Se in the form of sodium selenate and incubated at 25°C for different periods (1, 123 30, 60, 90 and 300 d). At the end of the ageing period, soil Se was fractionated by sequential extraction procedures into soluble, adsorbed and organically-bound Se fractions. Simultaneously, a pot trial was set up where wheat was grown in the Se-aged soils for six weeks. A rapid decline in Se solubility (> 50% within 24 h) was observed in the Oxisol, probably due to its high mineral oxides and clay contents. Over time, calcareous soils showed more pronounced Se ageing than non-calcareous soils as solubility reached 0 at 300 d, probably due to the fixation of Se onto calcite surfaces. In highly calcareous soils, plant Se concentrations decreased from 37 mg kg⁻¹ to 100 days in plants grown in non-calcareous soils. The soluble Se fraction at specific ageing times was best represented by a reversible first order model, and was primarily influenced by soil pH. Understanding how added Se behaves in soils over time could be used to make more informed decisions about the rate and frequency of Se fertiliser application in agronomic biofortification programs. The third experiment was undertaken to investigate time-dependent changes in the uptake and partitioning of Se in wheat. It also investigated whether the uptake efficiency of Se in wheat was influenced by timing of fertiliser application. In a pot trial, 3.33 μg kg⁻¹ Se was as ⁷⁷Se-enriched sodium selenate (Sefert) to wheat at two growth stages – stem elongation (GS1) and heading stage (GS2), by two methods – soil and foliar (foliar Se on its own and foliar Se + 2% urea-N). Wheat was harvested 3, 10 and 17 d and 3, 10, and 34 d after Se application at GS1 and GS2, respectively. Only foliar treatments were effective in raising grain Se concentrations (> 0.25 mg kg⁻¹) above the target level of 0.1 mg kg⁻¹ for biofortification. However, the poor efficiency of the soil-applied Se fertiliser was speculated to be predominantly caused by accidental leaching of the applied Se from the free-draining pots. This study showed that, when applied at an early growth stage, foliar Se with N improved the uptake of Se into wheat, compared to foliar application of Se on its own. At the later growth stage, N inclusion to foliar Se fertilisers significantly increased grain Se concentration in the grain (0.32 mg kg⁻¹) compared to foliar Se on its own (0.26 mg kg⁻¹), the majority of which was highly bioavailable. Speciation analysis data of the foliar-treated leaves suggested that the presence of N in foliar solutions improved the assimilation and translocation of organic Se compounds. Practical knowledge gained about the optimisation of Se fertiliser formulation, method and timing of application will be of importance in refining biofortification programs across different soil and climatic regimes.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 202

Using 77Se-Labelled Foliar Fertilisers to Determine How Se Transfers Within Wheat Over Time

Foliar selenium (Se) fertilisation has been shown to be more efficient than soil-applied fertilisation, but the dynamics of absorption and translocation have not yet been explored. An experiment was undertaken to investigate time-dependent changes in the absorption, transformation, and distribution of Se in wheat when 77Se-enriched sodium selenate (Sefert) was applied to the leaves at a rate of 3.33 μg Se per kg soil (equivalent to 10 g ha−1) and two growth stages, namely stem elongation, Zadoks stage 31/32 (GS1), and heading stage, Zadoks stage 57 (GS2). The effect of urea inclusion in foliar Se fertilisers on the penetration rates of Se was also investigated. Wheat was harvested at 3, 10, and 17 days and 3, 10, and 34 days after Se applications at GS1 and GS2, respectively. Applying foliar Se, irrespective of the formulation, brought grain Se concentration to a level high enough to be considered adequate for biofortification. Inclusion of N in the foliar Se solution applied at an early growth stage increased recoveries in the plants, likely due to improved absorption of applied Se through the young leaves. At a later growth stage, the inclusion of N in foliar Se solutions was also beneficial as it improved the assimilation of applied inorganic Se into bioavailable selenomethionine, which was then rapidly translocated to the grain. The practical knowledge gained about the optimisation of Se fertiliser formulation, method, and timing of application will be of importance in refining biofortification programs across different climatic regimes

