2025 Volume 94 Issue 4 Pages 425-439
The effects of seedling density and nitrogen application method on the characteristics of the high-yielding, good-tasting, and high-quality rice cultivar “Niji-no-kirameki” in flooded direct-sowing cultivation were examined, across cultivars and cultivation methods. Under the same nitrogen application methods in surface broadcast or hill sowing, “Niji-no-kirameki” produced higher yields than the existing cultivars “Koshihikari” and “Kinuhikari” that have similar heading periods, and had superior brown rice appearance quality. In addition, the short culm of “Niji-no-kirameki” gave it superior lodging resistance. Seedling density had almost no effect on the yield of “Niji-no-kirameki”, but the amount of nitrogen application had a large effect. There was a positive correlation between yield and the number of rough rice grains per square meter (NG), and the relationship between the direct-sowing and the transplanting was not different. However, the number of panicles required to produce the same NG was greater with direct-sowing, and the leaf color tended to remain lighter than with transplanting. In direct-sowing, the rice protein content was slightly higher when trying to obtain the same level of yield as transplanting. Therefore, in direct-sowing, the target yield of “Niji-no-kirameki” was 660 g m-2, with 31,000 of NG, leaf color at the full heading stage with a SPAD value of approximately 34, and a brown rice protein content of 6.5% (15% moisture basis) would be appropriate.
