Microbiological characteristics of a sandy loam soil exposed to tebuconazole and λ-cyhalothrin under laboratory conditions

Abstract

Changes in microbiological properties of a sandy loam soil in response to the addition of different concentrations of fungicide tebuconazole and pyrethroid insecticide lambda-cyhalothrin were assessed under laboratory conditions. To ascertain these changes, the potentially active soil microbial biomass, concentrations of ammonium and nitrate ions, numbers of total culturable bacteria, fungi, nitrogen-fixing bacteria, nitrifying and denitrifying bacteria were determined. Substrate-induced respiration (SIR) increased with time in both control (ranged from 13.7 to 23.7 mg/O(2)/kg(-1)/dry soil/h(-1)) and pesticide treated soil portions. For both pesticides, SIR values ranged from 12-13 to 23-25 mg/O(2)/kg(-1)/dry soil/h(-1) on days 1 and 28, respectively. Also, concentrations of nitrate and ammonium ions, numbers of total culturable bacteria, denitrifying bacteria, nitrogen-fixing bacteria (for the insecticide) and fungi (for the insecticide) were either unaffected or even stimulated by the pesticide treatments. The adverse impacts of the pesticides were observed for nitrate concentrations (on days 1 or 7), numbers of nitrifying bacteria (on day 1), denitrifying bacteria (for the insecticide on days 1 and 14), nitrogen-fixing bacteria (for tebuconazole on day 1) as well as numbers of fungi in tebuconazole-treated soil (on days 1 and 14).

Changes in functional diversity of soil microbial community with addition of antibiotics sulfamethoxazole and chlortetracycline

“…This may indicate that antibiotics could act as nutrients for soil microbial growth (Schmitt et al 2005;Thiele-Bruhn and Beck 2005;Westergaard et al 2001). Similar results had been reported that fungicides and insecticides increased bacterial biomass because they were also used as carbon and nutrient sources for microbial growth (Cycoń et al 2006;Monkiedje et al 2002;Wang et al 2004).…”

Enhancement of deltamethrin degradation by soil bioaugmentation with two different strains of Serratia marcescens

“…The observed low rate of degradation during the first 2 weeks might be the result of the necessity of bacterial adaptation to the presence of pyrethroid, adaptation of introduced strain to soil conditions as well as proliferation of indigenous bacteria that can use deltamethrin as an additional source of carbon and energy. This suggestion may be supported by the increase in the numbers of specific group of microorganisms in soil after application of different pyrethroids and other chemicals, which was observed in many studies (Cycoń et al 2006;Vig et al 2008;Zhang et al 2009;Cycoń et al 2010). The initial delay in deltamethrin degradation may also be explained by the fact that soils used in this study had no contact with pyrethroids and other pesticides for at least 10 years, and the number of bacteria capable of pesticide utilization was very small.…”

“…Moreover, a relatively high deltamethrin concentration (100 mg kg -1 of soil) was also an important factor affecting microbial growth. However, synthetic pyrethroids applied at the recommended field rate are non-toxic to soil microorganism, as these organisms do not have sensitive targets (Rangaswamy and Venkateswarlu 1993;Widenfalk et al 2004;Cycoń et al 2006). The delay in pesticides and other chemicals degradation just after their application into soil indicating the period of time needed for the proliferation of a small population of pesticide-degrading microorganisms to the optimal level required for an effective degradation of the pesticide was also observed in some studies (Mrozik et al 2010;Chen et al 2011a, b).…”

Biodegradation kinetics of the benzimidazole fungicide thiophanate-methyl by bacteria isolated from loamy sand soil

“…The observed fast disappearance of TM in nSS not previously treated with this fungicide suggested that TM applied even at a high concentration (100 mg kg -1 ) did not affect the degradative potential of the autochthonous microorganisms. Generally, fungicides applied at recommended field rates are non-toxic to bacteria, as they do not have sensitive targets (Strickland et al 2004;Cycoń et al 2006Cycoń et al , 2010Wang et al 2009). The DT50 of TM calculated for nSS was 3.0 days, which supported the previous study, showing that this fungicide breaks down rapidly (\4 days), and is transformed to the very stable compound MBC (Fleeker et al 1974;Roberts et al 1998).…”