Influence of Freeze-Thaw and Flooding on the Loss of Soluble Organic Carbon and Carbon Dioxide from Soil
- F. L. Wang * and
- J. R. Bettany
Freeze-thaw and flooding significantly affected the loss of water soluble organic carbon (SOC) and carbon dioxide carbon (C-CO2) from a well-drained Black Chernozemic soil (Udic Boroll) in a leaching-incubation study. At the end of 12 wk, the total loss of SOC was 90, 107, 399, and 224 mg kg−1 for soils with normal (incubated at field capacity moisture), freeze-thaw, flooding and flooding-freeze-thaw treatments, respectively. The E4/E6 values of the leachates obtained from the four treatments ranged from 10 to 32, suggesting that SOC in the leachates was mainly low molecular weight in nature. The rate of the SOC leaching changed over time and the amount of SOC leached from the flooded treatments reached a maximum in the middle of the incubation period. In contrast, the rate of SOC leaching for unflooded treatments appeared little changed with no distinctive rate maximum. The cumulative loss of C-CO2 and total C (sum of SOC and C-CO2) from the treatments decreased in the order of flooding > normal > flooding-freeze-thaw > freeze-thaw. The rates of C-CO2 evolution decreased with time for the freeze-thaw treated soils whereas the rate of C-CO2 evolved from the normal treatment initially decreased and then increased after 8 wk of incubation, suggesting transient kinetics for the system. For the flooding treatment, the rate of C-CO2 evolution showed a similar pattern to that of SOC leaching. There was a high linear correlation between the cumulative C-CO2 evolved and SOC leached from the soil.
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