Isoproturon mineralization in an agricultural soil |
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Authors: | Talaat El Sebaï Marion Devers-Lamrani Bernard Lagacherie Nadine Rouard Guy Soulas Fabrice Martin-Laurent |
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Institution: | 1.INRA, Soil and Environmental Microbiology,Université de Bourgogne,Dijon,France;2.Agricultural Microbiology Department,National Research Centre,Cairo,Egypt;3.Université Victor Segalen Bordeaux II, UMR 1219, INRA, Faculté d’?nologie, ISVV,Villenave d’Ornon,France |
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Abstract: | The impact of soil moisture content and temperature on isoproturon (3-(4-isopropylphenyl)-1,1-dimethyl-urea IPU]) mineralization
activity was assessed on an agricultural soil regularly exposed to this herbicide. Mineralization of 14C-IPU was monitored on soil microcosms incubated at different temperatures (10°C, 20°C, 28°C) and soil moisture contents (9%,
12%, 15, 18%, 21%, 24%). An increase in temperature and/or soil moisture significantly enhanced the maximum rate and percentage
of IPU mineralization while it decreased the lag time before mineralization. The maximum rate and percentage of IPU mineralization
respectively ranged from 0.18% day−1 and 9% for the lowest temperature and soil moisture content pair (10°C–9%) to 1.51% day−1 and 27.1% for the highest pair (28°C–24%). Statistics revealed a cross interaction of temperature and soil moisture content
on the maximum rate of IPU mineralization. The optimum conditions for IPU mineralization, estimated from the double Gaussian
model, were 25.8°C and 24% soil moisture content. The influence of fluctuations in soil moisture content on IPU-mineralization
was investigated by subjecting the soil microcosms to drought stress. When IPU was added at the end of the drought stress,
it had no statistical effect on IPU mineralization. However, when it was added before the drought stress, two mineralization
phases were observed: (1) one corresponding to the drought stress for which mineralization was low and (2) another one observed
after restoration of soil moisture content characterized by higher mineralization rate. It can be concluded that climatic
fluctuations affect the activity of IPU mineralizing microbial community, and may lead to an increase in IPU persistence. |
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