- Cover crop spring growth is starting to occur
- Chemical control and rate should be dependent on cover crop species and growth stage
- Complete termination is the key to starting off a successful cropping season
Temperatures throughout the winter were low and hindered early spring growth of cover crops. Spring green up and growth of cover crops is now occurring. Consider terminating cover crop stands sooner rather than later, especially if the soil and environmental conditions allow.
While cover crops provide a solid agronomic benefit regarding soil erosion, nutrient capturing, and residue management, THEY ARE NOW WEEDS! Complete control of cover crops during the early spring is critical. There are two main types of cover crops, broadleaves and grasses, and we need to distinguish the best way to manage these different types.
Broadleaf Cover Crops: While most of the broadleaf cover crops do winterkill, do not assume this has happened this year. Cold winters generally mean more winter kill, but do not assume complete kill. It is now time to scout to see if winter has allowed for some survival. There are some species, such as Crimson clover and Austrian winter peas, which do not winterkill. The key to success in managing these broadleaf cover crops is to not rely solely on glyphosate as your chemical means of control. The addition of a growth regulator may provide more consistent control and another effective site of action for resistance management.
Grass Cover Crops: We can further split the grasses into two groups—annual ryegrass and not annual ryegrass. While glyphosate is probably the most used herbicides to manage all of these grass species, herbicide rate and timing may be different.
If annual ryegrass has any significant growth, it can become very difficult to manage. The standard recommendation for annual ryegrass is to apply glyphosate at 1.13 lb ae/acre (Roundup PowerMAX @ 32 fl oz) with the appropriate adjuvants to plants less than 6” in height. If annual ryegrass is taller than 6”, increasing the rate of glyphosate may be warranted.
We have a little more flexibility with other grass species, cereal rye included. The standard glyphosate recommendation would be to apply at a rate of 1.13 lb ae/acre with the appropriate adjuvants to stands less than 18” tall. Again, if the cover crop is taller, we may need to increase the glyphosate rate.
The key to successfully terminating our cover crops is to manage them with the right herbicide while they are still small. While some of these standard recommendations allow for termination to occur after significant spring growth, that would be a worst case scenario and not one of our BMPs for a standard growing season. Cover crops have provided their benefits, and now is the time to consider termination to ensure maximum yield of the following cash crop.