Effect of soil properties on time-dependent fixation (ageing) of selenate

© 2020 Elsevier B.V. Previous biofortification studies have established that the residual effect of added selenium (Se) fertilisers on second-season crops is minimal. To explore the fate of exogenous Se in soil, chemical and biological methods were employed to assess the change in Se bioavailability with time. Eight soils varying in physicochemical properties were spiked with sodium selenate (0.5 mg kg−1 Se) and incubated at 25 °C for different periods (1, 30, 60, 90 and 300 d). At the end of the incubation, soil Se was fractionated by a sequential extraction procedure into ‘soluble’, ‘adsorbed’ and ‘organically-bound’ Se fractions. Simultaneously, wheat was grown in the Se-aged soils, under controlled conditions for six weeks, and uptake was determined. A general decrease in Se solubility over time was observed, but the rate of decrease varied depending on soil type. A reversible first order model fitted the Se ageing kinetics well, except in an Oxisol. The most pronounced ageing was observed in calcareous soils. Concentrations of Se in the shoots of wheat grown in freshly spiked soils ranged from 71.8 ± 17.5 mg kg−1 in calcareous soils to 110 ± 31.6 mg kg−1 in non-calcareous, low-OM soils. With ageing, shoot Se concentrations decreased t

Improving the efficacy of selenium fertilizers for wheat biofortification

© 2019, The Author(s). Increasing the selenium (Se) concentration of staple crops by fertilization is a valuable pathway to increase Se in the human diet, thus preventing Se deficiency. A pot trial was set up to investigate whether the application of 3.33 µg kg−1 of Se (equivalent to 10 g ha−1) to wheat can be made more efficient by its co-application with macronutrient carriers, either to the soil or to the leaves. In the soil, Se was applied either on its own (selenate only) or as a granular, Se-enriched macronutrient fertilizer supplying nitrogen, phosphorus, potassium or sulfur. Selenium was also applied to leaves at head emergence with, or without, 2% w/v N fertilizers. With grain Se concentrations varying from 0.13–0.84 mg kg−1, soil application of selenate-only was 2–15 times more effective than granular Se-enriched macronutrient fertilizers in raising grain Se concentrations. Co-application of foliar Se with an N carrier doubled the Se concentration in wheat grains compared to the application of foliar Se on its own, the majority of which was in the highly bioavailable selenomethionine fraction. Results from this study demonstrate the possibility of improving the efficacy of Se fertilizers, which could enrich crops with Se without additional application costs in the field

Author Correction: Improving the efficacy of selenium fertilizers for wheat biofortification

Correction to: Scientific Reports https://doi.org/10.1038/s41598-019-55914-0, published online 20 December 201

Selenium dynamics in cereal biofortification: optimising fertiliser strategies and assessing residual fate

