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Nutrient deficiencies concern growers

Hot, dry weather conditions
are bringing out the worst in many fields across the Midwest. Fabian Fernandez,
University of Illinois Extension specialist in plant nutrition and soil
fertility, said potassium deficiencies have become the most noticeable.

However, is what you are
seeing in the field worth worrying about? Fernandez offers a few reminders and
tips for growers.

Adequate soil fertility levels.

If the soil does not have adequate fertility,
correct the problem by applying adequate levels of fertilizer. If severe
deficiencies occurred this year due to the dry conditions or if the problem
does not go away after some precipitation, Fernandez said it’s a good
indication of low fertility in that field.

Looking at previous soil
test information, previous fertilization rates, and yield history for the
field, along with additional soil testing, is the best way to determine if and
how much phosphorus or potassium may be needed. Of course, it is unlikely that
applying phosphorus or potassium now will help this crop, but if the fertility
of the field is a problem, correcting the problem before next year should be a
pretty high priority this fall after harvest, he said.

Soil water content.

Not only is water critical to supply the basic needs of the crop, but
also to dissolve nutrients and make them available to the plant. Temporary
nutrient deficiencies can be observed when the surface layer of the soil
becomes too dry and the root system of the crop is small and shallow.

This year, soil conditions
were fit for crops to develop an extensive root system, he said. This helped
crops draw water deeper in the soil during dry conditions. Keep in mind that
new roots tend to be the most important roots for nutrient uptake since they
are more active than older roots and are growing into “new soil” where
nutrients have not yet been removed. However, roots do not grow into dry soil
and will slow down their activity under dry conditions. Because of this, some
crops might be showing some nutrient deficiency.

Soil compaction.

Soil compaction can reduce the volume of soil, including nutrients and
water, which can be accessed by the plant because compaction can limit or
completely restrict root pene­tration. If patterns of a nutrient deficiency
develop following old crop rows or wheel traffic, Fernandez said it’s likely
the field is experiencing soil compaction. At this time, nothing can be done to
correct the problem, but it’s important to break that compaction after harvest
this fall if soil conditions are fit to do tillage.

Diseases and pests.

Diseases and pests compete for nutrients, affecting physiological
capacity (such as reduction in photosynthesis rates), and diminishing root mass
and root surface area that is important for nutrient and water uptake. Also,
weed competition can be a very large problem for crops, especially when
resources such as water and nutrients are limited. Making sure fields are
weed-free from the early season allows the crop to grow without competition and
to have all the water and nutrients that are in the soil available to them, he

“While there is very little
that can be done at this point to correct nutrient deficiencies, besides a  good
rainfall, the development of nutrient deficiencies in some fields or parts of
fields should be noted to determine if there is something that needs to be done
to correct the problem for next year,” Fernandez said.

By Jennifer Shike, University
of Illinois

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