December 18, 2020
It is time to start thinking about your cash crop, and that means terminating your cover crop (Figure 1). There are several options, and they depend on several factors:
- What is your planting system?
- Do you want to retain ground cover?
- Is the cover crop a mix or a single species?
Figure 1. Actively growing cover crop.
One option is to incorporate the cover crop biomass via tillage. This can provide a clean seedbed for planting; however, tillage may need to be aggressive in order to incorporate the plant matter and cut the root system. Vertical tillage may not be aggressive enough, so there is a chance that some of the benefits of your cover crop may be negated if tillage is the preferred method. Strip-till can be used with other methods of termination if the goal is to warm up the seed zone quickly while leaving some residue (Figure 2).1 If the cover crop is as tall as in Figure 1, tillage may not be the best option because the cover crop may not be killed. Additionally, nitrogen can be tied up by the biomass.
Figure 2. Corn strip-tilled into a cover crop.
Cover crops can be terminated using an herbicide application. Plants should be actively growing for the best results. Working with your Bayer Crop Protection field sales representative is strongly encouraged to ensure the best recommendation. Growth stage of the different species in your cover crop will need to be considered as well as potential impacts for your soon-to-be planted crop. Once you have a recommendation, good coverage is essential to prevent escapes. Always read and follow the label directions.
Rolling/crimping is a great option for no-till systems where a mat of residue is desired. Plants should be actively growing and have reached flowering or a reproductive stage (Figure 3). This can allow proper conditions for the crimper to stop the flow of water and nutrients at several points along the stalk. Timing can be challenging if several species are mixed, so if this is your planned method, please make considerations when selecting seed.2
Figure 3. Cover crop flowering.
Mowing is similar to rolling/crimping in that the plants need to be flowering or in a reproductive stage to prevent regrowth. Mowing also allows for the biomass to remain on the soil surface and can provide benefits into the growing season. Extra nitrogen may be needed to support the crop because the biomass can tie up nitrogen as it decomposes.
Livestock operations can graze the cover crop for termination. Uniformity of termination may be a challenge and require follow-up options. If the correct cover crop was established to allow grazing, the goal is to graze 50% of the plants while the livestock trample the other 50%.1
The final option is allowing weather to terminate the cover crop. Species that are subject to killing freezes will terminate naturally as temperatures drop for a sustained amount of time. If this is the chosen method, it is recommended to plant early to allow for ample cover crop growth.
For any of the mentioned methods of termination, timing is a key consideration. Crops should be planted after the cover crop has reached necrosis or is still green. Some species of cover crop, such as cereal rye, can have an allelopathic affect that may impact emergence.
Sources:
1Essman, A. and Loux. M. 2020. Cover Crop Termination. Agronomic Crops Network. Ohio State University. https://agcrops.osu.edu/newsletter/corn-newsletter/2020-05/cover-crop-termination.
2Lancaster, S., Dille, A., Tomlinson, P., and Presley, D. 2020. Cover crop termination considerations. eUpdate. Kansas State University. https://webapp.agron.ksu.edu/agr_social/article/cover-crop-termination-considerations-372-4.
Websites verified 11/18/2020.
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.