Abstract:

To explore the effects of soil phosphorus levels and exogenous microbial agents on soil functioning(soil physico-chemical properties,soil enzyme activities,and arbuscular mycorrhizal fungi(AMF)community composition and structure)of the rhizosphere soil of maize,a two-factor interaction experiment was conducted to study the effects of two levels of low phosphorus and normal phosphorus and four treatments of inoculation with AMF,phosphate-solubilizing bacteria(PSB),AMF-PSB and no inoculation of exogenous agent(CK)on rhizosphere soil indexes in different growth stages of maize.The results showed that the soil total phosphorus content was the highest at jointing stage and silking stage under the condition of normal phosphorus level+AMF treatment,while the soil available phosphorus content was the highest at jointing stage and mature stage under the condition of normal phosphorus level+AMF treatment.At jointing stage and silking stage,alkaline phosphatase activity was the highest under low phosphorus+AMF treatment,and the activity of alkaline phosphatase under low phosphorus+AMF treatment and low phosphorus+PSB treatment was higher than that under normal phosphorus level.Under low phosphorus level,total phosphorus content and available phosphorus content were higher than CK treatment,and the increase rate was higher than that under normal phosphorus level.At low phosphorus level,soil pH value was lower than CK treatment under the condition of inoculated foreign bacteria,and also lower than CK treatment under normal phosphorus level at jointing stage.Under the low phosphorus level,the CK treatment had the highest observed number of AMF community OTUs and α-diversity indexes,while under the normal phosphorus levels,the observed number of OTUs and α-diversity index in the CK treatment group were lower than those in the AMF and PSB treatments.Non-metric multidimensional scaling analysis indicated that the composition and structure of soil AMF communities were convergently regulated by the types of inoculated exogenous microorganisms.In summary,inoculating AMF and PSB agents in low-phosphorus alkaline maize fields in northern China can improve soil physicochemical properties and increase soil alkaline phosphatase activity,but it also increases competition and exclusion among soil AMFs.

Key words: Arbuscular mycorrhizal fungi(AMF), Phosphorus-solubilizing bacteria(PSB), Alkaline phosphatase, AMF community composition and structure