THE INFLUENCE OF PLANTING AND SOIL CHARACTERISTICS ON MINERALIZATION OF 2,4,5-T IN RHIZOSPHERE SOIL

Phytoremediation is a potential means of addressing sad contamination. It is not understood, however, what limits or fosters the degradation of xenobiotics in planted soil, This study examined the relative infl uence of plant species and soil type on biodegradation in the rhizosph ere. In a complete design, three plant species (sunnov;er, Timothy gra ss, and red clover) were grown in three field-collected soils (Jules s ilt loam [a coarse-silty, mixed (calcareous), mesic Typic Udifluvent]; Miamian clay loam [a fine, mixed. mesic Typic Hapludalf]; Parke silt loam [a fine-silty, mixed, mesic Ultic Hapludalf]). Soil characteristi cs and microbial activity, biomass, and mineralization of 2,4,5-trichl orophenoxyacetic acid (2,4,5-T), were determined in soil before and af ter planting. In general, the characteristics of an unplanted soil wer e correlated to ifs microbial biomass and activity. Not suprisingly th en, soil type was the most significant determinant of xenobiotic degra dation in both planted and unplanted systems. In spite of this strong soil effect, planting always resulted in a significant increase in 2,4 ,5-T mineralization. The magnitude of this effect varied with soil. Th e soil initially low in organic matter, K, and P, appeared to gain the most from being planted. The plant species used produced a minor effe ct, but resulted in significant (mineralization) differences only in h igher fertility sails.