Effect Of Organic Material Addition On Phosphorus Availability And Microbial Community In Red Paddy Soil

Phosphorus is one of the essential nutrients for crop growth and development.The strong adsorption of soil particles leads to low soil phosphorus availability and a high demand for phosphate fertilizer.However,phosphorus is a non-renewable resource.Long-term and large-scale consumption may lead to insufficient phosphorus resources and pose a threat to future food security.Phosphorus fertilizer reduction and efficiency increase are urgent problems to be solved for sustainable agricultural development.The addition of organic materials is an important agricultural measure to improve the effectiveness of soil phosphorus,and its effect is affected by the phosphorus content of organic materials.Compared with rice straw,the phosphorus content of Miscanthus lutarioriparius straw has a high.As an organic material applied to paddy fields,it is expected to solve the problem of resource utilization of abandoned Miscanthus lutarioriparius and promote the reduction and efficiency of phosphate fertilizer in paddy fields,but it has not been reported so far.The value of Miscanthus lutarioriparius straw as a supplementary phosphorus source in paddy fields depends on its effect on soil phosphorus availability.Microorganisms are the driving force for phosphorus transformation and activation.Clarifying the effect of Miscanthus lutarioriparius straw addition on soil microbial community composition is conducive to revealing its phosphorus availability regulation mechanism.Therefore,in this study,the typical red paddy soil was used as the research object.Under the conditions of sterilized and unsterilized soil,rice straw was used as the control to study the effect of fermented Miscanthus lutarioriparius straw addition on soil phosphorus availability and microbial community composition,its response to phosphorus fertilizer application.In order to study the changes in soil phosphorus form,soil enzyme activity,bacterial community structure,and the copy number of the pho D gene and the pqq C gene in soil,the indoor simulated flooding culture experiment was carried out by soil physical and chemical properties,Hedley phosphorus classification,fluorescence microplate enzyme detection,high-throughput sequencing,and real-time fluorescence quantitative PCR analysis of phosphorus cycle-related genes.The main results are as follows:（1）The addition of organic materials can increase the soil available phosphorus content.Under the sterilization treatment,the soil available phosphorus content of rice straw was 3.94mg/kg～8.56 mg/kg,and the soil available phosphorus content of fermented Miscanthus lutarioriparius straw was 4.80 mg/kg～9.59 mg/kg.Under the unsterilized treatment,from the5th day of culture,the soil available phosphorus content of the rice straw was 5.44 mg/kg～9.88mg/kg,and the soil available phosphorus content of the fermented Miscanthus lutarioriparius straw was 5.74 mg/kg～10.71 mg/kg,and the DOC/Olsen P ratio of the fermented Miscanthus lutarioriparius straw was significantly lower than that of the rice straw,indicating that the fermented Miscanthus lutarioriparius straw was beneficial to improve the soil available content.（2）The addition of organic materials could increase the content of soil phosphorus components,and the increase of soil H₂O-P and Na HCO₃-P active phosphorus was more significant by adding fermented Miscanthus lutarioriparius straw.The correlation showed that soil organic carbon was significantly negatively correlated with Na OH-P,HCl-P and O-P,indicating that straw addition was beneficial to the conversion of occluded phosphorus to medium phosphorus and active phosphorus,thereby increasing soil available phosphorus content.（3）The addition of organic materials could increase the activities of soilβ-glucosidase（BG）,β-cellobiase（CBH）,acid phosphatase（ACP）and alkaline phosphatase（ALP）.Among them,the addition of fermented Miscanthus lutarioriparius straw increased the activity of soil phosphatase（ACP+ALP）significantly,indicating that the fermented Miscanthus lutarioriparius straw was beneficial to the dissolution of soil organic phosphorus,thereby improving soil phosphorus availability.（4）Compared with no straw addition,the addition of organic materials enriched the alpha and beta diversity of microbial communities.The dominant flora of the microbial community at the phylum level was generally consistent under different treatments.The abundance of Firmicutes was higher and positively correlated with organic carbon,indicating that carbon source substrates played an important role in organic phosphorus mineralization.Na OH-Po is an important phosphorus component affecting microbial communities.The addition of organic materials increased the abundance of the pho D gene and the pqq C gene in soil,indicating that organic materials could improve the ability of soil organic phosphorus to transform into inorganic phosphorus and replace part of the adsorbed phosphorus in soil.In summary,in the typical red paddy soil of southern China,fermented Miscanthus lutarioriparius straw can directly or indirectly promote soil phosphorus transformation,thereby improving soil phosphorus availability.Therefore,the straw of Miscanthus lutarioriparius can help to reduce the application of phosphate fertilizer in farmland,and increase the efficiency,and also find a reasonable resource treatment method for Miscanthus lutarioriparius abandoned by Dongting Lake.