|Wauchope, Robert - Don|
Submitted to: Transactions of the ASAE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/20/2001
Publication Date: 1/2/2002
Citation: Vellidis, G.D., Lowrance, R.R., Paige, G., Wauchope, R.D. 2002. Herbicide transport in a restored riparian forest buffer system. Transactions Of The American Society Of Agricultural Engineers. 45(1):89-97. Interpretive Summary: Riparian (streamside) buffers are increasingly used as a technique for improving water quality in agricultural watersheds and to restore the functions of aquatic ecosystems. Although it has been shown that mature riparian forest buffers are effective in reducing concentrations and loads of herbicides moving from agricultural areas, the use of a restored riparian buffer has not been demonstrated. We measured herbicide (atrazine and alachlor) concentrations in a restored riparian buffer in the Coastal Plain near Tifton, Ga. A riparian buffer system was restored in 1991 according to USDA- Natural Resources Conservation Service guidelines. Vegetation was planted in a three zone arrangement with hardwoods in Zone 1 (near the stream), pines in zone 2 (upslope from Zone 1) and a Zone 3 grass filter strip above Zone 2. Herbicide movement was monitored from an application strip above the buffer in 1993 and 1994. During the period of high herbicide movement in surface runoff that occurred in both Spring seasons after application, the buffer system reduced atrazine and alachlor concentrations by a factor of about 20 times. Concentration reduction was greatest in the grass buffer at the beginning of the buffer system where the input concentrations were highest. There was very little herbicide transport in shallow groundwater or in streamflow. The restored buffer was nearly as effective as a previously studied mature buffer in reducing concentrations of herbicides reaching the stream. Restoring riparian buffer systems is an effective way to limit herbicide movement to Coastal Plain streams.
Technical Abstract: The effect of a restored riparian forest buffer system (RFBS) on transport of two herbicides, atrazine and alachlor, was studied during 1993-1994. Herbicides were applied in April of each year above a three zone riparian buffer system that was restored in 1991. Bromide was applied as a tracer with the April, 1993 herbicide application. The buffer system was managed based on USDA recommendations and averaged 38 m in width. The system included a grass buffer strip immediately adjacent to the application area (Zone 3); an area of planted pines downslope from the grass buffer (Zone 2); and a narrow area of planted hardwoods containing the stream channel system (Zone 1). Most of the herbicide transport in surface runoff occurred before June 30th with about 25 cm of cumulative rainfall after herbicide application. During this period of higher herbicide transport, atrazine and alachlor concentrations averaging 12.7 Fg L-1 and 1.3 Fg L-1 , respectively, at the field edge were reduced to 0.66 Fg L-1 and 0.06 Fg L-1, respectively as runoff neared the stream. The effects of dilution versus other concentration reduction factors (infiltration, adsorption) was estimated for surface runoff using the bromide concentration data. Concentration reduction was greatest per meter of flow length in the grass buffer adjacent to the field. There was only minor transport of herbicides through the buffer system in shallow groundwater. Average herbicide concentrations were at or below detection limits in groundwater near the stream for the entire study period.