Comparisons of yield performance and nitrogen response between hybrid and inbred rice under different ecological conditions in southern China

In order to understand the yield performance and nitrogen （N） response of hybrid rice under different ecological conditions in southern China, field experiments were conducted in Huaiji County of Guangdong Province, Binyang of Guangxi Zhuang Autonomous Region and Changsha City of Hunan Province, southern China in 2011 and 2012. Two hybrid （Liangyoupeijiu and Y-liangyou 1） and two inbred rice cultivars （Yuxiangyouzhan and Huanghuazhan） were grown under three N treatments （N1,225 kg ha-l; N2, 112.5-176 kg ha-l; N3, 0 kg ha-1） in each location. Results showed that grain yield was higher in Changsha than in Huaiji and Binyang for both hybrid and inbred cultivars. The higher grain yield in Changsha was attribut- ed to larger panicle size （spikelets per panicle） and higher biomass production. Consistently higher grain yield in hybrid than in inbred cultivars was observed in Changsha but not in Huaiji and Binyang. Higher grain weight and higher biomass production were responsible for the higher grain yield in hybrid than in inbred cultivars in Changsha. The better crop perfor- mance of rice （especially hybrid cultivars） in Changsha was associated with its temperature conditions and indigenous soil N. N2 had higher internal N use efficiency, recovery efficiency of applied N, agronomic N use efficiency, and partial factor productivity of applied N than N1 for both hybrid and inbred cultivars, while the difference in grain yield between N1 and N2 was relatively small. Our study suggests that whether hybrid rice can outyield inbred rice to some extent depends on the ecological conditions, and N use efficiency can be increased by using improved nitrogen management such as site-specific N management in both hybrid and inbred rice production.