Planting maize (Zea mays L.) reasonably densely and adding amounts of appropriate nitrogen fertilizer are essential measures to improve the efficiency of maize yield and nitrogen use. In this study, two planting densities of 7.5 × 10⁴ plants ha⁻¹ and 12.0 × 10⁴ plants ha⁻¹ were established with the maize varieties DengHai 618 (DH618) and XianYu 335 (XY335). Simultaneously, 18 levels of nitrogen application were established, including a lack of nitrogen (N0) and increments of 45 kg ha⁻¹ nitrogen up to 765 (N765) kg ha⁻¹. The variables studied included the effects of the rate of nitrogen application on the characteristics of dry matter accumulation and the yield under drip irrigation, and they were integrated into water–fertilizer integration. The results indicated that the yield, harvest index, and dry matter accumulation of maize displayed a trend of increasing and then tending to be flat as the amount of nitrogen applied increased. The use of linear plus platform equation fitting indicated that the change in yield with nitrogen administered had the lowest turning point at N = 279 and N = 319, respectively. The next parameter that was measured was the harvest index. When highly dense maize was grown before silking, the rate of nitrogen applied was more obviously impacted by the accumulation of dry matter. The harvest index contributed 22.9–27.2% of the yield, and the total dry matter accumulation before and after silking contributed more than 70% of the production. Increasing the amount of nitrogen fertilizer is beneficial to prolonging the dry matter accumulation time and increasing the dry matter accumulation rate. The accumulation amount of dry matter was positively correlated with accumulation time and rate, and the correlation between dry matter and accumulation rate was greater. In conclusion, applying the right amount of nitrogen can dramatically increase the harvest index, accumulation of materials, and yield, with dry matter accumulation having the greatest influence on yield. The creation of dry matter is influenced by the time and rate of its accumulation, with its rate serving as the primary controlling factor.

Stalk lodging in Huang-Huai-Hai summer maize is a serious problem that reduces maize yields and precludes the use of mechanical grain harvesting equipment. In order to determine the effect of nitrogen management on the lodging resistance of maize stalk, three nitrogen application rates of 150, 250, and 350 kg ha⁻¹ (denoted as N150, N250, and N350), and different nitrogen application periods (sowing, 6-leaf, 12-leaf, silking) were set. Plant morphology, stalk mechanical strength, total carbohydrate, nitrogen content, and yield were measured in the different treatments. The results showed that as the nitrogen application rate increased and nitrogen application was postponed, the stalk breaking force, plant height, ear height, center of gravity height, stalk basal internode diameter, rind penetration strength, content of carbohydrate, and total N of maize stalk also increased. The stalk lodging resistance was improved by the increased nitrogen application rate and postponed nitrogen application by increasing the stalk material accumulation and mechanical strength. The nitrogen application rates had no significant effect on grain yield. Under N250 and N350, the treatments with no base fertilizer significantly decreased the kernel number per ear, reflected in some in grain yield. In summary, under the conditions of integrated water and fertilizer drip irrigation and fractional nitrogen fertilizer applications, increased nitrogen fertilizer input can stimulate the growth of high-quality maize populations, significantly improve stalk lodging resistance in the early growth stage, delay stalk senescence, improve stalk strength and influence stalk composition in later growth stages. Based on the summer maize grain yield and stalk lodging resistance, under N250 treatment, a base fertilizer combined with topdressing at the 12-leaf and silking stages was beneficial to the growth of summer maize.

The rational application of nitrogen fertilizer and close planting are two important ways to obtain high yields and efficient growth from maize (Zea mays 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 × 10⁴ plants ha⁻¹ and 12.0 × 10⁴ plants ha⁻¹, respectively. Application rates of nitrogen within the range of 0–765 kg ha⁻¹ per 45 kg ha⁻¹ 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 × 10⁴ plants ha⁻¹ density, the best yield was 17.6–20.2 t ha⁻¹, and the required nitrogen application rate was 219–337 kg ha⁻¹. Under conditions of 12.0 × 10⁴ plants ha⁻¹ density, the best yield was 18.7–21.9 t ha⁻¹, and the required nitrogen application rate was 243–378 kg ha⁻¹. 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 × 10⁴ plants ha⁻¹, the recommended nitrogen application rate was 340 kg ha⁻¹, 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 × 10⁴ plants ha⁻¹, the recommended nitrogen application rate was 380 kg ha⁻¹, 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.

Nitrogen is pivotal for high-yield maize (Zea mays L.), but excessive nitrogen application and improper timing remain common in production. Clarifying nitrogen strategies and population nitrogen accumulation under high density is urgent. This study set two density levels (7.5 × 10⁴ plants ha⁻¹; 12.0 × 10⁴ plants ha⁻¹) and eight nitrogen management methods: the no nitrogen (N0), all-basal nitrogen (Fbase, total nitrogen: 360 kg ha⁻¹), and post-silking topdressing methods (total nitrogen: 360 kg ha⁻¹) with nitrogen proportions of 0% (F0%, post-silking topdressing: 0 kg ha⁻¹), 20% (F20%, post-silking topdressing: 72 kg ha⁻¹), 40% (F40%, post-silking topdressing: 144 kg ha⁻¹), 60% (F60%, post-silking topdressing: 216 kg ha⁻¹), 80% (F80%, post-silking topdressing: 288 kg ha⁻¹), and 100% (F100%, post-silking topdressing: 360 kg ha⁻¹). Fertilization was applied via drip irrigation. Results demonstrated that the highest yield was obtained under F60% at 7.5 × 10⁴ plants ha⁻¹ and under F40% at 12.0 × 10⁴ plants ha⁻¹. Appropriate post-silking nitrogen increments synergistically improved kernel number per ear and 1000-kernel weight. The post-silking nitrogen topdressing proportion significantly affected maize stand nitrogen accumulation. At maturity, the highest nitrogen accumulation was observed under F60% at 7.5 × 10⁴ plant ha⁻¹ density and under F40% at 12.0 × 10⁴ plants ha⁻¹ density. For the 7.5 × 10⁴ condition, the duration of the rapid nitrogen accumulation period was extended by 11.9–39.2 days and maximum nitrogen accumulation increased by 15.52–57.20%; at 12.0 × 10⁴, maximum nitrogen accumulation rose by 15.89–64.46%. In summary, appropriately increasing the proportion of post-silking nitrogen application can enhance maize yield, nitrogen accumulation, and nitrogen uptake efficiency. Specifically, a 60% post-silking nitrogen application ratio is recommended for a 7.5 × 10⁴ plants ha⁻¹ density and a 40% ratio for a 12.0 × 10⁴ plants ha⁻¹ density. These two strategies can significantly increase kernel number per ear and 1000-kernel weight, thereby improving maize yield and nitrogen use efficiency.