The Study On The Role Of Microorganisms In The Process Of Reducing Phosphorus Fertilizer And Increasing Efficiency Of Paddy Soil In Black Soil Area

Phosphorus is not only an essential element in the process of plant growth,but also a non-renewable resource.In agricultural production,after chemical P fertilizer was applied,the utilization rate of crops was only 15-20%,and most of them were fixed in the soil.Microorganisms were important participants in the process of soil P cycle.This study is based on the positioning experiment of different phosphate fertilizer application rates of Liaoning Academy of Agricultural Sciences.The experimental treatment includes four chemical phosphate fertilizer application gradients:P₀:no phosphate fertilizer application,P₉₀:90 kg P₂O₅/hm~2,P₁₈₀:180 kg P₂O₅/hm~2,P₃₆₀:360 kg P₂O₅/hm~2.The soil during the ninth year of rice harvest was selected,and combined with the analysis of soil P occurrence form,microbial biomass,alkaline phosphatase activity,microbial community structure and functional genes,the change characteristics and microbial action mechanism of soil P pool under different chemical P fertilizer application gradient(field experiment)and adding compost organic fertilizer(indoor culture experiment)were studied.The research results are expected to provide theoretical support for the measures of reducing P and increasing efficiency of farmland in black soil area.The main results were as followed:1.The occurrence forms of soil P pools and the action mechanism of microorganisms in paddy soils with different chemical P application gradients in the ninth year of the field experiment were analyzed.The results of soil P pool study showed that compared with the blank control(P₀)without P application,the contents of soil TP and Olsen-P increased significantly with the increase of P application rate.Furthermore,through the further analysis of P forms by Tissen method,it was found that the contents of soil A-P,S-P and MLPo increased significantly with the increase of P application rate,and the content of LPo was the highest in P₉₀ treatment.The Pearson correlation thermograms of different P forms showed that MLPo was significantly positively correlated with A-P,P-P and S-P(P<0.05).Furthermore,high-throughput sequencing was used to analyze soil microbial community and phoD functional genes.The results showed that P₉₀ significantly increased the richness and diversity of soil bacteria and fungi compared with P₀,but had no significant effect on phoD-harboring bacteria,and its microbial ecological network was more stable than other treatments.Based on the comprehensive analysis of rice yield(P₉₀ highest),soil available P content,microbial community abundance and network structure,we think that the amount of 90kg P₂O₅/hm~2 P application is the optimal amount in this paddy soil.However,the ecological network structure of phoD-harboring bacterial community was the most stable and complex in P₀ treatment,and the key species changed from Rhizobium in no-P treatment to Pseudomonas in P treatment.The correlation network analysis between microorganisms and P showed that microorganisms had the greatest influence on organic P,especially MLPo was significantly correlated with 56 genera.Partial least square path analysis showed that phoD-harboring bacterial community had a significant positive effect on S-ALP and S-ALP had a significant positive effect on organic P.2.Furthermore,the soil treated with P₀ in the above field experiment was selected,and the synergistic effect of adding organic fertilizer on soil P was analyzed by indoor culture experiment.The results showed that compared with control(CK),soil Olsen-P,LPo,MLPo,moderately stable organic P(FAPo)and microbial biomass carbon(MBC)increased in the treatment of compost.Compared with CK,microbial biomass P(MBP)and alkaline phosphatase activity(S-ALP)increased significantly after 60 days of compost.Through the regression analysis of Olsen-P and organic P forms,it was found that there was a significant positive correlation between Olsen-P and organic P components(LPo and MLPo).The correlation analysis between microbial index and P showed that MBP was significantly positively correlated with LPo,Olsen-P and MLPo,and negatively correlated with FAPo,S-ALP was negatively correlated with LPo and positively correlated with HAPo,and MBC was positively correlated with Olsen-P and LPo,indicating that the addition of compost promoted the turnover of P by microorganisms.The above results showed that the addition of compost promoted the mineralization of organic P by soil microorganisms and improved the availability of P.