Which Crop Inputs Have the Greatest Impact On Canola Yield?.

Seed, fertilizer, and herbicide are among the major crop inputs in canola production systems on the Northern Great Plains. A four-year field experiment was conducted at six sites on the Canadian prairies to determine the impact of various crop input levels on weed management and canola yield. Treatments included a) open-pollinated and hybrid cultivars, b) seeding rates of 75 and 150 seeds m^-2, c) 0, 50 and 100% of recommended fertilizer rates, and d) 0, 50 and 100% of recommended herbicide rates. Increasing levels of individual inputs were added to the lowest input combination and high levels of individual inputs were removed from the highest input combination. The same input levels were applied to the same plots in four consecutive years. Canola was grown in rotation with barley in a zero-tillage production system and both phases of the rotation were present each year. Weed growth was reduced and canola yield was increased with hybrid compared with open-pollinated cultivars. A higher canola seeding rate consistently resulted in greater weed suppression but did not always result in greater canola yield. Low fertilizer rates did not affect canola yield in the first year but progressively resulted in reduced canola yields in succeeding years. Canola grown without herbicides for weed control had lower yields in all years and weed competition had the largest negative impact on canola yield in the third and fourth years of the study. However, canola yields with 50% and 100% herbicide rates were often similar, especially if hybrid cultivars were grown and higher seed rates were utilized. Overall, choosing a hybrid cultivar and using an effective herbicide program had the greatest positive effect on canola yield in this multi-site study. An economic analysis of these results is being conducted to advise canola growers on improved and more cost-effective canola production systems.