Strategic cultivar and planting density integration: Optimizing canopy structure for enhanced yields in sweet maize

High plant density (PD) can differentially impact maize yields depending on cultivar characteristics due to varying responses of canopy structures to high PD, making canopy optimization essential to improve yield. This is especially important for sweet maize, which has received limited attention in dense planting in China. A 2-year (2021–2022) field experiment evaluated the performance of two sweet maize cultivars, MT6855 and YZ7, under three PDs: 4.5, 6.0, and 7.5 plants m⁻² (PD1, PD2, and PD3). Results showed that increasing PD significantly boosted fresh ear yield in MT6855 while having minimal effect on YZ7. Notably, fresh ear yield of MT6855 under PD2 increased by 14.8% compared to PD1. As PD increased, both cultivars exhibited greater plant height, ear height, internode length, and leaf spacing, along with reduced internode diameter. Higher densities also decreased leaf width, leaf area, leaf angle, and net photosynthetic rate but significantly increased leaf area index, leaf orientation value, and canopy photosynthetic capacity. MT6855 consistently outperformed YZ7, with shorter leaf length, wider leaf width, lower leaf angle, higher leaf orientation, improved photosynthetic parameters, and higher SPAD (Soil Plant Analysis Development) values. Fresh ear yield was significantly positively correlated with canopy photosynthetic capacity, leaf width, and leaf orientation value and negatively correlated with leaf angle. These findings suggest that the compact cultivar MT6855 with 6.0 plants m⁻², optimizes canopy structures and enhances photosynthetic capacity, resulting in higher yields. This research offers practical insights for improving sweet maize yield through strategic cultivar selection and PD, supporting food security and sustainable agriculture in China.