Abstract
Spikelet number per unit area (spikelet number) is an important factor for high rice yields. Spikelet number reportedly has a positive correlation with nitrogen accumulation in the shoots at the heading stage, but the coverage of the correlation is unclear. In the present study, we examined the relationship between nitrogen accumulation and spikelet number in the high-yield cultivars ‘Hokuriku 193’ and ‘Mizuhochikara’ under the condition of high nitrogen application. Nitrogen accumulation in rice shoots at the heading stage increased with an increase in the amount of applied nitrogen, but the spikelet number did not increase significantly when the amount of applied nitrogen was increased from 24.5 to 33.5 g m-2. Analysis of the relationship between nitrogen accumulation in rice shoots at the heading stage and spikelet number by using the linear-plateau model revealed that the nitrogen accumulation required to achieve maximum spikelet number was 22.0 and 20.0 g m-2, and that the maximum spikelet number was 54680 and 58951 spikelets m-2 in ‘Hokuriku 193’ and ‘Mizuhochikara’, respectively.
