Frost Damaged Soybeans

Now I would like to talk a little about the differences between how soybeans react to frost as opposed to corn. In the last post I talked a little about frost damage on corn. And because of the way corn grows, a frost early in the season usually doesn’t cause serious problems. When we look at soybeans the game changes, soybeans don’t have the protection from frost that corn does because the growing point of the soybean plant is exposed as soon as it emerges. Just like we talked about with corn, the best thing to do with soybean is have a little patience to see if the individual plants will survive. This picture shows what to look for when assessing frost damage on soybeans.

If the plant was damaged by frost below the cotyledonary node, it will not survive. But if the plant was injured by frost, but only down to the area above the cotyledonary node, the plant will be able to generate new growth from the auxiliary buds at the node. This new growth from these buds will be very similar to the original plant if it had not been damaged. Recovery will be good with little or no impact on final yield. If there are a mix of plants that will recover and several that are frosted and will not survive it is important to take stands counts from many areas of the field to determine the next step. We may find some areas that are hurt more than others, but the number I use to make decisions on replant is 100,000. If you have at least 100,000 plants an acre it is too good to justify the cost and time to replant. if replant is needed try to identify if you can fill in areas of the field, or if it is best to tear it up and start over. And just like corn, this crop has been stressed, so make sure you give it time to recover before you add any more to it with herbicide applications.

Frost Damaged Corn

The past weeks weather has slowed the great progress we have seen with planting and crop emergence. Some areas even experienced snow and frost, so I am going to give you a few thoughts on what this means if you were in one of these areas. First we need to look at how corn grows, when corn emerges the growing point of the plant is still well below the soil surface. In fact the growing point does not reach the soil surface until the plant reaches v5 to v6 growth stage. That means that at least 5 full leaves are developed and you can identify the leaf collar on the plant.

Fortunately most of our corn was not at the v5 stage yet. If you did experience some frost on smaller corn the best thing to do is wait and watch. The frosted leaf tissue will turn yellow and start to wilt as it turns brown and begins to decay over the next week. If you dig some plants and split them open you will see that the plant material below ground will be white and firm, this is a good sign and tells you that the plant is alive and will recover with the return of warm weather. The plant will continue to grow and push up through the damaged tip, as it does so its important to watch and make sure the new growth is able to open the new leaves to collect sunlight and recover. In some rare cases I have seen where it helps to clip the frosted tips off to enable the new growth to come through, but this is rare. From here forward the crop will recover, but it’s important to remember that it has been stressed, so make sure we do not do anything to add to the stress; like apply any herbicides for a few days.

Plant by Soil Temperature, not the Calendar

Planting is moving fast this year, with most areas of the Midwest way ahead of last year and the five year average according to USDA crop progress reports. Planting early can help to maximize yield potential along with allowing more time for the crop to mature this fall. Here is an article that quotes Dr. Bret Bean, Extension Agronomist from Texas. Many of the things he notes also are important for growers here in the upper mid-west. Click here to read the full article.