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The main purpose of this study was to analyze the characteristics of nitrogen leaching from tobacco fields in order to understand the differences of nitrogen leaching from farmlands and tobacco fields. A long-term positioning experiment was conducted in Kaiyang county, Guizhou province of China (107°06′40″E, 26°52′24″N). In this area, the soil texture is silt loam. The mean rainfall is 1 129.9-1205.9 mm. Two cropping system were included. One was rotation (tobacco-winter fallow-maize) and the other one was continuous cropping (tobacco-winter fallow-tobacco). Four treatments with rotation cropping system were set up: no fertilizer (CK), chemical fertilizer (NPK), chemical fertilizer with manure (NPK + M), chemical fertilizer with bio-organic fertilizer (NPK + BM). One treatment with continuous cropping was also set up: chemical fertilizer with continuous cropping (NPK + L). The experiments were carried out in the fields from 2015 to 2017. In 2015, the leaching barrels were buried into the soils at 90-cm depth in the fields for monitoring leaching solution from the soils. The leaching solution was collected each a month for determination of inorganic N and total N. The organic N, net N leaching rate and apparent N leaching rate were calculated. The results showed that the annual leaching amount of inorganic nitrogen was 3.62-6.08 kg/hm², and the net leaching rate was 0.09%-3.29%. The leaching loss of inorganic nitrogen mainly occurred during the growing season of tobacco fields, especially in May to June, which accounts for 40.33%-65.86% of the total leaching amount. The nitrogen in leaching solution were mainly in organic form. During the growing season of tobacco, the inorganic nitrogen accounted for 27.82%-33.39% of the total leaching nitrogen, and organic nitrogen accounted for 66.61%-72.18% of the total leaching nitrogen. Rainfall was a main factor affecting the nitrogen leaching from tobacco fields, and the monthly leaching amount of inorganic nitrogen was nonlinearly related to the monthly rainfall. Application of chemical fertilizer resulted in a significant increase of leaching inorganic nitrogen. Organic fertilizer combined with chemical fertilizer decreased the leaching amount of soil solution. The amounts of soil leaching solution in chemical fertilizer + manure and chemical fertilizer + bio-organic fertilizer treatment were lower than that in chemical fertilizer treatment. Bio-manure combined with chemical fertilizer significantly reduced leaching of inorganic nitrogen, and its inorganic nitrogen leaching amount was decreased by 39.44% compared with chemical fertilizer treatment. Compared with the treatment of rotation, the continuous cropping treatment significantly reduced soil water leaching and reduced the net leaching rate of nitrogen fertilizer by 59.57% (P<0.05). To sum up, under the current conventional management of flue-cured tobacco, the leaching intensity of inorganic nitrogen in the tobacco field in the rainfed agricultural area is not high. The results could provide valuable information for formulating suitable strategies of fertilization management in tobacco fields. [ABSTRACT FROM AUTHOR]

[Objective] The present paper aimed to explore the metabolic differences between the local flue-cured tobacco variety Jiucaiping 2 selected by the Bijie Tobacco Company and the control variety Yunyan 87 planted in the Bijie area, lay the foundation for further revealing the molecular mechanism of the aroma style characteristics of Jiucaiping 2 tobacco leaves, and provide theoretical basis for the promotion and application of this variety. [Method]Taking Yunyan 87 as the reference material, the metabolome analysis of Yunyau 87 and Jiucaiping 2 fresh tobacco leaves from three tobacco leaf production areas ( Dayi, Kele, Tiejiaug) in Hezhaug county, Bijie city was carried out by liquid chromatography-mass spectrometry. [ Result] A total of 1880 peaks were detected in the tobacco samples, and principal component analysis showed significant metabolic differences between Jiucaiping 2 and Yunyan 87 in three tobacco producing regions. Metabolite difference analysis was performed with difference multiple greater than 2 and the P < 0. 05 oft-test as the standard. The order of ion quantity differences among different production areas was Dayi > Kele > Tiejiaug. At the same time, it was identified that 46 ion peaks had au increased accumulation in Jiucaiping 2 from three production areas, while 49 ion peaks had a decreased accumulation in Jiucaiping 2 from three production areas. A flavonoid metabolite M_9637[luteolin 7-(6'-malonylglucoside) ]was further identified among the peaks with increased accumulation in Jiucaiping 2. Widely-targeted metabolic analysis of phenolic acids and flavonoids in two tobacco varieties revealed an increasing trend of accumulation of two types of flavonoids (isorhamnetin and quercetin) in Jiucaiping 2. The analysis of nomicotine and nicotine showed that both metabolites tended to accumulate and decrease in Jiucaiping 2. [Conclusion] In the study, the comparative analysis of the metabolites of Jiucaiping 2 and Yunyan 87 in three tobacco producing areas found that the metabolism of flavonoids in Jiucaiping 2 was higher than that of Yunyan 87, and the metabolism of nicotine was lower than that of Yunyau 87. The differences in the accumulation of the above two types of substances may be the basis for the formation of the aroma style characteristics of Jiucaiping 2 tobacco leaves. [ABSTRACT FROM AUTHOR]