Moderate Amount of Phosphorus Enhanced Winter Wheat Yield and Fertilizer Uptake Efficiency by Reducing the Loss of Gaseous Nitrogen and Increasing the Accumulation of Phosphorus and Nitrogen in Plants

Optimum phosphorus (P) management is important for retaining winter wheat grain yield while reducing the environmental risk caused by N loss. P fertilizer strongly influences nitrogen losses, nutrient translocation, and greenhouse gas emissions. However, important uncertainties remain about the optimization of P management to simultaneously achieve yield maximization and yield-scaled Nr loss minimization in winter wheat systems. We conducted a two-season winter wheat rotation with contrasting P fertilization treatments (0, 45, 90, 135 and 180 kg P2O5 ha−1; hereafter, P0, P1, P2, P3, and P4, respectively) per season to assess the effects of the amount of P input on grain yield, nitrogen use efficiency, and the balance of nitrogen/P accumulation and loss. The results showed that an increased P amount significantly boosted winter wheat grain yield, but the tendency slowed down when the input was over 135 kg P2O5 ha−1. Although there was no significant difference in yield between the P2 treatment and the P3 treatment, the phosphorus fertilizer utilization efficiency was significantly higher in the P2 treatment. Specifically, the treatment with 90 units of phosphorus application (P2) produced a significant increase in the yield of wheat compared with the treatment without phosphorus fertilizer application (P0), with a yield increase ranging from 5.96% to 37.86%. Yield gains were primarily associated with a significant increase in the accumulation and translocation of nitrogen and phosphorus, resulting in an increase of 45.85–156% and 40.25–52.46% in the utilization efficiency of phosphorus and nitrogen fertilizers. Under the P2 treatment, the nitrogen transport volume, phosphorus transport volume, and nitrogen assimilation volume significantly exceeded those in the other treatments. Under the P2 treatment, the nitrogen and phosphorus transport volumes in the vegetative organs were significantly increased. The P2 treatment led to a significant decline in the emission flux and cumulative emission of nitrous oxide and ammonia volatilization, significantly reducing the global warming potential and greenhouse gas emission intensity. These observations offer empirical and conceptual support for optimizing P application in winter wheat cropping systems, promoting a mutually beneficial scenario for agricultural production and ecological protection.