Planting Agronomic Insights for Northeast Iowa May 16th, 2025
Wow, what a difference 10 days of sun, heat, and calm winds make! I knew farmers could plant fast, but I’m guessing 90% of the crop went in the ground in 10 days. The old adage “plant in the dust, and your bins will bust” may hold true as long as we get timely rains. I want to pass on some observations I’ve made in the past couple weeks.
Insights
We don’t know it at the time, but there is always a date or dates that planting doesn’t work out. It sometimes takes until weeks later to realize when that was. This year it appears like April 17th for sure, and possibly April 6th. From what I’ve seen fields planted April 15th and earlier looks good. The soils with more clay, and the last few feet between tile lines stayed just wet and cool long enough to slow down the emergence, and the ground crusted over preventing the crop form pushing through. Sometimes rotary hoeing was enough, but in many cases replants were necessary.
Needed Moisture
With the May planting now almost complete, a few things to think about. I am seeing some seeds, mainly soybeans, laying in dry soil. Especially if there was a lot of residue, and/ or cloddy ground. These seeds will be needing a rain to absorb the necessary moisture for emergence.
Wind Injury to Plants
There is plenty of wind around today and for the next few days, this could lead to some sandblasting injury on the young tender plants. We hope this is only cosmetic, but any time a plant is injured it is more susceptible to diseases. The growing point is still well down in the plant, so the new growth should come out just fine. Attached is a picture of some sandblasting injury in a previous year.
Emergence and Growth Stages
The corn that was planted in mid April is currently V2-V3, and the beans are mostly in the unifoliate/Vl stage. I have attached a picture of a V3 corn plant, showing the three “collars” on the leaves to identify the stage. A lot of the corn and beans planted last week are now emerging.
Pre Emergence Herbicides
Pre herbicides sprayed in May and laid on top have not had any rain for incorporation. A rule of thumb is that for the group 15 pre-emergent herbicides it takes between 0.25″ and 1″ to activate the molecule, with Harness/Keystone taking the least, Dual/Outlook in the middle, and Zidua taking the most moisture for activation.
Post Emergence Spraying
We will begin post emerge spraying the early planted corn next week, and I see a few farmers starting to sidedress the early corn as well.
Waterhemp Watch
On the note of growing degree units, waterhemp needs around 350 total heat units to emerge. As of May 15th we have accumulated 385 for the year. I am starting to see waterhemp up in spots, especially where no pre-emerge herbicide has been applied. With the heat and additional moisture, waterhemp will take off.
As always, reach out to me with questions or concerns you have or come across out in your fields. Everyone, Stay Safe! Connect with your agronomist >
Northeast Iowa Heat Units Accumulated
April 14 Plant Date – 287
May 7 Plant Date – 146
*It takes roughly 75 heat units for corn to sprout, and approximately 125 for emergence, so it was no surprise to see May planted corn emerging in a week.
Northeast Iowa Rainfall Data
April 2025: 4.8″ | 30-year average 4.2″ |
May 2025: 0.3″ | 30-year average 4.8″ |
