IMPROVING EMERGENCE IN WINTER CANOLA IN THE PACIFIC NORTHWEST

For farmers who use tillage in the inland Pacific Northwest (PNW), winter canola can struggle to establish stands due to soil crusting. Winter canola is typically planted at 2.5 cm or deeper into moisture in August or early September, but rainfall and subsequent dry downs can create a soil crust that the seedlings cannot penetrate. A lightweight and inexpensive low-intensity nozzle-type rainfall simulator was constructed and used to induce soil crusting within a two-factor greenhouse experiment to evaluate emergence of winter canola planted into soil columns. The simulator is equipped with three flat-fat TeeJet nozzles mounted to an oscillating spray boom to evenly cover a 1.25 meter x 1 meter area. A pump mounted to a 100 liter water tank supplies a flow delivered at a constant pressure through the system. The spatial distribution of the simulated rainfall event was measured using 42 water cups evenly spaced throughout the 1.25 square meter area. The uniformity of the distribution was calculated with the Christiansen uniformity coefficient. Factors were rainfall accumulation (0-, 2.5-, 5-, and 10-mm) and the closing tool used to create the soil pack over the seed row (split rubber wheels, spiked wheels, and a Technotill drill). Measurement included daily emergence, penetration resistance at days 5 and 10, and bulk density in the seed row. Matric potential and soil temperature were monitored in the columns throughout the study. The 10-mm rainfall accumulation led to an increase in penetration resistance in the crust as well as a reduction in emergence. The spiked wheel closer improved emergence within the 10-mm rainfall accumulation group, but had its most significantly positive effect on emergence when paired with a light (2.5-mm accumulation) or medium (5-mm accumulation) amount of rainfall. Our trial shows that farmer options for improving stand establishment in tilled field canola production that are prone to soil crusts are limited but using a spiked wheel closer can improve emergence results.