O'Donovan, J. T., Turkington, T. K., Edney, M. J., Juskiw, P. E., McKenzie, R. H., Harker, K. N., Clayton, G. W., Lafond, G. P., Grant, C. A., Brandt, S., Johnson, E. N., May, W. E. and Smith, E. 2012. Effect of seeding date and seeding rate on malting barley production in western Canada. Can. J. Plant Sci. 92: 321-330. Barley (Hordeum vulgare L.) growers in western Canada often have difficulty achieving malting grade. This is usually due to unfavourable climatic conditions, but sub-optimal agronomic practices may also be a factor. Field experiments were conducted in 2006, 2007 and 2008 at eight locations in western Canada (24 site-years) to evaluate the effects of seeding date (relatively early and late) and seeding rate (100, 200, 300, 400 and 500 seeds m^-2) on AC Metcalfe barley yield and malt quality parameters. Delayed seeding often resulted in negative effects including increased protein concentration, decreased kernel plumpness and yield. However, at 6 site-years, higher yields occurred at the later seeding date. 300 seeds m^-2 was usually optimal; maintained or improved yield, decreased protein concentration, increased kernel uniformity and time to seed maturity, and decreased tillering. In most cases, seeding at more than 300 seeds m^-2 did not result in an improved outcome, and there was a risk of reduced yield and kernel plumpness at rates above this level. A multivariate analysis indicated that relatively low barley plant densities were associated primarily with northern locations with low soil pH.