Effects Of Biochar And Wood Vinegar On Phosphorus Fractions And Phosphorus Bacterial Diversity In Saline-alkaline Soil

Saline-alkali soil is poor in nutrients,especially phosphorus is easily fixed in the soil and its availability is low.Therefore,improving the utilization rate of phosphorus in saline-alkali land has become an important issue to be solved urgently.In this study,the saline-alkali soil was selected as the research object,and biochar and wood vinegar were selected as soil amendments to conducted a pot experiment,including no biochar and wood vinegar（CK）,biochar 0.6 t/hm²（BC）,wood vinegar 0.6 t/hm²（WV1）,wood vinegar 1.2 t/hm²（WV2）,wood vinegar 1.8 t/hm²（WV3）,the co-application of 0.6 t/hm²biochar and 0.6 t/hm²wood vinegar（BC＿WV1）,the co-application of0.6 t/hm²biochar and 1.2 t/hm²wood vinegar（BC＿WV2）,and the co-application of 0.6 t/hm²biochar and 1.8 t/hm²wood vinegar（BC＿WV3）,a total of 8 treatments,to explore the effect of biochar and wood vinegar on phosphorus fractions and phosphorus bacterial diversity in saline-alkaline soil,which provide theoretical guidance for the efficient utilization of phosphorus in saline-alkaline soil.The alone application and co-application of biochar and wood vinegar had no significant effect on soil total phosphorus,but increased soil available phosphorus,Resin-P,Na HCO₃-P_i,Na OH-P_i,concentrated HCl-P_i,and Na HCO₃-P_o,BC＿WV3 treatment was the most significant,and the increases were 49.24%,56.17%,31.26%,35.10%,11.30%,and 31.63%,respectively,while the contents of Na OH-P_oand dilute HCl-P_idecreased at each treatment,and the contents of Na OH-P_oand dilute HCl-P_iin the BC＿WV3 treatment decreased the most,which were 24.99%and 4.89%,respectively.Except for the BC and BC＿WV1 treatments,the other treatments significantly reduced concentrated HCl-P_ocontent.In addition,biochar and wood vinegar increased the proportion of active phosphorus pool,ranging from 5.65%to 8.13%,while decreased the proportion of moderately stable phosphorus pool and stable phosphorus pool in soil,which were 11.22%-11.98%and 80.37%-82.26%,respectively.Biochar and wood vinegar promoted the conversion intensity of soil organic phosphorus and inorganic phosphorus,and the BC＿WV3 treatment had the largest increase,which were 122.75%and 92.93%,respectively.Meanwhile,each treatment significantly increased the counts of soil organic phosphorus and inorganic phosphorus bacteria,and the counts of phosphorus bacteria at the co-application of biochar and wood vinegar were significantly higher than those of the alone application of wood vinegar,and the BC＿WV1,BC＿WV2 and BC＿WV3 treatments increased by39.77%,56.44%,52.24%and 37.82%,37.36%,40.90%,respectively.At the same time,each treatment increased soil microbial biomass phosphorus and phosphatase activity.The highly applied rates of wood vinegar and the co-application of biochar and wood vinegar were beneficial to promote the diversity and richness of soil organic phosphorus bacteria and inorganic phosphorus bacteria.The application of biochar and wood vinegar to saline-alkali soil significantly changed the composition of soil phosphorus bacteria,in which Proteobacteria and Actinobacteria,Alphaproteobacteria and Gammaproteobacteria,Pseudomonas were the important components of organic phosphorus bacteria community at phylum,class,and genus level,respectively.Proteobacteria,Alphaproteobacteria and Gammaproteobacteria,Pseudomonas and Rhizobium were the dominant components of inorganic phosphorus bacteria at phylum,class and genus levels,respectively.Path analysis showed that Resin-P was the main contributing factor to characterize the change of soil available phosphorus,and the path coefficient was 0.6791*.Resin-P,Na OH-P_iand acid phosphatase activities had a significant direct effect on the change of soil available phosphorus content,and Na HCO₃-P_o,alkaline phosphatase activity and inorganic phosphorus bacterial diversity all indirectly affected soil available phosphorus content through Resin-P,Na OH-P_iand acid phosphatase activities.