Assessing on yield difference of double-cropping rice in South China driven by radiation use efficiency

Double-cropping rice in South China continued to break through the total yield record, but the yield potential of single-cropping rice wasn’t realized. Radiation use efficiency (RUE) has been singled out as an important determinant of grain yield in cereal species. However, there is no information on whether this yield gaps involved differences to RUE in double-cropping rice. Field experiments were performed over two years to evaluate the effects of intercepted radiation (IP) and RUE, on the above-ground biomass production, crop growth rate (CGR), and harvest index (HI), in four representative rice varieties, i.e., Xiangyaxiangzhan (XYXZ), Meixiangzhan-2 (MXZ2), Nanjingxiangzhan (NJXZ), and Ruanhuayoujinsi (RHYJS) during the early seasons and late seasons of rice cultivation in South China. The results revealed that grain yield of early season was 8.2% higher than late season. The yield advantage in early season was primarily owing to higher spikelet per panicle and above-ground biomass resulting from a higher RUE. The spikelet per panicle in the early season were 6.5, 8.3, 6.9, and 8.5% higher in XYXZ, MXZ2, NJXZ, and RHYJS than late season. The higher grain yield in early season was more closely related to RUE in middle tillering stage (R2=0.34), panicle initiation (R2=0.16), maturation stage (R2=0.28), and intercepted photosynthetically active radiation (IPAR) in maturation stage (R2=0.28), while the grain yield in late season depended higher IPAR in middle tillering stage (R2=0.31) and IPAR in panicle initiation (R2=0.23). Conclusively, the results of this research show that higher RUE contribute to yield progress of early season rice, while the yield improvement of late season rice is attributed to higher radiation during early reproductive stage. To rationally allocate the RUE of the double-cropping rice with high RUE varieties or the adjustment of sowing period deserve the further studied.