Yield Component Differences between Direct-Seeded and Transplanted Super Hybrid Rice

Abstract

Super hybrid rice Liangyoupeijiu was grown by transplanting (TP) at a spacing of 20 cm×20 cm with one seedling per hill and by direct-seeding (DS) at a seeding rate of 22.5 kg ha^-1 (about 120 seeds m^-2) in Changsha, Hunan Province, China in 2004 – 2010. Grain yield and yield components were measured each year, and some physiological factors were determined in 2009. There was no significant difference in mean grain yield across years between DS and TP. DS produced more panicles per m² but less spikelets per panicle than TP. The differences in number of spikelets per m², spikelet filling percentage and grain weight between DS and TP were not significant. A large number of panicles per m² in DS was derived from the increased number of tillers per m² rather than increased rate of panicle-bearing tillers, and the number of tillers per m² was mainly determined by the number of hills per m² because the number of tillers per hill was small in DS plants. Tillering rate, tillering duration as well as carbohydrate and nitrogen metabolism were critical to the reduced number of tillers per hill in DS. In DS plants with fewer spikelets per panicle, the numbers of primary branches and secondary branches per panicle, spikelets per primary and secondary branches, and also panicle length and spikelets per unit panicle length were smaller. These differences were attributed to the smaller source leaf size as well as lower root activity and the nutritional status at panicle initiation.