Is Fall Tillage Following Soybean Necessary? Mike
Rankin
Tillage is one of those topics that is
difficult to discuss in specific terms because virtually every situation is
different. What's the best
chisel point to use? Should I
sell the plow and buy a new no-till planter?
Am I better off with an offset disk or a field cultivator?
The list of questions is exhaustive.
One thing we do know is that plant residue left on top of the soil
surface drastically reduces soil loss and nutrient movement to surface
waters. Ultimately it becomes a
balancing act of leaving crop residue, planting in timely fashion into a
seedbed that is not too wet or too dry, and maintaining net income per acre
(not to be confused with maximum yield per acre).
To be sure, there are certain soil types in Fond du Lac County where
no-tilling into heavy corn residue is a tall order.
However, I know of no situation where insuring some crop residue
remains on the soil surface throughout winter and after planting is not an
attainable goal, especially following corn.
That brings us to the point of this article……soybeans.
We grow about 50,000 acres of soybeans in the county.
This compares to a figure of 15,000 acres only ten years ago.
Unlike corn, soybeans offer little in terms of overwintering crop
residue. The leaves and stems
from soybeans disintegrate faster than a 3rd inning Brewers' lead.
Virtually ANY type of tillage reduces surface crop residue to
something well under the desired 30 percent level after planting.
With a few thousand acres of soybean spread across the county, the
environmental impact may be minimal. With
50,000 acres, the stakes become higher.
During my Iowa State University graduate school days, I recall a
constant rally call across the state was to not fall plow soybean ground.
To this day, it still holds true.
I would submit that it's probably time to bring the rally cry north. Let's take a look at the advantages and disadvantages of such
a practice.
There are sometimes clear advantages to doing a minimum amount of
tillage following corn on our heavier soil types (e.g. faster soil warm-up
and earlier planting in the spring). However,
soil condition is much different following a soybean crop. It's difficult to measure in scientific terms, but the soil
is clearly more "friable" or "loose."
Typically, one tillage pass is all that is needed to have a field
ready for planting. Why not
make that one pass in the spring and forego the fall tillage?
This leaves a maximum amount of crop residue on the surface over
winter but certainly not so much that it will significantly delay spring
planting. Remember, the maximum
amount of soybean residue is equivalent to a rather small percentage of
total corn residue. |
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Even with a minimum amount of tillage in the spring, it's hard to hold soybean residue on top of the soil surface. Any fall tillage makes it impossible to maintain a residue cover after planting. |
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The advantages are clear. You're
saving the cost of one tillage pass in the fall and saving a whole lot of
soil and water-dissolved nutrients from reaching ditches or streams.
"Phooey!" you say? Next
spring, check which fields have the deepest erosion channels running
across their surface. For
those who want to take the next step and "dabble" with no-till
corn, there is no better place to begin and have a higher likelihood for
success than planting directly into soybean residue.
What about disadvantages? I
know of none that would fit every situation.
Make sure that the soybean residue is evenly spread behind the
combine. This is very
important if you plan to no-till but also critical to insure even field
drying where a single tillage pass is planned in the spring. Another potential problem is winter annual, biennial, and
perennial weeds. Again, for
no-till these need to be dealt with prior to planting.
A fall herbicide application to kill weeds such as dandelion is
becoming more popular among no-tillers.
Where tillage is planned, these weeds are much less of a concern. Okay, let's get to the bottom line. What about crop yields? Although there is plenty of research data in Wisconsin comparing no-till vs. conventional till corn planted after soybean, there is surprisingly little information with direct comparisons of simply not tilling or tilling in the fall. This past spring, I established three such replicated research trials in county. Interestingly, of the three farmer-cooperators involved in the project, one had always fall-plowed soybean ground, one never did, and the third did some fields but not others. Stay tuned for the results.
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