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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. [ABSTRACT FROM AUTHOR]

The Watershed Analysis Risk Management Framework (WARMF) model is adapted to simulate flow and nitrate-N transport in an agricultural watershed in Quebec, Canada. The model was evaluated for the St. Esprit Watershed (24.3 km²), which is a part of the 210 km² St. Esprit river basin, a tributary of the L'Assomption Watershed (4,220 km²). WARMF's hydrologic calibration and validation was performed using data from the gauge station located at the outlet of the watershed. Water-quality data collected were used to guide water quality calibration/validation. Simulations were carried out from 1994 to 1996; data from 1994 and 1995 were used for model calibration and data from 1996 were used for model validation. The model performed reasonably well in simulating the hydrologic response and nitrate losses at the outlet of the watershed. The R² between the observed and simulated monthly stream flow for calibration was 0.92, and that for validation was 0.94. The corresponding coefficients of efficiency (E) were 0.89 and 0.91. The R² and E values for calibration/validation of NO3--N loads simulation were 0.89/0.84 and 0.86/0.75, respectively. Thus, the model simulated monthly flow and nitrogen losses with a good degree of accuracy over the entire year. [ABSTRACT FROM AUTHOR]

The hydrologic performance of DRAINMOD 5.1 was assessed for the southern Quebec region considering freezing/thawing conditions. A tile drained agricultural field in the Pike River watershed was instrumented to measure tile drainage volumes. The model was calibrated using water table depth and subsurface flow data over a two-year period, while another two-year dataset served to validate the model. DRAINMOD 5.1 accurately simulated the timing and magnitude of subsurface drainage events. The model also simulated the pattern of water table fluctuations with a good degree of accuracy. The R2 between the observed and simulated daily WTD for calibration was >0.78, and that for validation was 0.93. The corresponding coefficients of efficiency ( E) were >0.74 and 0.31. The R2 and E values for calibration/validation of subsurface flow were 0.73/0.48 and 0.72/0.40, respectively. DRAINMOD simulated monthly subsurface flow quite accurately ( E > 0.82 and R2 > 0.84). The model precisely simulated daily/monthly drain flow over the entire year, including the winter months. Thus DRAINMOD 5.1 performed well in simulating the hydrology of a cold region. [ABSTRACT FROM AUTHOR]