The weekly crop survey released May 23 showed 98% of Iowa's 2011 corn crop was planted as of that date. On May 15, the previous week, Iowa's planting progress finally pushed above the 5-year average and approached the progress on the same date as last year. The Iowa corn crop as of Monday May 23 was 74% emerged.
The next USDA-NASS weekly report will likely show all of Iowa's corn planted and most of it emerged. Those survey results will be release May 31, a day later than usual because of the Memorial Day holiday occurring on Monday May 30. The weekly crop progress surveys are usually released every Monday afternoon.
Roger Elmore, Iowa State University Extension corn agronomist, provides the following observations regarding this year's corn crop and what farmers should be looking for as the corn has emerged and is off to a good start.
"Growing up with corn and throughout my career, I've heard, and said, 'You can row the corn!' This has nothing to do with braiding hair. Here's the way I understand the use of those words":
Rowing corn - A definition: The ability to observe rows of freshly emerged corn from the end of the field or as you drive by at 25, or even 55, miles per hour. It is a remote measure of crop growth.
Perhaps it's a big deal because it denotes a milestone for the crop and marks, hopefully, the end of the planting season at least for that specific field. Certainly it tells us there are enough plants emerged together to display long lines of green converging on the horizon. An amazing sight. No pun intended!
"You can row the corn" Story County, IA May 19 2011
It's time to walk fields, see what's really happening out there
But, don't let the beauty of the long straight rows of freshly emerged corn lull you into contentment. This is the time to walk your fields. If something catches your eye or looks amiss, put on your CSI (crime scene investigation) hat and check it out. Count the emerged plants. Look for a wide variability in plant to plant spacing. Small differences are less important than achieving proper plant populations. (See the articles on Planter Speed and Uniformity on the Planting tab on the Iowa State University agronomy corn production Web page).
Look for variation in plant emergence and size. Uniform plant emergence and plant population are far more important than plant spacing in most fields.
Dig some of the slow-to-emerge plants or dig some kernels in the areas where there are skips and compare them to earlier-emerged, neighboring plants. Ask yourself, why are they different? The answer may surprise you. Check planting depth, sidewall compaction, surface compaction, residue proximity, surface crusting, germination failure, insect feeding, mesocotyl rot, weed competition. The list can go on and on. (See the articles on Crop Establishment and Appearance on the Early Season tab on the ISU agronomy corn production page). Perhaps the planter speed was too fast, the seed bed too wet, etc.?
Slow heat unit accumulation handicaps slow-emerging plants
The photos (figures 2 & 3 in this article) show a row segment with four plants at different stages ranging from germinating, to VE, to V1. It takes 90 to 120 growing degree day units (GDD) from planting to emergence and another 84 GDD for every new leaf from VE to V10. With this in mind, there is about 150 GDD difference between the first plants to emerge (positions 1 and 4) and the seed in position 2 which is just sprouting. As of week ending May 20, although normal GDD accumulation is about 13 per day, we only accumulated about seven per day in the last week.
This slow heat unit accumulation will handicap un-emerged plants relative to those that emerged earlier and set up lower yield potential on the late emerging plants. Seed depth and/or surface crop residue of the two later seeds or plants (positions 2 and 3 in Figure 3) may have differed from that of plants 1 and 4 and slowed their emergence. Fortunately there were less than 5% un-emerged plants in this Story County field.
The conclusions you reach during your CSI investigation may not help you now or for that matter anytime this growing season. But it will help you next year. Plan ahead! Now is the time to walk your fields!