Phytate utilization of maize mediated by different nitrogen forms in a plant-arbuscular mycorrhizal fungus-phosphate-solubilizing bacterium system

A pot experiment was conducted to investigate the organic phosphorus (P) (phytate) utilization of Zea mays L. with different nitrogen (N) forms (NH4+ and NO3-) when both arbuscular mycorrhizal (AM) fungus (Funelliformis mosseae) and phosphate-solubilizing bacterium (PSB, Pseudomonas alcaligenes) are present. The soil was supplied with either KNO3 or (NH4)(2)SO4 (200 mg kg(-1) N) with or without phytin (75 mg P kg(-1)). Results showed that the application of NH4+ to the soil in a plant-AM fungus-PSB system decreased rhizosphere pH and increased phosphatase activity. It also enhanced the mineralization rate of phytin, which resulted in the release of more inorganic P. The application of NO(3)(-)promoted mycorrhizal colonization and hyphal length density in the soil. The inorganic P in the hyphosphere decreased, but more P was transferred to the plant through the mycorrhizal hyphae. Hence, in addition, the application of the two different N forms did not significantly alter the content of plant P. The plant supplied with different N fertilizers acquired P through different mechanisms associated with other microbes. NH4+ application promoted phytin mineralization by decreasing soil pH, whereas NO(3)(-)application increased inorganic P uptake by strengthening the mycorrhizal pathway.