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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #122581
Title: PESTICIDE RUNOFF AND WASHOFF FROM SIMULATED RAINFALL IN CONVENTIONAL- TILLAGE PEANUT PRODUCTION.

Author
item Johnson, Wiley - Carroll
item Wauchope, Robert - Don
item Sumner, Harold

Submitted to: American Peanut Research and Education Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2001
Publication Date: 7/9/2001
Citation: Johnson, W.C., Wauchope, R.D., Sumner, H.R. 2001. Pesticide runoff and washoff from simulated rainfall in conventional-peanut production [abstract]. American Peanut Research and Education Society Abstracts. 33:64.

Interpretive Summary:

Technical Abstract: Studies were conducted in Tifton, GA to determine the amount of pesticide runoff and washoff from peanut production using simulated rainfall. Ethalfluralin and metolachlor were applied preplant incorporated and preemergence, respectively, to two replicate mesoplot runoff plots. Rainfall was simulated approximately 24 hours after application using raindrop irrigation sprinklers, raised 1.8 m above the soil surface. Approximately 25 mm of simulated rainfall was produced over a 2 hour period. The procedure was repeated at mid-season, when peanut achieved full canopy closure, applying rhodiamine WT dye and chlorothalonil. Runoff from both simulations was collected in an excavated pit at the end of the peanut rows. Amounts of ethalfluralin, metolachlor, and chlorothalonil in runoff water were determined using methylene chloride extraction of unfiltered runoff samples. Amounts of rhodiamine were measured by fluorescence. Maximum and average runoff concentrations (ppb) were ethalfluralin: 17 and 7; metolachlor: 280 and 104; rhodiamine: 818 and 179; chlorothalonil 495 and 163. Amounts lost in runoff in the four events were 0.02-0.05, 0.09-0.41, 0.090-0.17 and 0.24-1.1% for ethalfluralin, metolachlor, rhodiamine and chlorothalonil, respectively. These results confirm that soil incorporation reduces runoff losses and relatively high concentrations of foliar-deposited pesticides may be present in runoff. Compared to soil applications, the higher foliar wash-off concentrations may be offset by a lower runoff volume from a soil with full crop canopy closure. The rhodiamine runoff data also suggests a dramatic solubility effect, in which the highly soluble chemical is rapidly leached below the soil surface before runoff.