Cover crops have key benefits, including reduction of soil erosion, conservation of residual soil nitrogen & other soil nutrients, improvement of internal soil drainage, and value as a “green manure” crop. However, when these cover crops are partially, or fully, uncontrolled in the spring, they become weeds!
For best results, it is critical that we remove the cover crop as quickly as possible in the spring. As a general “rule of thumb,” most cover crop species will break dormancy in the spring when daytime high temperatures get near 60 degrees (Fahrenheit), with nighttime temperatures in the mid-30s or higher, and soil moisture levels are adequate. Note that these are the same conditions that prompt winter annual and perennial weeds to start spring growth.
Complete control of cover crops during early spring is critical. Consider the following agronomics regarding the growth and development of cover crops:
While cover crops such as turnips and radishes will perish during the winter due to their inability to survive temperatures much below freezing, crimson clover and annual ryegrass usually survive these temperatures quite well. Winter cereal crops generally also survive winter conditions with ease. These include cereal ryegrass, oats, wheat and triticale.
Control of cereal ryegrass can be difficult. Listed here are a few recommendations for successful control:
- Glyphosate (Roundup PowerMax®) applications of 32 fluid ounces per acre should be made prior to ryegrass reaching 18” tall. Our experience strongly suggests that lower glyphosate rates will result in inconsistent control.
- Once ryegrass is beyond 18” in height, we recommend increasing the glyphosate rate to 44 fluid ounces per acre, with addition of nionic surfactant at 0.25% volume-per-volume. Note that once ryegrass reaches 24” in height, it becomes extremely difficult to achieve complete control, resulting in matting of the dead ryegrass, excessively wet soils, and (possibly) a weed that could be burdensome throughout the growing season.
- If ryegrass is greater than 12” in height, we recommend avoiding inclusion of any tank mix partners with glyphosate. Realistically, we only get one chance to control this weed! For this reason, we need to: “Hit it hard, and hit it now!”
- The use of a contact herbicides (e.g., cell membrane disruptor herbicides) such as Gramoxone Inteon (Paraquat), Liberty, and others, is not generally recommended for cereal ryegrass control. Complete control of ryegrass with a contact herbicides requires weed heights less than 6 inches, abundant sunlight, warm temperatures, and optimum weed coverage with the herbicide. Therefore, while successful control of ryegrass with a contact herbicide is possible, it requires considerable management.
Control of annual ryegrass should be a grower’s top priority!
Surviving annual ryegrass should now be treated as a weed. It can grow as much as 2 inches per day when ambient temperatures are at or above 60 degrees, Fahrenheit. Glyphosate (eg. Roundup PowerMax®) applications of 44 fluid ounces per acre should be made in order to achieve consistent control of annual ryegrass taller than 12 inches. Further, we also recommend omitting any additional tank mix herbicides during the application. (Annual ryegrass can rapidly become a very difficult weed to control after the plant breaks dormancy.) Especially avoid tank mixes with all of the contact herbicides, since they tend to burn the leaf tissue very quickly. This interferes with adequate absorption and translocation of glyphosate throughout the plant. Also, be sure to include FS MaxSupreme at 2.5 gals/100 gals of spray solution to the spray solution.
If you have a ryegrass/clover (legume) mix…
For control of a grass/legume mix, you will need to include a plant growth regulator product such as 2,4-D or dicamba with the glyphosate in order to ensure consistent control of the legume. The earlier the application, the more consistent the control should be. Use a minimum of 2.5 gallons of FS MaxSupreme per 100 gallons of spray solution (provides 8.5 lbs./100 gal. of true AMS) on the cover crop/legume mix when it is less than 6 inches in height. If the grass/legume mix is larger than 6 inches, we recommend adding additional AMS to reach the rate of 17.5 pounds per 100 gallons of spray solution.