Nitrogen response of regenerated tillers varied among node positions in ratoon rice

Rice ratooning produces a ratoon crop (RC) with regenerated tillers in different nodes on the stubble of main crop (MC). It is crucial to apply nitrogen (N) at 15 d after heading and 1–2 d after harvest of MC for promoting bud initiation (NB) and tiller growth (NT), respectively to achieve high grain yield of RC. However, limited information is available on the N response of regenerated tillers in different node positions of RC. The hypothesis is that N response varied among node positions of regenerated tillers. [METHODS] Field experiments were conducted in 2019 and 2020 to compare yield performance of regenerated tillers of upper and lower node positions in RC under various combinations of NB and NT treatments and two cutting heights (15 and 45 cm) using a rice variety Huanghuazhan. showed that there was no significant difference in grain yield among N treatments of regenerated tillers in upper node (3rd and 2nd nodes from the top for 15 and 45 cm cutting height, respectively). However, NB and NT significantly increased the grain yield of regenerated tillers in lower nodes by 23.5 %− 52.7 % and 49.3 %− 115.7 %, respectively, which was mainly attributed to increased panicles m−2 for both cutting heights. N application also increased total dry weight and total N uptake of regenerated tillers in lower nodes, but not in upper node. Furthermore, a significant and positive correlation between grain yield and total N uptake was observed for regenerated tillers in lower nodes, but not in upper node. Our results indicate that regenerated tillers in lower nodes were more responsive to N application than those in upper node. [IMPLICATIONS] Therefore, optimization of N management for RC should emphasize on the N response of regenerated tillers in lower nodes for achieving high grain yield of RC.