PARENT SESSION
PW7 - Biotransformation / Metabolisms / Degradation
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P783) Reduction in herbicide loss from band application/water table control in a corn soybean rotation.

Gaynor, John^*,1, Tan, Chin¹, Drury, Craig¹, Reynolds, W.¹, Welacky, Tom¹, ¹ AAFC, GPCRC, Harrow, Ontario, Canada

ABSTRACT- Improvements in water quality is variable with conservation tillage because of the dominance of climatic factors. Herbicide in surface and subsurface runoff from a corn-soybean rotation was measured following water table control and banded herbicide application. Water table control included free drainage from tile at 60 cm depth (D), controlled drainage by modifying tile drainage to 30 cm depth (CD) and controlled drainage with subsurface irrigation to a nominal depth of 30 cm (CDS). Herbicides (atrazine at 1.1 kg/ha, metribuzin at 0.5 kg/ha and metolachlor at 1.05 kg/ha) were either applied to the whole plot or in a 15 cm band over the row for a one-third reduction in application amount. Herbicide transported in surface and subsurface runoff was dependent upon time and intensity of rain after application (losses averaged <1 to 4% of application). Residual amounts (<0.02% of application) of atrazine and des-ethyl atrazine were found following previous years application. Controlled drainage with subirrigation increased herbicide loss relative to D and CD mainly through surface runoff. In some years, band application reduced herbicide loss. More herbicide residue was found in soil from D than CDS because of less favourable environment for biotic activity. Band application appears to be effective in reducing non-point source loss of herbicide.

Key words: herbicides, runoff, water table control, banded herbicide application