Seeding a cover crop can be useful, but make sure it fits your rotation
The use of cover crops is nothing new. Thomas Jefferson and George Washington talked about cover crops in the late 1790s. And you’ve probably heard people talking about “green manure” crops that used to be more common where you farm. There are various reasons that cover crops slipped from popularity, and some good reasons that they are on the comeback in some situations.
In general terms, cover crops are non-crop plant species selected to seed into crop production fields. They can be seeded during the crop season, but often times are seeded as a “follow-up” to the growing season. The main goal of a cover crop is to conserve resources and boost the ecosystem.
Cover crops contribute to those goals by potentially increasing soil infiltration to reduce runoff and soil erosion. And, the right kinds of cover crops provide improved wildlife habitat.
That’s aboveground. In the soil, properly managed cover crops can increase soil porosity and organic matter, which tends to increase water-holding capacity, again, reducing runoff and erosion.
If you plant legumes, like the green manure crops on granddad’s place, you can fix nitrogen to credit into your fertility plan.
Cover crops can also be a part of weed and disease management.
Yes, cover crops have benefits that we know about and some that we haven’t discovered yet. On the other hand, cover crops also have a few management issues that you need to consider.
When you are making a plan for cover crops, you must have a goal. If you are doing it because your neighbors are doing it you might want to rethink why you are doing it. There are a lot of different crops that are utilized in a cover crop situation:
• Tillage Radish
• Hairy Vetch
• Italian Ryegrass, Marshal Ryegrass, Lolium multiflorum
One cover crop in particular has been a hot topic lately: ryegrass Lolium multiflorum. For the record, I categorically advise against ryegrass. It has the potential of turning into a problematic weed on cropland. In other parts of the world, ryegrass is resistant to several different herbicide modes of action that would make it very difficult to control in our fields (ALS, ACCASE, Glycines, Chloroacetamides and Glutamine synthase inhibitors).
Some other cover crops have weedy characteristics too. As you consider cover crops, you need to have a plan to kill it or be willing to interplant. We have solid herbicide options to kill most of the cover crops at certain timings. However, if the spring is delayed or we have a very wet spring and can’t get across the field to spray, those options will need to be altered on a field-by-field basis. Managing the cover crop becomes an integral part of spring planting. This can cause problems when its time to plant our normal cash crop. The delayed planting of some fields this spring could be the difference of making a great crop or a bad crop.
In June and July, I receive several calls on rotation restrictions following our soybean and corn herbicides. Most herbicide labels don’t have any information on what the cropping rotation or grazing restrictions are when the following crop is a cover crop.
Cover crops depend on good fall growth to serve their purpose of reducing soil erosion, increasing nutrient retention or breaking the hard pan.
Failure in fall can severely reduce tonnage and your conservation goals.
Choose the cover crop that best fits your reasoning. I don’t believe that one blend of species will be the right blend for every producer.
Dr. Kelly Nelson at the University of Missouri research station in Novelty, Mo., is demonstrating seeding times and rates of different cover crops in corn and soybeans. Dr. Kevin Bradley at the University of Missouri is researching the use of cover crops to suppress weeds into corn or soybean crops. Bradley’s work was presented at the recent Pest Management Field Day. This was the first year of data from those plots.
There is a lot of research/information needed to fully integrate cover crop systems for our trade territory. I do believe they have benefits, but with the benefits come hurdles. Through sound research and your on-farm experience you can use cover crops to your benefit. Find a wide range of information on cover crops at the Midwest Cover Crops Council: http://www.mccc.msu.edu. Contact your local store for more information and recommendations.
Dr. Weirich is director of agronomy for MFA Incorporated.