Distribution of Active Aluminum Forms and Affecting Factors in Tea Plantation Soils from Northwest Guizhou

The toxicity of active aluminum in soils is mainly associated with its chemical forms. In this study,forms of active Al in a tea plantation in northwest Guizhou were studied based on analysis of 106 soil samples with sequential chemical extraction procedure,and the affecting factors for active Al in the plantation were discussed. The results showed that the total Al contents in different soils decreased in the order of tan soils brown soils yellow soils yellowish-brown soils. However,w( Tac-Al) in different soils decreased in the order of yellow soils yellowish-brown soils brown soils tan soils. The slight difference existed in the distribution pattern of active Al contents for different soil types. Hy-Al and Ha-Al,which were relatively stable forms,constituted the dominant part of the total active Al content,accounting for nearly 70. 0% of the total. The average content of different active Al forms was as follows: Hy-Al Ha-Al Ex-Al Or-Al In-Al. In the present study,some highly significant correlations were found between different active Al chemical forms with correlation analysis. Especially,the correlation coefficient between w( Hy-Al) and w( Tac-Al) was up to 0. 975( P 0. 01). Additionally,the contents of Tac-Al in the soils from the studied region were found to generally increase with an increase in soil acidity and soil organic matter. The total Al content was not responsible for the total active Al content in soils. It was found that soil acidity and soil organic matter were the affecting factors of active aluminum in the soils.