ABSTRACT:
This study evaluated the effectiveness of various tillage/herbicide management practices for reducing atrazine and cyanazine runoff from tile-outlet terrace systems. Of particular interest was the effectiveness of the 66ft (20-meter), no-spray setback area around tile-outlet riser pipes needed to meet label requirements compared to (1) tilled, 100% sprayed area; (2) no-till, 100% sprayed area; and (3) tilled, 100% sprayed area with herbicide incorporation. Four practices were replicated three times on 12 individual tile-outlet terraces in Iowa, Missouri, and Nebraska. Atrazine and cyanazine were applied at rates ranging from 0.88 to 2.5 lb./acre (0.99 to 2.8 kg/ha). Three runoff events were sampled in Iowa and Missouri, and one in Nebraska. Concentrations of atrazine and cyanazine were greatest from the tilled and no-till plots where 100% of the contributing area was sprayed. Conclusions include (1) incorporation into no-till or disk-till reduced herbicide runoff concentrations by approximately 25% compared to surface application alone; (2) the setback reduced herbicide losses in proportion to the area not sprayed; (3) no-till reduced total herbicide mass loss 94% and 91% for cyanazine and atrazine, respectively, because of a 72% reduction in total runoff volume; and, (4) a comparison of tilled and no-till based on one runoff event suggests greater herbicide mass loss from no-till; however, based on three events no-till shows a reduction in mass loss.
Footnotes
T.G. Franti is an assistant professor, biological systems engineering, University of Nebraska-Lincoln; C.J. Peter, DuPont Corporation; D.P. Tierney, Novartis Crop Protection Inc.; R.S. Fawcett, Fawcett Consulting; and S.A. Myers Missouri Valley Agri-Services. This manuscript was submitted in April of 1996 and was accepted in March of 1997.
- Copyright 1998 by the Soil and Water Conservation Society
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