Vol. 15—1961 - NorthEastern Weed Science Society

11/
Persistence of Soil-Incorporated EPTCand Other Carbamates ­
47..
ABSTRACT
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L. L. Danielson, W. A. Gentner, and L. L. Jansen ­
Studies were initiated in 1958 to determine the herbicidal activity of
several soil-incorporated carbamate herbicides and to investigate the
formulation, soil, and climatological factors involved in their persistence
in the soil. Investigations included preliminary and terminal field
studies and several greenhouse studies.
1. Field studies of EPTC, CDEC,eIPC, isopropyl N-(3-methylphenyl)­
carbamate, BCPC, and CEPCusing the logarithmic sprayer indicated that
EFTCand CDECretained their herbicidal characteristics when soil.incorporated
at rates of 16 IblA or less. EPTCwas more persistent than CDEC, on
the basis of plant bio-assay responses.
2. In greenhouse studies, a soil-incorporated. commercial formulation
of EPTCdissipated most rapidly under conditions of surface-irrigation and
was inversely related to soil organic-matter content.
3. The commercial formulation of EFTCin water was compared to technical
EFTCapplied in acetone, benzene, xylene, kerosene, and No. 2 fuel oil.
Rate of dissipation of EFTCwas most rapid when it was applied in kerosene.
The persistence characteristics of commercial EPTC in water and technical
EFTC in kerosene were confirmed in field studies.
4. Rate of dissipation of soil-incorporated commercial EPTCwas accelerated
as temperatures increased whereas rate of dissipation of technical
EPTCin k~rosene was not significantly affected in the present studies.
5. Several concentrations of selected Burfactants decreased the rate of
dissipation of soil-incorporated technical EPTC formulated in kerosene.
6. These investigations clearly demonstrate that soil-incorporated
carbamates differ widely in selectivity and persistence depending on chemical
structure, formulation, soil composition, method of irrigation, and
temperature. These data have broad implications in the performance of all
soil-incorporated carbamatesand possibly all herbicides applied in organic
solvents. It appears from these data that the period of persistence of
soil-incorporated carbamates can be controlled within limits by the constituents
used in formulation. These data also .euggest the possibili.ty that the
period of actiVity of granular herbicides can be regulated by selectiQn of
suitable solvents, surfactants, and granular carriers having specific
characteristics.
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Paper submitted for publication in Weeds.
Plant Physiologists, Crops Research Division, Agricultural Research Ser~
?! vice, U. S. Department of Agriculture, Beltsvillej Maryland~