Corn Populations
Corn population studies have been conducted for many years, and results from the most recent
studies indicate that corn populations of 30-35,000 seem to be the optimum. Some interesting
questions regarding corn populations for some of the more expensive seed corn hybrids have been
asked. What populations are optimum for corn when it’s priced anywhere from under $150 per bag to
over $250 per bag, which would equate to a per acre seeding cost from $62-$104 (at 33K per acre).
As it turns out, there really isn’t much difference for optimal population regardless of seed cost.
Iowa State ran a comparison examining seeding rates for corn priced from $140 to over $300 per bag,
using a selling price of $3.25 (which is a little low) but the optimum was essentially the same (between
30-35K). Although as seed price increased the advantage to the 30K population became a little more
evident.
Emerson Nafziger ran a comparison of corn seeding rate economics comparing $5 corn at $200
per bag to $3 corn at $300 a bag (a very wide range). The optimum populations were 35K (for the first
scenario) and 33K (for the second). He used those specific corn prices and seed costs because there was
such a large difference.
Corn planting date studies again show what we’ve discovered of late, early and late April corn
have the advantage over mid May corn. Although there were a number of instances the past two years
in which late planting (May and into June) have yielded as well as April. But the unusually high rainfall
(and cooler temperatures) of the past two years were mostly responsible for that.
Lastly is the issue of row widths. About 10 years or so ago, 20” rows began to be experimented
with. And there are some producers which utilize that row width. Research across the Midwest showed
an advantage to the narrower row width as you moved north in the corn belt. Probably because of a
shortened growing season and utilizing a larger amount of sunlight by having corn shading the rows
quicker to take advantage of as much photosynthetic capacity as possible. At pollination, you want to
see 95% plus sunlight interception. Any time sun hits the ground and is not intercepted by corn leaves is
lost potential energy.
The past two years, advances in planters allowed twin row planters. These have twin 7” rows
spaced 30” apart. Again the goal is to capture sunlight more efficiently and quicker, leading to higher
yields. Researchers and producers across the Midwest have compared those row widths. Emerson
Nafziger has data from 2008-09 which shows no yield response to twin row corn at populations from the
high 20’s to the low 40’s. This research was conducted at Urbana, so it’s only one location. Thus far it
appears that 30” is still the optimum for our area.
Corn Storage Fundamentals
We all know that quite of bit of this years’ corn crop was put into storage under less than ideal
conditions, thus making it somewhat more vulnerable to potential storage losses though mold growth,
heat, etc. And you’ve probably all heard of stories over the past month or two of corn that has been
found out of condition. It was tough to get the corn crop uniformly dried for good storage conditions
over the winter. It will be even more important to make sure that the grain mass is uniform in
temperature and moisture once spring arrives and we get warmer temperatures, which can cause a
greater concern for corn spoilage.
Several things to keep in mind for those stored bushels. First, remember that stored grain will
vary considerably in moisture even though it has all been run through the dryer. It went in the dryer
with individual kernels varying in moisture by 15-20% from driest to wettest, and it exited varying in
moisture. The difference is that there was much more wetter corn entering and much more of the drier
corn exiting. But, there was considerable variance between individual kernels. It doesn’t take many wet
kernels to cause problems, and that has already happened.
If you haven’t taken a load or two out of each bin, do so. That helps reduce broken kernels and
improve air flow. Also level the bin after. Air will travel though the easiest route. Make sure the bin
allows air flow uniformly throughout the mass, otherwise you’ll get problems, even with a stirrator.
As temperatures rise this spring, make sure you warm the grain mass to within 10-15 degrees of
the outside air temperature. This will reduce moisture condensation. And moisture condensation is one
of the biggest enemies of stored grain. Once moisture increases, heat will be formed, and then it’s like a
snowball rolling downhill: your problem will escalate. It may take just a couple of days to move a drying
front through the grain mass, or it may take several weeks. It all depends upon fan speed and bushels.
Check the condition of the grain now and again every few weeks. Turn on the fan. When the fan
is running, open one of the bin lids and smell the air exiting for signs of odor. Walk across or probe the
surface to see if crusting has occurred.
