Effect of optimized application of nitrogen on nitrogen volatilization in Nicotiana tobacum shoots at rapid growth and maturity stages

A pot experiment equipped with volatilization devices was used to study the effects of applied nitrogen (N) amounts and basal/top-dressing fertilizer ratios on N volatilization of "Yueyan 97" flue-cured tobacco shoot at rapid growth and maturity stages. The treatments used in the study included T1 (zero N fertilization), T2 0.30 g(N)·kg^-1(soil) and 7∶3 basal/top-dressing fertilizer ratio, conventional fertilization mode and T3 0.15 g(N)·kg^-1(soil) and 3∶7 basal/top-dressing fertilizer, optimized fertilization mode. The results showed that compared with T1 and T2, T3 significantly improved flue-cured tobacco shoot NO volatilization at maturity stage. However, for NO₂ at maturity stage, it was net absorption for all the three treatments, there was not significant difference among three treatments at maturity stage. Among the three treatments, average shoot N₂O volatilization of T2 at both rapid growth and maturity stages was largest. This was followed by T3 and then T1. Shoot N₂O volatilization losses in T2 and T3 at maturity were 3.06 and 6.12 times of that at rapid growth stage, respectively. There was no significant difference in tobacco shoot NH₃ volatilization among three nitrogen treatments at rapid growth stage. While at maturity stage, T3, compared with T2, obviously increased shoot NH₃ volatilization. While reduced N application and optimized basal/top-dressing fertilizer ratio decreased aerial plant organ N₂O volatilization at rapid growth and maturity stages, it increased NH₃ volatilization at maturity stage. The above results suggested that although optimized N application (by postponement) enhanced N absorption at middle and late growth periods of flue-cured tobacco, it facilitated endogenous N₂O formation and volatilization. There was no definitive effect of optimized N application (by postponement) on flue-cured tobacco N volatilization inhibition.