Spatial Variability of Contents of Nicotine in Flue-cured Tobacco Leaves and and Soil Medium and Trace Elements in Tobacco Planting Fields in Central Henan province, China

Collection and measurement of soil and tobacco leaf samples1.1 Sample collecting methodIn early June 2021, soil samples and flue-cured tobacco leaf samples were collected from tobacco planting fields in Pingdingshan, Xuchang and Luohe, Henan Province. The annual planting area of flue-cured tobacco in the study area is 3.67×10 5 hm2 . Sampling points must have representation and homogeneity. In the tobacco planting area, a mixed soil sample was collected every 33.3km2 , and in the low hilly land of tobacco-growing area, a mixed soil sample was collected every 20.00km2 . Using handheld GPS position indicator, to collect samples from multiple points in a circular area with a radius of 10 m. Collected about 1 kg of soil samples from the plough layer (0-20 cm) and brought them back to the laboratory, also collected leaf sample correspondingly (tobacco plants from 8 to 12 leaf from top to bottom, each 2.5kg). A total of 1259 soil samples were collected.1.2 Measurement methodThe contents of nicotine were determined by ultraviolet spectrophotometry (Wang RX. 2003). The contents of medium and trace elements of soils in tobacco planting fields were determined by microwave digestion-flame atomic absorption spectrometry (Zhang et al. 2010).1.3 Data analysis methodGeostatistical method: using the relevant parameters of the semivariance function to analyze the spatial structure of the nicotine content in tobacco leaves and soil medium and trace elements in soils of tobacco planting fields in the study area ( Miressa Duffera et al. 2007).Software platform:(1) SPSS10.0: descriptive statistical analysis;(2) GS+5.3: Semivariance function analysis ( Miressa Duffera et al. 2007; Liu et al. 2009).(3) ArcGIS: digital map, Kriging interpolation (Rodriguez Martin et al. 2007; Zhao et al. 2011).