Fertilization Enhances Carbon Sequestration as Carbonate in Arid Cropland: Assessments of Long-Term Experiments in Northern China

Soil inorganic carbon (SIC), primarily calcium carbonate, is the most common form of carbon in soils of arid and semi-arid regions accounting for more than 35% of Earth’s land surface, where SIC stock is 1–9 times higher than soil organic carbon (SOC) stock. Numerous studies using data as SOC under various fertilization treatments demonstrated widespread increases in SOC stock as results of fertilization in northern China, and whether there would be significant carbonate accumulation in arid croplands, in association with the increases of SOC is not clear.

Therefore, the researches from Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences wanted to better understanding of carbon sequestration as all forms in various systems, including carbonate in arid and semi-arid lands. They obtained two sets (65 each) of archived soil samples collected in the early and late 2000’s from three long-term experiment sites under wheat-corn cropping with various fertilization treatments in northern China, and determined SOC, SIC and their stable ¹³C compositions over the range 0-100 cm in soil profiles.

The results show an overall increase of SIC content in soil profiles of all sites over time. Particularly, fertilizations led to large SIC accumulation with a range of 101-202 g C m^-2 y^-1 in the 0-100 cm soil layer, and accumulation of pedogenic carbonate under fertilization varied from 60 to 179 g C m^-2 y^-1 in the 0-100 cm, which indicate that organic amendments significantly enhanced carbonate accumulation.

The study demonstrates that more carbon was sequestrated in the form of carbonate than as SOC in the arid cropland in northern China, and increasing SOC stock through long-term straw incorporation and manure application also enhanced carbonate accumulation in soil profiles. The study was published in Plant and Soil in July 2014.