Objectives Application of nitrogen (N) fertilizer plays important roles in maintaining soil fertility and crop production. Responses of grain yield and soil NO3−-N concentration to N application rates were studied to guide efficient and sustainable fertilization under winter wheat-summer maize rotation system in Huang-Huai-Hai region of China.
Methods The objective of this study was achieved through a long-term (2006‒2013) winter wheat-summer maize rotation experiment conducted on a fluvo-aquic soil in Huang-Huai-Hai region of China. The ten N application rates were: 0 (control), 60, 120, 180, 240, 300, 360, 420, 500, and 600 kg/hm2. The wheat and maize yields were recorded, and soil NO3−-N in 0–200 cm profile were measured.
Results Nitrogen application rate, fertilization year, as well as interaction between fertilization year and N application rate significantly affected the yields of both wheat and maize. Winter wheat yield increased with increase in N application rate, but N 300 kg/hm2 reached the highest wheat yield. Increase in N application rate increased summer maize yield, but the increment became stable from N 120 to 600 kg/hm2. The N rate increased the sustainable yield index of winter wheat, but did not affect that of summer maize. The N rates above 300 kg/hm2 increased the soil NO3−-N content. The cumulative peak of soil NO3−-N content gradually decreased with increase in the year of experiment, and the peak of soil NO3−-N content in 2008, 2011 and 2017 were found in 40–60 cm, 80–120 cm and 80–160 cm soil depths, respectively.
Conclusions Based on our results, N 240 kg/hm2 and 180 kg/hm2 could be recommended as optimal nitrogen application rates for winter wheat and summer maize cultivation in fluvo-aquic soil of Huang-Huai-Hai region. These N application levels could ensure the stability of wheat and maize yield and prevent the increment and accumulation of nitrate N in deep soil.
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