Carbon and nitrogen losses from undisturbed soil columns under short-term flooding conditions

Short-term flooding (few days to several weeks) of usually well-drained soils — often occurring after snowmelt in spring and after heavy precipitation in summer — is a natural event in many regions of the world. Using incubation-leaching and gas sampling techniques in the laboratory, we examined the impact of flooding on the loss of carbon and leaching of nitrogen from five undisturbed soil columns. The soils varied in management, salinity and carbon content. After 8 wk of incubation, the amounts of soluble organic carbon leached by 0.001 M CaCl2 solution from flooded soils ranged from 153 to 630 mg C kg−1. In contrast, only 28–107 mg C kg−1 was leached from nonflooded soils. The amounts of soluble organic nitrogen leached from the flooded soils ranged from 10 to 30 mg N kg−1 compared with 5.9–12 mg N kg−1 from nonflooded soils. In the flooded soils, ammonium nitrogen dominated the total inorganic nitrogen leached (99.5–99.9%) whereas in nonflooded soils leachable N was mainly nitrate and nitrite (97.4–99.9%). Methane was emitted from the flooded soils (10–138 mg C kg−1 over 8 wk). The rate of carbon dioxide evolution in flooded soils increased linearly with time and total evolution ranged from 72 to 552 mg C kg−1, whereas CO2 evolution in the nonflooded soils was steady with total evolution ranging from 159 to 1279 mg C kg−1 after 8 wk. Key words: Prairie and forest soils, short-term flooding, C and N losses, methane emission