By Matt VanTilburg
If you planted a cover crop in 2017, the good news is you were protecting your field all winter and improving the soil health. Now as spring arrives, it is time to focus on the termination of the cover crop and growing a productive cash crop. Termination can be achieved by several methods: rolling, winterkill, tillage and chemical control. In addition to how, the timing of when to kill the cover is also a consideration. The different types of covers, weather, cash crop and comfort level all play a role in the decision process.
How do you kill a cover crop?
My experience with terminating covers over the years has been with tillage and chemical control. If you must employ tillage to kill the cover, be aggressive and till early in the spring before much growth occurs. If you wait and have a lot of biomass on top, you can have a mess that will require several trips to get field conditions in shape to plant. If you spray early and use a vertical tillage tool, it appears to work the best if you must till. I would recommend you leave several test strips across the field to compare the two methods.
What about using a herbicide?
I have experienced the best luck terminating a cover crop with a herbicide application. With all the cover crop cocktail mixes available, I base my herbicide recommendation on whether the mix contains annual rye grass or cereal rye. The two sound similar, but are quite different when it comes to terminating them. Annual rye grass has the reputation of being hard to kill, but as long as you follow a few guidelines you will control it also. The first step is to make sure the ARG is actively growing for the glyphosate to translocate through the plant. Avoid applying glyphosate when nighttime temperatures fall below 50 degrees. AGR is not the first thing to green up in the spring, so patience is key to success. On the other hand, ARG needs to be sprayed before its first node develops. Pushing glyphosate to its limits of temperature and timing means there’s no room to skimp on carrier; 12 to 15 gallons of water, conditioned with spray-grade AMS to avoid tying the herbicide up with ions in hard water. Avoid atrazines and mesotriones in the spray tank to guard against antagonism as well. I recommend killing a grass cover crop two weeks before planting a corn crop.
What are the options for killing cereal rye?
Cereal rye and blends with it are commonly used before planting soybeans, and the window to terminate is relativity long. Cereal rye has proven to be easy to work with from a late-planting standpoint, and easy to kill in the spring. It is quickly becoming the go-to cover crop for many operations. Options in the spring include killing at green-up, chemical “haircut,” rolling/crimping and planting green. Killing it at green-up is low risk and a good place to start your first year with cereal rye. Terminating it early will keep the biomass small and cease taking up soil moisture. Depending on the spring weather, this may or may not be a good option. Another option with cereal rye is to give it a “chemical haircut.” By this I mean stunting it with 2,4-D and a residual soybean herbicide, minus glyphosate. This mix will set the rye back and keep it shorter to plant into and then terminate it later. In this method, you can still use 2,4-D for potential marestail control. The “plant green” option is the most challenging way to approach the spring planting, but can be the most rewarding. Cereal rye will produce the most biomass and, when it leans over, provides a nice thatch. The thatch protects the soil from the sun and water evaporation. In a dry year, the rye thatch can be a huge benefit. Applying glyphosate at planting is still one of the best options for termination. The window to add chemistry for marestail and residuals is small, so be careful.
What about rolling or crimping rye?
The last method I have the least experience with is rolling/crimping the rye. Basically, instead of spraying the rye before planting, you crimp it to terminate. The rye has to be jointed or mature enough for this method to work. It seems to work best for the crimper and the planter to be the same width and run the same direction. If the rye is thick enough, the rolled rye will provide some weed control as well.
The bottom line is you have a lot of options to terminate cover crops in the spring. As a lot of things in agriculture, spring weather can change the best of plans made on a snowy winter day. Be prepared to change your plan as the weather unfolds. Talk to neighbors or friends that are using covers and gather their ideas. Chisel plows and cover crops can be similar, not everybody owns the same chisel and not everyone handles covers the same way. The challenge is to find what works for you.
VanTilburg writes from VanTilburg Farms in Celina, Ohio, 419-305-2245, [email protected]