A Starry Solution: Using Rock Dust to Remineralise Soil

If you’ve ever undertaken a volunteer programme abroad or spent time working on a farm, then you’re likely to have developed an appreciation for the importance of soil. One of the central pillars of WorkingAbroad is nature conservation, and soil – the seemingly dull but yet secretly fascinating substance – lies at the heart of this. 

At the recent 22nd World Congress of Soil Science in Glasgow, held between July and August of this year, Brazilian soil professors David A.C. Manning and Suzi Huff Theodorob spoke about a novel method for remineralising soil that involves the use of silicate rock dust. A reminder of the incredibly interconnected nature of our planet, this method implies that that which was once the stuff of stars could in fact solve one of the most common problems faced by farmers around the world today.

The use of rock dust to remineralise soil is not only cheaper than the application of modern fertilisers but also has numerous ecological, social and even political benefits. This technique encourages local resources in farming, combats farming inequality, reduces farmers’ dependency on imported fertilisers and addresses several global sustainable development goals. Although less applicable in the UK where temperate soils dominate, the use of rock dust as a fertiliser has already taken off in several agro-exporting countries in South America, most notably in Brazil. 

The science of rock dust

Soil can be defined as a mixture of organic matter, minerals, gases, liquids, and organisms as well as the support system of our modern agricultural societies. The scientific word is ‘pedolith’ and derives from the Greek ‘πέδον’, to literally mean ‘fundamental stone’, or ‘earth’. Agricultural soil must contain essential nutrients, but these are ‘being removed faster than they are being replenished’. Moreover, most fertiliser is imported, and as a result, acquiring it involves complex supply/chain issues as well as high costs. Manning and Theodorob suggest that ‘crushed silicate rocks’ could be a somewhat under-appreciated, but highly viable, alternative option for remineralising soil. 

Each time a crop is removed from the soil, vital nutrients are removed with it, and they must be added back in. Geological silicate rocks from the earth can be crushed to form these essential ‘plant nutrients’ that agricultural soil depends upon. 95 per cent of the earth’s crust and mantle is made up of silicate materials, and these materials can be found in almost all igneous rocks as well as in meteorites from space. Rock dust, unlike fertiliser, is, therefore “one of the most readily-available resources on the planet.” 

Since the 1990s Brazil has already begun to use this technique, which is especially helpful for local farmers who are unable to access expensive fertilisers. Rock dust has been applied to “upwards of five million hectares of land” in Brazil, which totals almost eight per cent of all arable land in the country.

The geopolitics of fertiliser

This method has geopolitical, as well as economic significance, due to the dependence of Brazil – the world’s largest producer of major cash crops – on fertiliser from Russia and the resulting impact of the war in Ukraine on food production. 

Brazil imports 85% of its fertilisers and a quarter of these come from Russia. The sanctions enforced by the EU after the invasion of Ukraine, therefore, had a direct impact on Brazilian farmers. Within days of the February 24th invasion, officials warned farmers in Brazil that fertiliser (absolutely essential to their agricultural practice) would run out in only three months’ time. In May, New York Times reporters Jack Nicas and André Spigariol succinctly stated that “[the war in Ukraine] is a danger not only to the Brazilian economy but also to the world’s ability to feed itself.”

Thankfully, careful forward planning and US sanctions permitting the purchase of Russian fertiliser in Brazil have prevented a disastrous outcome. Nevertheless, the technique of using rock dust in place of fertiliser could, in the future, serve as a safety net for food production in similar times of crisis. 

Reaching sustainable development goals

In 2015, the United Nations set out 17 Sustainable Development Goals in their agenda for 2030. Of these, the sustainable remineralisation of soil could contribute to achieving a total of eight goals. These include goal one – no poverty; goal two – zero hunger; goal three – good health and wellbeing; goal ten – reduced inequalities; goal eleven – sustainable cities and communities; goal twelve – responsible consumption and production; goal thirteen – climate action and goal fifteen – life on land. The importance of soil in farming for the future of global sustainability and food planning cannot be overstated, and rock dust is beginning to play a starring role.

Opportunities to work with soil

Working with soil can, of course, involve farming, but also forest restoration, environmental and medical projects as well as collaboration with local communities. If you’re keen to get involved, you can browse some of our many programmes supporting healthy ecosystems around the world today. These include the reforestation of lake Úlfljótsvatn in Iceland, restoration in the Peruvian Amazon and an environmental farming project in Nepal. WorkingAbroad also provides volunteer opportunities in South America, including Ecuador, Peru and the Galapagos Islands.

Written by WorkingAbroad Blogger Anna Juliet Stephens