Study on the correlations between transplanting date and nitrogen fertilizer efficiency of flue-cured tobacco (Nicotiana tabacum L.)

A field experiment was carried out to investigate the effects of different transplanting dates(5th, 15th and 25th of May) on the responses and correlations of flue-cured tobacco(FCT) seedlings to N fertilizer. The results show that when the transplanting date were postponed from 5th of May to 15th and 25th of May, both the yield and N accumulated in leaves and stems were remarkably increased by 5.1%-6.1%, 19.8%-55.2%; the corresponding agronomic nitrogen use efficiency, physiological nitrogen use efficiency, soil nitrogen dependent rate and nitrogen harvest index were increased by 37.4%-49.8%, 30.4%-54.8%, 26.9%-29.1% and 2.9%-5.7% respectively. Positively significant correlation were existed between postponed transplanting date and the indexes calculated such as agronomic nitrogen use efficiency, partial factor productivity for nitrogen fertilizer and soil nitrogen dependent rate; and also among these indexes. Therefore, postponing the transplanting date to 15th-25th in May is an effective way to improve tobacco yields and nitrogen fertilizer efficiency.