The response of Hongda, a flue-cured tobacco cultivar, to nitrogen fertilizer rate.

Nitrogen fertilizer is essential for the yield and quality of flue-cured tobacco. Honghuadajinyuan (i.e. Hongda) is a special flue-cured tobacco variety in Yunnan, which differs in nitrogen application rates from other varieties. In 2016 and 2017, different nitrogen application rates were established in Yunnan to compare, with other varieties, Hongda's agronomic, economic, chemical indicators and soil residual nitrogen. As nitrogen fertilizer rate increased, the ratio of fresh weight to dry weight (RFD) and the proportions of inferior tobacco (PIT) initially decreased and then increased in contrast to the proportions of superior tobacco (PST) and average price. Total sugar and reducing sugar contents in flue-cured tobacco leaves decreased as nitrogen fertilizer rate increased, while total nitrogen, nicotine, and protein contents increased. The highest sensory evaluation scores were obtained with 45 and 60 kg N ha−1. Soil nitrate contents increased with increasing nitrogen fertilizer rate and significantly increased when nitrogen application rate exceeded 60 kg N ha−1. A quadratic model was suitable for Hongda's response to nitrogen fertilizer rate and 60 kg N ha−1 can meet the needs of the growth of this flue-cured tobacco variety. Abbreviations: Hongda: Honghuadajinyuan; RFD: ratio of fresh to dry weight; PIT: proportion of inferior tobacco; PMT: proportion of medium tobacco; PST: proportion of superior tobacco; SPAD: soil and plant analyzer development. [ABSTRACT FROM AUTHOR]