Temporal and Spatial Variability of the Soil Main Nutrients in Xiangxi Tobacco-planting Area

PurposeThe purpose of this paper was to provide a theoretical basis for scientific management of tobacco planting soil and improvement of tobacco quality.

MethodBased on the methods of spatial autocorrelation, semi-variance function and fractal dimension, the spatiotemporal variation of soil main nutrient from Xiangxi area were studied. Two sets of data were used for analysis in this study in 2000 and 2015.

ResultFrom the basic statistical characteristics and distribution frequency point of view, in the past 15 years, the average content of alkali hydrolyzable nitrogen in tobacco growing soil in Xiangxi had increased from 119.60 mg/kg to 147.01 mg/kg, with an increase rate of 22.92%. The average content of available phosphorus in tobacco growing soil in Xiangxi had increased from 7.26 mg/kg to 38.15 mg/kg, with an increase rate of 425.62%. The average content of available potassium in tobacco growing soil in Xiangxi had increased from 164.62 mg/kg to 219.34 mg/kg, with an increase rate of 33.24%. The results showed that the soil available potassium increased significantly. From the view of temporal and spatial variation, the nugget effect values of nitrogen, phosphorus and potassium contents and the fractal dimension value of D increased, but the value of Moran’s I decreased. From the temporal and spatial distribution changes, in 2015, the content of soil available nitrogen became more suitable for tobacco production, the areas of appropriate and high content levels increased significantly, increased by 5.93% and 29.53%; and the " low” rating dropped to 35.45% lower than in 2000. The content of available potassium in soil in 2015 " high” and " high” level of the area increased significantly, increased by 25.98% and 55.30%; and the " low” and " low” rating declined sharply, respectively, than in 2000 decreased by 27.49% and 57.14%. In 2015, the content of soil available K " very low”, " appropriate”, " high” and " high” level of the area increased, which increased by 0.60%, 2.90%, 19.51% and 0.89%; and the " low” rating dropped to 23.91% lower than in 2000.

ConclusionIn the past 15 years, the growth of soil nutrient in Xiangxi had increased greatly; the largest increase was the content of available phosphorus in the soil, followed by the content of available potassium, and the content of alkaline nitrogen in the last.