Impact of top-pruning time on the fertilizer N use efficiency of flue-cured tobacco as assessed by ¹⁵N tracing technique

ABSTRACT

To evaluate the impact of top-pruning time on fertilizer N use efficiency (NUE) of flue-cured tobacco, we adopted ¹⁵N tracing technique and conducted a 2-year experiment from 2014 to 2015 in eastern China. The experiment included three top-pruning points of time: 5th, 25th and 45th day after flowering (DAF), abbreviated, respectively, as TP5, TP25 and TP45. The amounts of plant N derived from fertilizer (Ndff) and soil (Ndfs) were observed during 0–55th DAF. Results showed that top-pruning slowed down the increase of Ndff in tobacco organs, particularly in the leaf, but accelerated the increase of Ndfs dramatically. The proportion of Ndff (%) accounted for the total N reduced dramatically after top-pruning. This reduction might attribute to the selectivity of plant to different N sources as influenced by top-pruning while had little relationship with soil N supply, according to the analysis on the soil total mineral N and mineral ¹⁵N. The average NUE for the 2 years was 32%, 41% and 47%, respectively, for TP5, TP25 and TP45, showing significant (p < 0.05) differences. We concluded that the tobacco preferred to uptake soil N rather than fertilizer N after top-pruning; thus, optimizing the top-pruning time might be one of the approaches to improve the in-season NUE of flue-cured tobacco.

KEYWORDS:

• Top-pruning
• nitrogen
• use efficiency
• tobacco
• ¹⁵N

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China: [51409086]; Natural Science Foundation of Fujian Province: [2016J05069]; Young Talent Project of Horticultural College of Fujian A&F University (received by Hou Maomao); Postdoctoral Science Foundation of Fujian A&F University (132300198); and Key project on high-efficient utilization of rainwaters in Qianxinan tobacco cultivated area: [2015(41)].