Improvement of maize post-silking agronomic traits contributes to high grain yield under N-efficient cultivars

Screening maize (Zea mays L.) cultivars for high grain yield while conserving nitrogen (N) fertilizer is of long-term strategic importance in addressing food security and environmental pollution issues. Limited knowledge exists regarding the differences in N efficiency of modern high-yielding cultivars and the agronomic traits that contribute most to grain yield. Revealing these physiological traits is crucial for understanding the limiting factors of grain yield potential in maize cultivars. A three-year (2018–2020) field experiment was conducted using 16 maize cultivars under low-N (LN) and high-N (HN) conditions. Low N stress reduced grain yield by 43% and yield components grain number per ear (GN), 100-grain weight (HKW) and number of ears per hectare (EN) by 22%, 12% and 13%, respectively. Analysis of the relationship between grain yield and agronomic traits has indicated a strong correlation with the accumulation of dry matter (DM) and N, most notably during the post-silking stage. The 16 cultivars were classified into four types according to the average yield of the test cultivars under the conditions of HN and LN as the dividing line. Under HN and LN conditions, the H0HN (efficient under both HN and LN conditions) cultivar type exhibited 21% and 60% higher grain yields compared to the L0LN (inefficient under both HN and LN conditions) cultivar type. The direct path coefficient linking GN to grain yield is 0.592, representing the primary contribution to the variance in grain yield. Under both HN and LN conditions, the H0HN cultivar type demonstrated a significant enhancement in post-silking dry matter accumulation, with increases of 30% and 64% over the L0LN cultivar type, respectively, while the N accumulation post-silking was elevated by 56% and 139%. The cultivars with H0HN and L0HN (efficient only under HN conditions) types had the potential to increase grain yield by 2.4%–6.1% and save 5.5%–15.7% of N fertilizer. Compared with L0LN cultivar type, H0HN cultivar type have higher N uptake efficiency and partial fertilizer productivity of N. In conclusion, the target traits for breeding modern N-efficient cultivars include higher post-silking DM accumulation and N accumulation. These traits play a positive role in increasing GN and the HKW, thereby fostering an increase in grain yield.