LAUSR

Abstract The seedling establishment phase is important for the productivity and profitability of rice ( Oryza sativa L.) production. To evaluate the role of climatic and physiological factors in different growth seasons in determining the rice grain yield, field experiments were conducted with four seedling establishment methods: manual transplanting (TP), seedling throwing (ST), machine transplanting (MT), and direct seeding (DS). Three nitrogen application rates were also tested (zero, medium, and high N rate) under single, early, and late seasons in the Middle and Lower reaches of the Yangtze River in 2013 and 2014. The results showed that the average grain yields of MT, ST and TP did not differ significantly under the N rate of 127.5–142.5 kg N/ha. Under the high N rate (187.5–202.5 kg/ha), the average grain yields in TP were 6.5%, 10.6%, and 36.7% greater than those in MT, ST, and DS, respectively, suggesting that TP rice had greater yield potential than the others, irrespective of rice seasons. In the single season condition, the grain yield advantage of TP over MT and SC might be attributable to the higher panicle-bearing tiller rate and greater sink size in TP with high N rates. It is less clear why the yield was not significantly higher in the double season. On the other hand, the average grain yields were −3.5%–8.8%, 6.4%–15.0%, and 29.4%–37.1% lower under DS than under the other treatments in the single, early, and late seasons, respectively, suggesting that DS might be a promising choice with less input and stable yield output in the single season. The dramatic yield loss in DS in the late season might be attributed to the reduced grain setting rate (a 20.3%–33.3% decrease under DS compared with the other treatments in the late season), indicating that the current varieties used for TP in the late season were not suitable for DS cultivation. The correlation between the grain yield and climate factors suggests that the light and temperature accumulation in the double season might be a barrier to narrowing the yield gaps between DS and TP rice in early and late rice, but was not the yield-limiting factor in the single season.