One of the most important issues related to cover crops is termination. Cover crops are great – until they compete with cash crops for nutrients, water, sunlight, space, etc. In a normal field situation a farmer will plant one cover crop or at least a single mix. In our case we had four different cover crop “treatments” to contend with. Despite this, we didn’t have any trouble terminating the cover crops in the entire area with a single herbicide mix.

cover crops terminated
Terminated cover crops in the plot area. Picture taken by Curt Emanuel on May 5, 2016, nearly three weeks after spraying.

The herbicide application we used was a burn-down of 1.5 lbs active ingredient(AI) glyphosate with 1 oz Sharpen (saflufenacil) sprayed/broadcast on April 16. There is little residual activity with this mix however, as you can see from the picture, it was very effective in terminating the cover crops as well as taking care of what weeds were present – which weren’t a lot, from what I saw, mainly chickweed and dandelion though I didn’t scout the field after the March 24 field day.

In 2014, the last time this field was planted in soybeans it had quite a bit of marestail (sometimes called horseweed, Latin name Conyza canadensis). In central Indiana marestail is often glyphosate-resistant and even when it isn’t, control becomes difficult once it gets above 6 inches tall. For this reason we will be using a Liberty variety of soybeans once it becomes dry enough to plant.

Purdue Extension has two publications that were useful in considering our herbicide selection: Biology and Management of Horseweed and Successful Cover Crop Termination with Herbicides.

It’s been cold and wet here for the past couple of weeks but we were fortunate to have some warm weather right after the burn-down which certainly helped with that application – as a general rule, daytime temperatures above 50 degrees for several days after herbicide applications increase the effectiveness. According to the National Weather Service daily highs in Indianapolis were at or above 80 degrees on April 17 through 20 (and 77 on the 16th), nearly ideal conditions. Hopefully things will dry up so we can provide a planting update in the near future.


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