Enhanced early growth rates in high cumulative temperature requirement maize (Zea mays L.) varieties drive superior production potential in rainfed North China Plain

The delayed onset of the rainy season in the North China Plain (NCP) frequently leads to postponed sowing or germination of summer maize in rainfed areas, thereby shortening the grain filling stage and reducing overall yield. Among the factors influencing maize production potential, cumulative temperature has emerged as a critical determinant. This two-year study assessed four maize varieties with differing cumulative temperature requirements: high cumulative temperature requirement maize varieties (HCTR, 2800–2990 °C; Zhengdan 958 and Xuntian 969) and low cumulative temperature requirement maize varieties (LCTR, 2200–2450 °C; Jifeng 2 and Junyi 86) under late sowing (end of June). Yield, biomass, leaf area index, photosynthetic characteristics, and crop growth rates were analyzed. Results showed HCTR varieties achieved significantly higher yields (19.8 %–25.7 %) than LCTR varieties, even with suboptimal cumulative temperatures (2508.8 °C in 2022; 2694.2 °C in 2023). HCTR varieties had superior hundred-grain weight (10.7 %) and grain number per cob (12.5 %). Aboveground biomass followed a logarithmic growth curve, with HCTR varieties outperforming LCTR throughout, especially at blister (R2, 29.0 %–31.8 %) and milk stages (R3, 9.0 %–12.6 %). This was due to earlier peak growth rates at R2 for HCTR, while LCTR peaked at R3. HCTR also showed higher relative chlorophyll content (5.9 %) and net photosynthetic rate (14.1 %) at R2, though these declined at R3 (4.4 % and 13.0 %, respectively), underscoring their earlier photosynthetic advantage. The key mechanism by which HCTR varieties maintain high yields under insufficient cumulative temperature could be as attributed to the advanced peak photosynthetic rate and optimized biomass allocation. To draw a conclusion, HCTR maize varieties are particularly well-suited for late showing in the rainfed dryland areas of the NCP. These findings provide a theoretical foundation and practical guidance for selecting high-yielding maize cultivars suitable for rainfed dryland areas similar to NCP.