Stoichiometric Characteristics Of Soil C:N:P And Their Relationship With Microbial Activity In Typical Farmland Under Long-term Fertilization

Soil organic carbon is the key of farmland soil fertility.Different fertilization measures are often used in farmland management to produce greater heterogeneity in soil nutrient input,that is,the stoichiometry of soil substrate resources is plastic,and the carbon,nitrogen and phosphorus stoichiometry of the decomposed substrate Microorganisms respond and regulate by taking a series of measures,including the response and regulation of their respiration process.Respiration releases soil organic carbon,and the availability of nutrients will increase soil carbon stocks by affecting the growth of microorganisms.According to the theoretical basis of ecological stoichiometry,this paper explored the response of soil carbon,nitrogen and phosphorus stoichiometric ratios and soil respiration to different long-term fertilization in in Gongzhuling,Zhengzhou and Qiyang,and then analyzed the effect of stoichiometric ratio on soil respiration,and then summarized and analyzed the effect of soil carbon,nitrogen and phosphorus stoichiometric ratio and soil respiration on soil organic carbon stocks,and finally got the stoichiometric control mechanism of soil organic carbon stocks.The main results are as follows:1.Compared with CK,long-term application of organic manure(M,NPKM)could significantly reduce the DOC:TDN ratio,increase the SMBC:SMBN of flu-aquic soil and red soil,while balanced fertilization(NPK)could significantly reduce the DOC:TDN ratio of black soil and flu-aquic soil,and increase the DOC:TDN ratio of red soil.At the same time,the SMBC:SMBN ratio of black soil,aquic soil and red soil was significantly increased.Both balanced fertilization and organic fertilizer can significantly reduce the ratios of DOC:AP,TDN:AP and C:N imbalance in soil.2.The average microbial respiration intensity per unit of organic carbon of red soil(2.61 mg g^-1SOC)and qCO₂(1.20?g mg^-1 MBC h^-1)were higher than those of aquic soil and black soil.The average microbial respiration intensity and qCO₂ of fluvial soil were 2.21 mg g^-1 SOC and 0.59?g mg^-1MBC h^-1.The average microbial respiration intensity and qCO₂ of black soil were 1.45 mg g^-1 SOC,and0.45?g mg^-1 MBC h^-1.Long-term application of organic fertilizers(M,NPKM,NPKS)significantly increased the microbial respiration intensity and qCO₂ per unit of organic carbon.3.The microbial respiration of unit organic carbon is significantly negatively correlated with TDN?SMBC?SMBN and p H,and is significantly positively correlated with TN?DOC:TDN?C:N imbalance.qCO₂ is significantly negatively correlated with TDN?SMBC?SMBN and p H,and is significantly positively correlated with TN?DOC:TDN?SMBC:SMBN and C:N imbalance.The primary influencing factor of microbial respiration intensity per unit of organic carbon was TDN,followed by DOC:TDN and SMBC.The primary influencing factors of qCO₂ were DOC:TDN,followed by soil p H and SMBC.4.TDN is the first factor affecting soil organic carbon stock,followed by SMBC?TN?DOC.The relative importance of DOC:TDN?qCO₂?C:N imbalance were 8.0%?6.8%and 6.6%.The soil organic carbon stock is significantly positively correlated with contents of TN?DOC?TDN?AP?SMBC?SMBN and p H,and is significantly negatively correlated with DOC:TDN?C:N imbalance?microbial respiration and qCO₂.5.SOC:TN and nutrient availability jointly explain 17%of SMBC:SMBN,while they together explain 43%of C:N imbalance.C:N imbalance?SMBC:SMBN?microbial respiration and nutrient availability together explain 85%of qCO₂.qCO₂?nutrient availability and C:N imbalance together explain 53%of soil organic carbon stock.In conclusion,SOC:TN affects qCO₂ and then indirectly affects carbon stock mainly by regulating the C:N imbalance.On the one hand,nutrient availability can directly regulate carbon stock.On the other hand,it can indirectly regulate carbon stock mainly by affecting qCO₂.This study highlights the important role of qCO₂ in the process of nutrient availability regulating organic carbon stock.