Dairy farms management and carbon storage in the soil fractions

The dairy sector is one of the main economic activities in the Spanish region of Galicia, located in the northwest of the country. In dairy farms, the type of farm management has a clear effect on climate change mitigation by modifying crucial processes such as carbon storage in the soil. This study aimed to evaluate the effect of the dairy farm management (extensive, intensive and organic) on carbon storage in each soil aggregate fraction in dairy farms of Galicia. A total of 21 dairy farms were selected of which 7 farms were based on intensive conventional production, 7 farms were based on extensive conventional production and 7 farms were based on organic production. In each farm, two plots were selected and for each plot, two composite soil samples were collected. In the laboratory, soil samples were fractionated in macroaggregates (250–2000 μm), microaggregates (53–250 μm) and silt + clay (< 53 μm) to estimate the carbon storage in each soil fraction. The results show that the organic farms implied a higher amount of carbon storage in the different soil fractions than the extensive and intensive farms, being the carbon storage in the smallest soil fractions very stable and maintained in the soil in the long-term.