Mineralization of [14C] glyphosate and its plant-associated residues in arable soils originating from different farming systems
✍ Scribed by von Wirén-Lehr, Sabine; Komoßa, Dieter; Gläßgen, Werner E.; Sandermann, Heinrich; Scheunert, Irene
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 343 KB
- Volume
- 51
- Category
- Article
- ISSN
- 1526-498X
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✦ Synopsis
The biomineralization of [14C]glyphosate, both in the free state and as 14C-residues associated with soybean cell-wall material, was studied in soil samples from four di †erent agricultural farming systems. After 26 days, [14C]carbon dioxide production from free glyphosate accounted for 34È51% of the applied radiocarbon, and 45È55% was recovered from plant-associated residues. For three soils, the cumulative [14C]carbon dioxide production from free glyphosate was positively correlated with soil microbial biomass, determined by substrate-induced heat output measurement and by total adenylate content. The fourth soil, originating from a former hop plantation, and containing high concentrations of copper from long-term fungicide applications, did not Ðt this correlation but showed a signiÐcantly higher [14C]carbon dioxide production per unit of microbial biomass.
Although the cumulative [14C]carbon dioxide production from plantassociated 14C-residues after 26 days was as high as from the free compound, it was not correlated with the soil microbial biomass. This indicates that the biodegradation of plant-associated herbicide residues, in contrast to that of the free compound, involves di †erent degradation processes. These encompass either additional steps to degrade the plant matrix, presumably performed by di †erent soil organisms, or fewer degradation steps since the plant-associated herbicide residues are likely to consist mainly of easily degradable metabolites. Moreover, the bioavailability of plant-associated pesticide residues seems to be dominated by the type and strength of their Ðxation in the plant matrix.