Effect of amending nitrogen on the total carbon of arable soil in semi-arid region

Wenxu Dong1, Yuying Wang1, Xiaoxin Li1, Chunsheng Hu1

1 Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021, China.  E-mail: [email protected]

Abstract

Soil inorganic carbon (SIC) exerts a strong influence on the carbon (C) sequestered in response to nitrogen (N) additions in arid and semi-arid ecosystems, but limited information is available on in situ SIC storage at the field level. This study determined the soil organic/inorganic carbon storage in the soil profile at 0–100 cm depths in 4 N application treatments (0, 200, 400, and 600 kg N ha-1 y-1) for 15 years in the North China Plain. Results showed that after 15 years of N fertilizer application the SOC contents at depths of 0-100 cm significantly increased, whereas the SIC contents significantly decreased at depths of 0-60 cm. However, the actual measured loss of carbonate was far higher than the theoretical maximum values of dissolution via protons from nitrification. Furthermore, the amount of HCO3- and the HCO3-/ (Ca2+ + Mg2+) ratio in soil leachate were higher in the N application treatments than no fertilizer input (CK) for the 0-80 cm depth. The result suggested that the dissolution of carbonate was mainly enhanced by soil carbonic acid, a process which can absorb soil or atmosphere CO2 and less influenced by protons through the nitrification which would release CO2.