Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with more than 85% of terrestrial plant species and play key roles in nutrient cycling and ecosystem functioning. Most plant individual stimulates nutrient availability through their fungal partner. Highly mycorrhizal-dependent plant species derive more benefits from AMF in comparison to low mycorrhizal dependency plant species. But the effects of AMF on the competition between mycorrhizal and non-mycorrhizal plants remained largely unclear, particularly in an environment with low phosphate bioavailability. The increased phosphate availability for host plants and enhanced plant phosphorus nutrition is a major outcome of the AM symbiosis and then AMF colonization could and consequently increase plant biomass. The larger plants are then expected to be successful competitors.
In our previous, AMF colonization significantly decreased phosphorus concentration and content of rape roots compared with non-inoculation treatments, while in contrast mycorrhizal association improved phosphorus nutrition of maize plants. The results clearly showed the beneficial effects of mycorrhizal associations on AMF host plants in competition with non-host plants. In this previous research, plants were cultivated in purple soil with higher phosphorus availability which is more important as this determined the effect of AMF inoculation on host plant P nutrition. Then in this research, calcareous fluvo-aquic soil with lower phosphorus availability was used and different form of inorganic phosphorus were measured to reveal the effect of AMF inoculation on competition between mycorrhizal plant and non-mycorrhizal plants species. Maize (Zea mays L.) and rape (Brassica napus L.) plants were cultivated in three different interaction patterns, namely intraspecific (monoculture), intespecific (intercropping) and no interaction (nylon net split). All plants were inoculated with Glomus intraradices, Glomus mosseae or remained uninoculated. The strength of competition was measured as the reduction in biomass caused by the presence of a competitor. The results showed that AMF inoculation decreased soil inorganic phosphate significantly and transformed more Ca₁₀-P and O-P into higher availability phosphorus form. In the intercropping treatment, the inoculation improved the plant growth and phosphorus uptake of maize, and meanwhile decreased the growth and phosphorus uptake of rape significantly. Our results clearly showed the strong competitive strength and phosphorus competitive strength of maize to rape., and the beneficial effects of mycorrhizal associations was due to the favorable growth of host plants over non-host plants. It reveals that AM fungus may play an important role in structuring plant community and needs a comprehensive insight to understand the effect of AM fungus on plant biodiversity in ecosystems.