Selenium (Se) is an essential micronutrient for humans and animals and hence, a low intake of Se in the diet can lead to health problems. The application of Se fertilisers to staple crops, a process called agronomic biofortification, can effectively improve humans’ Se intake levels. The overarching aim of this study was to develop improved strategies for Se biofortification through an enhanced understanding of Se dynamics in arable systems. A pot trial was set up to investigate whether the application of 3.33 µg kg-1 of Se (equivalent to 10 g ha-1) to wheat can be made more efficient by its co-application with macronutrient carriers, either to the soil or to the leaves. In the soil, Se was applied either on its own (selenate only) or as a granular, Se-enriched macronutrient fertiliser supplying nitrogen, phosphorus, potassium or sulphur. Selenium was also applied to leaves at head emergence with, or without, 2% w/v N fertilisers. With grain Se concentrations varying from 0.13–0.84 mg kg-1, soil application of selenate-only was 2–15 times more effective than granular Se-enriched macronutrient fertilisers in raising grain Se concentrations. Foliar Se application was superior to soil-applied Se treatments in increasing grain Se levels, especially when foliar Se was co-applied with an N carrier. Under foliar Se+N treatments, grains accumulated twice as much Se as those fertilised with foliar Se only, the majority of which was highly bioavailable (selenomethionine). This study was perhaps the first to show the efficiency of co applying foliar Se with N in improving Se uptake and recovery in wheat. Such findings support the hypothesis that the efficacy of existing agronomic practices for Se biofortification can be improved through the use of macronutrient carriers, which could potentially reduce costs associated with fertiliser application and management. The second experiment shed light on the residual fate of Se in different soils over a 300-day period, using both chemical and biological assays to estimate Se availability. Eight soils varying in physicochemical properties were spiked with 0.5 mg kg -1 Se in the form of sodium selenate and incubated at 25°C for different periods (1, 30, 60, 90 and 300 d). At the end of the ageing period, soil Se was fractionated by sequential extraction procedures into soluble, adsorbed and organically-bound Se fractions. Simultaneously, a pot trial was set up where wheat was grown in the Seaged soils for six weeks. A rapid decline in Se solubility (> 50% within 24 h) was observed in the Oxisol, probably due to its high mineral oxides and clay contents. Over time, calcareous soils showed more pronounced Se ageing than non-calcareous soils as solubility reached 0 at 300 d, probably due to the fixation of Se onto calcite surfaces. In highly calcareous soils, plant Se concentrations decreased from 37 mg kg-1 to 100 days in plants grown in non-calcareous soils. The soluble Se fraction at specific ageing times was best represented by a reversible first order model, and was primarily influenced by soil pH. Understanding how added Se behaves in soils over time could be used to make more informed decisions about the rate and frequency of Se fertiliser application in agronomic biofortification programs. The third experiment was undertaken to investigate time-dependent changes in the uptake and partitioning of Se in wheat. It also investigated whether the uptake efficiency of Se in wheat was influenced by timing of fertiliser application. In a pot trial, 3.33 µg kg-1 Se was as 77Se-enriched sodium selenate (Sefert) to wheat at two growth stages – stem elongation (GS1) and heading stage (GS2), by two methods – soil and foliar (foliar Se on its own and foliar Se + 2% urea-N). Wheat was harvested 3, 10 and 17 d and 3, 10, and 34 d after Se application at GS1 and GS2, respectively. Only foliar treatments were effective in raising grain Se concentrations (> 0.25 mg kg-1 ) above the 6 target level of 0.1 mg kg-1 for biofortification. However, the poor efficiency of the soil applied Se fertiliser was speculated to be predominantly caused by accidental leaching of the applied Se from the free-draining pots. This study showed that, when applied at an early growth stage, foliar Se with N improved the uptake of Se into wheat, compared to foliar application of Se on its own. At the later growth stage, N inclusion to foliar Se fertilisers significantly increased grain Se concentration in the grain (0.32 mg kg-1) compared to foliar Se on its own (0.26 mg kg-1), the majority of which was highly bioavailable. Speciation analysis data of the foliar-treated leaves suggested that the presence of N in foliar solutions improved the assimilation and translocation of organic Se compounds. Practical knowledge gained about the optimisation of Se fertiliser formulation, method and timing of application will be of importance in refining biofortification programs across different soil and climatic regimes

Selenium dynamics in cereal biofortification: optimising fertiliser strategies and assessing residual fate

