Premature heading and yield losses caused by prolonged seedling age in double cropping rice

Abstract Increasing the frequency of harvests through multiple cropping is a promising way to increase global food production. In double cropping rice, prolonged seedling age leads to yield losses; however, the underlying mechanisms that cause yield reduction are poorly understood. In this study, field experiments were conducted in the early and late growing seasons of 2013 and 2014 in Zhangbang village, Wuxue county, Hubei province, China. Two seedling age treatments (control and prolonged) were studied in a randomized complete block design with four replications. Compared to the control seedling age treatment of 30–35 days, grain yield was reduced in the prolonged seedling age treatment of 40–46 days by 17.9% in the early growing season of 2013 and 2014, and 18.2% in the late growing season of 2014. Yield loss resulted from reduced biomass and grain weight. Premature heading was observed in the prolonged seedling age treatment in both growing seasons; main stem heading occurred 8–13 days earlier and tiller stem heading about 8 days later compared to the control seedling age treatment. Full heading was completed within 12 days in the control seedling age treatment, while in the prolonged seedling age treatment within 27–33 days. In the prolonged seedling age treatment, yield loss resulted from the reduced grain yield of both stem types, one bearing premature-heading panicles and the other bearing normal-heading panicles. Single-stem measurements, including biomass, grain weight, plant height, leaf area, length and width of flag leaf, and degeneration of panicle branches and spikelets, significantly changed in both stem types. Overall, it is important to prevent prolonged seedling age in double cropping rice mainly through the reasonable arrangement of crops in a rotation system.