| Soil phosphorus is one of the essential nutrient elements for crops and is closely related to the growth and development of plants.Most of the phosphorus in the soil exists in the form of insoluble state,which is not easily absorbed and utilized by plants,resulting in phosphorus becoming one of the most important nutrient limiting factors in agricultural production.Exogenous application of phosphate fertilizer is an important means to supplement the lack of phosphorus in the soil,but the phosphate fertilizer applied to the soil is easily fixed by the soil through a series of physical,chemical and biological effects,so the seasonal utilization rate of phosphate fertilizer is relatively low,usually only 20-30%.The world’s phosphate rock reserves are limited and are non-renewable resources.The current reserves of phosphate rock resources and high-quality phosphate rock are constantly decreasing.It is imperative to realize the sustainable benefits of phosphate rock resources.On the other hand,excessive application of phosphate fertilizer in agricultural production not only increases input costs,but also increases the risk of soil nutrient loss in farmland,leading to problems such as eutrophication of water bodies and threatening environmental security.In recent years,biochar has been widely used in the agricultural environment.Studies have shown that biochar can reduce soil acidity and improve soil fertility,and biochar has an important impact on soil microbial community structure and biological activity,as well as soil phosphorus conversion.At present,domestic and foreign researches on the effects of biochar on soil quality and the environment have made more progress,but the interaction between biochar and phosphorus form conversion,soil enzyme activity and microbial community structure is still not very clear.Therefore,this study used Eureka lemon as the test variety,purple fluvo-aquic soil as the test soil,and biochar produced from agricultural wastes（corn stalks and rice husk stalks）as the test materials.),traditional fertilization（F）,chemical fertilizer+20t·hm-1 rice husk biochar（FP）,chemical fertilizer+10t·hm-1 rice husk biochar+10t·hm-1 corn biochar（FPM）,organic fertilizer+There are 6treatments of 20t·hm-1 rice husk biochar（PP）,fresh organic fertilizer+20t·hm-1 rice husk biochar（NPP）.Using Tiessen and Moir to improve the Hedley phosphorus grading method,explore the effect of biochar on soil phosphorus form;use spectrophotometry to explore the effect of biochar on soil phosphatase activity;use real-time fluorescent quantitative PCR technology to treat different fertilization treatments Quantitative analysis of phoC and phoD gene copy numbers;combined with terminal restriction fragment length polymorphism（T-RFLP）technology to analyze phoC and phoD gene microbial community structure;use redundancy analysis（RDA）method to study phoC and phoD The relationship between genetic microbial community structure and environmental parameters is expected to provide a scientific basis for the agricultural utilization of biochar.The main findings are as follows:（1）The nutrient characteristics and plant growth of each treatment under different fertilization treatments are significantly different.Among the various fertilization treatments,the soil pH of the F treatment was the lowest,and the combined application of biochar could significantly increase the soil pH,and the PP treatment and NPP treatment had the best effect,and the rhizosphere soil pH was 6.20 and 6.29,respectively.Compared with CK treatment,biochar treatment can significantly increase soil total phosphorus,available phosphorus and organic matter content,and the rhizosphere soil nutrient content changes more obviously.In the rhizosphere soil,compared with the CK treatment,the organic matter content of the treatment with biochar increased by 11.74%～64.78%,the total phosphorus content increased by 64%～100%,and the rhizosphere soil available phosphorus content increased most significantly.The effective phosphorus content is 4.05～5.80 times that of CK treatment.After combined application of biochar,soil total nitrogen,total phosphorus,nitrate nitrogen,available phosphorus,available potassium,and organic matter showed more obvious rhizosphere effects than CK and F treatments.The combined application of biochar can effectively promote the growth of lemons,Compared with treatment F,the dry weight of lemon roots increased by 24.56～61.40%,and the biomass of lemons increased compared with treatment F.It is9.94～46.27%.