Indirect allelopathic effects of Xanthium italicum Morretti on soil properties and microbial communities.
We evaluated the effects of ethanol and aqueous extracts of invasive weed Xanthium italicum Morretti on soil properties and soil microbial communities and the possible involvement of secondary metabolites in the invasion process. The application of both extracts increased the soil organic matter, total and available N, P, K. These extracts increased the available P by 11.5% and 13.6%, and available K by 108.8% and 126%, respectively. Aqueous extract stimulated the enzyme activities (increased the activities of urease, invertase, protease and alkaline phosphatase by 30%, 118%, 100.7% and 47.8%, respectively) than ethanol extract. Culture-dependent approach revealed that application of ethanol and aqueous extracts increased the quantity of soil bacteria by 590.5% and 301.4%, respectively, while, the growth of fungi and actinomyces were inhibited significantly. The AWCD values obtained from different soils followed the order: control > aqueous extract > ethanol extract. These indicated that application of ethanol and aqueous extracts significantly altered the soil microbial communities, which might consequently affect the interaction between above- and below-ground interactions.