Corn Crop Appears Sulfur-Deficient In Western Illinois
URBANA, ILL.
Though sulfur is an essential
nutrient for crop production,
it has received
little past emphasis because
deficiency was seldom observed.
An intensive study in
the late 1970s showed that
sulfur deficiency was not a
major concern for Illinois, but
in more recent years, the frequency of sulfur deficiency
in corn has increased, though it is not
widespread.
Several factors may be contributing to an increase
in sulfur deficiency: less atmospheric
sulfur deposition, the result of strict air pollution
standards; less incidental sulfur in fertilizers,
insecticides, and fungicides; fewer
livestock operations, causing less application
of manure; increased use of conservation
tillage, which may reduce early-season
mineralization of the organic sulfur in the
soil; and greater rates of removal from soil,
resulting from increasing grain yields.
Sulfur deficiency causes yellowing of foliage
and is sometimes confused with nitrogen
deficiency. However, unlike nitrogen,
sulfur does not readily move inside the
plant, so deficiency tends to be more visible
in newer leaves, whereas nitrogen deficiency
shows up in older leaves. A typical symptom
of sulfur deficiency is the development of a
pattern of dark and light streaks, termed interveinal
chlorosis, in the newer leaves.
Deficiency symptoms often show up in
soils with low organic matter (including
sandy soils), in soils with low pH, and when
cold and wet conditions reduce the mineralization
process needed to make sulfur in organic
matter available to the crop. Since
sulfate is leachable, often corn shows a deficiency
early in development that disappears
once the root system taps into the
sulfur that has accumulated in the subsurface
soil.
Over the last few years I have been conducting
a study to evaluate corn response to
sulfur applications. Last year I described
some of the results obtained to that point.
Some reports I received this week from
western Illinois suggest that sulfur deficiency
may be showing up in different fields
across a large geographic area that includes
bottomlands as well as fields in bluffs and other
landscape positions with various soil properties.
The photo here was taken in one of these fields.
I suspect a main reason for this deficiency
symptom is relatively low sulfur concentrations
in the soil exacerbated by dry conditions that do
not allow the crop to extract sufficient sulfur
from the soil.
As the root system develops and starts tapping
more soil volume, and provided there is sufficient
rainfall, the deficiency will most likely disappear.
Still, if a sulfur application is deemed
necessary, I recommend using a fertilizer containing
sulfate (SO42-), which is the plant-available
form of sulfur. I would not apply elemental
sulfur, as it takes too long for this material to
become available for the crop.
I also recommend applying sulfur into the soil.
While a foliar application may temporarily relieve
the symptoms, ultimately sulfur needs to
be taken up through the root system in order to
satisfy crop needs. Also, a foliar application of
ammonium sulfate can cause leaf burn and
would counter any visual improvement resulting
from sulfur. Current research indicates that
corn response to sulfur is maximized at a rate of
20 to 25 lb of sulfur per acre. Most sulfur fertilizers
contain nitrogen, so if a sidedress nitrogen
application is planned in a field showing sulfur
deficiency, applying a nitrogen source with sulfur
could be an effective way to provide both nutrients.
I recommend doing the application
sooner rather than later.
A test trial is the only way to determine
whether a particular field could be responsive
to sulfur. If you are planning to apply sulfur and
would like to participate in the ongoing sulfur
research project, I am looking for volunteers
again this year. The study design is very simple:
at least three alternating strips with and without
sulfur. If you are interested, please contact
me (217-333-4426, fernande@illinoisedu). Not
only would your participation provide useful information
on your specific field, but the more
coverage of the state we obtain, the better we
can predict on a broader scale where sulfur applications
would most be needed. Δ
A corn plant showing interveinal chlorosis in the newer leaves, a typical
symptom of sulfur deficiency.
Photo courtesy Andrew Campbell