Liming and selenium application impact on plant available selenium in selected soils of Malawi

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.