ARS | Publication request: Fate of Herbicides and Their Degradation Products Entering a Forested Riparian Buffer Following Herbicides Application to an Adjacent Corn Field

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 2008
Publication Date: June 30, 2008
Citation: Rice, C., Bialek Kalinski, K.M., Mccarty, G.W., Hively, W.D., Angier, J. 2008. Fate of Herbicides and Their Degradation Products Entering a Forested Riparian Buffer Following Herbicides Application to an Adjacent Corn Field. Meeting Abstract.

Technical Abstract: The fate of two herbicides, atrazine and metolachlor, were followed as they entered and moved through a forested riparian wetland located in the mid-Atlantic coastal plain of Maryland. The herbicides were applied as pre-emergent treatments to a 20-ha corn field directly upgradient of the riparian wetland. Data will be presented for more than 4 years of monitoring by researchers at the USDA-ARS Beltsville Agricultural Research Center. Pesticide movement and degradation was analyzed in the context of hydrological processes, including surface runoff, groundwater movement, and atmospheric delivery through rainfall and wash off from the forest canopy. Herbicide loading to the riparian buffer was determined by measuring fluxes into a first order stream arising in the buffer area and by measuring concentrations in groundwater upwelling zones. Delivery through rainfall and canopy wash off was measured during rain events. When rain events occurring within the first month after application produced surface runoff from the field, large fluxes of herbicides were observed. These surface runoff events were always accompanied by large increases in herbicide flux in the receiving stream within the riparian buffer. Rainfall flux data indicated that wash off from the tree canopy was also an important source of this increased flux of pesticides observed in the stream. Fluxes of pesticides in rain collected outside the forested buffer area were always lower than fluxes of pesticides collected in rain obtained beneath the forest canopy, both as stem flow and direct through-fall. These findings support the conclusion that forest canopy runoff models are needed to better assess efficacy of forested riparian buffers at reducing pesticide delivery to streams in mid-Atlantic ecosystems.