21 April 2020

Rock dust helps soils store carbon and boosts crop yields, research shows

Simple method could help mitigate the climate crisis, improve food and soil security, and cut farmers’ costs

Ploughed soil in a field of crops
Ploughed soil in a field of crops

  • Adding crushed basalt to soils in the lab increases their potential to store four times more carbon dioxide, according to University of Sheffield study
  • Rock dust increases yields of cereal crops by up to 20 per cent and could reduce the need for fertilisers and agricultural lime
  • Simple method could help mitigate the climate crisis, improve food and soil security, and cut farmers’ costs

Adding basalt rock dust to farmers’ fields could help soils to store four times more carbon dioxide (CO2) and increase crop yields, according to new research by academics at the University of Sheffield.

The study, published in Global Change Biology, found that adding the dust increased yields of the cereal crop sorghum by as much as 20 per cent. A single application of basalt enabled the soil to absorb between two and four tonnes of damaging CO2 over five years – four times more than untreated soils – suggesting the method also has potential to mitigate the climate crisis.

Removing greenhouse gases from the atmosphere, along with slashing emissions from fossil fuels, is crucial to meeting the Paris Agreement target of limiting global temperature rises to 1.5C above pre-industrial levels. According to the UN’s Intergovernmental Panel on Climate Change, cropland and grassland soil has the potential to store up to 8.6 gigatonnes of CO2 per year – equivalent to almost 1.5 times the annual emissions of the United States.

The team of scientists at the University of Sheffield’s Leverhulme Centre for Climate Change Mitigation, affiliated to the Institutes for Sustainable Food and Energy, used the University’s world-class controlled environment facility to conduct the experiments. 

Basalt contains at least six nutrients that are essential for plant growth and very low concentrations of toxins. The study found adding it to the soil increased yields of sorghum - the world’s fifth most important crop for food and animal feed – by up to 20 per cent. This was achieved without the use of phosphate and potassium fertilisers – making the method suitable for organic farmers.

The basalt also helped to mitigate soil acidification. This is usually treated with agricultural lime – the production of which accounts for two per cent of agricultural greenhouse gas emissions in the United States.

The mining, grinding, distributing and spreading of the basalt could effectively reduce the carbon removal rates by 10-30 per cent – but the research shows this would still leave the technique as effective as other land management practices designed to address climate breakdown.

Our results suggest adding basalt rock dust to fields could help our soils to soak up four times more damaging carbon dioxide from the atmosphere. This simple technique could also reduce the need for fertilisers and agricultural lime – cutting carbon emissions and lowering costs for farmers. Our study is a first step towards rolling out this climate mitigation method across the cereal fields of Europe and North America. The benefits for our climate, food and soil security could be significant.

Michael Kelland

PhD Researcher at the University of Sheffield and lead author of the study.

These results from controlled environment studies are an important first step towards understanding how a carbon dioxide removal strategy called enhanced weathering might work with basalt, an abundant silicate rock, and croplands. Our study used a relatively high application rate of basalt as a ‘proof-of-concept’ test for this carbon dioxide removal approach. Our encouraging findings emphasise the need for large-scale field trials with this rock fertiliser.

Professor David Beerling

Director of the Leverhulme Centre for Climate Change Mitigation at the University of Sheffield and co-author of the study

Contact 

Sophie Armour, Media & PR Officer at the University of Sheffield: 07751 400 287 / 0114 222 3687 / sophie.armour@sheffield.ac.uk

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