Soil microbes control how much arsenic ends up in rice
Soil Health
If you grow rice or buy it at the store, the microbes living in flooded paddy soil are quietly deciding how much arsenic and cadmium end up on your plate, and this research shows which farming tweaks can turn that dial down.
Rice grows in flooded fields, and that soggy soil is packed with microbes that can turn naturally occurring arsenic into different chemical forms, some of which the rice plant absorbs more easily than others. This research tracked those microbes across rice paddies in Bangladesh, East Africa, Sri Lanka, Vietnam, and Southern Europe, and found that certain fertilizers (like pig manure) make arsenic worse, while a mix of compost, rice husk ash, and smart fertilizer timing can actually shrink arsenic levels in the grain.
Key Findings
Methylated arsenic species (MMA, DMA) peaked during grain-filling and correlated with anaerobic microbes like methanogens and sulfate-reducing bacteria, while pig slurry boosted Firmicutes abundance and increased arsenic mobilization
Across global field sites, arsenic was highest in Vietnam and Southern Europe (linked to sulfur-oxidizing and sulfate-reducing bacteria plus methanogenic archaea), while Sri Lanka showed elevated cadmium linked to fungi and aerobic bacteria
In Bangladesh's topsoil-depleted, erosion-prone fields, combining soil test-based fertilizer with organic amendments (compost, rice husk ash, green manure) improved soil fertility and cut inorganic arsenic in porewater and grain, especially during the Boro season
chevron_right Technical Summary
A new thesis traces how soil microbes drive arsenic and cadmium buildup in rice grains, and shows that targeted fertilizer and compost strategies can reduce toxic arsenic in both soil water and the rice we eat.
Abstract Preview
Original paper
Rice paddy microbiology and grain mineral nutrition
Rice production faces significant arsenic and cadmium contamination threats, posing global risks to food safety and agricultural sustainability. This thesis investigates interactions between soil c...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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