Objectives Many environment-controlled experiments have demonstrated that mycorrhizal symbiosis formed between arbuscular mycorrhizal fungi (AMF) and plant roots can increase plant phosphorus uptake effectively. However, the practical field application of AMF varied greatly in results. In the present study, field trial was established with mycorrhized maize seedlings transplanted to field, to test the effectiveness of AMF inoculation on maize growth, nutrient uptake, grain yield, and also to explore the suitable conditions for field application of mycorrhizal technology.

Methods A field trial was carried out in Yanqing District, Beijing from May to October, 2018, with an inbred line maize strain Zea mays L. cv. B73 as tested plant. The plots were treated with or without P application (+P, –P). The seedling bags (containing 250 g of soil each) were inoculated with or without AMF inoculum (+M, –M). The tested AMF strain was Rhizophagus irregularis Schenck & Smith BGC AH01, and added in rate of 10 g inoculum per bag for +M treatment. The germinated maize seeds were sown into the bags and grew for two weeks before transplanted into field plots. At the elongation stage, the maize leaf photosynthetic rate and stoma conductance were measured by portable photosynthesis system, the plant dry weight, mycorrhizal infection rate, and the P contents of roots and shoots were determined. At the full ripening stage, the 100-grain weight, grain yield and nutrient contents were determined.

Results Whether in –P or +P plots, the AMF infection intensity and arbuscular abundance in roots of mycorrhizal maize seedlings were significantly higher than those of non-mycorrhizal seedlings. In –P plots, the seedling mycorrhization treatment significantly increased the dry weight of maize roots. The growth dependence of maize on AMF in –P plots was 163.7%, which was higher than that in +P plots (124.1%). The photosynthetic rate and stoma conductance of –P–M treatment were significantly lower than those of the other 3 treatments, whereas there was no significant difference among –P+M, +P–M and +P+M. In –P plots, seedling mycorrhization significantly increased P contents in shoots and roots, and the P contents were not significantly different from those in +P plots. Meanwhile, seedling mycorrhization also significantly increased plant biomass and P uptake, grain yield, 100-grain weight and grain zinc, manganese and magnesium contents. By contrast, in +P plots, seedling mycorrhization showed no significant effects on all the tested indexes.

Conclusions Seedling mycorrhization is capable of providing a steadily promoting effect of AMF on maize growth and nutrient uptake including P, Zn, Mn and Mg, which is almost equally efficient as P fertilization in improving maize yield and grain qualities. Therefore, seedling mycorrhization technology could be applied to save P fertilizer rate without loss of crop yield and serve as an alternative strategy for supporting sustainable agriculture.