Differences in Organic C Mineralization Between Aerobic and Submerged Conditions in Paddy Soils of Southern Jiangsu Province,China

Moisture regime plays a crucial role in the mineralization of soil organic carbon （SOC）. In this paper, the dynamics of SOC mineralization in typical paddy soils of Changshu, Jiangsu Province, China, was investigated by incubation test in laboratory. The differences in SOC mineralization under aerobic and submerged conditions of paddy soils were also studied. Results showed that the daily mineralization of SOC under different moisture regimes was significantly different in the whole incubation period, at the beginning of the incubation, it decreased quickly under aerobic condition, but increased rapidly under submerged condition, and both remained constant after 10 d of incubation. The differences in SOC mineralization were found to be mainly at the beginning period of the incubation and decreased along with the incubation time. Thus, the difference was not significantly different at the later incubation period. The respiration intensity, daily and cumulative mineralization of SOC under aerobic condition was 2.26-19.11, 0.96-2.41, and 0.96-2.41 times than those .under submerged condition, respectively. Statistic analyses showed that the higher the contents of microbial biomass carbon and nitrogen, the more significant difference in respiration intensity between aerobic and submerged conditions, but the higher the contents of microbial biomass nitrogen and dissolved organic carbon, the more significant difference in daily mineralization of SOC between the two conditions. The decrease in soil microbial activity under submerged condition was the main reason leading to the decrease in respiration intensity, but the decrease in SOC mineralization was also correlated with the changes in dissolved organic carbon over the whole incubation period.

The effect of dolomite amendment on soil organic carbon mineralization is determined by the dolomite size

Background:The size of lime material is vital for the efficiency of ameliorating soil acidity,thereby influencing soil biochemical processes.However,the effects of different sized lime material application on soil organic carbon(SOC)mineralization are yet to be elucidated.Therefore,a 35-day incubation experiment was conducted to determine the effects of three particle size fractions(0.5 to 0.25,0.25 to 0.15,and<0.15 mm)of dolomite on SOC mineralization of two acidic paddy soils.Results:CO_(2) emission was increased by 3–7%,11–21%,and 32–49%for coarse-,medium-,and fine-sized dolomite treatments,respectively,compared to the control in both soils.They also well conformed to a first-order model in all treatments,and the estimated decomposition rate constant was significantly higher in the fine-sized treatment than that of other treatments(P<0.05),indicating that SOC turnover rate was dependent on the dolomite size.The finer particle sizes were characterized with higher efficiencies of modifying soil pH,consequently resulting in higher dissolved organic carbon contents and microbial biomass carbon,eventually leading to higher CO_(2) emissions.Conclusions:The results demonstrate that the size of dolomite is a key factor in regulating SOC mineralization in acidic paddy soils when dolomite is applied to manipulate soil pH.