Interaction of Nitrogen and Phosphorus on Wheat Yield, N Use Efficiency and Soil Nitrate Nitrogen Distribution in the North China Plain

To establish the optimal fertilization rate to maintain high wheat yield and low environmental risk in the North China Plain, a two-year field experiment (2016–2018) was conducted with six combinations of two N rates (N0; N1: 240 kg ha−1) and three P rates (P0; P1: 150 kg ha−1; P2: 240 kg ha−1) to investigate the effects of these regimes on wheat grain yield, N assimilatory enzyme activity (nitrate reductase, NR and glutamine synthetase, GS), N...