By： Gevao, Bondi and Jones, Kevin C. and Semple, Kirk T.
The role of native soil microorganisms in the formation and release of non-extractable C-14-residues, previously treated with C-14- Dicamba, was investigated to examine their significance to the longer-term environmental effects on non-extractable pesticide residues. A 90 d study compared the fate of Dicamba under sterile and non-sterile regimes. In addition, soils were aged for 30 d and repeatedly extracted with a 0.01 M CaCl2 Solution, to an extraction end point, to produce non-extractable residues. The extracted soil containing non-extractable residues was mixed with clean soil that had been freshly spiked with non-labeled Dicamba at 0.2 mg kg(-1) to increase the bulk volume of the soil and stimulate microbial activity. Sub-samples were then introduced into microcosms to compare the extent of microbially facilitated release and mineralisation with release rates in sterile microcosms. The results show that microorganisms play a significant role in the formation and release of non-extractable Dicamba residues. The release of C-14-activity in sterile microcosms was linked to physical mixing of the extracted soil with field soil prior to the beginning of the incubations. The released C-14-activity may be further mineralized, reincorporated into humus, or taken up by plants or other soil inhabiting biota
The role of native soil microorganisms in the formation and release of non-extractable C-14-residues, previously treated with C-14- Dicamba, was investigated to examine their significance to the longer-term environmental effects on non-extractable pesticide residues. A 90 d study compared the fate of Dicamba under sterile and non-sterile regimes. In addition, soils were aged for 30 d and repeatedly extracted with a 0.01 M CaCl2 Solution, to an extraction end point, to produce non-extractable residues. The extracted soil containing non-extractable residues was mixed with clean soil that had been freshly spiked with non-labeled Dicamba at 0.2 mg kg(-1) to increase the bulk volume of the soil and stimulate microbial activity. Sub-samples were then introduced into microcosms to compare the extent of microbially facilitated release and mineralisation with release rates in sterile microcosms. The results show that microorganisms play a significant role in the formation and release of non-extractable Dicamba residues. The release of C-14-activity in sterile microcosms was linked to physical mixing of the extracted soil with field soil prior to the beginning of the incubations. The released C-14-activity may be further mineralized, reincorporated into humus, or taken up by plants or other soil inhabiting biota
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