Co-benefits for agriculture of enhanced rock weathering as a carbon dioxide removal strategy

Enhanced weathering of crushed basalt applied to agriculture fields is one important tool for drawing down carbon dioxide in the atmosphere to keep warming less than 1.5oC. As the crushed rock is weathered by carbonic acid, formed by combining atmospheric carbon dioxide and water, bicarbonate ions are produced creating a pump, moving carbon from the atmosphere to ground water and eventually to oceans. In large scale field trial in central Illinois, we explored potential co-benefits of the annual application of basalt to a maize-soybean ecosystem. Rapid and sustained increases in soil pH occurred soon after basalt application. The increase in pH altered soil P and N cycling, causing an 11-16% increase in grain yield in maize/soy and an increase in grain N concentration. The liberation of Si during weathering also increased its concentration (from ~24 to ~47 mg/L in soybeans in 2019) in plant tissues, decreasing palatability to insect herbivores. In addition to reducing carbon dioxide and nitrous oxide emissions from intensive row crop agriculture, basalt application may reduce fertilizer demand and reduce the need for applying agricultural lime.