The Influence of Temperature, Moisture, and Prior EPTC Application on the Degradation of EPTC in Soils

Abstract

Laboratory and field studies were conducted to compare the degradation rate of EPTC (S-ethyl dipropylthiocarbamate) in soils with a previous history of EPTC application vs. soils with no prior EPTC application. Laboratory experiments showed a rapid breakdown of14C-carbonyl EPTC to14CO2in Kennebec silt loam (sil) and Tripp very fine sandy loam (vfsl) with prior exposure to EPTC. A single prior application of EPTC to Tripp vfsl was sufficient to increase the rate of14CO2evolution. The rate of EPTC degradation in Tripp vfsl with a history of EPTC exposure was dependent on soil moisture from below 3% and independent of moisture above 3%. Patterns of degradation at 5, 15, and 25 C in the Kennebec sil with and without prior history were described by exponential decay. EPTC was degraded more rapidly at 15 and 25 C in the Kennebec sil with a prior EPTC history. Under field conditions the breakdown of EPTC in a Kennebec sil with and without prior exposure to EPTC was similar to laboratory results.