Abstract
An applicability of nitrogen-deep placement culture (NDPC) in warmer area suffered from poor number of spikelets and low sink-source ratio, and responsibilities of NDPC for not only japonica rice cultivars (Tsukushibare, Hiyokumochi), but also japonica-indica rice hybrids (Milyang 23, Suweon 258) and indica rice cultivar (IR 661) were studied. Results were as follows : 1) The ratio of ear culm length of rice cultivars was not significant between NDPC and ordinary culture (OC) . 2) All cultivars on NDPC enlarged leaf area index due to increase of tiller numbers and leaf elongation. 3) Dry matter production during 30 days after heading of japonica-indica rice hybrids increased, but that of the others decreased on NDPC. Canopy of japonica-indica rice hybrids didn't reach rank growth. 4) All cultivars on NDPC increased spikelet numbers, but decreased ripened grains. Therefore, yield was not significant between NDPC and OC. But the yield of Japonica-indica rice hybrids increased. 5) The sink-source ratio of rice cultivars was not significant between NDPC and OC. 6) It was concluded that the rice cultivar with high fertilizer responsiveness like japonica-indica hybrid was suitable to increasing the yield on NDPC in warmer area.
