Delineating the relationship between planting density and agronomic performance in hybrid winter wheat for elevated yield and nitrogen utilization in the eastern Huang-Huai-Hai Region

Abstract

The study aimed to clarify the impact of different planting densities on accumulation and remobilization of dry matter and nitrogen as well as yield in hybrid winter wheat varieties and their relationships, providing the theoretical basis for high-yield cultivation of hybrid winter wheat in the eastern Huang-Huai-Hai region. During the 2021–2023 winter wheat growing seasons, hybrid variety ‘Jingmai 17’ and conventional variety ‘Jimai 22’ were selected as experimental materials. The study investigated the effects of three planting densities (150 plants/m², 300 plants/m², and 450 plants/m²) on the flag leaf SPAD value, leaf area of per culm (LAC), dry matter and nitrogen accumulation and remobilization, grain yield (GY), and its components during the winter wheat growth period. The findings indicated that the hybrid variety ‘Jingmai 17’ maintained a larger LAC after anthesis, exhibited a slower decline in flag leaf SPAD value during the middle to late grain-filling stages, and had a longer duration of green leaf area post-anthesis, which was conducive to the accumulation of photosynthetic assimilates. This was evidenced by the higher biomass at maturity and post-anthesis, as well as biomass remobilization, thousand-grain weight (TGW), and grain numbers per unit area (GN), compared to ‘Jimai 22’, displaying a distinct heterosis with a yield exceeding standard of up to 10.6%. At a planting density of 300 plants/m², both varieties achieved a suitable LAC, which helped to maintain flag leaf SPAD values during the grain-filling stages, and a slower rate of leaf senescence post-anthesis. This suitable population density enhanced the biomass at maturity, post-anthesis, and the harvest index (HI), resulting in higher GN and TGW, and thus, a higher yield. At 300 plants/m², both varieties not only had higher nitrogen accumulation at maturity but also maintained high pre-anthesis nitrogen remobilization and remobilization rate, and the higher yield resulted in moderate nitrogen use efficiency (NUE). Notably, ‘Jingmai 17’ exhibited significant heterosis in nitrogen harvest index (NHI) and NUE. In conclusion, the hybrid variety ‘Jingmai 17’ demonstrated significant heterosis, and a planting density of 300 plants/m² was found to optimally balance yield and NUE.