Selenium (Se) is an essential micronutrient for humans and animals and hence, a low intake of Se in the diet can lead to health problems. The application of Se fertilisers to staple crops, a process called agronomic biofortification, can effectively improve humans’ Se intake levels. The overarching aim of this study was to develop improved strategies for Se biofortification through an enhanced understanding of Se dynamics in arable systems. A pot trial was set up to investigate whether the application of 3.33 µg kg-1 of Se (equivalent to 10 g ha-1) to wheat can be made more efficient by its co-application with macronutrient carriers, either to the soil or to the leaves. In the soil, Se was applied either on its own (selenate only) or as a granular, Se-enriched macronutrient fertiliser supplying nitrogen, phosphorus, potassium or sulphur. Selenium was also applied to leaves at head emergence with, or without, 2% w/v N fertilisers. With grain Se concentrations varying from 0.13–0.84 mg kg-1, soil application of selenate-only was 2–15 times more effective than granular Se-enriched macronutrient fertilisers in raising grain Se concentrations. Foliar Se application was superior to soil-applied Se treatments in increasing grain Se levels, especially when foliar Se was co-applied with an N carrier. Under foliar Se+N treatments, grains accumulated twice as much Se as those fertilised with foliar Se only, the majority of which was highly bioavailable (selenomethionine). This study was perhaps the first to show the efficiency of co applying foliar Se with N in improving Se uptake and recovery in wheat. Such findings support the hypothesis that the efficacy of existing agronomic practices for Se biofortification can be improved through the use of macronutrient carriers, which could potentially reduce costs associated with fertiliser application and management. The second experiment shed light on the residual fate of Se in different soils over a 300-day period, using both chemical and biological assays to estimate Se availability. Eight soils varying in physicochemical properties were spiked with 0.5 mg kg -1 Se in the form of sodium selenate and incubated at 25°C for different periods (1, 30, 60, 90 and 300 d). At the end of the ageing period, soil Se was fractionated by sequential extraction procedures into soluble, adsorbed and organically-bound Se fractions. Simultaneously, a pot trial was set up where wheat was grown in the Seaged soils for six weeks. A rapid decline in Se solubility (> 50% within 24 h) was observed in the Oxisol, probably due to its high mineral oxides and clay contents. Over time, calcareous soils showed more pronounced Se ageing than non-calcareous soils as solubility reached 0 at 300 d, probably due to the fixation of Se onto calcite surfaces. In highly calcareous soils, plant Se concentrations decreased from 37 mg kg-1 to 100 days in plants grown in non-calcareous soils. The soluble Se fraction at specific ageing times was best represented by a reversible first order model, and was primarily influenced by soil pH. Understanding how added Se behaves in soils over time could be used to make more informed decisions about the rate and frequency of Se fertiliser application in agronomic biofortification programs. The third experiment was undertaken to investigate time-dependent changes in the uptake and partitioning of Se in wheat. It also investigated whether the uptake efficiency of Se in wheat was influenced by timing of fertiliser application. In a pot trial, 3.33 µg kg-1 Se was as 77Se-enriched sodium selenate (Sefert) to wheat at two growth stages – stem elongation (GS1) and heading stage (GS2), by two methods – soil and foliar (foliar Se on its own and foliar Se + 2% urea-N). Wheat was harvested 3, 10 and 17 d and 3, 10, and 34 d after Se application at GS1 and GS2, respectively. Only foliar treatments were effective in raising grain Se concentrations (> 0.25 mg kg-1 ) above the 6 target level of 0.1 mg kg-1 for biofortification. However, the poor efficiency of the soil applied Se fertiliser was speculated to be predominantly caused by accidental leaching of the applied Se from the free-draining pots. This study showed that, when applied at an early growth stage, foliar Se with N improved the uptake of Se into wheat, compared to foliar application of Se on its own. At the later growth stage, N inclusion to foliar Se fertilisers significantly increased grain Se concentration in the grain (0.32 mg kg-1) compared to foliar Se on its own (0.26 mg kg-1), the majority of which was highly bioavailable. Speciation analysis data of the foliar-treated leaves suggested that the presence of N in foliar solutions improved the assimilation and translocation of organic Se compounds. Practical knowledge gained about the optimisation of Se fertiliser formulation, method and timing of application will be of importance in refining biofortification programs across different soil and climatic regimes