You may need to move grain around to get some mixing and to get some of the wetter grain to a
drying bin. We’ve been getting reports of corn coming out of bins at higher moisture levels than it went
in. So take a couple of checks of moisture levels in your bins. Get some samples from the middle and
lower levels of the bin if possible to compare.
Experts are cautioning to not store poor quality corn any longer than winter. Don’t take chances
if you have grain that is in questionable condition. Run the fan and check for odor. Check for
condensation on the underside of the bin roof. Remove the centers of bins, level the grain and take
moisture readings from various portions of the grain mass.
Nitrogen Sources
It sure looks like Mother Nature wants to keep winter around a bit longer than many of us
would prefer. Officially, spring begins March 20th, but many producers are hoping that spring weather
will arrive sooner. We’re going to need as many days as possible to get quite a few field operations
completed before planting can commence: fall (now spring) tillage, eliminating ruts in fields or parts of
fields, fertilizer to apply, manure to spread, etc.
Most areas saw very little fall anhydrous ammonia applied. Which means the NH3 system will be
fully stressed this spring. I think most folks realize that not all fields will get NH3 applied prior to
planting, it’s just not possible to get over that many acres in a timely fashion without delaying planting.
Thus we need to be examining the use of alternative nitrogen sources and timings.
Of the 3 main nitrogen sources, NH3 is the most commonly used. It’s cheaper and is applied
below the surface, which can reduce N losses (but not all). Urea and liquid are the other two sources.
Both have been used in the past with similar results to NH3, if used correctly.
When nitrogen is applied to the soil, it breaks down into ammonium and then nitrate.
These are the two forms that the corn crop uptakes. And nitrate is the form that can be lost (leaching or
denitrification) from the soil. Comparing the 3 N sources, note that NH3 takes the longest amount of
time to break down compared to ammonium and nitrate. While liquid N is half ammonium and nitrate,
which means it can be lost the quickest. The longer we can keep nitrogen from breaking down to nitrate
the more protected it is from loss through leaching or denitrification.
In terms of potential N losses, all forms are vulnerable. N is lost in one of several ways: 1) under
saturated soil conditions, nitrate can be converted to a gas by soil microbes (denitrification); 2)nitrate
can be leached out; or 3) if left on the soil surface, N can convert to a gas. Nitrogen stabilizers (N-serve,
Instinct, Agrotain, etc.) can be used to reduce some of these potential losses.
1) If the soil is saturated and any of the N has been converted to nitrate, soil microbes will
cause nitrate to be converted to a gas and lost. But only the portion of the N that has
converted to nitrate.
2) If water is moving through the soil profile and any of the N has been converted to nitrate,
leaching can occur, and tile lines take it out of the field. Again, only nitrate can be leached.
3) If left on the soil surface, with warming soil temperatures, heavy residue and high
evaporation occurring, urea can be lost through volitization. This doesn’t happen
immediately, but, depending upon the above factors, within 7-14 days. Urea is found not
only in dry urea but also in liquid N, as 50% of liquid N is urea.
No system is foolproof. So take precautions- Apply liquid or dry N sources at planting time, not
weeks ahead. Consider using nitrogen stabilizing products. Incorporate liquid and dry if not expecting
rain within 7 or so days. Consider using some of the coated urea products as the coating will prevent N
loss for 4-8 weeks, although you might want to incorporate to prevent movement of the granules off the
field. Sidedressing is the most efficient method of applying N, and you can actually reduce your normal
rate.
All 3 nitrogen sources have been used with success. It’s just that you have to manage them
differently. HN3 is injected, which eliminates surface loss. But you can lose NH3 via leaching or
denitrification. Urea, if not incorporated (by tillage or rain) within 7-10 days can be lost via volatilization
under certain conditions. Use of coated urea will reduce that loss. Liquid N is half urea and half equal
portions of ammonium and nitrate. The nitrate portion is vulnerable immediately to loss (as described
above).
Be aware, you’ll more than likely have to use one of these alternative sources this year. Make
sure you plan ahead for best results. For instance, spinners may not be as precise at application, so a
double spread may be necessary. Just be prepared. Of course, there are good and bad in each N source.
Anhydrous may be the cheapest source of N, but it’s the most expensive to apply.