Nitrogen Fertilization Regime for “Koisomeshi”, a New Rice Cultivar for Use in the Food–Service Industry

The food–service industry demands inexpensive but palatable rice. The rice cultivar “Koisomeshi” was bred for high yield and good palatability to satisfy this demand. To obtain the suitable nitrogen fertilization regime for “Koisomeshi”, we examined the effects of nine treatments, combining three nitrogen levels at the early stage of rice growth (3, 6, and 9 g m–2) and three nitrogen levels applied as top dressing at the panicle formation stage (0, 3, and 6 g m–2) on the yield and appearance quality of grains for over three growth seasons. Grain yield was high under 3 or 6 g N m–2 top dressing, which was attributed to the increase in spikelet number per area. Appearance quality of grains decreased with increasing nitrogen application, especially in top dressing. Based on these results, we concluded that the nitrogen applications at 6 g m–2 at the early growth stage and 3 g m–2 at the panicle formation stage were the most suitable for “Koisomeshi”. In addition, an appropriate transplanting date should be selected to achieve good appearance quality of grains because appearance quality varied greatly with the weather conditions during the ripening period.