DEKALB, Ill. — As farmers prepare for the 2013 growing
season, some may be questioning the impact of last year’s drought on available
nutrients in the soil.
“We host two weather-recording sites at the research center,
so our weather is recorded every 15 minutes,” said Russ Higgins, University of
Illinois Extension commercial agriculture educator at the Northern Illinois
Agronomy Research Center.
For 2012, the coldest day at the research center near
Shabbona was on Jan. 20 at 0.1 degrees, and the warmest day was on July 7 at
“We haven’t reached 100 degrees since 1988,” said Higgins,
during and educational seminar at the Northern Illinois Farm Show.
The total precipitation at the center was 20.3 inches, 59
percent of normal. Last year was the second driest on record for the U of I
center — in 2005, rainfall totaled 20.1 inches.
“We only had two 1-inch-plus rainfall events in 2012 on
April 15 and May 31,” the educator reported. “Just one year ago, we had two
4-inch rain events.”
During the autumn of 2012, a joint project was initiated
with the U of I and the Council for Best Management Practices.
“One of the reasons for the Soil Nitrogen Monitoring Project
was we were concerned about how much nitrogen was left over and how much will be
there in the spring,” the specialist explained. “Nitrogen left over from the
2012 crop is now primarily in the nitrate form, but if you fall-applied nitrogen
for the 2013 crop, there’s a good chance it is still in the ammonium
Nitrates can be a concern because they have the ability to
move in the soil profile and leach out through drainage tiles.
The second reason for doing this project, Higgins said, was
to look at if nitrogen was left over from the 2012 growing season and then
evaluate if farmers could adjust the rate of nitrogen applied for the 2013 crop
to save some money.
“We took samples at 130 sites at two depths — zero to 1 feet
and 1 to 2 feet,” he reported. “The average nitrate levels were 26 parts per
million in the north region, 16 parts per million in the central region and 18
parts per million in the south region.”
Although it is difficult to estimate how much nitrogen there
is in fields across Illinois from only 130 samples, Higgins said the data shows
about 136 pounds of nitrogen per acre currently is in fields that were in corn
“Some of the nitrate that is currently in fields is from
fertilizer, and some is from soil organic matter,” he explained. “It’s likely
the nitrogen we currently have is from a lack of loss of nitrogen because we
didn’t have the rain to lose the nitrogen.”
Higgins reminded producers that if they harvested cornstalks
in the fall of 2012, they may have to make adjustments for the potassium and
“You are only going to get optimum yield up to the point of
your most limiting factor of a macro or micro nutrient,” he said.
For the 2012 growing season, nutrients for the plants may
have been in the soil. However, they may not have reached the plants.
Higgins explained the three different ways nutrients can
reach roots, including root interception.
“Root interception is when the roots come in contact with
the nutrient,” he said. “Roots occupy about 1 percent of the topsoil.”
The second way is through mass flow or from water going
through the plant.
“Only about 1 percent of the water that goes through the
plant is required for photosynthesis. The majority of the water is transpired,”
the specialist said. “Mass flow is an important way to get nutrients, especially
nitrogen to the plant.
“Almost 80 percent of the nitrogen taken up by corn is
through mass flow,” he explained. “When it’s dry, the nitrogen may have been
there, but it couldn’t get into the plant.”
The final method is diffusion, which is when the nutrients
go from an area of high concentration to an area of low concentration.
“This is the primary way to get phosphorus and potassium
into plants,” Higgins said.
He identified several factors that effect nutrient uptake.
“The younger the plant, the better the uptake,” he said.
“Another factor is the nutrient status, and as the nutrient status increases,
the uptake decreases.”
Time of day has an impact.
“Most of the phosphorus and potassium uptake takes place at
night,” the specialist said. “And up to 100 degrees, uptake will increase by
Higgins discussed a research project currently in progress
at the U of I farm to evaluate the impacts of planting a cover crop.
“One of the reasons we’re really interested in doing
research on cover crops is a lot of the research has been done further south,”
he explained. “We have less growing degree days, and it’s not unusual for us to
be taking corn out in October and November, so we are trying to find out what
kind of cover crop we can get started.”
The research project was started in 2012, and cover crops
were planted after both corn and soybean harvest.
“After soybeans, we planted on Oct. 1,” Higgins said. “That
is late. We want to plant the cover crops by Sept. 15.”
Cover crops were planted into corn residue on Oct. 15.
“We know the amount of growth we have this year is almost
nonexistent. However, after the crops were planted, we only had about one-tenth
of an inch of rain,” the educator said. “Next year, we will try to plant the
cover crops earlier.”
Soil samples from the research plots were pulled in the
“In the spring, before we kill the cover crops, we will be
measuring biomass to determine the nutrients that were recycled,” Higgins said.