Abstract
Selenium (Se) is an essential micronutrient for humans and other animals. Its deficiency in food can cause cancer, cardiovascular and other diseases in humans. In high concentrations, Se is toxic for humans, animals and plants. The bioavailability of Se in soils largely determines the Se level in food, feed and therefore throughout the nutrition chain. Selenium content in soils is highly variable. The objective of this study was to quantify effects of applying Se to limed and unlimed soils using soils that were inherently deficient in Se. Application rates ranging from 0 to 10 g ha-1 did not increase available soil Se beyond the level of 0.121 mg Se kg-1 obtained after lime had been added at the rate of 5 t ha-1. The differences in extractable Se due to combined Se and lime applications were statistically significant (P <0.05). This study has reinforced the need to avoid soil management practices that increase available soil Se to levels that are potentially toxic to humans, animals and plants. Key words: Soil acidity, liming effects, extractable selenium, adsorption, toxicity.
Highlights
IntroductionSelenium is a component of glutathione peroxidase, which detoxifies peroxides as well as superoxide and hydroxide free-radicals, preventing damage to tissues, especially cell membranes (Spallholz, 2001; Rayman, 2000)
Selenium is an essential trace element to humans and other animals
In Malawi, selenium intake is low (20 to 30 μg Se per day), compared with 50 to 70 μg Se per person recommended in most countries as dietary reference intake (DRI) (Chilimba et al, 2011)
Summary
Selenium is a component of glutathione peroxidase, which detoxifies peroxides as well as superoxide and hydroxide free-radicals, preventing damage to tissues, especially cell membranes (Spallholz, 2001; Rayman, 2000). This trace element complements the function of vitamin E and has other functions, including participation in the mitochondrial electron transport system in muscles. For 20 kg child (aged six) who ingests 74% of the adult dietary intake (Environment Agency, 2009c), the estimated daily oral intake would be 1.3 μg g-1 bw day-1. In Malawi, selenium intake is low (20 to 30 μg Se per day), compared with 50 to 70 μg Se per person recommended in most countries as dietary reference intake (DRI) (Chilimba et al, 2011)
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