Grain yield and nutrient uptake and utilization in spring-sown waxy maize under varying plant densities and fertilization regimes

Increasing plant density and delaying the application of amino acid compound fertilizer enhance grain yield and nitrogen use efficiency. The combination of 7.5×10 4 plants ha −1 with a single application of amino acid compound fertilizer at the six-leaf stage achieves the highest total score and sustainability index. Greater grain yield is primarily attributed to enhanced post-silking dry matter and nitrogen accumulation. Elevated grain yield is associated with higher nitrogen agronomic efficiency and nitrogen recovery efficiency. Increasing maize plant density (PD) is key to enhancing grain yield (GY), and one-time application of slow-release fertilizers represents an efficient and resource-saving practice. However, the interaction between PD and fertilization mode (FM) in waxy maize production remains poorly understood. This study systematically evaluated the interactive effects of PD and FM on dry matter (DM) and nitrogen (N) accumulation, translocation, and distribution, and their relationships with GY and N use efficiency (NUE) in waxy maize. Two waxy maize varieties were grown across five PD levels (D1-D5: 4.5×10 4 , 5.25×10 4 , 6.0×10 4 , 6.75×10 4 , and 7.5×10 4 plants ha −1 ) and four FMs (F0, no fertilization; F1, conventional compound fertilizer at sowing plus urea topdressing at the six-leaf stage; F2, one-time application of amino acid compound fertilizer [Amino acid compound fertilizer (ACF)] at sowing; F3, one-time application of ACF at the six-leaf stage; total N-P 2 O 5 -K 2 O=225-75-75 kg ha −1 ) during the 2021-2023 growing seasons. Although higher PD reduced kernel weight and kernels per plant, increased population density compensated for these reductions, resulting in greater GY. Among all treatments, the D5F3 treatment (7.5×10 4 plants ha −1 with F3) achieved the highest GY, total score, and sustainability index. This outcome was driven by greater post-silking DM and N accumulation, an improved harvest index, and enhanced leaf reserve translocation. Given uniform fertilization rates across treatments, the higher yield under D5F3 led to superior N agronomic efficiency, N internal efficiency, N recovery efficiency, and N partial factor productivity. In conclusion, increasing PD and postponing ACF application enhance GY primarily by improving post-silking DM and N accumulation and harvest index, while concurrently increasing NUE. Field management strategies should therefore prioritize maximizing post-silking DM and N uptake to simultaneously improve yield and NUE in spring-sown waxy maize.