Corn Following Corn – Strike 2?
URBANA, ILL.
In 2010, following a very
wet start to the season and
damage to root systems
from which plants never fully
recovered, corn following corn
yielded much less than corn
following soybean in many
areas of Illinois. This came
after a number of years in
which corn following corn produced good yields,
in many cases equal to those of corn following
soybean.
While the spring planting season and crop
conditions were quite different this year than in
2010, we are again hearing that corn following
corn is producing lower yields than corn following
soybean in many areas of Illinois. This is not
likely the case everywhere, but it seems most
noticeable in areas where it’s been very dry
since July. I’ve heard of cases where corn following
soybean is yielding about 230 bushels
per acre, while corn following corn in the same
area, planted with similar practices, is yielding
in the range of 160 to 170. We don’t expect corn
following corn to average 60 or 70 bushels less
than corn following soybean over whole areas,
but this does illustrate what will again be a significant
issue in some fields this year.
Last year it was easy to make the case that,
with the wet fall and lack of fall tillage in 2009,
large amounts of surface residue and cool, wet
conditions at planting, followed by heavy rain
and root injury, all added up to yield losses for
corn following corn. In 2011, we don’t have as
clear a picture for why we are seeing this problem.
For one thing, the fall of 2010 was very dry
and harvest was early; this, together with the
pent-up desire to do tillage to relieve effects of
wet conditions for the previous two years, led to
a huge amount of fall tillage last year. Surface
residue was well buried in most fields following
corn in 2010, and we can’t blame residue for
this problem in 2011.
So what did happen in 2011 that resulted in a
second year of substantial yield loss in corn following
corn? It’s never possible to paint a complete
picture, but I’ll offer the following:
1. The spring of 2011 started out well, with
some corn planted in early April. Almost all of
this was corn following soybean, given that such
fields tend to dry out faster and need less work
in the spring. It turned wet and cool after that,
and planting stalled at about 10 percent complete
through the rest of April. So planting was,
on average, late in 2011.
2. Once the calendar turned to May and it
dried up enough for fieldwork, planting got underway
in a big rush, with about 60 percent of
the crop planted over the first two weeks of May.
Many – probably most – fields planted during
this period were wetter than would have been
ideal. And because fields that were corn the year
before almost always dry out more slowly than
those that were in soybean, those who started
planting corn following corn in early May
planted into even wetter and cooler soils than
those planting after soybean. This not only
caused more compaction, “undoing” much of
the benefit of tillage last fall, but it also brought
issues of residue interference, seed placement,
and effects of heavy equipment in many corn-on-
corn fields.
3. As a result of these problems, many reported
that corn following corn looked bad from
the start, with uneven stands, poor color, and
other problems we associate with planting into
such cool, wet conditions. Some who attempted
to apply extra nitrogen, foliar nitrogen, micronutrients,
or other things to try to bring the
crop around generally found that their efforts
didn’t do a lot of good. Starter fertilizer helped
make some stands look more uniform, but it did
not completely solve the problem.
The heavy rainfall in May and June in some
areas was a repeat of what we saw in 2010. But
with the crop not nearly as far along in 2011
and with June temperatures not as high as in
2010, immediate effects of this heavy rain on
the corn crop were not as severe in 2011 as in
2010. This did, though, delay even more the return
of the crop to normal color and growth in
corn following corn.
4. When the rains stopped in many areas in
late June and soils dried in July and August,
the effects were much more severe in most corn-on-
corn fields than in fields where corn followed
soybean. Due to drier soils, root systems generally
developed better and remained healthier in
2011 than in 2010. But with the effects of compaction,
slower growth due to less (and a less
green) canopy, residue, possible tillage effects,
and other factors in corn following corn, it
seems that the ability of the roots to extract
water was compromised compared with corn
following soybean. Both crops seemed to pollinate
okay, but corn following corn showed more
leaf stress in July and August, and reduced
light interception was evident in many fields
where corn followed corn. This increased kernel
abortion and decreased the ability of the crop to
fill the kernels it had.
5. In the driest areas, corn following corn lost
canopy color and died prematurely, often before
corn following soybean. This stopped the filling
of kernels, and in many cases led to more stalk
quality problems.
6. It is discouraging that, after corn-on-corn
has done so well in recent years, we now have a
second year of lower yields in many corn-oncorn
fields. Many will find that their profitability
will be higher with corn following soybean
than corn following corn this year, even accounting
for what have often been lower returns
from soybeans than from corn in recent years.
Of course, we can’t simply decide to plant
more corn acres following soybean in 2012 than
we did in 2011; we planted only about 9 million
acres of soybeans in Illinois both years, and
acres of corn following soybean the next year
can’t exceed that number. So as long as corn
acreage stays near the 12 million acres of recent
years, some 20 percent to 25 percent of Illinois
corn will have to be corn following corn.
A special request. Given the severity of this
yield problem and the fact that it has now happened
for a second year, I think we should work
to get a better handle on it and try to come up
with possible research to address it. I ask that
anyone who is seeing the problem this year send
me an email with the following information:
a brief description of the yield differences
you’re seeing
where the differences are the worst
whether any corn-on-corn fields seem to
have escaped this problem to yield nearly as
well as corn following soybean, and, if so, what
was different in those fields that might explain
this result
Thank you for your assistance. Δ
DR. EMERSON NAFZIGER: Extension Agronomy
Professor, University of Illinois