Most plants associate with arbuscular mycorrhizal (AM) fungi which can enhance their growth and nutrient uptake. Outcomes of the AM symbiosis can be highly variable, depending on soil fertility, plant functional group (C3, C4) and AM fungal diversity. This study assessed the growth and nutrient (C, N, P) responses of two C3 (Triticum aestivum and Hordeum vulgare) and two C4 (Sorghum bicolor and Zea mays) plants to different AM fungal inocula (no AM fungi, single AM fungal species, and four AM fungal species) under high and low P conditions. Higher AM fungal diversity resulted in greater P concentration and aboveground biomass of H. vulgare and S. bicolor. Triticum aestivum did not respond to AM fungi, while Z. mays responded positively but a similar positive response of Z. mays growth and nutrition occured when it was colonised with single or multiple AM fungal species. These findings suggest that, although C3 crop plants are less responsive to AM fungi than C4, some C3 and C4 species can benefit from higher AM fungal diversity in the soil.