Ethion degradation and its correlation with microbial and biochemical parameters of tea soils |
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| Authors: | Avhik Bishnu Ashis Chakraborty Kalyan Chakrabarti Tapan Saha |
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| Institution: | (1) Institute of Environmental Studies and Wetland Management, DD-24, Sector–I, Salt Lake City, Kolkata, 700064, India;(2) Department of Agronomy, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, 741252, West Bengal, India;(3) Department of Agricultural Chemistry and Soil Science, Calcutta University, 35 Ballygunge Circular Road, Kolkata, 700019, India |
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| Abstract: | Ethion, a highly persistent insecticide in soil, is extensively used in tea cultivation in the tropics. The studies on the
environmental impact of ethion in tea soil ecosystems are scanty. Silty loam and sandy loam soils from tea fields of Dooars
(Typic Uderthents) and Hill (Typic Dystrudepts), respectively, were investigated for the degradation and effect of ethion
application on soil microbial and biochemical variables under controlled laboratory conditions. Ethion degraded faster in
the Hill soil than in the Dooars soil. Higher temperature (30°C) aided in faster degradation due to the increased microbial
activity in the soils. Ethion application at field rate (FR) had lower half-lives (70 days at 20°C and 42.3 days at 30°C for
Dooars soil; 65.4 days at 20°C and 39 days at 30°C for Hill soil) than at ten times FR (10FR; 75.2 days at 20°C and 44.2 days
at 30°C for Dooars soil; 70 days at 20°C and 41.8 days at 30°C for Hill soil). Soil microbial biomass carbon, ergosterol content,
fluorescein diacetate hydrolyzing and β-glucosidase activities declined in all the treatment combinations up to day 60 for
both FR and 10FR doses at 20°C, irrespective of the soil types. At 30°C, the decreasing trend was observed up to day 30 for
both the soils. The toxicological effect of ethion on microbiological and biochemical parameters persisted till their corresponding
half-lives. The microbial metabolic quotient and microbial respiration quotient were altered, but was short-lived, indicating
ethion induced disturbances. The recovery of the depressive action at 10FR ethion spiking on the studied variables was of
slightly longer duration than noticed at FR application, although the depressive effect was overcoming after the respective
half-lives of ethion. The microbial and biochemical soil parameters were negatively correlated with application of ethion
up to day 60 of incubation. |
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