Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


Printer Friendly Version

May 13, 2013




How will Corn Planted Two Weeks Ago Fare?


I am fairly optimistic that most of the corn in late April and early May East-Central and Southeast Iowa will be OK, since our soil temperatures did not drop as much as in the northern and western part of the state, and only got into the mid to upper 40s for a day before rebounding. However, be sure to watch fields to confirm that corn is emerging properly and there is a good stand.  Depending on the individual situation, potential issues are:


1.    Corn planted several days before the ground cooled may experience “cork-screwing” as it attempts to emerge,

2.    Corn planted just before the ground cooled may have experienced “imbibitional chilling” (absorbing cold water), which may cause the seed to swell but have little germination, and

3.    Pythium seedling rots promoted by cool, wet soils.


I heard someone on the radio state that all corn planted in late April or early May will need to be replanted.  That is clearly not the case, but careful scouting to evaluate emergence is appropriate.


In the event that a field or portion of field does not have the desired stand, refer to Roger Elmore’s (Extension Corn Production Specialist) article at for guidance.


Be Sure Soils are Fit to be Planted


Jim Fawcett notes, “Although corn usually yields best when planted by early May, mudding it in to achieve that goal will likely cost more yield than delaying planting a day or two. This is anything but an average spring, so I wouldn’t expect to see average results with early planting. This may be a year where corn planted in the May 10-15 window yields more than that planted in late April and early May. That’s what we saw last year.


Small mistakes made at planting time can haunt you the rest of the season. Many producers can get most of their corn planted in about 3-4 days, so starting a day too soon and planting half the corn under marginal conditions usually doesn’t make sense. Some points to consider with corn planting this spring:


1.    Don’t plant into wet soils. This can lead to sidewall compaction which can lead to season-long problems. The roots will have difficulty growing through the compacted zone made by the planter and will be pancaked into a flat plane in the direction of the planter. This can lead to uneven corn growth, rootless corn, and K deficiency symptoms due to poor root growth. Poor root growth will be an even greater problem later if the summer turns dry.

2.    Don’t plant too shallow. When soil moisture is plentiful producers are tempted to plant corn more shallow. For every corn field I see with problems caused by planting too deep, I see a hundred fields with problems caused by planting too shallow. If the seed ends up being less than 1.5 inches deep, problems such as rootless corn and K deficiency symptoms are much more likely to occur. Even if the seed is placed 1.5 inches deep, sometimes the soil can settle after planting or there can be soil erosion so that the plant actually “sees” a more shallow depth. Corn should be planted 1.5-2” deep and error on the deep side.

3.    Shoot for corn stands of 34,500-37,000 plants per acre. Ideal corn seeding rates have been increasing at the rate of about 400 seeds/A/year. Average corn yields per plant haven’t changed much in the past 50 years. Most of the yield gain has been from breeding corn that can tolerate an increased population. If you are still planting the same population you did 10 years ago, you’re paying 2013 seed prices and only getting 2003 yields.

4.    Pay attention to details at planting. A little extra time making sure planter settings, seed spacing, depth, and population, and soil conditions are correct can pay big dividends, especially with today’s prices.”


How Long Do I Have to Wait After Applying Anhydrous Before Planting?


It is often recommended to wait 7 days after applying anhydrous before planting, but in reality there is no magic numbers of days to wait to prevent fertilizer burn to corn. I have seen stand reductions even when the nitrogen is applied in the fall, and corn can be planted immediately after application without problems. The main thing is to be sure to apply the anhydrous 7-8 inches deep and get a good seal. Most of the anhydrous will diffuse to a zone about 6 inches in diameter within 24 hours. If the anhydrous is applied 8 inches deep and you are planting 2 inches deep, you will still have the anhydrous zone 3 inches below the seed. When the anhydrous is applied when the soil is too wet, more will diffuse closer to the soil surface. One way to reduce future problems is to apply the anhydrous at an angle to the corn rows so if there are injury problems later you won’t be taking out entire rows of corn. At this point in the season, it may be time to switch priorities and think about getting the corn planted first and worry about the nitrogen later.


Should I switch my maturity?


A general rule is that if planting is delayed until May 25, you should select a hybrid that matures five days earlier than an adapted full-season hybrid for that area. If planting is delayed another seven days, select a hybrid that matures another five days earlier than the previous one. In general, the date to switch maturities is later in southern Iowa.






Bean Leaf Beetle


A few soybean fields have already been planted.  These fields, fields planted to food-grade soybeans, and fields with a history of bean pod mottle virus should be monitored for bean leaf beetle activity as they emerge.  However, it appears there will not be wide-spread problems with bean leaf beetles on emerging soybeans in 2013.  Erin Hodgson, Extension Entomologist, and Adam Sisson, Extension Program Specialist, noted that bean leaf beetle survival is probably just above normal this year; see  However, the overwintering population in general appears to be small, so the slightly above normal survival rate should not be problematic.  Tom Hillyer, Hillyer Agriservices, noted that he is seeing very few bean leaf beetles on emerged volunteer soybeans, which is another indicator of a low overwintering population.




June 26, 2013, 1:00 p.m.

ISU NE Research & Demonstration Farm Spring Field Day – Nashua

As details become available, they will be posted at

June 27, 2013

Special Session for Certified Crop Advisors (9:00 a.m.) &

ISU SE Research & Demonstration Farm Spring Field Day (1:00 p.m.) - Crawfordsville

As details become available, they will be posted at





If you have any questions, please feel free to contact the Iowa State University Extension Office.
maroon ball East Central and Southeast Iowa Crops Home Page maroon ball ISU Extension and Outreach maroon ball ISU maroon ball ISU Extension Agronomy maroon ball ISU Agronomy
maroon ball Calendar maroon ball Search maroon ball Jobs maroon ball Feedback maroon ball Internet Resources maroon ball State Extension Sites in Other States maroon ball Local Extension Offices in Other States maroon ball ISU Extension and Outreach Policies

Last Update: May 13, 2013
To subscribe or unsubscribe to newsletters or for questions or comments, contact: Virgil Schmitt

Nondiscrimination Statement and Information Disclosures