Abstract
The spikelets produced, amouting to as much as 71, 000 per m2 in a dense-planting plot, had been attained by combining of 487 panicles per m2 and 148.8 spikelets per panicle. The panicle number per m2 was almost the same as the culm number per m2 at transplanting. In a sparse-planting plot, the panicle number per m2 did not decrease but increased in the spikelets per panicle up to 180.9, and thus 87, 700 spikelets per m2 were obtained. The efficiency of spikelet production for Yu-Za 29 was apparently higher than Nipponbare cultivated in Kyoto. The significantly large number of spikelets per m2 was attributed to both a more efficient use of nitorgen in producing spikelets and increases in nitrogen absorption up to heading (23.4 to 23.6 gm-2) and in leaf dry weight at heading (328∼333 gm-2). Efficiency of nitrogen use in producing spikelets of Yu-Za 29 was higher in sparse-planting plots than in dense-planting plots. No differences in culm lengths and internode lengths lower than the 3rd one (N3) were observed between the planting densities, but breaking resistance of N3 and N4 lowered in the dense planting plot. Consequently, the lodging index of N3 (distance between fulcra is 5cm) exceeded 200. Improvement of nitrogen use efficiency in producing spikelets as well as high resistance to lodging in Yu-Za 29 are considered to be compatible with an increase in the sparsity of the planting density in comparison with the conventional dense planting cultivation in Binchuan.
