Plant population and row spacing are an important agronomic management practice for corn production. In Manitoba, the typical row widths for corn are 30 or 22 inches with plant population density of 26,000 to 32,00 seeds/ac (Manitoba Corn Growers Association guide, 2004).  However, more recently many farmers have been testing higher plant populations on farm. As the number of new shorter season hybrids available in western Canada increase, it is important to take a new look at these two important agronomic variables in Manitoba.

This study evaluated the effect of five plant population densities and two row spacing on corn yield, growth, and cob dry down for two hybrids under Manitoba growing conditions. This number of treatment factors represented a significant research effort, which has been greatly needed as some of the last public research in Manitoba on corn plant populations was conducted over 50 years ago in the 1960s.

Growing conditions during the study period were very dry and limited corn growth and grain yield. Corn plants were visibly drought stressed during the study. It is important to interpret study results with these conditions in mind.

Using regression, we identified that corn grain yield was highest between 35,000 and 41,000 plants ac-1.  Row spacing did not influence grain yield or any of the other corn growth measurements in the study.  Cob moisture dry down was influenced by corn population with higher plant populations having higher moisture contents than lower populations. Despite the dry growing conditions experienced during this study, our results support planting on the higher end of this range or increasing plant population to 35,000 plants ac-1.