Arbuscular mycorrhizal fungi enhance soybean phosphorus uptake and soil fertility under saline-alkaline stress

Fungus-fertilizer interactions can enhance agricultural productivity and effective resource utilization, however, the study of the effect of arbuscular mycorrhizal fungi (AMF) and phosphorus on soil fertility and nutrient uptake of soybeans under salinity stress is still unclear. In this study, a mixture of three AMFs (Funneliformis mosseae, Rhizophagus intraradices, and Diversispora epigaea) was inoculated into the salt-sensitive soybean (Glycine max (L.) Merr.) cultivar 'Wuxing No.2' in a pot experiment set up for inoculation, no inoculation and five levels of phosphorus (P₂O₅) supply (such as 0, 50, 100, 250, 500 mg P kg^-1), bacterial phosphorus interactions totaling 10 treatments, each treatment 7 replications. Soil nutrient content and soybean nutrient uptake and translocation rates were determined at seasons of flowering pods, tympanic period and harvest period, respectively. Under low phosphorus (50 mg kg^-1) conditions, the soil available phosphorus content at the seasons of flowering pods increased by 23.11% compared with the uninoculated group. The accumulation of nitrogen, phosphorus, and potassium in the plants increased significantly, with the phosphorus content in leaves reaching 4.72 mg·g^-1, which was 98.50% higher than that in the high-phosphorus non-inoculated treatment. Meanwhile, it optimized nutrient partitioning, promoting the transfer of phosphorus to the stalks (with the phosphorus transport rate in stems being 37.27% in the + AMF P50 treatment) to support grain formation. In contrast, the uninoculated group required a higher phosphorus level (250 mg kg^-1) to reach the peak of biomass, with the root fresh weight peaking at 13.71 g. The low phosphorus inoculation treatment can improve soil fertility and plant nutrient uptake and utilization, and promote the efficient use of agricultural resources.