By Joel Ransom, NDSU
The cold weather these past few days had the potential toplsc.ransom.corn damage emerged corn particularly in the eastern third of the state. Normally there is no need to be overly concerned about frost events at early growth stages of corn when the growing point is still below the surface of the soil. However, over the weekend temperatures dropped into the mid-20s and low 20s in a few places. These very low temperatures coupled with dry soil conditions, which offer less buffering capacity against the cold air, had the potential to kill corn plants. The most severe damage will probably occur in the lowest points in the fields and in field margins where there may have been more surface compaction. Corn leaves are sensitive to temperatures below freezing (see attached photo). Plants with just leaf damage will quickly grow new leaves and little or no long term impacts on growth and development will be noted. Most frost related yield loss at this early stage of corn development is associated with stand loss and not leaf damage
. In cases where the growing point is damaged, no new green tissue will emerge. New regrowth in plants that have not been killed will be evident within three to five days, especially with the warmer weather that we have recently been experiencing.
For fields that have experienced significant stand loss, an important question is whether they should be kept or replanted. We are early enough in the season that replanting with corn can be a viable option. Evaluating fields as soon as possible would enable a more timely decision. To evaluate plant stands to determine if replanting is needed and would be profitable, estimate your plant population by counting the number of emerged plants in a thousandth of an acre (17’ 5” and 23’ 10” row lengths for 30 inch and 22 inch row spacing, respectively) in about 20 places in your field and then multiple the average of those counts by 1,000. Use Table 1 to estimate the likely yield of your current crop and your likely yield if you replant. As you can note from this table, a half stand is about as productive as a full stand that will be planted after May 20th. The worksheet in the extension publication “Estimating Yield and Dollar Returns from Corn Replanting” by R.L. Nielsen and published by the Purdue Extension can be a useful tool in evaluating the profitably of replanting.
In most circumstances, the original stand of corn should be destroyed before you replant. Late planted plants that grow next to an early-planted plant will be at a competitive disadvantage and will very likely not produce an ear.