Properly terminating a cover crop in the spring is as important as properly establishing a cover crop in the fall. Annual ryegrass seems to be the one cover crop that has the most questions about termination. And if you don’t kill it at the correct growing stage, the chance of killing it as it is jointing and forming a seed head goes way down.
I have a few pointers to help take the stress out of terminating annual ryegrass. It is important to observe annual ryegrass as it comes out of dormancy and starts growing. The day on the calendar in the spring is irrelevant. It is all about growing degree days, just like corn production, and the more heat units in the spring, the faster it will reach a growth stage that is difficult to kill.
Staging the plant is important. We recommend terminating annual ryegrass before it develops its first node. After the third node, termination is less effective. The height of the plant will be in that 6” to 10” range by the time the first node appears.
When applying glyphosate to terminate a cover crop in the spring, pay attention to the weather. We need three consecutive evenings about 38° F with daytime temperatures 55° F or higher. It is very important to have 4 to 5 hours of sunlight for metabolism to kick into gear before spraying. And the spray tank solution needs a pH that is buffered at 4.5 to 5.5 for glyphosate to be effective.
I seem to deal with the two extremes when it comes to timing. Some farmers are so afraid of the plant getting away from them that they spray before it is able to properly translocate the herbicide. The other extreme is the farmer that does not keep an eye on the growth and lets the plant grow beyond the right termination window.
Controlling annual ryegrass is a little like trap shooting. If you pull the trigger too early you may get a piece of it, but not what you wanted, and waiting too long can yield the same undesirable results. Being patient, timing everything out and zeroing in on the target can make this management practice a successful portion of a positive cover crop experience.
Be sure to have a discussion with your ag-chemical provider as well as the person operating the spray rig well in advance of your termination needs. If these individuals don’t take your termination needs seriously, you need to seriously consider getting some new members on your termination team. Have a great spring and “Keep Growing”.
Go to the following link for some really good publications on properly managing annual ryegrass: http://ryegrasscovercrop.com/resources/publications/.
Seed Specialist, ProHarvest Seeds