Abstract
Rice seedlings sown at densities of 250 g and 300 g dry seeds per nursery box were grown for 15 or 24–25 days before being transplanted to the paddy field. From each high-density seedling mat, 3–4 seedlings per hill were planted with a rice transplanting machine, which was modified to pick a small area of the seedling mat. The plant age in leaf number of each seedling was 3.0–3.6 and the plant height was 8–12 cm at the transplanting time. Planting accuracy was high; the frequency of vacant hills was 0.0–6.3％ without consecutive blank hills. The number of high-density seedling mats required for transplanting was 4.7–7.2 per 10 a. The heading and maturity dates of high-density seedling were 1–2 days later than those of conventional seedlings. There was no significant difference between the crops grown from the conventional and high-density seedlings in terms of traits such as maximum tiller number, panicle number, grain yield, perfect grain ratio, and grain protein content. Judging from the height of seedlings in the nursery boxes and the increase in stem number after transplanting, the nursery management and transplanting time were considered suitable for late transplanting at a higher temperature. Use of high-density rice seedling mats, allowed to obtain high quality high yield rice without changing the conventional way of nursery management and using new nursery materials, except for the introduction of a new rice transplanting machine.
