PRIMARY tillage tools - AGCO Iron

Straight talk on crop residue management
"Carbon management
in the
Bt era."
By Dr. Rob Zemenchik, CCA
It’s a pretty sure bet that you’re experiencing more
“trash” challenges, maybe quite a bit more, than ever
before. There are several reasons for this:
• University studies show lignin content
(the “glue-like” substance that holds plant cells
together) of Bt corn to be 33 to 97 percent
higher than in traditional, non-Bt hybrids.
That’s why Bt corn is harder to work through
your machinery than before.
• Since today’s full-season hybrids and higher
populations contribute to higher trend-line
yields, there’s more residue than ever in your
fields.
• Today’s plants frequently show stay-green
characteristics at maturity, thus tougher to
manage.
• Year-to-year yield volatility has increased, and
with it the amount of residue produced, so
annual field operations are less routine and
should be adjusted accordingly.
Over the years, fall tillage has been largely a soil
compaction management tool. Now tillage is
becoming equally important, if not more so, as a crop
reside management tool. This is especially true the
farther north you farm, as residue decomposition is of
necessity assisted by mechanical means.
A 200-bushel corn crop can leave four to six tons of
residue an acre behind your combine. Conservation
compliance goals vary from field to field. However,
to leave approximately two tons or so on the surface
at planting from such a crop you’d have the challenge
of properly sizing, mixing, and decomposing two to
four tons of trash an acre.
Helping you in this task are the millions of
microorganisms in every teaspoon of soil. These
“bugs”, along with soil moisture, warm temperature,
and residual nitrogen not utilized by the crop,
are ready to work on your crop residue. But, rest
assured, the decomposition process is much slower
if you don’t incorporate residues. That’s because
sizing and mixing assist decomposition—90 percent
a biological process.
Nutrients cycled in this manner, in high-yield
environments, build soil organic matter and offset
CO2 losses said to be given off by tillage. Another
important factor is timing. Once your combine leaves
the field and your soil testing and fertilization are
complete, do yourself a big favor by immediately
tackling the residue. Biological action ceases at 4°C
or 40°F. In high yield continuous corn, supplemental
nitrogen is often applied at 20 pounds of nitrogen per
ton of residue. Dry forms are okay if you incorporate.
Note that you can refine this nitrogen rate with stalk
tests if time and expense permit.
As for tillage depth, keep in mind that there’s
no magical number of inches to go down. This
depth should always be dictated by economics in
combination with attention to encountering or even
introducing possible soil problems related to alkali
subsoils, clay-like subsurface horizons, or inadequate
mixing that can lead to nutrient stratification. Some
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