Fighting selenium deficiency

Approximately 1 billion people worldwide suffer from a deficiency of selenium, an essential nutrient for liver, heart, thyroid and immune function. Since selenium deficiency is prevalent in South-East Asia, researchers are studying the best biofortification for lowland rice production.

In a study funded by the Commonwealth Government of Australia, the soil retention of three types of selenium was tested. The research appears in the Soil Science Society of America Journal.

According to researchers at the University of Adelaide, biofortification of rice with selenium is most easily performed by adding selenium-enriched fertilisers to rice either as a spray or as a fertiliser amendment to the soil. Lowland rice soil is usually flooded, unlike upland rice soil which served as the control variable in the experiment.

Lakmalie Premarathna, University of Adelaide, and the author of the paper, measured the availability of selenium in rice crops when a pre-plant fertiliser was added.

“Elemental selenium is unsuitable as a pre-plant fertiliser for lowland rice as it is not readily oxidised in the soil to soluble forms that crops can absorb,” she says. Selenite and selenate were also ruled out because they became poorly available forms of selenium when subjected to flooding.

Adding selenium in foliar sprays is more labour intensive than adding selenium-enriched fertilisers to the soils at planting, but the fate of various forms of fertiliser selenium in flooded (lowland) rice soils is not well understood, according to Premarathna.

However, lowland rice paddies are drained a few weeks before harvesting. She suspects that levels of selenium could potentially return to suitable levels for crop absorption. Research is ongoing at the University of Adelaide to find the best biofortification for lowland rice production systems.