Physiological Regulation of Crop Growth Rate in Quality Protein Maize under Crop Establishment and Weed Management Practices

A two-year field experiment (2024–2025) was conducted under temperate conditions to investigate the physiological regulation of crop growth rate (CGR) in quality protein maize (QPM) as influenced by crop establishment methods and weed management practices. Pooled relationships among leaf area index (LAI), net assimilation rate (NAR), and CGR were examined during three growth intervals (30–60, 60–90, and 90–120 days after sowing, DAS). At 30–60 DAS, CGR increased significantly under weed management treatments. Weed-free and mulch treatments recorded the maximum CGR, showing a 47–53% enhancement over the weedy check, whereas chemical weed control treatments resulted in a relatively lower increase of 26.6–32.7% during both years. In the mid-growth stage (60–90 DAS), CGR was jointly regulated by LAI and NAR, with the combined model explaining 88–92% of CGR variation across years. During late growth (90–120 DAS), CGR under weed-free and polyethylene mulch treatments was 28–34% higher than the weedy check, and NAR emerged as the dominant determinant, accounting for 89–93% of CGR variability, while LAI showed weak or non-significant effects. Crop establishment and weed management practices influenced CGR indirectly by modifying canopy development and assimilatory efficiency rather than through direct treatment effects. The consistency of physiological relationships across both seasons highlights the robustness of growth regulation mechanisms in QPM and provides a mechanistic basis for refining crop establishment and weed management strategies aimed at improving biomass production and yield stability.