Effect Of The Combined Application Of Fungal Residues And Chemical Fertilizers On The Soil Organic Carbon Composition And Yield In Paddy Fields

As an excellent organic material additive to soil,fungal residue can reduce the application of chemical fertilizer and also plays an important role in maintaining soil fertility.In order to explore the effect of different proportion of fungal residue fertilizer on soil organic carbon components,evaluate the ecological role of fungal residue in optimizing soil fertility.We evaluated the soil microbial biomass carbon（MBC）,dissolved organic carbon（DOC）,particulate organic carbon（POC）,labile organic carbon（LOC）and mineralized carbon（MC）,and the correlation between different forms of carbon components and yield after nine applications of chemical fertilizers（C）and fungal residues（F）in paddy fields,at the rates of 0,50,and 100%.In order to provide theoretical basis and technical support for evaluating the effect of bacterial residue on paddy soil quality and rational utilization.The main results are as follows:（1）The content of soil microbial biomass carbon,dissolved organic carbon,particulate organic carbon and labile organic carbon was significantly increased by applying fungal residue and chemical fertilizer.Microbial biomass carbon and dissolved organic carbon were the highest in C₅₀F₁₀₀,particulate organic carbon,labile organic carbon and mineralized carbon were the highest in C₁₀₀F₅₀.But not with the increase of dosage has been increasing trend,high amount of fungal residue or fertilizer will have a downward trend.MBC/SOC is the highest in C₅₀F₀,and DOC/SOC is the highest in C₁₀₀F₀.Compared with chemical fertilizer alone,MBC/SOC and DOC/SOC of fungal residue combined with chemical fertilizer decreased slightly.POC/SOC is the highest in C₁₀₀F₁₀₀,and the validity of three kinds of LOC(A_LC)and CPMI are the highest in C₅₀F₁₀₀.Compared with chemical fertilizer alone,the POC/SOC of fungal residue combined with chemical fertilizer increased.Compared with the control（C₀F₀）,the combined application of fungal residue and chemical fertilizer increased the availability(A_LC)and CPMI of the three LOC.（2）The combination of fungal residue and chemical fertilizer can increase mineralized carbon,activated carbon pool,potential mineralized carbon pool content and mineralization rate,but under the condition of high amount of the combined application of fungal residue and chemical fertilizer,the contribution of mineralized carbon,activated carbon pool and potential mineralized carbon pool content and mineralization rate will have a decreased.Although the combined application of fungal residue and chemical fertilizer can increase the content of mineralized carbon,it can not increase the loss rate of organic carbon and play a very good role in carbon sequestration.In addition,there was an obvious orthogonal interaction between fungal residue and chemical fertilizer,and the effect of fungal residue on organic carbon was better than that of chemical fertilizer.There was a significant positive correlation between all forms of organic carbon.Among the different soil factors,except for the negative correlation between C/N and various forms of organic carbon,there was significant or extremely significant positive correlation between various forms of organic carbon and different soil factors.（3）The combined application of fungal residue and chemical fertilizer is not only beneficial to the increase of panicle-forming rate and yield of rice,but also to the increase of plant height,1000-grain weight,panicle number and grain number per panicle of rice.The effect of single application of chemical fertilizer on economic coefficient was not as good as that of single application of fungal residue,but the contribution of single application of fungal residue to 1000-grain weight and panicle number would be reduced.MBC,DOC,LOC₂ and LOC₃ mainly affect their output directly,and their indirect effects are small.Compared with the direct effect,POC and MC mainly affect the yield through the indirect influence of other carbon components.Therefore,in order to achieve high yield,the increase of MBC and LOC₃ must be considered first.Although the direct impact of POC and MC is negative,the total indirect impact of POC,MC is positive,and are greater than its direct impact,so in production practice,POC and MC also play a positive role in rice yield.