Nature of the interference mechanism of mugwort (Artemisia vulgaris)

Mugwort is a noxious perennial weed that interferes with the growth and est ablishment of crop species. The present study was designed to understand th e role of allelopathy as a potential mechanism of interference by mugwort. Soils amended with mugwort plant material and leachates were analyzed for t heir chemical characteristics. The effect of amended soils on seedling grow th of red clover was studied. The influence of NP fertilization and charcoa l on modification of allelopathic potential of amended soils, in terms of t heir effect on soil characteristics and red clover seedling growth, was als o investigated. In addition, red clover seedling growth was compared in ste rilized and nonsterilized soils amended with mugwort leachate and NP fertil ization. In general, addition of mugwort leachates and plant matter (amende d soil) resulted in chemical changes in soil, including changes in availabl e phenolics. Red clover seedling growth was reduced in amended soils, when compared to that in nonamended soils. Although the different amounts of NP fertilization in nonsterilized soil amended with mugwort leachate could not counteract its interference to red clover growth (root reduction, 67-79%; shoot reduction, 34-44%), the addition of charcoal did eliminate leachate e ffects on red clover growth. This indicates the probable allelopathic inter ference of mugwort to red clover growth. Addition of NP fertilization might have resulted in higher microbial activity, which is likely to influence q ualitative and/or quantitative availability of phenolic compounds. Data on phenolic levels and red clover growth in sterilized and nonsterilized soil amended with mugwort leachate and NP fertilization indirectly indicate the significance of soil microbes in mugwort interference to red clover.