Each Monday during the planting and growing season Iowa State University agronomists on campus at Ames hold a telephone conference with the 12 ISU Extension field agronomists around the state. The field agronomists report what’s going on with planting progress in their locations and also report problems or issues they are seeing with crops, pests and any other concerns farmers are calling them about.
Northwest Iowa in particular had areas that picked up a lot of rain last week and corn and soybean planting progress has been delayed a week or more for many farmers. Paul Kassel, ISU Extension agronomist at Spencer in northwest Iowa, addressed this question: Will this planting delay affect corn yields? Here’s his answer.
How mid-April corn planting compares to mid-May for yield potential
“ISU conducts some date-of-planting studies where we purposely plant corn at different dates each spring to see the effect of planting date on corn yield and grain dry down,” says Kassel. “A study at the ISU Northwest Research Farm near Sutherland in 2014 and 2015 shows two different outcomes from a mid-April planting date compared to a mid-May planting date.”
Corn planting date – 2014
bu/acre grain moisture %
April 22 183 21.2
May 9 182 21.1
April vs. May difference -1 -0.1
Corn planting date – 2015
bu/acre grain moisture %
April 15 223 13.3
May 18 204 14.9
April vs. May difference -19 +1.6
This data shows that a delay in planting can have a small effect, like in 2014, or a larger effect, like in 2015. “A person needs to ask why the difference between the two years? Why did we get a 19-bushel-per-acre yield difference in 2015 and only a 1-bushel yield difference in 2014?” notes Kassel.
The two growing seasons were actually very similar in terms of total rainfall, temperature and stress, he explains. “However, the 2015 season was somewhat dry until some plentiful rainfall came in mid-August. Logic would tell you that the late season rainfall would benefit the later planting date but that was not the case.”
Even with a 19-bushel yield penalty, corn yielded 204 bushels per acre
Looking at these yield results, you notice that even with the 19 bushel per acre yield penalty for delayed planting in 2015, the corn yielded 204 bushels per acre and thus outperformed both planting dates in 2014. “The simple explanation might be that the 2015 season was a slightly better corn growing season than the 2014 season,” he says.
So what is the take-home message from this study and others like it? Kassel says, “Even though we would like to have our corn planted by May 1, we can still achieve good corn production with good grain dry down with early to mid-May planting dates.”
Information to answer your 2016 planting season questions
Wet conditions in some parts of Iowa have kept farmers out of the fields for much of the past week. Here are links to recommendations and information from Iowa State University agronomists to help answer questions farmers are asking based on planting progress and cool, wet soil conditions this spring.
Imbibitional Chilling and Frost Damage to Corn and Soybean Seedlings
Corn Emergence and Cool Temperatures
When Will This Early Planted Corn Emerge?
Influence of Soil Temperature on Corn Germination and Growth
Stand Assessment and Replant Decisions