Location: Agroecosystems Management ResearchTitle: Seeding date affects fall growth of winter canola (Brassica napus L. ‘Baldur’) and its performance as a winter cover crop in central Iowa Author
|Kaspar, Thomas - Tom|
Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2015
Publication Date: 2/5/2016
Citation: Martinez-Feria, R., Kaspar, T.C., Wiedenhoeft, M.H. 2016. Seeding date affects fall growth of winter canola (Brassica napus L. ‘Baldur’) and its performance as a winter cover crop in central Iowa. Crop, Forage & Turfgrass Management. 2(1). doi: 10.2134/cftm2015.0181. Interpretive Summary: Winter cereal rye has been the most commonly used cover crop in Iowa, but occasionally it can cause yield decreases in the following corn crop. Recent research indicates that cereal rye is a host for fungal pathogens of corn seedlings and these pathogens may be reducing corn yield. As a result, interest has increased in finding a non-grass cover crop species that is not a host to corn pathogens. Many potential non-grass cover crop species, however, do not overwinter in Iowa or the upper Midwest. In this study, we investigate the use of winter canola as a potential cover crop for corn-soybean rotations in Iowa. The objective of our research was to characterize the effect of fall seeding date on growth and winter survival of this potential cover crop. In general, winter canola performed best at the early seeding dates in this study and its growth was tightly correlated to the fall air temperatures, despite large differences between the two years. The winter canola cultivar and the management, however, used in this study did not result in consistent overwintering and growth in the spring in Iowa even when sufficient leaf development was achieved in the fall. Although this does not exclude winter canola’s use as a fall cover crop, more research into other planting options or cultivars would be needed before it could be used as a winter cover crop in Iowa. The impact of this research is that points out to plant breeders and the seed industry the need to select or breed non-grass cover crops that can overwinter in the Midwest without snow cover. Additionally, the methods developed in the study to predict and map the fall planting dates needed to reach the fifth leaf stage can be used to develop cover crops planting date guides or decision aides for farmers and government agency personnel.
Technical Abstract: In recent years, interest has increased in finding non-grass cover crop species that could be planted after soybean (Glycine max (L) Merr.) and before corn (Zea mays L.) in Iowa crop rotations. In this study, we investigate 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 winter canola variety ‘Baldur’ was seeded at four dates in the falls 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 at the early seeding dates. 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 the 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 was tightly correlated to the GDD accrued after emergence. The winter canola cultivar and the 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.