Source of Selenium
Se
Source of Selenium?
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The natural source of Se is through the food.
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The food Se level is dependant on the soil Se status.
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Highly leached soils in high rainfall areas & those derived from Se poor parent material are likely to be Se poor.
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In SA, soils along the Eastern seaboard are prime candidates as well as intensively farmed soils under irrigation.
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Soil Se levels <300 ppb would be severely deficient.
Factors affecting Selenium uptake
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The uptake of Se by grasses is generally good & is more efficient than legumes.
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Most fodder crops (roots, grains, forage) take up similar levels of Se to grasses (ryegrass, Eragrostis). Uptake in maize silage is similar to ryegrass.
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Selenium will leach under heavy precipitation (heavy rain, irrigation).
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Some forms of lime interfere with the uptake of selenium.
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High crop yields will dilute the Se content (e.g. spring flush).
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Recycled Se is bound-up in the soil by the OM & by the soil colloids & is rendered unavailable to the plant.