Herbicide runoff study published in Forest Science
A recent issue of Forest Science includes an article by M.A. McBroom and others
titled “Runoff of silvicultural herbicides applied using best management
practices.” The authors are affiliated with Stephen F. Austin State University
and NCASI. Results indicate that the best management practices applied in the
study watersheds were very effective in controlling herbicide runoff and
protecting aquatic ecosystems. The abstract follows.
“Nine small (2.2–2.9 ha) and four large (70–135 ha) watersheds in East
Texas, USA, were instrumented to compare herbicide runoff under different
silvicultural systems with best management practices (BMPs). Two treatments
were evaluated: conventional, with clearcutting, aerial herbicide site
preparation, and hand-applied banded herbaceous release; and intensive, in
which subsoiling, aerial fertilization, and a 2nd-year aerial herbicide
application were added. Herbicides were applied as operational tank mixes. The
highest imazapyr concentration found in stream water was 39 μg L-1 during
the first storm after application (23 days after treatment [DAT]) and in-stream
concentrations during runoff events dropped to <1 μg L-1 in all
streams by 150 DAT. The highest hexazinone concentration was 8 μg L-1 for
the banded application and 35 μg L-1 for the broadcast application
the following year and fell to <1 μg L-1 in all streams by 140
DAT. The highest sulfometuron methyl concentration found during a runoff event
was 4 μg L-1and fell to <1 μg L-1 streams by 80 DAT.
Approximately 1–2% of applied imazapyr and <1% of hexazinone and
sulfometuron methyl were measured in storm runoff. Herbicide was found in
streams during storm events only (all herbicides were <1 μg L-1 in
all true baseflow samples), and peak concentrations during runoff events
persisted for relatively short times (<24 h). These results suggest that
silvicultural herbicide applications implemented with contemporary BMPs are
unlikely to result in chronic exposure of aquatic biota; therefore, herbicide
use under these conditions is unlikely to degrade surface waters.”
Contact information
Reference
McBroom, M.W., J. Louch, R.S. Beasley, M. Chang,
and G. Ice. Runoff of silvicultural
herbicides applied using best management practices. Forest Science 59(2): 197-210.