Agronomic benefits of enhanced weathering using basalt

What is it about?

Application of crushed silicate rocks (such as basalt) to agricultural soils can potentially improve crop health and thereby contribute to improving food security, as well as help mitigate climate change through natural sequestration of carbon dioxide. In this study we investigated whether there were any agronomic benefits or risks during the first growing season associated with the basalt amendment. The trial was the first of its kind in the United Kingdom, using an application rate determined by the maximum spreading rate of commercial lime spreaders (18.9 tonnes ha-1) and in a temperate climate. In the trial, the effect of basalt amendment was tested on two different cultivation types, namely conventional ploughing, as well as regenerative no-till/direct drill. At harvest we observed approximately 10 and 20 % increase in yield, for the ploughed and direct drill fields, respectively. The large difference in yield is primarily ascribed to a slightly higher soil pH in the basalt amended plots, which again may be explained by a calcium carbonate content in the basalt. We also observed a significantly higher tissue and grain potassium concentration, as well as a higher tissue calcium concentration. However, other circumstances may have contributed to the relatively high difference in yield. The 2022 growing season in NE England was unusually dry and it’s likely that the addition of silica from the basalt helped make the plants more resilient to drought conditions, although it could not be determined to which extent this was a driving factor. We did not detect any difference in the uptake of heavy metals and hence deem crops amended with this basalt safe for consumption.

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Photo by Jonathan Larson on Unsplash

Photo by Jonathan Larson on Unsplash

Why is it important?

For two reasons: Rolling out the application of crushed silicate rocks on agricultural fields is pivotal in the pursuit to scale land-based enhanced weathering and hence carbon dioxide sequestration. However, if carbon dioxide removal is the only benefit of spreading crushed silicate rock, farmers may not be inclined to do so in large numbers. Hence, it’s important to show that it’s safe to use and has agronomic benefits under different climatic conditions, soil types and crops. This study is one piece in that puzzle. A large proportion of the world's agricultural soil has been stripped for nutrients. Applying crushed silicate rock may help in restoring some of those nutrient pools.

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