The Microscopic Process Of Organic Matter Transformation On Microsurface In Paddy Soil With Different Phosphorus Contents

The dynamic change of organic matter is of great significance to the carbon balance in paddy soil,and phosphorus deficiency in the subtropical region affects the soil C fixation.The soil biogeochemical interface?BGI?is one of the core areas of organic matter turnover,The process of soil organic matter turnover is usually carried out in the whole soil body,it is not clear that the microscopic process of P on the turnover of organic matter at the soil biogeochemical interface and its in situ dynamic change mechanism.Therefore,the microfluidic technology was used to simulate the soil biogeochemical interface,and the effects of exogenous carbon and phosphorus addition on the dynamics of micro-interface elements,organic matter structure and microorganisms in the phosphorus-deficient paddy soil were researched by the in-situ detection technologies.This study can provide a new microscopic view of soil organic matter changes,at the same time,provide scientific basis for strengthening the soil nutrient management of rice fields and increasing the yield of rice fields.In this study,a typical subtropical paddy soil was used as the research object,and simulated rhizosphere secretions were used as the carbon source and NaH₂PO₄ as the source of phosphorus,studied extremely phosphorus deficient soil(Soil 1,Olsen-P 0.74 mg·kg^-1)and phosphorus deficient soil(Soil 2,Olsen-P 3.41 mg·kg^-1)Micro-interface behavior of organic matter and its response to external carbon and phosphorus addition.The experimental treatments are:?1?Soil 1;?2?Soil 1+C;?3?Soil 1+C+P;?4?Soil 2;?5?Soil 2+C;?6?Soil 2+C+P.The main results are as follows:?1?The fluorescence intensity of organic matter,the relative level of humus and the degree of humification were different in the two soil solutions during the cultivation period.It is different that the relative percentages of C and N atoms,the percentage of organic matter,enzyme activity and microbial morphology in the two soils.?2?The addition of carbon and phosphorus promoted the growth and reproduction of microorganisms,and the effect of co-application of carbon and phosphorus is stronger.In the soil solution,the addition of carbon and phosphorus promotes the transformation of organic matter from a relatively simple structure to a complex polymer-condensed aromatic compound,and the co-application of carbon and phosphorus had a stronger promoting effect.Addition of carbon and phosphorus can increase the thickness of organic matter in the soil,and the application of carbon alone promotes the activity of microorganisms,while the co-application of carbon and phosphorus promotes the reproduction of microorganisms.The etching results showed that the relative atomic percentages of C and N in the soil decreased as the soil depth increases.Organic matter was more likely to accumulate in the surface soil.The accelerating effects of organic matter accumulation and microbial growth and reproduction at the 100s and 600s levels were synchronized with the surface.?3?The addition of carbon and phosphorus reduced the enzyme activity,and the sensitivity of microorganisms to P in soils with extremely phosphorus deficiency is greater than that of element C,the opposite is true for soils with phosphorus deficiency.Exogenous addition of C and P promoted the growth and reproduction of microorganisms in the short term,and the microorganisms eventually reached a steady state with time.The electron microscope results further proved that the addition of carbon and phosphorus promote the growth and reproduction of microorganisms,and the co-application of carbon and phosphorus had a stronger promoting effect.