Assessing the Usefulness of Mobile Apps for Noise Management in Occupational Health and Safety: Quantitative Measurement and Expert Elicitation Study

Abstract BackgroundOverexposure to occupational noise can lead to hearing loss. Occupational noise mapping is conventionally performed with a calibrated sound level meter (SLM). With the rise of mobile apps, there is a growing number of SLM apps available on mobile phones. However, few studies have evaluated such apps for accuracy and usefulness to guide those with occupational noise detection needs in selecting a quality app. ObjectiveThe purpose of this study was to evaluate the accuracy and usefulness of SLM mobile apps to guide workplace health and safety professionals in determining these apps’ suitability for assessing occupational noise exposure. MethodsThe following three iOS apps were assessed: the NIOSH (National Institute for Occupational Safety and Health) Sound Level Meter, Decibel X, and SoundMeter X apps. The selected apps were evaluated for their accuracy in measuring sound levels in low-, moderate-, and high-noise settings within both simulated environments and real-world environments by comparing them to a conventional SLM. The usefulness of the apps was then assessed by occupational health specialists using the Mobile App Rating Scale (MARS). ResultsThe NIOSH Sound Level Meter app accurately measured noise across a range of sound levels in both simulated settings and real-world settings. However, considerable variation was observed between readings. In comparison, the Decibel X and SoundMeter X apps showed more consistent readings but consistently underestimated noise levels, suggesting that they may pose a risk for workers. Nevertheless, none of the differences in sound measurements between the three apps and the conventional SLM were statistically significant (NIOSH Sound Level Meter: PPP ConclusionsUnder the conditions of this study, the NIOSH Sound Level Meter app had equivalent accuracy to the calibrated SLM and a degree of usefulness according to the MARS. This suggests that the NIOSH Sound Level Meter app may be suitable for mapping noise levels as part of a monitoring strategy in workplaces. However, it is important to understand its limitations. Mobile apps should complement but not replace conventional SLMs when trying to assess occupational noise exposure risk. Our outcomes also suggest that the MARS tool may have limited applicability to measurement-based apps and may be more suited to information-based apps that collect, record, and store information

Rapid Assessment of Oxidative Damage Potential: A Comparative Study of Engineered Stone Dusts Using a Deoxyguanosine Assay

The popularity of engineered stone (ES) has been associated with a global increase in occupational lung disease in workers exposed to respirable dust during the fabrication of benchtops and other ES products. In this study, the reactivity and subsequent oxidative reduction potential of freshly generated ES dusts were evaluated by (i) comparing different engineered and natural stones, (ii) comparing settled and respirable stone dust fractions and (iii) assessing the effect of ageing on the reactivity of freshly generated stone dust. An established cell-free deoxyguanosine hydroxylation assay was used to assess the potential for oxidative DNA damage. ES dust exhibited a higher relative reactivity than two of the three natural stones tested. Respirable dust fractions were found to be significantly more reactive than their corresponding settled fraction (ANOVA, p < 0.05) across all stone types and samples. However, settled dust still displayed high relative reactivity. The lower reactivity of the settled dust was not due to decay in reactivity of the respirable dust when it settled but rather a result of the admixture of larger nonrespirable particles. No significant change in respirable dust reactivity was observed for three ES samples over a 21-day time period, whereas a significant decrease in reactivity was observed in the natural stone studied. This study has practical implications for dust control and housekeeping in industry, risk assessment and hazard management

Prohibition of engineered stone: Literature review and gap analysis

In May 2023, Safe Work Australia commissioned the University of Adelaide to undertake a literature review and gap analysis of the scientific evidence to inform recommendations related to the three options for prohibition on the use of engineered stone in Australia.The report was independently peer reviewed by an expert from Monash University in June 2023.The final report was provided to Safe Work Australia in July 2023 and was used to inform the development of the Decision Regulation Impact Statement: Prohibition on the use of Engineered Stone.</p