Enhanced rock weathering -- a nature-based carbon dioxide removal process that accelerates natural weathering -- results in significantly higher first year crop yields, improved soil pH, and higher nutrient uptake, according to a new scientific paper, released in PLOS ONE, a peer-reviewed open access mega journal published by the Public Library of Science since 2006.
Enhanced rock weathering (ERW) involves spreading finely crushed silicate rock such as basalt on agricultural land. It is a scalable and permanent climate technology with the potential to sequester gigatonnes of carbon dioxide from the atmosphere. Co-authored by sscientist at UNDO, a leading enhanced rock weathering project developer, and Newcastle University, the peer-reviewed publication is the latest enhanced rock weathering (ERW) study assessing the impact on crops in a temperate climate.
Dr XinRan Liu, Head of Science and Research at UNDO and co-author of the paper, commented: “Nutrient limitations in agricultural soils are a major concern for farmers in relation to sustaining and increasing crop yields. This latest study highlights how the spreading of basalt rock on farmland can lead to higher crop yields and can be effective in a temperate climate. This research demonstrates the potential for enhanced rock weathering to contribute to improved farmer livelihoods and food production, whilst also removing CO2 from the atmosphere.”
The results from the ongoing trial’s first year demonstrate that the crop yield was on average 15% higher (9.3% and 20.5% between ploughed and direct drill amended plots respectively) across two different cultivation techniques.
The trial results also showed a stabilising effect on the soil pH, with the soil pH being on average 0.2 and 0.29 pH units higher in the basalt-amended plots, compared to the control plots. This change is a result of alkaline products generated as the rock minerals dissolve. The effect of silicate mineral dissolution on the soil pH could represent an attractive agronomic benefit for farmers as an elevated soil pH allows crops to access more nutrients in the soil.
Basalt rock is rich in minerals that slowly release nutrients during dissolution. These nutrients act as a natural soil amendment and are essential for plant growth. The study found higher nutrient concentrations in the crops grown in the basalt-amended soil, including tissue calcium, grain and tissue potassium, suggesting that ERW can boost nutrient availability for plants and, as a result, may improve crop yield.
Taking account of the unusually dry growing season conditions in 2022, these findings indicate that basalt amendment could enhance productivity and crop yields, contributing to more sustainable and resilient food production systems in the face of future changes in growing season weather as a result of global warming.
Professor David Manning, Professor of Soil Science, Newcastle University, and co-author of the paper, commented: “The results of this trial give further scientific credibility for enhanced rock weathering and greatly improve its value proposition to farmers. Newcastle University is pleased to partner with UNDO. Our joint research into the co-benefits for farmers of basalt amendment is helping to pave the way for the widespread adoption of enhanced rock weathering in the agricultural community.”
The trial results also show no additional toxic elements taken up by crops in the plots where basalt had been spread. There was no negative impact on the natural environment in this trial, which indicates the food produced from it is safe for consumption. UNDO’s basalt has been approved for use in organic farming systems by respected certification bodies such as the Soil Association.
“Use of enhanced rock weathering to remove carbon dioxide and naturally enhance soil health represents a potential win-win for farmers and climate as this technology is able to capture carbon dioxide while simultaneously supplying some of the key nutrients that crops require for successful growth. By using locally-sourced rocks, rather than inputs (e.g. fertilisers) obtained from overseas, supply chains are also shortened, further reducing the overall carbon footprint of food production.
“Crucially, enhanced rock weathering is a technology that can be readily adopted by the agricultural sector because it does not require farmers to invest in new equipment, technology or training, but simply utilises the existing equipment and infrastructure for spreading fertiliser or other soil amendments.”
The authors of the paper hope that the agronomic co-benefits of enhanced rock weathering will further incentivise farmers across the UK and worldwide to take advantage of this nature-based carbon removal solution.
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Enhanced rock weathering is the acceleration of natural rock weathering, whereby the CO₂ in rainwater interacts with silicate minerals in e.g. basalt, mineralises and is safely stored as solid carbon for hundreds of thousands of years. To speed up this natural geological process, UNDO spreads crushed basalt rock, a by-product of the mining and quarrying industry, across agricultural land. As this mineral-rich rock breaks down, these trial results confirm that it releases nutrients, raises and stabilises soil pH, and increases crop yield.The IPCC 2022 Mitigation of Climate Change report suggests that enhanced rock weathering could remove up to 4 billion tonnes of CO2 per year - equivalent to 40% of CO2 removal targets.
The trial was conducted during the 2022 growing season on the Newcastle University-managed Nafferton Farm, located in north-east England, UK, to assess the impact of basalt amendment on spring oats crops across two different cultivation types. Control plots that had not been spread with crushed basalt rock were established and monitored as a point of comparison.
The trial design consisted of 16 plots in four blocks. Each block included two different field management practices (direct drill and ploughed) and nested within each cultivation type was one basalt amended and one control plot. The crop grown in 2022 was spring oats.
Tissue samples were collected at the peak of the growing season. Grain samples were collected during harvest. Soil samples were collected 256 days after the basalt was applied.
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