Abstract
The ecotoxicological impact of leptospermone, a β-triketone bioherbicide, on the bacterial community of two arable soils was investigated. Soil microcosms were exposed to 0 × (control), 1 × or 10 × recommended dose of leptospermone. The β-triketone was moderately adsorbed to both soils (i.e.,: Kfa ~ 1.2 and Koc ~ 140 mL g−1). Its dissipation was lower in sterilized than in unsterilized soils suggesting that it was mainly influenced by biotic factors. Within 45 days, leptospermone disappeared almost entirely from one of the two soils (i.e., DT50 < 10 days), while 25% remained in the other. The composition of the microbial community assessed by qPCR targeting 11 microbial groups was found to be significantly modified in soil microcosms exposed to leptospermone. Pyrosequencing of 16S rRNA gene amplicons showed a shift in the bacterial community structure and a significant impact of leptospermone on the diversity of the soil bacterial community. Changes in the composition, and in the α- and β-diversity of microbial community were transient in the soil able to fully dissipate the leptospermone, but were persistent in the soil where β-triketone remained. To conclude the bacterial community of the two soils was sensitive to leptospermone and its resilience was observed only when leptospermone was fully dissipated.
Highlights
Agriculture is facing critical challenges to ensure high crop production and quality, while preserving environmental and human health (Brussaard et al, 2010)
The soil behavior of leptospermone was evaluated with adsorption isotherms in P and Saint Jean de Fos (SJF) soils, and Freundlich relationships were used to evaluate the sorption behavior according to OECD guideline
Koc-values, representing the adsorption of the pesticide normalized by soil organic carbon content, were slightly higher for P soil (143.86 mL g−1) than SJF soil (136.66 mL g−1)
Summary
Agriculture is facing critical challenges to ensure high crop production and quality, while preserving environmental and human health (Brussaard et al, 2010). Among pressures exerted by agriculture on the environment, synthetic plant protection products (PPPs) are of concern because they can persist in arable soils and be transferred to different compartments of the environment where they are frequently detected (Margni et al, 2002; Polyrakis, 2009) In this context, the use of natural active compounds, known as biopesticides, may be an interesting alternative for crop protection as they are considered to be less harmful and environmentally safer (Dewhurst, 2001; Dayan et al, 2009, 2011; Cantrell et al, 2012; Seiber et al, 2014). The biopesticide market has been gaining greater approval and interest for pest management (Copping and Menn, 2000; Cantrell et al, 2012; Seiber et al, 2014)
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