（2）The results of phosphorus classification test show that there are obvious differences in the phosphorus content of various forms under different fertilization methods.The range of soil active phosphorus in each treatment ranged from 26.31 to 187.92 mg·kg-1.The non-rhizosphere soil of the F treatment had the highest active phosphorus content,reaching 187.92 mg·kg-1,and the PP treatment had the highest active phosphorus content in the rhizosphere soil.It is 95.64 mg·kg-1.Combined application of biochar increased the content and proportion of moderately active phosphorus most significantly.Compared with CK treatment,the content of moderately active phosphorus in soil treated with biochar increased significantly by 73%-107%,and the effect of combined application of biochar increased significantly.The effect of the moderately active phosphorus content in rhizosphere soil is more obvious,and the PP-treated rhizosphere soil has the highest intermediate active phosphorus content(226.53 mg·kg-1).After applying biochar,it is beneficial to reduce the steady-state phosphorus content of non-rhizosphere soil.There was no significant change in O-P content among various fertilization treatments.Moderately active phosphorus is the most important form of phosphorus in the experimental soil,accounting for40.66%～61.39%of the total phosphorus in the soil.Through Pearson correlation analysis,it was found that there was a significant positive correlation between the lemon biomass and the moderate active phosphorus content in rhizosphere soil（P<0.05）.（3）The phosphatase activity of each treatment is significantly different under different fertilization methods.F treatment will significantly reduce soil alkaline phosphatase activity,and its rhizosphere soil alkaline phosphatase activity is only 0.34 umol·g-1·d-1,and the combined application of biochar will increase the alkaline phosphatase activity,PP and NPP treatment has the best effect on increasing soil alkaline phosphatase activity.In rhizosphere soil,NPP treatment has the highest alkaline phosphatase activity(3.13 umol·g-1·d-1).In non-rhizosphere soil,PP The alkaline phosphatase activity(1.70 umol·g-1·d-1)was the highest.There was a significant positive correlation between alkaline phosphatase activity and soil pH under different fertilization treatments（P<0.05）.In non-rhizosphere soils,CK treatment has the highest acid phosphatase activity,12.85 umol·g-1·d-1,combined with biochar will reduce acid phosphatase activity,and PP treatment has the lowest acid phosphatase activity.It is only 6.4 umol·g-1·d-1,which is 50.22%lower than that of CK treatment.In rhizosphere soil,acid phosphatase activity was significantly negatively correlated with soil pH（P<0.05）.Generally speaking,the activity of acid phosphatase in soil is much higher than that of alkaline phosphatase,and it plays a dominant role in soil.In lemon roots,alkaline phosphatase activity is much higher than acid phosphatase activity,which plays a leading role in plant roots.（4）Using T-RFLP technology to analyze the phoC and phoD gene microbial community structure,the results show that the Shannon diversity index of phoC gene microorganisms varies from 1.21 to 2.21.The Shannon diversity index of phoD gene microorganisms varied from 2.40 to3.24.The relative microbial diversity index of the rhizosphere soil is higher.The combined application of biochar increases the diversity of the phoC and phoD gene microbial communities in the soil.The phoD gene microbial community structure is more complex,and the phoD gene microbial community Shannon diversity index and richness index They are 1.41～2.12 and 2.55～6.15times of the phoC gene,respectively.Quantitative analysis of the copy numbers of phoC and phoD genes showed that the combined application of biochar reduced the copy numbers of phoC and phoD genes in non-rhizosphere soils,with a decrease of 71.61%-92.80%.In rhizosphere soil,the copy number of phoD gene increased by PP and NPP treatment,which increased by 82.31%～128.86%compared with CK treatment.Pearson correlation analysis showed that the copy number of phoD gene was significantly positively correlated with pH（P<0.01）,and was significantly positively correlated with alkaline phosphatase activity（P<0.05）.The results of RDA analysis showed that total phosphorus content in soil is the most critical environmental factor affecting the structure of phoC gene microbial community in non-rhizosphere soils,while in rhizosphere soil,phoC gene microbial community structure is regulated by more environmental factors.phoC between different treatments The differences in the structure of genetic microbial communities are more obvious than in non-rhizosphere soils;in both rhizosphere and non-rhizosphere soils,the phoD gene microbial community structure is regulated by multiple environmental factors,among which pH is the most critical environment affecting the phoD gene microbial community structure factor. |
