The Effect Of Iron Reduction In Paddy Soil On Decomposition Of Organic Carbon

Paddy field is a widely distributed farmland ecosystem in China.It is a special ecosystem between the terrestrial ecosystem and the aquatic ecosystem.Due to the intermittent waterlogging of the paddy soil,special redox conditions are caused,which in turn affects the cycling process of various elements in the soil.When the paddy soil is flooded and in the absence of oxygen,Fe(?)in the soil can oxidize the organic carbon in the soil instead of oxygen as an electron acceptor.There are many biotic and abiotic reactions in this process that directly affect the process of soil carbon cycle and greenhouse gas emissions.Therefore,this study collected four soils with different iron and organic carbon contents.Through the incubation experiment with controlled conditions,the soil properties,different oxygen concentrations and the addition of exogenous Fe(?)were applied to the soil Fe(?)reduction drive.The main conclusions of the decomposition of organic carbon are as follows:Under anaerobic conditions,the reduction of Fe(?)was significantly correlated with the incubation time of the four paddy soils during the one week of incubation.The soil iron reduction rates of Changsha,Zhangzhou,Xianning and Yueyang were 230.9 respectively.221.5,230.6,292.7 mg·kg-1d-1,the decomposition ratio of organic carbon caused by Fe(?)reduction in soil was 25.9,38.9,29.2,20.7%,respectively.The content of organic carbon in different soils and the content of iron in soil are the main influencing factors affecting the decomposition of organic carbon caused by Fe(?)reduction.2.The effect of oxygen concentration on organic carbon emissions from iron reduction is significant.At 20% oxygen concentration,Fe(?)in soil samples from Zhangzhou and Xianning could not be completely reduced.The remaining three soil samples only increased the time required for Fe(?)to be completely reduced as the oxygen concentration in each treatment increased.During the Fe(?)reduction,the organic carbon oxidized by Fe(?)reduction accounts for more than 50% of the decomposition of organic carbon in the soil sample.3.The effect of adding Fe(?)on the decomposition of organic carbon caused by soil Fe(?)reduction is also significant.Adding only a very small concentration of Fe(?)in natural waters can significantly reduce Fe(?)reduction and organic carbon decomposition in aerobic treatment.Reduction of Fe(?)and decomposition of organic carbon can also be slowed down in anaerobic treatment.However,after the Fe(?)in the soil is completely reduced,the addition of Fe(?)has no effect on the decomposition of organic carbon.In summary,the reduction of Fe(?)in soil causes soil carbon loss,and exogenous Fe(?)can significantly inhibit the decomposition of organic carbon;in soils with higher organic carbon content and iron content,oxygen to some extent It can suppress Fe(?)reduction and reduce organic carbon emissions.