Studies On Radiation Use Efficiency Of Super Hybrid Rice

Radiation use efficiency(RUE) has been widely applied to the international research of field crops;it attaches great importance on crop growth simulation and analysis of potential output.However,RUE is rarely reported in China,especially about super rice both in domestic and abroad.To analysis the canopy structure,yield and RUE of super hybrid rice,this study was conducted with two levels of nitrogen fertilizer,and three groups of rice varieties,super hybrid rice,common hybrid rice and conventional rice,in Yong'an County(YA) and Guidong County(GD) in Hunan Province in 2007.The key outcomes of this study are as followings:(1)There existed discrepancy among nitrogen level treatments and among variety groups in tiller,leaf area index(LAI),dry matter weight of above-ground biomass(DW), SPAD,net assimilation rate(NAR),crop growth rate(CGR).Super hybrid rice possessed significantly higher of DW,SPAD and CGR than common hybrid rice and conventional rice.(2) Nitrogen level had not significantly effect on grain yield,where the cultivation sites significantly affected the yield performance.The average yield in Guidong site was 17.3%higher than that in Yong'an site.The differences of yield among tested varieties was significant.Super hybrid rice showed the highest yield,more than 11 t/ha in Guidong site, which was 9.7%higher than that of conventional rice,and 13.2%higher than that of common hybrid rice.The key for the high yield of Super hybrid rice existed in its abundant of productive panicles and spikelets number per panicle.(3) Nitrogen treatment significantly affected the leaf shape.The leaf length,leaf width,leaf area,leaf general angle and the opening angle of Common hybrid rice the greatest,where smallest of conventional rice.Comparatively,super hybrid rice got much appropriate and higher efficient of leaf area and looseness to ensure proper straightness.(4) The RUE of tested varieties varied from 2.41g/MJ to 2.85g/MJ.Nitrogen treatment had not significant effect on the value.The RUE of super hybrid rice,common hybrid rice,conventional rice were respectively 2.71g/MJ,2.40g/MJ and 2.74g/MJ in Yong'an site,and 2.82g/MJ,2.66g/MJ and 2.81g/MJ in Guidong site.RUE in the two experiments sites showed the same trend,i.e.,super hybrid rice and common hybrid rice higher than conventional hybrid rice.(5) The value of Intercept photosynthetically active radiation(IPAR) of Super hybrid rice,common hybrid rice and conventional rice were 692.8 MJ/m~2.688.3 MJ/m~2,and 609.9 MJ/m~2 in Yong'an site,and 684.2 MJ/m~2,684.1 MJ/m~2,and 659.9 MJ/m~2 in Guidong site,showed the trend that IPAR of the super hybrid rice and common hybrid rice were higher than that of conventional rice.The study indicates that improved IPAR and RUE in coordination is a key for super hybrid rice to get the highest yield.