Nitrogen and Planting Density Improve Biological Yield and Quality of Silage Corn Across Different Maize Varieties in the Huang–Huai–Hai Region

The diversity of silage corn types has increased in the Huang–Huai–Hai region, including dual‐purpose, general‐purpose, and silage‐specific types. We investigated the yield and quality in response to different silage corn (dual‐type: Jiyu3421; general‐type: Jiyu 757, and silage‐specific type: Jingke 516) at different planting densities (D1, 6.75 × 10 4 ; D2, 7.50 × 10 4 ; D3, 8.25 × 10 4 ; D4, 9.00 × 10 4 ; and D5, 9.75 × 10 4 plants/ha) and nitrogen topdressing levels (non, N0; 60 kg/ha, N60; and 120 kg/ha, N120) over 2 years. Results showed that nitrogen topdressing significantly increased both total fresh matter yield and ear fresh weight yield of silage corn, with the maximum total fresh matter yield rising by up to 16.3%. Both total fresh matter and ear fresh weight yield showed a quadratic relationship with planting density, and those in N60 were more sensitive to planting density than in N0 or N120. Jiyu3421 and Jingke516 were suitable for medium density, whereas Jiyu757 had better yield at low density. Regarding quality, starch content was highest in N60D3, followed by N120D1 and N0D5. The highest crude protein content occurred in N120D3, followed by N60D5 and N0D1. Jingke516 exhibits superior quality compared with other cultivars under high topdressing nitrogen. Further analysis revealed that nitrogen use efficiency in N120 was greater than that in N60 and showed a positive correlation with planting density. Conversely, nitrogen absorption efficiency decreased significantly under N120, exhibiting a strong negative correlation with planting density. Overall, our findings demonstrate that nitrogen‐density combinations have different effects on yield and quality regulation, and nitrogen‐density adaptability among varieties varies significantly. Under 120 kg/ha base nitrogen fertilizer, all the silage corn types enhanced nitrogen absorption and utilization when the nitrogen topdressing and planting density combinations of 60 kg/ha–8.25 × 10 4 plants/ha, 60 kg/ha–6.75 × 10 4 plants/ha, and 120 kg/ha–8.25 × 10 4 plants/ha, respectively. These combinations synergistically improved both yield and quality in silage corn.