Phosphorus Occurrence And Soil Microbial Activation And Utilization Potential Analysis Under Different Phosphorus Supply Levels In Purple Soil

In agricultural production,phosphorus can improve the drought resistance,cold resistance of crops,high yield,quality and other aspects of crops has a very important role.In recent years,due to the excessive input of phosphorus,phosphorus accumulates in soil,which has become a potential source of non-point source pollution.How to improve the utilization efficiency of fertilizer phosphorus and soil accumulated phosphorus and achieve the goal of"reducing phosphorus and increasing efficiency"has important theoretical significance and application value.Phosphorus fertilizer is also affected by microorganisms such as mycorrhiz,phosphorus-solving bacteria and rhizobium,etc.For a long time,there have been many studies on the enhancement of phosphorus uptake by microorganisms in roots,but the contribution potential of mycorrhiz and microorganisms to crop phosphorus uptake under field conditions is lacking.Therefore,this study used the field location test(0,25,50,100,200,400 kg/ha)to study the occurrence of P in purple soil under different P supply levels in Yongxing Town,Jiangjin District,Chongqing.On this basis,the expression of different functional genes involved in soil P geochemical cycle was compared by using high-throughput quantitative PCR.to evaluate the potential of microbial activation and utilization of accumulated phosphorus.The contribution of arbuscular mycorrhizal fungi to phosphorus nutrient status of host plants was analyzed by field in situ experiments,which provided a theoretical basis for tapping the potential of soil microbial phosphorus supply.The main research results are as follows:(1)The results showed that the contents of Olsen-P and total P in soil increased significantly with the increase of P application.The soil available P decreased by 4.669mg/kg for every 100kg/ha of P deficiency under the condition of no P application.Under the condition of P application,the accumulation of available P was different with the increase of P surplus under different P supply levels.The maximum was that when P application amount was 400 kg/ha,the soil available P decreased by 100kg/ha of P surplus.The increase of available P was 11.72 mg/kg.P classification results show that the inorganic phosphorus content increased with the increase of fertilizer rate of components,after long-term fertilization,active phosphorus(Resin-Pi,Na HCO₃-Pi and Na HCO₃-Po)and stability of P(C.HCl-Pi,C.HCl-Po and Residual-P)accounts for the percentage of the total phosphorus with the increase of fertilizer rate at first and lowered later in the active phosphorus(Na OH-Pi?Na OH-Po and D.HCl-Pi)after the first drop,treatment P400 active phosphorus in dealing with the highest,active phosphorus and phosphorus decrease stability,to active phosphorus transformation;The phosphorus content of organophosphorus components also increased with the increase of fertilizer application rate.Residual-P increased with the increase of the Residual level,but no significant difference was found between treatments.C.HCl-Pi and Na OH-Pi were the main phosphorus sources of inorganic phosphorus,and Na HCO₃-Pi,resin-P,D.HCl-Pi and C.HCl-Pi were the potential phosphorus sources of plants in the non-fertilization treatment.With the increase of fertilizer application,Na OH-Pi became the main phosphorus source.Path analysis showed that among the organic and inorganic phosphorus components,the most contribution to available phosphorus was resin-pi,Na HCO₃-Pi,Na HCO₃-Po and Na OH-Po,and the phosphorus extracted by sodium hydroxide was the main form of organic phosphorus.(2)The adsorption characteristics of phosphorus are highly consistent with the Langmuir,Freundlich and Temkin isothermal equations,and the correlation of determination coefficients is extremely significant.The adsorption curve showed multiple adsorption levels,and the desorption amount increased with the increase of the concentration of equilibrium solution.Compared with other treatment curves,P200 and P400 showed a larger jump.Fertilization decreased the soil maximum adsorption capacity(Qm),and K increased significantly with the increase of fertilizer application rate.Fertilization enhanced the soil buffer capacity(MBC)to phosphorus,and the higher the fertilizer application rate,the higher the buffer capacity.Increasing the adsorption saturation(DPS)of soil phosphorus,treating P200 and P400 with DPS values far greater than the critical value of 25%,poses great environmental risks.QM was negatively correlated with available P,p H and organic matter.K was positively correlated with available P,and the correlation coefficient reached 0.5779.K was positively correlated with organic matter,and negatively correlated with p H.MBC was positively correlated with available phosphorus(correlation coefficient was 0.8028),positively correlated with organic matter and negatively correlated with p H,which did not reach significance.RDP was positively correlated with available phosphorus(correlation coefficient was 0.7826),positively correlated with organic matter,and negatively correlated with p H,which was not significant.DPS was significantly positively correlated with available phosphorus,with a correlation coefficient of 0.9429,positively correlated with organic matter,and negatively correlated with p H,which was not significant.(3)The enzyme analysis showed that the activities of soil acid phosphatase(AP)and alkaline phosphatase(ALP)reached the peak at 50 kg/ha,and the enzyme activities increased first and then decreased with the increase of phosphorus application rate,indicating that low phosphorus application level promoted the activity of acid phosphatase,while high phosphorus application rate inhibited the activity of phosphatase.High-throughput quantitative PCR data showed that different phosphorus supply levels had significant effects on the genes related to the key processes in the phosphorus cycle(organic phosphate mineralization,inorganic phosphorus dissolution,inorganic phosphorus hydrolysis).In the fertilizer rate of 50 kg/ha,organic phosphate rock of gene phn K and pho D,inorganic phosphorus dissolving gm GDH,pqq C and hydrolysis genes PPX gene copy number,the biggest difference between with other processing significantly,showed that fertilizer rate under the experimental condition is25 kg/ha is conducive to mineralization,dissolution and hydrolysis activity of the biochemistry of soil phosphorus cycle.After that,the copy number of each gene decreased gradually with the increase of fertilizer application rate,and showed obvious inhibitory effect under high phosphorus concentration.When the fertilizer application rate was over 200 kg/ha,the copy number of all genes except gene phn K was significantly lower than that without phosphorus application.(4)Field test results show that the in situ not rotating under the processing of corn biomass,content of phosphorus and phosphorus uptake than rotating handle,show no rotary processing,and corn form symbiotic relationship of mycorrhizal fungi,the hyphae can absorb phosphorus nutrients from the environment,can meet the needs of crop growth,therefore,the indigenous AMF can form symbionts with corn,improve phosphorus nutrition of maize,and effectively promote the growth of maize,preliminary illustrates the AMF potential applications in the field conditionsIn conclusion,different phosphorus supply levels have effects on the contents of Olsen-P,total phosphorus,inorganic phosphorus,organic phosphorus,phosphatase activity and P cycle functional genes in the soil.Considering environmental and economic factors,25-100 kg/ha fertilizer application rate is the best.