David Ring was spraying cover crops in Dubois County more than two weeks ago. The weather has interrupted spraying for some, but many are thinking about spraying cover crops before they get too tall. The trade-off is letting them grow and add more roots and trap more nutrients, and perhaps help dry out the soil, vs. allowing them to get too big and become a mat that keeps the soil wetter once the cover crop is dead.
Where you are in the state will make some difference as to when you spray to kill cover crops. The crop itself may also determine when you spray. If it is rye, then you want to spray at least by the time it is knee-high. If not it will likely bolt and grow several inches to several feet in a matter of days.
Picking the right spray conditions is important, advises Barry Fisher, state agronomist with the Natural Resources Conservation Service. If you're spraying annual ryegrass, you need to follow the glyphosate label carefully, not skimp on rates, and take other precautions you take when the weather is cool. Glyphosate does not work as well on cover crops when the weather is cool, and annual ryegrass can be difficult to control.
One method many people are using is to spray during the middle part of the day, and stop spraying by mid-afternoon, or earlier. While the technique is somewhat controversial in professional circles, those who stand by it say it's important due to the cool weather. As the afternoon gets later and it cools off, the plants shut down and don't translocate the herbicide into the roots. It must be translocated to get good kill.
Later in the season once it warms up, then glyphosate application timing doesn't matter. However, pay special attention to conditions until the temperatures warm up and stay there, most agronomists say.
Plant Cover Crops In A Drought Year? You Bet
Cover crops can help conserve moisture, keep soil covered and provide residue going into the cropping season. Download our free report Cover Crops: Best Management Practices