A recently published article describes a UK study on carbon in soils. Soils are estimated to hold more carbon than stored in the whole atmosphere and all Earth's plants. This realization emphasizes the importance that soils should be carefully managed to retain soil carbon.
Most soil research focusses on the top 30 centimeters. This research wanted to go beyond this scope, by analyzing the percentage of carbon in soil samples up to 1 meter. The researchers took samples from 180 different sites representing different grassland types and three different ways of grassland management; intensive, extensive and intermediate.
Intensively managed grassland fields receive a large amount of fertilizer (100 kg nitrogen/ha/year), are heavily grazed by animals (2-3.5 or more livestock units/ha), are cut two or three times a year and have low plant diversity (10 species/m2). Extensively managed grassland fields receive less fertilizer (25 kg/ha/year), are lightly grazed (<1 livestock unit/ha), are cut once a year and have high plant diversity (average 21 species/m2). Intermediary managed fields receive 25-50 kg of fertilizer (nitrogen/ha/year), are grazed by 1.5 livestock units/ha, are cut once a year and have middling plant diversity (15 species/m2).
Soil carbon concentrations decreased as management intensity increased, but intermediate management showed the largest amount of soil carbon. Total percentage of carbon in intermediate managed grassland was 10.7% greater than in intensively managed grassland and 7.8% greater than in extensively managed grassland. A higher percentage of carbon in intermediately managed grassland in comparison to extensively managed grassland is assigned to differences in soil bulk density, likely due to compaction and fertilizer application rates.
The researchers also found that 60% of the total amount of carbon in 1 meter is stored in the top 30 centimeters. They estimate that the stock of soil carbon up to 1 meter in the UK is 2097 Tg (1 Tg=1 million metric tons).
Soil is an important natural capital and should be correctly managed to maximize the storage of carbon. The Atlas Natural Capital has many maps on carbon sequestration in soils. For example: