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Effect of freezing and thawing on microbial activity and glyphosate degradation in two Norwegian soils
Author(s) -
Stenrød Marianne,
Eklo Ole Martin,
Charnay MariePaule,
Benoit Pierre
Publication year - 2005
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.1107
Subject(s) - glyphosate , mineralization (soil science) , soil water , chemistry , incubation , pesticide , agronomy , environmental chemistry , zoology , soil science , environmental science , biology , biochemistry
Little research has been done on pesticide dissipation in cold climates and there is a need to focus on the influence of climate on pesticide degradation in soil. Glyphosate, N ‐(phosphonomethyl)glycine, is a herbicide frequently used for controlling perennial weeds through application after harvest and was used as a model compound for this study. The effect of freeze–thaw activity on the availability of glyphosate in soil, and consequently its mineralization by soil microorganisms, was studied through laboratory incubations of repacked soil cores treated with 14 C‐labelled glyphosate and subjected to different freeze–thaw treatments. Winter simulation regimes applied were constant thaw (+5 °C), constant freezing (−5 °C), unstable conditions with short fluctuations (24 h of −5 °C followed by 24 h of +5 °C), and long duration fluctuations (3 weeks of −5 °C followed by 3 weeks of +5 °C). Distribution of 14 C‐glyphosate was followed during the incubation through measurements of the mineralized fraction ( 14 CO 2 ), soil water fraction, KOH extractable fraction, and non‐extractable fraction. Microbial parameters used to characterize the soils were estimates of size of microbial biomass, overall microbial activity and microbial diversity. The constant freezing treatment exhibited the lowest amount of glyphosate mineralization. The constant thawed treatment and the treatments with fluctuating temperature exhibited significantly increased mineralization. These results were in accordance with the observed concentration of glyphosate in soil water; the higher the activity, the lower the concentration. The amount of glyphosate extractable with KOH and the resulting non‐extractable fraction, however, were not significantly affected by soil type or temperature regime. The glyphosate mineralization pattern was comparable with the overall microbial activity in the soils. Observed different levels of diversity might explain some of the difference in total glyphosate mineralization between soils. Copyright © 2005 Society of Chemical Industry