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Hybrid rice (Oryza sativaL.) cultivars play an important role in rice production due to its high yield potential. Optimum nitrogen (N) rate is necessary to achieve the maximum yield of hybrid. The main objective of this study was to reveal the responses of yield and yield component of hybrid rice ‘Eryou 107’ to different N rates in Nanjing and Taoyuan, a special eco-site. Leaf area index (LAI), dry matter accumulation was also compared. Rice yield showed a quadratic response to N rates at both sites with maximum yields approximately 10 t ha−1at the 195 kg ha−1N rate in Nanjing and maximum yield above 18 t ha−1at the 375 kg ha−1N rate in Taoyuan. Panicle per m2was positively linear related to N rate at both sites in both years, while spikelets per panicle showed a quadratic relation. Larger sink size was the primary contributor to higher yields in Taoyuan compared with Nanjing, and panicle per m2was the main cause. With the increasing N rate, LAI increased linearly and the dry matter accumulation first increased than declined at both sites. Greater effects of N rates on yield and yield components, LAI, and biomass was observed in Taoyuan than Nanjing. Higher LAI, biomass, and larger sink size resulted in the higher yields and more N rate for maximum yields in Taoyuan, compared with Nanjing. [ABSTRACT FROM PUBLISHER]

Abstract: A number of field studies have reported very high rice yields in Taoyuan, Yunnan province, China, and the physiological and ecological factors associated with high yield have been explored. However, little attention has been paid to differences in plant type. The main objective of this study was to reveal the plant type characteristics associated with the high rice yield through the comparison of two sites: Taoyuan, Yunnan province and Nanjing, Jiangsu province, China. The physiological and environmental factors were also discussed. Field experiments were conducted at two sites in 2006 and 2007. Three Indica F1 hybrid varieties, Eryou 107, Xieyou 107 and Eryouhang 1 in 2006, Eryou 107 and Xieyou 107 in 2007 were grown at two sites under optimum crop management to achieve maximum attainable yields. Leaf area, leaf length, leaf width, leaf angles, specific leaf weight (SLW) and specific leaf nitrogen (SLN) at heading, yield and yield components at maturity were determined. Daily radiation, air temperature and relative humidity (RH) were monitored. The highest yield of 18.5tha−1 was achieved by Eryou 107 at Taoyuan in 2006, and average yield of all varieties at Taoyuan was 96% and 85% higher than Nanjing in 2006 and 2007, respectively. The higher yield at Taoyuan was attributed primarily to the larger sink size, which was mainly caused by the greater number of panicles per m2. Biomass production was greater at Taoyuan than at Nanjing in 2006 and 2007, while differences in harvest index were very small. Compared with Nanjing, the rice planted in Taoyuan has greater leaf area index about 10 with smaller area per stem, shorter, wider and thicker leaves and smaller leaf angles. These results indicate that in addition to the higher biomass accumulation (main physiological factor) and the intense solar radiation with the large diurnal temperature range (main environmental factor), the greater leaf area index (LAI) with smaller area per stem, may be an important morphological factor contributing to the high yield in Taoyuan. [Copyright &y& Elsevier]