Effect of N application on N volatilization from the aerial part of tobacco in South China

A pot experiment with the volatilization device, was conducted to study the effect of N application amount and ratio of basal to top-dressing fertilizer (T1: no N fertilization; T2: conventional N fertilization with N application amount of 300 g (N)·kg-1 (soil) and ratio of basal to top-dressing fertilizer of 7:3; T3: optimization of N fertilization with N application amount of 150 g (N)·kg-1 (soil) and ratio of basal to top-dressing fertilizer of 3:7) on N volatilization from the aerial part of tobacco 'Yueyan 97' at the vigorous and maturity stages. Results showed that, compared with T1 and T2, T3 significantly improved the tobacco shoot NO volatilization rate at maturity stage. However, for N2O at this stage, it was net absorption for all the three treatments, and there was no significant difference among their average absorption rate. Among the three treatments, the average shoot N2O volatilization of T2 at both the vigorous and maturity stages, was the largest, and then was the T3, and T1 was the smallest. Shoot N2O volatilization loss of T2 and T3 at maturity stage was, respectively, 3.06 and 6.12 times of that at the vigorous stage, respectively. There was no significant difference in tobacco shoot NH3 volatilization rate among three N treatments at the vigorous stage. While at maturity stage, compared with T2, T3 obviously increased the shoot NH3 volatilization rate. Reduced N application amount and optimizing the base fertilizer ratio could decrease aerial part N2O volatilization at the vigorous and maturity stages, while increased NH3 volatilization at maturity stage. Above results showed that, optimizing applying N (N postponed) although promoted N absorption in the middle and late period of tobacco, promoted the formation of endogenous N2O and volatilization. Therefore, the regulation of optimizing applying N (N postponed) on inhibition of tobacco N volatilization was not distinct.