Moderate Printed Seeding Density Improves Seedling Establishment, Population Development, and Yield Formation in Machine-Transplanted Hybrid Indica Rice

Uneven seed placement in nursery trays reduces seedling uniformity and can reduce the reliability of mechanical transplanting in hybrid rice, but the optimum printed seeding density remains unclear. This study evaluated the effects of printed seeding density on seed distribution, seedling quality, transplanting performance, canopy productivity and yield formation in machine-transplanted hybrid indica rice. A two-year split-plot field experiment was conducted in Xuzhou, China, using Runliangyou 313 and Yangxianyou 903. Five printed seeding densities (1400–2600 printed points tray−1) were compared with two local weight-based broadcasting controls, representing practical establishment systems rather than seed-number-matched contrasts. Moderate printed densities improved seed distribution uniformity, strengthened the seedling mat, reduced transplanting defects and supported productive tiller formation. T3 and T4 produced the highest harvested yields, increasing yield by 13.3–15.5% over the standard broadcasting control. These gains were associated with higher panicle number, greater post-anthesis dry matter accumulation and higher harvest index. The results indicate that moderate-density printed seeding can improve establishment quality and grain yield under wheat-rice rotation conditions.