Preferential Bromide and Pesticide Movement to Tile Drains under Different Cropping Practices
- J. Fortin *a,
- E. Gagnon-Bertrandb,
- L. Vézinac and
- M. Rompréd
- a Département des sols et de génie agroalimentaire, Pavillon Paul-Comtois, Université Laval, Québec, QC, Canada G1K 7P4
b Ministère de l'Environnement du Québec, Direction des politiques agricoles, 675, Blvd René-Lévesque Est, Québec, QC, Canada G1R 5V7
c Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec (MAPAQ), Direction régionale du Bas Saint-Laurent, 335, rue Moreault, Rimouski, QC, Canada G5L 9C8
d Institut de Recherche et de Développement en Agroenvironnement (IRDA), 2700, rue Einstein, Sainte-Foy, QC, Canada G1P 3W8
Subsurface drainage systems are useful tools to study chemical leaching in soils. Our objective was to compare the breakthrough behavior of bromide, atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamid] to tile drains under two fall tillage practices (conventional tillage [CT] with a moldboard plow, and reduced tillage [RT] with a chisel plow) in field plots cultivated with corn (Zea mays L.). Leachate volume were greater in RT than in CT, with no statistical differences. Soil analysis showed that bromide migrated deeper in the soil profile than both herbicides, with little tillage effect. All chemicals were detected in drainage water at the same time and followed an event-driven behavior. Tillage had no effect on atrazine and metolachlor found in drainage water, while bromide concentration peaks were higher in RT than in CT in 1999. Concentration peaks were recorded earlier for atrazine and metolachlor than for bromide. Plots of cumulative relative chemical mass (cumulative mass divided by total mass measured in drainage) as a function of cumulative drainage were mostly linear for bromide, while they were S-shaped for both herbicides. Drainage that corresponded to 50% of relative cumulative mass ranged from 40 to 55% for bromide and from 5 to 28% for both herbicides. Rapid chemical movement to tile drains suggested that preferential flow was important in both CT and RT, and that these tillage practices had little influence on this phenomena.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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