Effects Of AM Fungi And Phosphate Solubilizing Bacteria On Alfalfa Production Performance And Soil Phosphorus Availability

In agricultural production,phosphate fertilizer is often used to improve crop yield.However,excessive application of chemical fertilizer will increase production costs and soil pollution.Application of bacterial fertilizer in soil can not only improve the utilization rate of phosphate fertilizer,but also increase crop yield of plant.At the same time,it can reduce the pollution caused by excessive use of chemical fertilizer in agriculture and make agriculture sustainable development.Objective:In this study,alfalfa(Medicago sativa L.)was used as the research object.The effects of arbuscular mycorrhizal fungi(AMF)and phosphate solubilizing bacteria(PSB)inoculated on alfalfa production performance and soil phosphorus availability were studied under different phosphorus application levels.The relationship between alfalfa growth indexes under the interaction of bacteria and phosphorus,as well as the effect of bacteria phosphorus interaction on alfalfa Growth and soil availability were studied,and the best bacterial phosphorus suitable for alfalfa high quality and high yield was screened coupling mode.Methods:A two factor randomized block design was used in the experiment,in which two factors,bacteria and phosphorus,were set up.For the tested strain,AMF Funneliformis mosseae(Fm)was selected.For the PSB,Bacillus megaterium(Bm)was selected.There were four levels of phosphorus application and bacterial inoculation.The treatment group was inoculated with Funneliformis mosseae,and the average amount of fungus was 10 g/pot.In the Bacillus megaterium inoculation treatment group,the average amount of bacterial solution in per pot was 10 m L.In the mixed inoculation group,each pot was applied Bacillus megaterium 5 g(about 8500 inoculation potential units)and 5 m L.After adding the same quality bacteria as the mixed inoculation group,the treatment group of no bacteria(J₀)was sterilized for 30min at 121?.Four levels of phosphorus application were set up:0(P₀),50(P₁),100(P₂)and 150mg/kg(P₃),respectively.Four inoculation treatments were as follows:no inoculation(J₀),Funneliformis mosseae(J₁),Bacillus megaterium(J₂)and double inoculation(B.megaterium+F.mosseae)(J₃),a total of16 treatments.Each treatment was repeated six times.Results:1)Under the same treatment,the contents of dry matter yield(DM)of alfalfa,crude protein(CP),neutral detergent fiber(NDF)and acid detergent fiber(ADF),plant phosphorus content,phosphorus utilization efficiency,organic acid and organic matter showed a trend of first increase and then decrease with the increase of phosphorus application rate.The partial productivity and agronomic efficiency of P fertilizer decreased with the increase of P application rate,while the content of soil phosphatase activity,total phosphorus(TP)and available phosphorus(AP)in soil increased with the increase of phosphorus application rate.The mycorrhizal infection rate,aboveground biomass,the CP content and dry matter yield of alfalfa in P₂(100 mg/kg)treatment were significantly higher than those in P₀and P₁treatment(P<0.05).Under the condition of J₁treatment,the phosphorus content of alfalfa in the treatment of P₂was significantly higher than that of other treatments(P<0.05).The contents of TP and AP in soil in P₂and P₃treatments were significantly higher than those in P₁treatments(P<0.05).Under the condition of J₂treatment,the phosphorus content of alfalfa in the treatment of phosphorus application was significantly higher than that in the treatment without phosphorus application(P<0.05).The total DM of alfalfa reached the maximum under J₂P₁treatment.The content of TP and AP in P₃treatment was significantly higher than that in P₀treatment(P<0.05).Under the condition of J₃treatment,The partial productivity and agronomic efficiency of P fertilizer reached the maximum at P₀treatment,and the contents of TP and AP in soil at P₃treatment were significantly higher than those of other treatments(P<0.05).The other indexes reached the maximum at J₃P₂treatment.2)The mycorrhizal infection rate,production performance,chlorophyll,soluble sugar and phosphorus utilization efficiency of inoculated alfalfa were significantly higher than those of non inoculated(J₀)treatment(P<0.05).The DM of alfalfa,plant phosphorus content,phosphorus use efficiency,the TP and AP in soil content of alfalfa under single inoculation and mixed inoculation were significantly higher than those under non inoculation(P<0.05),and the DM of alfalfa,the TP and AP in soil content reached the maximum in J₃treatment.The correlation coefficient between AP content in rhizosphere soil and DM of alfalfa was the largest,and the fitting effect was the best.The contents of TP and AP were significantly positively correlated with the total DM of alfalfa.In each stubble,there were extremely significant differences between J,P and J�P treatments(P<0.01).3)According to the growth,nutritional quality,chlorophyll content and soluble sugar content of alfalfa,the priority of the subordinate function was J₃P₂>J₁P₂>J₃P₁treatment.The order of organic acid content in rhizosphere soil was acetic acid>malic acid>oxalic acid>citric acid.Conclusion:When the phosphorus application rate was 100 mg/kg,AM fungi and phosphate solubilizing bacteria mixed inoculation was conducive to promoting the growth of mycorrhiza,significantly increase the content of AP in soil,and the effect of improving the growth and phosphorus nutrition of alfalfa was the best.Therefore,it is of great significance to study the mechanism of PSB for improving the utilization efficiency of phosphorus in alfalfa.