Terminating cereal rye to prevent yield loss in corn and soybeans

Clearing up the confusion about when to terminate cereal rye in corn and soybean.

Soybeans starting to emerge from the ground.
Planted green soybean. Photo by Monica Jean, MSU Extension.

Cereal rye is the most common cover crop that Michigan growers plant each fall. Cereal rye can help prevent soil erosion and help provide suppression of winter annual and early spring weeds, such as horseweed (marestail). As temperatures are warming up, now is the time to start thinking about how and when to terminate cereal rye in fields that will be planted to corn or soybean.

Cereal rye is fairly easy to terminate with glyphosate. In fact, glyphosate at 1.13 pounds acid equivalent (lbs. a.e.) per acre (i.e., Roundup PowerMax 3 at 30 fluid ounces per acre) plus ammonium sulfate has been extremely effective in terminating cereal rye at several different growth stages. Michigan State University Extension understands that knowing when to manage cereal rye can be a challenge. Here are a few tips you can follow to maximize the benefits and effectively terminate your cover crop, setting yourself up for a successful productive cash crop.

Avoid yield losses in corn by terminating cereal rye 10-14 days before planting corn

Seeding cereal rye following soybean is a great opportunity to get roots in the ground when soil nitrates are high and there is little residue left to protect the soil from wind and water erosion through the winter. However, some farmers report seeing lower yields in corn when planted following a cereal rye cover crop. This yield loss may have a few causes. One explanation may be that after cereal rye is terminated, soil organisms can tie up some of the available soil nitrogen as they work hard to decompose the high carbon cereal rye residue. High cereal rye residues can also deplete soil moisture under limited rainfall conditions and may also act as a refuge for potentially damaging insects, like seed corn maggot.

A good strategy to help reduce the chances of corn yield loss is to terminate cereal rye 10-14 days before planting corn. The earlier termination gives soil organisms a head start in the decomposition of cereal rye, reducing nitrogen tie-up. Another strategy to help overcome nitrogen tie-up is to apply 30-50 lbs. of nitrogen per acre at planting, especially in a 2-inch by 2-inch application. Terminating cereal rye earlier than corn planting can also preserve soil moisture in a dry spring that may limit corn seed germination and growth, ultimately affecting yield at the end of the season.

It is fair to say that cover crops require management just like a crop would, so keeping an eye on the forecast to prevent exacerbating drought conditions is important. If you are a novice to cover crops, having a more conservative approach to cover crop management would be recommended and outlined in our Cover Crop Recipes.                                                                               

Maximize weed suppression in soybeans by delaying cereal rye termination

Soybeans tolerate cereal rye residue better than corn, so you have the option to delay termination and allow the cereal rye cover crop to grow for more time. Allowing cereal rye to grow in the spring ahead of planting soybeans maximizes the weed suppression and soil building benefits of a cereal rye cover crop.

One way to maximize cereal rye biomass growth is to plant soybeans into living cereal rye and then terminate the cereal rye shortly after planting, commonly referred to as planting green. If planting green, it is generally best to terminate cereal rye within a week after soybean planting. Delaying cereal rye termination longer can lead to reduced soybean emergence, delays in soybean development and reduced soybean yield. This is especially apparent when conditions are dry following planting like what was experienced in 2023.

Additionally, if you are planting into high cereal rye residues, there are some tips to consider to ensure good seed-to-soil contact and consistent emergence. Please check out this article from Brook Wilke from the Kellogg Biological Station on his thoughts on planting green into cereal rye.

Soybean plots with horseweed growing between the rows.
Horseweed suppression five weeks after soybean in plots with (a) no cover, (b) cereal rye terminated one week prior to and (c) one week after soybean planting. Photos by Christy Sprague, MSU.

Have you checked if your winter-kill cover crop was winter-killed?

Record warm temperatures this winter may mean that the cover crops you thought would winter kill may be greening up. To learn more about cereal rye and other cover crop termination decisions for this spring, attend the Cover Crop Termination Field Day on April 24 in East Lansing, Michigan, and check out the latest update to the MSU Extension Cover Crop Termination Bulletin.

Living radish cover crop with snow on the ground.
Living radish cover crop in snow. Photo from Madelyn Celovsky, MSU Extension.

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