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Dissipation and persistence of major herbicides applied in transgenic and non-transgenic canola production in Quebec

Syan, Harvinder Singh, Prasher, Shiv O., Pageau, Denis, Singh, Jaswinder
European journal of soil biology 2014 v.63 pp. 21-27
Brassica napus var. napus, canola, cultivars, environmental impact, glufosinate, glyphosate, herbicide residues, herbicide resistance, high performance liquid chromatography, leaves, oilseed crops, pesticide application, planting, soil, soybeans, transgenic plants, trifluralin, weed control, Quebec
After soybeans, canola is the second most important oilseed crop in Canada, with more than 99% of the canola cultivation consisting of herbicide resistant (HR) varieties. The expansion in HR canola cultivation has led to the increasing use of the same herbicides for weed control which has resulted in a growing concern about their impact on the environment. The present study was conducted to investigate the dissipation and transport of the herbicides, glyphosate and glufosinate, in soil used for the transgenic production of canola and a comparison was made with the herbicide, trifluralin, used in non-transgenic canola. Commercially grown HR transgenic canola varieties and a conventional canola variety were planted in a randomized complete block design. The plots planted with Roundup Ready and Liberty Link cultivars were treated with glyphosate and glufosinate, respectively, at the 2–3 leaf stage and at the rosette stage in each replication. On conventional canola plots, trifluralin was incorporated into soil a day before planting. Soil samples were collected from two depths, 0–0.15 m and 0.15–0.30 m, at different time intervals (1, 7 and 20 days) after the application of the herbicide. Analysis of the soil samples was done by HPLC (high performance liquid chromatography) to determine the residual amounts of herbicide in the soil. Glufosinate was found to be the least persistent herbicide, while trifluralin persisted the longest. The overall order of persistence was Trifluralin > Glyphosate > Glufosinate. Trifluralin was found at lower depths (0.15–0.30 cm) at 7 and 20 days after the herbicide application, with higher residual concentrations than the other herbicides used in the HR canola.