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.

Wednesday, December 2, 2020

Please join us for the 2021 Agronomy Update Virtual Meetings!

The 2021 Agronomy Update Meetings will be virtual this year due to COVID-19. The meetings will present the latest information on hybrid/variety performance, an analysis and discussion of last year's growing season, and updated recommendations for field crop production. CEUs will be offered in Crop Management for Certified Crop Advisers. There is no charge for this event, but registration is required. There are two sessions to choose from, both sessions will present the same information. Please choose the one that best fits your schedule.


Joe Lauer, UW-Madison Corn Agronomist

  • 2020 weather impact on corn performance
  • What has 20-yrs of strip-tillage research shown us for corn production?
  • The impact of environment on corn silage yield and quality

Shawn Conley, UW-Madison Soybean and Small Grain Agronomist

  • Agronomically optimal soybean seeding rates and associated risk across North America
  • Does precision planting matter in soybean?
  • Wheat grain and straw yield, grain quality, and disease benefits associated with increased management intensity

Matt Akins, UW Assistant Scientist & Dairy Extension Specialist and Kevin Jarek, UW Crops and Soils Agent

  • Wisconsin's Forage Landscape - What Do the Trends Tell Us and What Does This Mean to Farmers?"

Meetings will be held on:

  • Tuesday, January 5  9:00 am to 11:50 am    Moderator: Bill Halfman, Monroe County, UW Agriculture Agent
  • Thursday, January 7  1:00 pm to 3:50 pm    Moderator: Josh Kamps, Lafayette County, UW Agriculture Agent

Register by January 3, 2021. Register at

Tuesday, November 24, 2020

2020 UW Crop Performance Trial Results

Photo by Mimi Broeske

One of the most important decisions a farmer makes is the selection of high performing, adapted hybrids and varieties. Selecting the correct hybrid/variety can often mean the difference between profit and loss. Increasingly, during the current bio-engineered era, the choice of hybrid or variety that a farmer selects dictates the management style for that field.

Plant breeders and agronomists test thousands of commercial and new experimental hybrids and varieties for several years at many locations over a range of plant populations, other management practices and environments. These crop performance trials determine which hybrids/varieties  have yielding ability superior to current commercial hybrids/varieties and estimate disease resistance and other important characteristics.

Since 1973, there have been 1120 trials conducted in the UW Corn Performance Trial program. Within a trial, the average difference between the top- and bottom-performing hybrid has averaged 71 bu/A (Figure 1). This difference among hybrids is a significant economic impact on corn profitability.

Figure 1. Grain yield difference between top- and bottom-performing corn hybrid in each UW trial since 1973.

For a copy of the 2020 crop performance trials see the following links:

Barley, Oat and Wheat:

These results are a good place to start when evaluating hybrids and varieties to grow during 2020. Certainly, an on-farm test in conjunction with seed company trials, and University trials would probably give the best information, if all hybrids/varieties of interest were in the trials. Since most farmers do not have the resources to conduct on-farm trials at several locations, using unbiased results from other trials to supplement on-farm yield results can increase the chance of picking a hybrid that will do well next year.