Seeding Date Affects Fall Growth Of Winter Canola (Brassica Napus L. 'Baldur') And Its Performance As A Winter Cover Crop In Central Iowa

In recent years, interest has increased in finding nongrass cover crop species that could be planted after soybean [Glycine max (L.) Merr.] and before corn (Zea mays L.) in central Iowa crop rotations. In this study, we investigated the use of winter canola (Brassica napus L.) as an alternative cover crop for Iowa, and characterize the effect of fall seeding date on its growth and winter survival. In a field experiment, the winter canola cultivar Baldur was seeded at four dates in the fall of 2012 and 2013. Aboveground biomass (AGB) production, nitrogen (N) accumulation, canopy cover, and winter survival were measured, and leaf development was tracked as a function of growing-degree days (GDD). In general, winter canola performed best when seeded in early September. During the 2012-2013 season, winter canola seeded in early September provided ample AGB production, N accumulation, and canopy cover during the fall and spring, and achieved good winter survival. Conversely, no plants survived extreme cold temperatures without snow cover during the 2013-2014 season. This was despite the early-seeded crop achieving the fifth-leaf stage, which is usually associated with sufficient winter survival potential. In both years, the number of leaves were correlated to GDD accrued after emergence. The winter canola cultivar and management practices used in this study did not result in consistent overwintering and growth in the spring in Iowa. More research into other planting options or cultivars is needed to fully understand the potential of this alternative cover crop in Iowa.