Friday, June 4, 2021

Frost During Early Corn Development and its Effect on Yield

Photo by Kent Kohn

This morning I received a series of texts from a crop consultant whose clients were concerned about the effect of last Friday's frost on corn yield. The question was, "Should they replant?" The short answer is "No." This frost event was a relatively early, correctable event that has caused a lot of anxiety, especially with above average corn prices. However, it is best to be patient. The growing point for corn is below ground and is often well insulated from freezing temperatures.

Most plant leaf damage caused by the recent frost is observed in fields with lighter soils, that were no-till, that had cover crops, and/or were along edges of waterways. Most plants are recovering with new leaves emerging, although the recovery process has been slower than I anticipated. With temperature forecasts in the 90s, new leaves should emerge. If new leaves do not appear, then the plant has died. This does not mean that the field must be replanted. Use decision guidelines from the UW publication, "Corn replant/late-plant decisions in Wisconsin."

Although last week's frost killed emerged corn leaves, the effect on yield will be negligible. By now, nearly a week after the frost, corn plants should be showing newly emerging leaves. There may be some tie-up of the leaves with the killed leaves, but eventually these newly emerged leaves will unfurl, and development will continue normally. 

Through the years we have done numerous leaf clipping studies where we have removed 100% of the leaves and measured its effect against an untreated check. In most years, corn grain yield was not affected when 100% of plants were defoliated between V1 and V4. On average there was a 7% yield decrease, however, the effect was significant in only 2 of 7 years that the experiment was conducted. Additionally, hail adjuster tables do not even begin adjusting for yield until the V7 stage of crop development.

Figure 1. Grain yield response of corn that was 100% defoliated between V1 and V4 at Arlington, WI.

Further Reading

Corn Replanting.