Rock dust, crop nutrition and climate change
Soils are the interface between the geosphere and the biosphere. They provide the minerals required for crop nutrition, and they regulate atmospheric CO2 to a greater extent than the ocean. These functions are often treated separately, with studies focusing on either crop nutrition or on soil organic carbon. The use of silicate rocks as remineralizers addresses both functions. Weathering releases nutrients, including silica, for crop growth, and consumes atmospheric CO2, generating bicarbonate in solution. If enough Ca is released, and with sufficient bicarbonate in solution, pedogenic calcite forms as a permanent sink for atmospheric CO2. This can be verified using C and O stable isotopes. The potential of silicate rocks for carbon capture can be estimated from their chemical composition, and varies between 70 – 500 kg CO2 per tonne of rock. Life cycle analysis shows that the carbon cost of mining, transport and spreading to land allows transport for over 500-1000 km before the carbon cost exceeds the benefits. Land management can take advantage of these processes to both increase crop production and to increase soil carbon, both improving soil health and quality.