Distributions of Available Ca and Mg Contents in Tobacco Soil at Different Altitudes——A Case Study of Tobacco-growing Area of Qujing in Yunnan

In order to clarify the changes and distributions of available Ca and Mg contents in tobacco soil at different altitudes,in total 2 552 soil samples between 1300 m and 2300 m altitude in tobacco-growing region of Qujing were collected and analyzed by statistical analysis and geostatistics.The results showed that the mean contents of soil available Ca and Mg in tobacco-growing soil Qujing were 2 640.86 mg/kg and 314.26 mg/kg,respectively.The content of soil available Ca was highest in the middle altitude region,suitable at the low and lower altitude regions,but lower at the high and higher altitude areas.The content of soil available Mg declined with the increase of altitude.The content of soil available Mg was higher in the low and lower altitude regions but suitable in other regions.The contents of soil available Ca and Mg were correlated negatively with altitude.The ratio of Ca/Mg in the middle altitude region was highest,but significantly lower in the low and lower altitude regions than other regions.The available Ca was correlated negatively with available P,positively with other soil nutrients.The available Mg was correlated negatively with alkali-hydro nitrogen and available P,positively with other soil nutrients.The content of soil available Ca gradually declined from east to west in Qujing.Available Mg was higher in south and north regions but lower in middle region,the ratio of Ca/Mg was higher in east region but lower in south,north and west regions.