Abstract:
Exploring the soil nutrient status and its variation characteristics of tobacco-growing soil in Kunming can provide scientific basis and guidance for rational management of quality tobacco production and fertilization. By GPS positioning, a total of 1146 and 1149 soil samples were collected from the plough layer (0~20 cm) of core tobacco fields in eight tobacco-growing counties of Kunming in 2010 and 2020, respectively. The soil pH and the contents of organic matter (SOM), hydrolyze nitrogen (N), available phosphorus (P, calculated with P
2O
5) and available potassium (K, calculated with K
2O) were selected as analysis index. Nutrients variation characteristics and integrated feasibility index (IFI) were evaluated and analyzed based on multiple comparison and fuzzy mathematical principle. At present, soil pH, OM, N, P and K were 6.03, 32.55 g·kg
−1, 122.68 mg/kg, 42.33 mg/kg and 312.49 mg/kg, respectively. The coefficients of variation of them were 15.75%, 48.69%, 33.46%, 80.98% and 48.96%, respectively, and the variation of pH was moderate, and other variations were high. Soil pH was generally at an appropriate level, but SOM, available N, P and K were on the high side. Compared to 2010, soil pH of Kunming was decreased by 0.15 units during the 10 years (2010—2020), and soil pH of Shilin, Jinning, Anning and Yiliang County was obviously decreased by 0.37, 0.22, 0.19 and 0.17 in 2020, respecyively. Meanwhile, Fumin and Xundian had no significant changes. Soil SOM, N, P and K increased by 1.87 g/kg, 7.21 mg/kg, 5.17 mg/kg and 53.05 mg/kg, respectively. In 2020, IFI of soil was ranged from 0.22 to 0.95, and the mean value of IFI was decreased by 0.03 compared with that of 2010, with significant inter-annual differences in 2010 and 2020. IFIs of Xundian, Anning and Shilin County soil were higher, followed by Fumin, Luquan and Songming, and Jinning and Yiliang were the lowest. The SOM, available N, P and K in the study area were increased gradually, and the overall soil fertility increased. Nevertheless, soil pH was decreased, and there was a trend of acidification. Therefore, nitrogen and phosphorus application should be strictly controlled and more attention should be paid to the improvement of acidified soil.