The Effect of Nitrogen Rates on Yields and Nitrogen Use Efficiencies during Four Years of Wheat-Maize Rotation Cropping Seasons

Nitrogen is a major limiting factor to crop production of the intensive wheat (Triticum aestivum L.)-maize (Zea mays L.) rotation cropping system in the North China Plain (NCP). This 4-yr study was to evaluate the effects of N application on soil NO3-N dynamics and N use efficiency under sprinkler irrigation in the Beijing region of the NCP. Th ere were four treatments, named CK, N1, N2, N3 with N application of 0, 110, 220, and 330 kg N ha(-1) per crop season, respectively. Results indicate that no water and NO3-N leached out of the 0 to 100 cm soil layer in the winter wheat seasons, whereas they moved into soil layers deeper than 100 cm in the summer maize seasons. Aft er the 4-yr cropping, the NO3-N concentration in the 0 to 120 cm soil profile decreased for CK, then remained relatively stable for N1 treatment, and increased greatly for N2 and N3 treatments. Generally, N application improved crop growth and increased N efficiencies and water use efficiency. Mostly, growth parameters and yields were not significantly (P > 0.05) different among the N1-to-N3 treatments, while N efficiencies decreased with N application increasing. Considering the economic benefit and environmental risk, N application rate of 110 to 130 kg N ha(-1) per crop season is recommended for the wheat-maize rotation cropping system under sprinkler irrigation in the Beijing area and those regions with similar climatic conditions and soil properties in the NCP.