Evaluation of Nitrogen Efficiency of Different Stay-Green Maize Hybrids

Stay-green trait is an important agronomic characteristic closely related to high yield, good quality, and stress resistance of maize. This study explored the differences in nitrogen uptake and translocation of different stay-green maize hybrids, aiming to provide a theoretical basis for the physiological mechanism of high nitrogen efficiency in maize.

The tested materials were the stay-green hybrid Shandan 650 and the non-stay-green hybrid Zhengdan 958. In 2023, 6 N treatments were applied: N1 (0 kg·hm^-2), N2 (60 kg·hm^-2), N3 (120 kg·hm^-2), N4 (180 kg·hm^-2), N5 (240 kg·hm^-2), and N6 (300 kg·hm^-2). In 2024, a nitrogen×density interaction experiment was conducted with three N levels—low N (LN, 0 kg·hm^-2), medium N (MN, 180 kg·hm^-2), and high N (HN, 240 kg·hm^-2)—and two planting densities—low density (LD, 60000 plants·hm^-2) and high density (HD, 75000 plants·hm^-2). After the silking stage of maize, indicators were determined for each treatment, such as SPAD value of ear leaves, total number of green leaves per plant, dry matter, and nitrogen accumulation in vegetative organs and grains. Meanwhile, nitrogen absorption and translocation rates as well as nitrogen use efficiency-related indicators were analyzed.

Grain yield of both hybrids initially increased and then stabilized with rising N rates, with Shandan 650 consistently outperforming Zhengdan 958 across all N and density treatments. Post-silking, Shandan 650 exhibited faster chlorophyll degradation (SPAD decline: 65.1% vs. 49.9%) and greater green leaf loss than Zhengdan 958, particularly under low N. Shandan 650 demonstrated superior N remobilization efficiency, especially under low N and high density, with significantly higher N translocation from leaves to grains. Overall, Shandan 650 achieved significantly higher N remobilization efficiency, nitrogen use efficiency, nitrogen agronomic efficiency, and nitrogen harvest index than Zhengdan 958. Furthermore, under high-density planting conditions, reasonable nitrogen reduction further enhanced its nitrogen efficiency performance.

The functional stay-green maize variety Shandan 650 maintains consistent greenness and photosynthetic capacity until a certain period before physiological maturity, at which point a rapid decline occurs along with nitrogen remobilization. Its strong nitrogen translocation capacity in vegetative organs enhances nitrogen translocation rate and nitrogen use efficiency, and higher nitrogen efficiency could be achieved under reasonable nitrogen reduction and density increase.