Harker, K. N., O'Donovan, J. T., Turkington, T. K., Blackshaw, R. E., Lupwayi, N. Z., Smith, E. G., Klein-Gebbinck, H., Dosdall, L. M., Hall, L. M., Willenborg, C. J., Kutcher, H. R., Malhi, S. S., Vera, C. L., Gan, Y., Lafond, G. P., May, W. E., Grant, C. A. and McLaren, D. L. 2012. High-yield no-till canola production on the Canadian prairies. Can. J. Plant Sci. 92: 221–233. Relatively high prices and increasing demand for canola (Brassica napus L.) have prompted growers to produce more canola on more cropland. Here we determine if canola seed yield and oil concentration can be increased over current levels with high levels of crop inputs. From 2008 to 2010, direct-seeded experiments involving two seeding rates (75 vs. 150 seeds m−2), two nitrogen rates (100 vs. 150% of soil test recommendation), and the presence or absence of polymer-coated nitrogen or fungicides, were conducted at eight western Canada locations in canola-wheat-canola or continuous canola rotations. Herbicides, insecticides and fertilizers other than nitrogen were applied as required for optimal canola production. Increasing recommended nitrogen rates by 50% increased canola yields by up to 0.25 Mg ha−1. High (150 seeds m−2) versus lower (75 seeds m−2) seeding rates increased canola yields by 0.07 to 0.16 Mg ha−1. Fungicide treatment or polymer-coated nitrogen blended with uncoated urea increased canola yields by 0.10 Mg ha−1 in 2010, but not in 2008. The highest canola input combination treatment following wheat (3.50 Mg ha−1) yielded substantially more than the same high input treatment following canola (3.22 Mg ha−1). Average site yields were influenced by site conditions such as soil organic matter, days to maturity, and temperature, but these site and environmental predictors did not alter treatment rankings. Using higher than the soil test recommended rate of nitrogen or planting 150 versus 75 seeds m−2 increased canola yields consistently across western Canada. Canola oil concentration varied among canola cultivars, but was consistently low when N rates were high (150% of recommended). Higher than normal seeding rates led to high canola seed oil concentration in some cases, but the effect was inconsistent.

B. 2014. Effect of nitrogen fertilizer application on seed yield, N uptake, and seed quality of Camelina sativa. Can. J. Soil Sci. 94: 35Á47. Camelina [Camelina sativa (L.) Crantz] is a new crop to western Canada, and research information on its response to nitrogen fertilizer is lacking. Two field experiments were conducted from 2008 to 2010 in Saskatchewan and Alberta, Canada, to determine the effect of N fertilizer application on camelina plant establishment, seed and straw yield, total N uptake in seed and straw, seed oil and protein concentration, N fertilizer use efficiency (NFUE) and percent recovery of applied N (%NR) in seed. Nitrogen fertilizer rates ranged from 0 to 160 kg N ha (1 in exp. 1 and from 0 to 200 kg N ha (1 in exp. 2. There was generally no detrimental effect of high N rates on plant establishment, with the exception of 1 site-year in which there was a slight linear decline in plant density as N rate increased. Seed yield, total N uptake in seed, NFUE and %NR responded to applied N rates at most site-years. Seed yield and total N uptake in seed usually increased while seed NFUE and %NR decreased with increasing N rate. Response trends of yield and total N uptake of straw to applied N were similar to that of seed at the corresponding site-years. Seed oil concentration decreased while protein concentration increased with increasing N rate. In exp. 1, fertilizer rates were not high enough to attain a maximum seed yield; however, maximum seed yields of 2013 kg ha (1 were achieved at an N rate of 170 kg N ha (1 in exp. 2. In conclusion, camelina responded to fairly high rates of applied N similar to responses reported for Brassica juncea on the Canadian prairies.

Harker, K. N., O'Donovan, J. T., Turkington, T. K., Blackshaw, R. E., Lupwayi, N. Z., Smith, E. G., Dosdall, L. M., Hall, L. M., Kutcher, H. R., Willenborg, C. J., Peng, G., Irvine, R. B. and Mohr, R. 2015. Canola cultivar mixtures and rotations do not mitigate the negative impacts of continuous canola. Can. J. Plant Sci. 95: 1085–1099. High-frequency canola (Brassica napus L.) rotations increase canola production risks. From 2008 to 2013, direct-seeded experiments involving several variations of continuous canola were compared with wheat (Triticum aestivum L.) and field pea (Pisum sativum L.) rotated with canola at five western Canada locations. Continuous canola rotations involved sequences of different herbicide-resistant canola and two-cultivar mixtures of herbicide-resistant canola from different sources in the same year. Fertilizers, herbicides, and insecticides were applied as required for optimal production of all crops. Rotating herbicide-resistant canola types over years or mixing two cultivars of the same herbicide-resistant type provided no pest management, yield or seed quality advantages compared with planting the same herbicide-resistant cultivar type each year. In 2013, weed biomass was lower in canola preceded by other crops than most continuous canola treatments. Compared with continuous canola, when 1 or 2 yr of wheat or field pea and wheat were inserted into 3-yr rotation cycles, 2010 root maggot damage was reduced 6% and 2013 blackleg [Leptosphaeria maculans (Desmaz.) Ces. & De Not.] incidence and severity were reduced 53 and 54%, respectively. Furthermore, yields were 22% higher when canola was grown only once in 3 yr compared with continuous canola and the wheat–canola–canola rotation. The most important mitigation strategy to ensure long-term sustainable canola production is to rotate canola with other crops.

Miller, A. J., Bork, E. W., Hall, L. M. and Summers, B. 2015. Long-term forage dynamics in pastures sprayed with residual broadleaf herbicide: A test of legume recovery. Can. J. Plant Sci. 95: 43–53. Legumes such as alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.) are important components of northern temperate pastures where they increase forage productivity and quality, but are susceptible to decline when exposed to broadleaf herbicides. Little is known about the long-term sward responses following herbicide use in northern temperate pastures, including the recovery of legumes and their subsequent contribution to forage production. We established five field sites over 2 yr to assess changes in grass, legume, total forage (grass+legume) and other forb biomass, as well as the recovery of a common weed, dandelion (Taraxacum officinale Weber), for up to 3 yr following a single application of two broad leaf herbicides with residual properties (aminopyralid and aminocyclopyrachlor). The importance of defoliation and the legume seed bank in facilitating legume biomass recovery were also evaluated with mowing and legume overseeding, respectively, in a strip/split-split design. Both herbicides had similar functional impacts on sward composition based on peak annual biomass, reducing legume biomass by an average of 71–100% across the 3 yr, equivalent to 63.4–22.6 g m−2 from year 1 to year 3, respectively. Although grass biomass did not change significantly with herbicides, net reductions in total forage were limited to 6.8% (28 g m−2) over the study, suggesting at least some ability of grasses to compensate for legume removal. Legume biomass was greater following overseeding and only in non-sprayed controls, but then decreased over time. Conversely, biomass of other forbs and cover of dandelion were lower shortly following herbicide application, only to reach levels similar to non-sprayed controls by the second growing season. Defoliation also influenced sward composition, favoring dandelion recovery following herbicide application. As both weed control and legume re-establishment are important objectives for livestock producers, the result of this study provides useful insight into the long-term impact of broad-leaf weed control on forage production in mixed swards of northern temperate pastures.