Nitrogen deficient corn, what’s the cause?
Editor’s note: This article is from the archives of the MSU Crop Advisory Team
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This
summer I received calls from several farmers indicating that they were
seeing signs of N deficiency on the lower leaves of corn, even though
they had applied what should have been adequate nitrogen. Some of these
situations involved the application of partially composted dried poultry
manure. In some cases similar N management programs were being used on
adjacent fields or different fields of a farm. In some fields the corn
was growing well, but in other fields with a similar N program the corn
was “firing” or showing signs of N deficiency. I also observed a lot of
fields showing “firing” of the bottom leaves. Why did this happen? The
answer to this question may be associated with the weather and rainfall
pattern this year. This problem appears to have been worse on sandy
soils with lower moisture holding capacity.
Two factors may contribute to this problem. During the first part of the
growing season soil moisture was generally more than adequate, but as
we moved into mid-July and August many areas of the state become dry and
drier. With good early soil moisture corn roots may have developed
predominantly in the surface soil. When the soil became dry the corn
root system was not able to supply adequate moisture to the plant. Much
of the nitrogen is moved to the root in the water moving to and taken up
by the root. Therefore, less water supply means less nitrogen supply.
Secondly, when soil becomes dry, microbial activity decreases and less N
is mineralized from soil organic matter or organic materials, such as
compost, biosolids, animal manures or legume cover crops that are added
to the soil. Therefore, even though adequate N was applied in one of
these materials less N was mineralized for crop use than was expected.
Therefore, soil moisture can have a significant effect on N availability
and uptake. Even though some fields may appear to be similar, slight
differences in clay or sand content can make a difference in moisture
supply. Soil compaction can also accentuate this problem by limiting
root development and moisture supply. Managing soils to improve soil
organic matter over time will improve soil quality and moisture holding
capacity