The 2019 planting season has been one of the most challenging, yet growers have dealt with similar situations and they are remarkably working their way through this one. There are some very good corn stands, while others have considerably lower than target populations. Replant decisions can be easy in worst cases, with little stand and huge bare areas. However, there are fields where it is very tough to decide whether or not to replant. Those fields require some extra attention and this article is meant to help with those field evaluations.
It is important to make the decision based on economics and not emotion. It is also important to be patient in waiting for soil conditions to be satisfactory. While this is easier said than done, jumping into the field when it is not ready can cause problems that are not easily corrected.
Conduct stand counts and utilize replant decision guides to decide whether to keep the existing stand. Make sure you know the cause of the poor stand. This season the cause may be obvious, but knowing all factors is important information to avoid further problems.
Refer to MU guide 4091 from Dr. Bill Wiebold and Dr. Ray Massey: "Corn and Soybean Replant Decisions" at the following link: http://extension.missouri.edu/p/G4091
This MU Extension guide will help you work through the costs associated with replanting and aid your decision whether or not to replant. There are definitely regional differences and they are referenced in the guide for North & Central Missouri and for Southeast & Southwest Missouri.
Considering the later time frame we are in now, it is important to evaluate stands based on the yield potential of the existing stand, and the yield potential that is expected at the possible replant date. Using the data Dr. Wiebold has collected from central Missouri, the following tables demonstrate the yield percentage expected by planting date and population. There are two charts below, one that represents moderate yields and another for typically high yielding fields.
|Moderate Yield Environments|
|Represents Average Upland & Non-Irrigated Fields|
|Yield as percent expected|
Using this chart, a population of 18,000 plants/acre that was planted May 6th has a higher yield potential (76%) than that expected if replanting Jun 5th and getting a full stand of 30,000 plants/acre (75%).
|High Yield Environments - Consistently over 190 bu/a Average|
|Represents High Yield Upland & Bottoms; and Irrigated Fields|
|Yield as percent expected|
In making decisions in a high yield environment there is certainly a need for a higher population. Irrigation adds to the stability and yield potential. An example in using the chart for high yield environments would be: a stand of only 24,000 plants/acre planted by May 1st would have better yield potential (82%), than replanting on May 31st and obtaining a full stand (77%).
Given the fact that; the later we get, the more acceptable the corn stand becomes; you may find it better to be planting soybean than replanting corn. Consider the numbers in the above charts to help you make those determinations.
If corn is to be chemically killed, refer to the following IPCM Article link from Dr. Kevin Bradley titled: Herbicide Options for Killing Failed Corn Stands
REVISED: February 21, 2017