Iowa Farmer Today
10-14-06
Corn, bean test maps, methods more uniform
By Tim Hoskins, Iowa Farmer Today
After years with the same regions, Iowa State University Crop Test’s district
lines got blurred this year.
The overall effect is now the six districts are the same for corn and soybeans.
The new districts are Northwest, Central West, Southwest, Northeast, Central
East and Southeast.
In the past, there were seven corn districts and three soybean districts.
The districts are divided with lines for south, central and north. However, there
are not any lines from east to west.
The color of the stars shows which test site is in the east or west. Sites in Central
Iowa will show two stars because they have a both an east and west test at that
location.
Overall, it means there are four locations in each district for each test, explains
Jim Rouse, who manages the test.
Beyond that, he says with the previous corn districts it was hard to understand
why the lines were drawn where they were. Also, corn hybrids now are marketed
by soil types.
“I don’t think there will be any problem with the new districts,” Rouse says.
To help avoid any confusion with the old districts, he did not number the districts.
Rouse says part of the blurring of the lines is to allow farmers to look at multidistrict averages.
Beyond the district changes, he says there are changes to the corn and soybean
tests.
The first change to the corn test was getting rid of the short and tall test.
Rouse says the short and tall tests were started when they planted two rows of
corn of each hybrid. The shading effect from taller corn plants could affect shorter
hybrids.
However, they plant four rows of corn and run the test on the middle two rows.
Therefore, the shading affect has no effect on test results.
Another reason to get rid of the short test is because they had very little
participation — 10-15 entries, he says.
The third reason for getting rid of short and tall tests is the differences in hybrids.
“There is not an objective way to determine a short hybrid,” he says.
While very tall or very short hybrids are obvious, Rouse says most hybrids are
between the two extremes.
This year, they split maturities between early and full for the regions, south to
north.
He says this could affect the results because fields are harvested when the fullseason hybrids have moisture in the low-20 percent range.
However, the early-season hybrids would have lower moisture content and,
therefore, the test weight or yields would appear to be less when the difference
was really the moisture content.
The soybean test also some changes.
The main difference is there is no conventional yield test in this year’s yield trials.
“We don’t get any conventional bean entries,” Rouse says. “We are not making a
value judgment.”
Because most of the entries are Ready Roundup, he needed a few more ways to
split the results.
Therefore, the soybean varieties are split in an early and full-season maturity for
each area. They are also split if they are soybean cyst nematode (SCN) resistant
or not.
Rouse says if a variety is SCN resistant or not is depends on the company
information.
If the seed company markets the variety as SCN resistant, it is considered
resistant. If not, then it is in the non-resistant area.
“We don’t evaluate SCN resistance,” he says.
The overall goal is help farmers narrow their searches as to what seed to plant.