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Interactions of Microorganisms and Soil during Fenamiphos Degradation
Author(s) -
Ou L.T.
Publication year - 1991
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1991.03615995005500030013x
Subject(s) - mineralization (soil science) , soil water , incubation , pesticide , environmental chemistry , chemistry , microorganism , soil test , zoology , environmental science , agronomy , soil science , biology , bacteria , biochemistry , genetics
Enhanced degradation of a number of pesticides occurs in soils with a history of previous exposure to the chemical. Little is known, however, about the duration of enhanced degradation after a single field application of a pesticide or the microorganisms responsible for the enhancement. Soil samples collected 2, 3, and 4 yr after one application of the nematicide fenamiphos [ethyl‐3‐methyl‐4‐(methylthio)phenyl (1‐methylethyl) phosphoramidate] at a rate of 4.48 kg ha −1 to an experimental site planted in potato ( Solanum tuberosum L.) near Hastings, FL, were used to determine mineralization rates and total‐toxic‐residue (TTR) disappearance rates. Both mineralization rates and TTR disappearance rates in samples collected 2 and 3 yr after field application were enhanced compared with the corresponding control samples. Half‐lives for TTR in soil samples collected 2 and 3 yr after field application of fenamiphos were 22 and 89 d, respectively, while half‐life values for the corresponding control samples were 131 and 130 d. During a 70‐d incubation period, 67.2, 27.8, and 9.8% of applied 14 C‐fenamiphos was mineralized in soil samples collected 2, 3, and 4 yr after field application, while 10.8, 11.5, and 9.5% of applied 14 C‐fenamiphos in the corresponding control samples was mineralized. Mineralization rates in soil collected 4 yr after field application were the same as in the control sample. Microorganisms capable of degrading fenamiphos could not be isolated from the soils. A mixed bacterial culture derived from soil collected 2 yr after the field application, in the presence of a small amount of this soil, however, did mineralize fenamiphos. Without the small amount of soil, the mixed culture did not mineralize the nematicide.