Abstract
Super hybrid rice genotypes have transformed the rate of genetic yield gain primarily due to intersubspecific heterosis, although the physiological basis underpinning this yield transformation has not been well quantified. We assessed the radiation use efficiency (RUE) and nitrogen use efficiency (NUE) of novel hybrid rice genotypes under four management practices representative of rice cropping systems in China. Y-liangyou 900 (YLY900), a new super hybrid rice widely adopted in China, was examined in field experiments conducted in Jingzhou and Suizhou, Hubei Province, China, from 2017 to 2020. Four management practices were conducted: nil fertilizer (CK), conventional farmer practice (FP), optimized cultivation with reduced nitrogen (OPT(-N)), and optimized cultivation with increased nitrogen (OPT(+N)). Yield differences across the treatment regimens were significant (p < 0.05). Grain yield of OPT(+N) in Jingzhou and Suizhou were 11 and 12 t ha(-1), which was 14 and 27% greater than yields obtained under OPT(-N) and FP, respectively. Relative to OPT(-N) and FP, OPT(+N) had greater panicle numbers (9 and 18%), spikelets per panicle (7 and 12%), spikelets per unit area (17 and 32%), and total dry weight (9 and 19%). The average RUE of OPT(+N) was 2.7 g MJ(-1), which was 5 and 9% greater than that of OPT(-N) and FP, respectively, due to higher intercepted photosynthetically active radiation (IPAR). The agronomic efficiency of applied N (AE(N)) of OPT(+N) was 17 kg grain kg(-1) N, which was 9 and 68% higher than that of OPT(-N) and FP. These results show that close correlations exist between yield and both the panicles number (R (2) = 0.91) and spikelets per panicle (R (2) = 0.83) in OPT(+N). We conclude that grain yields of OPT(+N) were associated with greater IPAR, RUE, and total dry matter. We suggest that integrated cropping systems management practices are conducive to higher grain yield and resource use efficiency through expansion of sink potential in super hybrid rice production.