Response Difference of Particle Size Compositions of Red Soil Planted with Flue-Cured Tobacco to Continuous Cropping Years
In order to study the difference of soil particle size compositions and its correlation with soil biochemical indicators under different continuous cropping years of tobacco,the soil samples of rotation,con-tinuous cropping for 3 years and continuous cropping for 8 years in typical red soil area of Yunnan Province were taken as research objects to determine the particle size compositions,chemical properties and enzyme ac-tivities,and then their correlation analysis and stepwise regression analysis were carried out.The results showed that the proportion of clay in the soil with continuous cropping tobacco for 8 years increased by 19.21％,and that of silt and sand decreased by 21.71％and 14.87％,respectively.With the increase of con-tinuous cropping years,the contents of soil organic matter(OM),total nitrogen(TN),hydrolyzable nitrogen(AN),total phosphorus(TP),available phosphorus(AP),total potassium(TK)and available potassium(AK),the cation exchange capacity(CEC)and the pH value showed decreasing trends,while the activity of urease increased significantly,and the activities of sucrase and catalase decreased.The results of stepwise re-gression analysis showed that the proportion of clay particles had significantly or extremely significantly inhibi-tory effects on soil TN,TP and TK contents and pH value.The proportion of silt particles had significantly or extremely significantly promoting effects on soil OM and AP contents,CEC,and catalase and sucrase activi-ties.Compared with rotation,continuous cropping resulted in an increase of the proportion of clay particles in tobacco-growing red soil and a decrease of soil permeability,thus affected soil nutrient mineralization and en-zymes activities.The results of this study could provide the data support and theoretical basis for continuous cropping soil improvement.
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