Effects Of Functional Biochar On Phosphorus Availability And Microbial Community In Aeolian Sandy Soil

In recent years,biochar has been widely used in soil quality improvement and pollution remediation as soil ameliorator.The application of biochar can improve the availability of phosphorus to some extent,but the higher p H value and the presence of cations such as calcium and magnesium in alkaline soil will limit the regulation effect of biochar on the availability of phosphorus.Therefore,it is necessary to consider the functional modification of common biochar in order to meet the applicability in alkaline soil.In this study,the calcareous aeolitic soil in Ningxia was selected as the test soil to improve the utilization rate of phosphate fertilizer.Biochar(BC),nano-hydroxyapatite(HAP)and sodium humate(HANa)were selected to prepare functional biochar materials.Through soil microcosmic culture experiment,combined with natural culture and aseptic culture scenarios,the differences of soil available phosphorus input and phosphorus form regulation after applying BC,HAP and modified functional biochar were explored and compared.At the same time,the vertical migration capacity of phosphorus in soil treated with different materials was investigated through soil column leaching experiment.The contribution of humic acid to reducing phosphorus leaching loss was compared and analyzed by applying humic acid alone and using it as substrate.Finally,high-throughput sequencing was used to explore the response characteristics of soil bacterial and fungal microbial communities,and to explore the internal mechanism of the regulation of functional biochar application and phosphorus conversion.The main results are as follows:1.Nano-hydroxyapatite was synthesized by chemical precipitation method,and the biochar was successfully modified to obtain BC-HAP(BC:HAP=1:1),the specific surface area of the modified biochar increased,which promoted the embedding of sodium humate(HANa),and finally prepared the composite functional biochar(BC-HAP-HANA),in which the embedding amount of sodium humate reached about 80%;The functional biochar materials were successfully prepared by scanning electron microscopy,transmission electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction and other characterization methods.2.Functional biochar BC-HAP-HANa(HANa loaded)and BC-HAP+HANa(HANa applied alone),as well as biochar treatment significantly increased soil alkaline phosphatase activity,as well as the contents of soil available P,total P,soil organic matter and soluble organic carbon.The promotion effect of high concentration treatment group was more significant(p<0.05).The results of soil phosphorus classification showed that the phosphorus in aeolian sand soil mainly existed in the form of dilute hydrochloric acid extracted phosphorus(Ca-P).BC-HAP-HANa and BC-HAP+HANa treatments promoted the transformation of insoluble phosphorus to Ca-P in soil.According to the results of soil phosphorus leaching tests,the application of HANa alone with solution will increase the environmental risk of phosphorus leaching loss in soil.The results of soil asepsis experiment showed that the contents of soil available P and soil organic matter in each treatment group were significantly decreased,which indirectly indicated that the transformation of available P had a certain effect on the microgenesis of soil organic matter in the process of change.3.The characteristics of soil microbial community change were mainly that the bacterial community was more sensitive to the change of soil microbial community,and the difference of bacterial community structure was significant among different treatments,and the difference of bacterial community structure increased with the increase of application concentration.In the species composition of bacterial community,the relative abundance of some carbon and nitrogen cycling-related microorganisms,such as Xanthobacteraceae and Nitrosomonadacea,increased,which was positively correlated with environmental factors SOM,TN,NH₄⁺-N and DOC.The relative abundance of Acidibacter,which was negatively correlated with environmental factors,decreased.Meanwhile,Gemmatimonadacea and Burkholderiaceae were also found to be significantly correlated with alkaline phosphatase,total phosphorus and available phosphorus.Compared with the control group,the diversity of fungal community structure in other treatments was not significantly changed,and Beta diversity was significantly affected.In general,the bacterial community changed more than the fungal community.In conclusion,the application of functional biochar composites can significantly increase the available P content in aeolian sand soil,and effectively promote the conversion of insoluble P form into dilute hydrochloric acid extracted P,which broadens the space for synergistic utilization of phosphorus in the future.Functional biochar loaded with sodium humate can significantly reduce the leaching loss rate of phosphorus in aeolian sandy soil,and effectively maintain the relative stability of phosphorus in aeolian sandy soil.At the same time,it was found that the application of functional biochar composites could recruit and significantly promote the change of carbon and nitrogen cycling microbial community,and indirectly affect the conversion of available phosphorus in aeolian sand soil.Anyhow,after the biological carbon nano hydroxyapatite,the humic acid embedding technology,the biochar modified method not only can significantly improve the utilization rate of phosphorus,can also activate the difficult use of phosphorus in soil and increase soil organic matter content,for the future of sand soil phosphorus efficient utilization and guarantee crop phosphorus absorption effectively,provide the theoretical basis and implementation strategy.