Impact of early season frost (before V4)

Encyclopedia Article

When low temperatures and frost injure young corn, producers need to carefully weigh their options apart from the immediate and discouraging appearance of the plant. In many cases, the best response may be no response or at least a slightly delayed response. Growing points, which are below the surface until the six-leaf stage (V6) should be intact unless the freeze was substantial.

Three management options were evaluated in research conducted during a frost situation in Nebraska in 1992. Frost that year injured thousands of acres of corn in the three- to four-leaf growth stage (V3-V4). See Photo 1. Damage ranged from slight to complete defoliation. Three field sites with different levels of defoliation (100% (Field A), 70% (Field B), and 55% (Field C)) were selected for research. Frost damage at each site was relatively uniform within the plot area. Within each location three treatments were applied: 1) leave the field as it was (control), 2) replant with corn or another crop, and 3) clip the corn plants above the soil surface. All three sites were irrigated, but irrigation applications were minimal due to abnormally wet conditions.

Photo of someone showing V4 corn damaged by frost
Photo 1. Corn at V4 damaged from frost event. Above-ground tissue is dead (brown) but the growing point was still below-ground and is alive (white-yellow tissue).

Yields from the control (#1) and clip (#3) treatmients were inversely proportional to the extent of frost-induced defoliation (Field C had less frost damage and yielded more than the fields which had greater damage) and directly related to stand survival (data not shown). See Figure 1. Clipping did appear to spread a bacterium from which developed a bacterial soft rot that reduced stands. Clipping may comfort the producer who is trying to remedy the situation, but may prove to be an unreliable solution.

Corn yield (bu/acre) following early-season frost
Percent defoliation at each
field due to frost
Control (#1) Replant (#2) Clipped (#3) LSD
100% (Field A) 101 b 123 a 64 c 22
70% (Field B) 153 a 162 a 146 a NS
55% (Field C) 202 a 143 b 195 a 20
NS = not significant
R.W. Elmore and B. Doupnik Jr. 1995. J. of Prod.Ag. 8:199-203

Figure 1. Response of frost damaged corn to three treatments at three different locations. Locations had differing levels of initial damage. Minden, NE (1992).

Replanting corn increased yield by 22% at Field A compared to the untreated control. Yet, yield was decreased by nearly 30% at Field C. Field B did not have significantly different yields between any of the treatments. It appears that if defoliation due to frost is greater than 70% then replanting may prove beneficial; if defoliation is less than 70% it may not increase yields.

Recovery from a moderate freeze when the growing point is below ground usually is rapid and almost complete. The long-term effect on yield, from losing the first four to five leaves, is usually minimal.

Plant recovery is slowed if air temperatures are below normal following the initial frost event. In this research, cool temperatures continued for ten days and bacterial soft rot developed at Fields A and B. This rot contributed to greater stand declines and played a significant role in the final results. To check for soft rot, split the seedling and look for dark, water-soaked tissue. For several weeks after the frost, injured plants continued to die from soft rot at or just above the growing point. Environmental conditions which include sunny, clear skies with slight-to-moderate wind speeds to be the most beneficial. These conditions dry the damaged foliage and aid in rapid re-growth.

Recommendations

Following a frost event, make a field-by-field assessment of final stand potential before deciding whether to replant. Depending on extent of frost damage, either leaving the plants alone or replanting will provide the best opportunity for corn recovery and maximum yields. If weather conditions are beneficial to recovery, a new leaf should develop three to four days after the frost. In this research, the most economical solution at the 55% and 70% defoliation levels was to leave the field alone and not replant. At the 100% defoliation level, replanting proved beneficial.

What can a producer do to reduce frost damage potential?

Cultural practices used by producers prior to frost created visible differences in the extent of frost damage and plant responses in the above research because the microclimates around the plants differed. For example, corn cultivated just prior to the frost sustained more damage than uncultivated corn. Corn without spring-applied irrigation was damaged more than corn with irrigation. Crop rotations differed in response; corn following corn was more affected by frost than corn following soybeans. Corn in north-south rows was harmed more than corn in east-west rows. Planting in different row orientations would spread risk of extensive crop losses to any one environmental event.

Portions of this text, written by Roger Elmore, taken from a Crop Watch article (University of Nebraska extension newsletter) June 12 ,1998.

Article based on publication: Corn recovery from early-season frost. R.W. Elmore and B. Doupnik, Jr. 1995. J. Prod. Agric. 8:199-203.

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Origin: 
Iowa State University Agronomy Extension Corn Production
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