Haipeng Zhang, Kailiang Mi, Morcillo Ma, Ting Chen, Hongcheng Zhang, Yanju Yang
Abstract Optimizing planting density is crucial for enhancing the yield potential of conventional japonica rice ( Oryza sativa L.) by regulating yield components and population characteristics. In a 2‐year field study, four conventional japonica rice varieties were evaluated under three planting densities: 16 × 30 cm (20.83 × 10 4 hills hm −2 ), 12 × 30 cm (27.78 × 10 4 hills hm −2 ), 10 × 30 cm (33.33 × 10 4 hills hm −2 ). Super‐high‐yielding varieties exhibited greater sink capacity and stronger source activity compared with high‐yielding varieties. However, differences in population traits such as the top three leaf pattern and panicle architecture were observed due to genetic variation. Increasing planting density improved yield in super‐high‐yielding varieties primarily by increasing panicle number at maturity. At the same time, higher density stimulated the growth of ineffective tillers, which reduced the productive tiller percentage. This led to a more rapid decline in leaf area during the reproductive stage, lower flag leaf chlorophyll (SPAD) values, restricted overall plant growth, and reductions in plant height as well as the length, width, and angle of the top three leaves. Panicle development was similarly constrained, resulting in shorter panicle length, fewer branch pedicels, and reduced seed‐setting rate, 1000‐grain weight, and spikelets per panicle. Despite these negative effects, the overall increase in total spikelets compensated for the declines in individual components, leading to net yield enhancement. In conclusion, a moderate increase in planting density for super‐high‐yielding conventional japonica rice varieties enhances sink capacity and is beneficial for yield improvement.