Abstract
A new rice cultivar Akita 63 which has a relatively heavy 1000-grain weight (30 g) is expected to possess a high yield potential. To develop a suitable nitrogen (N) fertilization method for maximizing the yield potential of Akita 63, we investigated the effects of three patterns of N fertilization; early topdressing (ET) [basal dressing, topdressing at the tillering stage, topdressing at ear formation stage, topdressing at the ripening stage = 6, 2, 2, 0 kg N / 10 a], late topdressing (LT) [4, 0, 4, 2 kg N / 10 a] and even fertilization (EF) [4, 2, 2, 2 kg N / 10 a]. ET markedly stimulated tillering, but produced a large number of non-productive tillers. The photosynthetic rate during the ripening stage was lower in the ET plot due to the lower leaf N content than in the other treatments. In LT, the development of tiller was slower, resulting in the smallest panicle number and yield among the three treatments. In EF, panicle number, spikelet number per unit area, N uptake and photosynthetic rate were the greatest, leading to the highest yield among the three nitrogen treatments. These results suggest that the even fertilization over the growth period is necessary to realize the high yielding potential of Akita 63.
