*2.1. Study Area*

The present study was conducted in an established research facility, which is part of the Northwest A&F University, located in the Shaanxi Province of China (34◦15−34◦20 N, 107◦56−108◦7 E; 460 m a.s.l.). The region has warm, temperate, and continental monsoon climate. The study area was divided into 20 subplots, each with an area of 5.5 × 6 m2, occupying a total area of 69 × 12 m2. The maize cultivar "Dafeng 26" used in the experiment, and the cropping system was the rotation of winter wheat and summer maize. Five nitrogen (0, 45, 90, 135, and 180 kg <sup>N</sup>·ha−1) and five phosphorus (0, 30, 60, 90, and 120 kg P2O5·ha−1) application levels were set in the subplots. All fertilizers were applied at the time of sowing, and other managemen<sup>t</sup> measures followed local practices. The location of the study area, plot setting and fertilization are shown in Figure 1.

**Figure 1.** Location of study area and fertilization of plot.
