The characteristics of nitrogen supply in yellow soil planted with tobacco.

【Objective】 In this paper,the characteristics of nitrogen mineralization and nitrogen supply of yellow soil planted with tobacco during the growing period of flue-cured tobacco were studied,thus providing a theoretical basis for nitrogen nutrition control of flue-cured tobacco. 【Method】 The field plot experiment adopted the in situ incubation and two experimental fields of yellow soil with different organic matter content were selected. Each experimental plot contained four treatments,i.e. fallow,planting tobacco without N,planting tobacco and supplied 90 kg N·hm2,planting tobacco,and supplied 120 kg N·hm-2. 【Result】 The results showed as follows. In flue-cured tobacco growth period,two peaks of soil nitrogen mineralization were observed,one was at the flue-cured tobacco rapid growing stage (42 days after transplanting),and the second was at the stage of top pruning (77 days after transplanting). During the growth period of the flue-cured tobacco,with the advance of time,the cumulation of the mineralizable N increased,until about 91 days after transplanting of the flue-cured tobacco,the cumulative amount of mineralizable N tended to slow. The effect of soil organic matter content on the dynamics of soil nitrogen mineralization rate was not significant,the use of nitrogen fertilizers resulted in the large fluctuations of the dynamics of soil nitrogen mineralization fluctuations. The soil mineral nitrogen was net fixed at early growth stage of flue-cured tobacco and net mineralization had a significant effect at the late growth stage. 【Conclusion】 Therefore,controlling soil nitrogen mineralization during the late growth period of tobacco can reduce soil nitrogen supply at late growth period of tobacco,at the same time,reduce the inorganic soil nitrogen fixation at the early growth stage of tobacco and promote the pre-release of inorganic nitrogen at the early growth stage of tobacco,and to a certain extent,can also alleviate the problems of excessive soil nitrogen supply at the late growth stage of tobacco.