April 13th, 2021
posted
by Andrew Blomme on 4/13/2021
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Weekly Newsletter
April 13th, 2021
There have been a lot of questions lately about if planters should be rolling yet. This newsletter will take a look at current soil temperatures and our 6-8 day forecast as well as the effect these may have on a seed as it begins to germinate.
Soil Temperatures
The two pictures below are the soil temperature maps for Iowa on April 11th and April 12th.
We are in a trend of decreasing soil temperatures. Soil temperatures for our area peaked around 57 degrees last week. Since then we have lost 7 degrees and are about to drop down below 50 degrees again. Generally, we would like to see soil temperatures above 50 degrees and rising for 3 consecutive days before planting, especially corn planting.
The weather forecast for the next 6-8 days makes it hard to believe soil temperatures will be trending upward. We have two very cold nights ahead of us, the potential for cold rain this weekend, and cold nighttime temperatures again earlier next week.
Cold Temperatures Effect on Seedlings
It is very important to get a crop off to a good start. The first bit of water a seed absorbs needs to be warm. If a seedling absorbs cold water or experiences cold temperatures within the first 24 hours of germination it can experience a condition called imbibitional chilling. Imbibitional chilling, seen in the picture below, leads to the "corkscrewing" effect of the mesocotyl as a corn plant germinates. This cold stress injury can severely diminish the number of seedlings that emerge and creates uneven uniformity in stand.
Iowa State University Extension released an article that talks about imbibitional chilling in 2019. The information in the article is still very relevant. You can find the article at the following link: Iowa State University Extension-Imbibitional Chilling
Soybean seeds generally handle less than ideal soil conditions better than corn seed but they are not immune to cold stresses. The University of Nebraska has an article that talks about the effect of planting into cold soils for soybeans. You can find this article at the following link: UNL Cropwatch.
Summary
Soil temperatures and the weather forecast make it hard to get excited to get the planter out of the shed. It may end up being the best course of action to wait until the middle of next week to plant if current conditions and weather forecasts hold true. You can find soil temperature data at the following link: Iowa 4 Inch Soil Temperatures. Clicking on the maps on the website provides a bigger version to view. I encourage everyone to regularly check soil temperatures over the next few days before deciding anything.
Every year we only get one chance at raising the best crop we can. Let's be patient and give it a chance to start out on the right foot.