Is Replant Necessary?
Much of the region has received significant rainfall in the last week, and judging by the questions we’ve received, several of you were wondering how to manage planting before a predicted rain event. Now that planting is further along for many, some of those fields have seedlings emerged or germinating seeds and may now have standing water or areas where the soil is saturated. There is more data on the response of seedlings to flooding or saturated soils than on how germinating seeds respond. Some research has suggested that there may be hybrid differences in response to flooding/saturation, but this data is very limited.
Seeds are a living biological organism that requires oxygen and soil oxygen may become depleted within 48 hours or saturation. Cool temperatures may help extend the survival, but generally seeds or seedlings won’t survive more than four days of saturated conditions. Air temperatures greater than 77 F reduce the ability of germinating seeds or seedlings to survive saturated soils.
We’re also getting questions regarding replant. To determine if a replant is necessary, first take accurate stand counts, then decide whether to keep any of the existing stand and spot in, or destroy the entire field with tillage or use herbicides.
Taking good and accurate stands counts is essential in the replant process. Compare the yield potential for existing stand counts to the yield potential of the replant date to determine if a replant will even be beneficial. Keep in mind that it will take an approximate five percent yield increase over the existing plant stand to pay for replanting costs.
This guide from Purdue University Extension is a great resource to use when running the numbers and determining if a replant will be beneficial.
In wheat, we’re scouting for freeze damage. Wheat is more tolerant to cold temperatures during Feeke’s growth stages 2-4, but after vernalization, wheat becomes progressively less tolerant to cold temperatures. Freeze damage symptoms may not appear until several days after the event and symptoms also are affected by the temperatures after the event with more rapid tissue damage with higher temperatures directly after the freezing temperatures.
To scout for wheat freeze damage, check low lying fields or low lying areas within a field first, especially if the freezing temperatures occurred on a still night. To estimate damage and yield loss collect all the stems in a 1 square foot section of row (@ 19.25” in 7.5” row width) from a low area of a field and also from a higher point in the field. Don’t include small tillers.
1.) Count the number of damaged stems and/or dead growing points in each sample.
2.) Divide the number of damaged stems by the total number of stems in the sample area to get a rough idea of percent damaged plants.
3.) If the percent damage is greater than 20 percent, then re-sample other areas to confirm the counts. Small numbers of damaged plants don’t necessarily indicate a potential for yield loss as smaller plants can compensate from growth of younger tillers. Potential yield loss is generally lower than the percentage of damaged plants and potentially could be less than half of the percentage of damaged plants.
4.) Estimate the number of healthy plants per square foot and compare to the chart from the University of Kentucky for yield potential based on healthy plants plus tillers per square foot.
Let us know if you have any questions or concerns regarding planting and replanting,
Terry, Dan, Rod and Denny