|Lerch, Robert - Bob|
Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Other
Publication Acceptance Date: 7/31/2002
Publication Date: 7/31/2002
Citation: GHIDEY, F., ALBERTS, E.E., LERCH, R.N. EVALUATION OF HERBICIDE LOSSES FROM THREE FIELD-SIZE WATERSHEDS. AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS MEETINGS PAPERS. 2002. ST. JOSEPH, MI. PAPER 022142. Interpretive Summary: Runoff and soil losses from the Midwest claypan region are relatively high during the seedbed preparation period when agri-chemicals are applied. Because of this, herbicide losses to surface runoff could be critical for the runoff events that occur immediately after application. In this study, herbicide concentrations in surface runoff from three field-size watersheds located in the claypan soil region of north-central Missouri were measured from 1993-1997. The effects of herbicide application method and timing of the runoff event related to herbicide application on the transport of atrazine and alachlor (or metolachlor) to surface runoff were evaluated. Herbicide concentrations in runoff were extremely high for the events that occurred within a few days after application; more than 90% of the annual herbicide loss occurred within 4 wk following application. Atrazine and alachlor losses to surface runoff were 140 and 36% higher when herbicides were surface applied and not incorporated compared to surface applied and incorporated. Thus, for runoff-prone soils, such as the Midwest claypan region, farming systems which do not incorporate soil applied herbicides are vulnerable to significant herbicide losses by surface transport. No-till systems are particularly vulnerable to herbicide losses from claypan soils. This study will help farmers and producers to efficiently manage herbicides and thus reduce the loss of excess agri-chemicals to surface runoff/leaching.
Technical Abstract: Herbicide concentrations in surface runoff from three field-size watersheds located in the claypan soil region of north-central Missouri were measured from 1993-1997. During each runoff event, water samples were collected from the outlets of the drainage areas for atrazine, alachlor, and metolachlor analysis. Herbicide concentrations in runoff were extremely high for the events that occurred within few days after application. More than 90% of the annual herbicide loss occurred within 4 wks following application. Concentrations in runoff were very low (< 1.0 :g L**-1) or non-detectable for all the events that occurred after 8 wks following herbicide application. Atrazine and alachlor (or metolachlor) losses to surface runoff accounted for 8.7 and 3.6% of the total applied in the soil when herbicide was surface applied and not incorporated, and 1.4 and 1.0% when herbicide was surface applied and incorporated, respectively. The study indicated that the timing of runoff relative to chemical application played an important role in the transport of herbicides to surface runoff.