| Summary: | The rational application of nitrogen fertilizer and close planting are two important ways to obtain high yields and efficient growth from maize (<i>Zea mays</i> L.). This study utilized the maize varieties DengHai 618 and XianYu 335 as test materials from 2019 to 2020 and the maize variety XianYu 335 as the test material in 2021. The planting densities were 7.5 × 10<sup>4</sup> plants ha<sup>−1</sup> and 12.0 × 10<sup>4</sup> plants ha<sup>−1</sup>, respectively. Application rates of nitrogen within the range of 0–765 kg ha<sup>−1</sup> per 45 kg ha<sup>−1</sup> were considered the nitrogen application gradient. The results showed that as the nitrogen application rate increased, the yield of the maize increased at first and then tended to remain flat. Under conditions of 7.5 × 10<sup>4</sup> plants ha<sup>−1</sup> density, the best yield was 17.6–20.2 t ha<sup>−1</sup>, and the required nitrogen application rate was 219–337 kg ha<sup>−1</sup>. Under conditions of 12.0 × 10<sup>4</sup> plants ha<sup>−1</sup> density, the best yield was 18.7–21.9 t ha<sup>−1</sup>, and the required nitrogen application rate was 243–378 kg ha<sup>−1</sup>. With the increase in the nitrogen application rate, the dry matter weight showed a linear/platform relationship in each growth period. The best nitrogen application rate was obtained for dry matter accumulation in various stages by fitting the nitrogen application rate and dry matter accumulation in different stages. It is concluded that when the planting density was 7.5 × 10<sup>4</sup> plants ha<sup>−1</sup>, the recommended nitrogen application rate was 340 kg ha<sup>−1</sup>, and the distribution ratio of the nitrogen application rates before and after silking were 61.2% and 38.8%, respectively. When the planting density was 12.0 × 10<sup>4</sup> plants ha<sup>−1</sup>, the recommended nitrogen application rate was 380 kg ha<sup>−1</sup>, and the distribution rates before and after flowering were 65.8% and 34.2%, respectively. In summary, increasing planting density can improve maize yield, and the amount of nitrogen applied should be increased before flowering.
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