Purple corn
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EmailEditor’s note: This article is from the archives of the MSU Crop Advisory Team
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There
have been a number of reports of purple-colored corn seedlings this
year. These symptoms are not unusual for Michigan, but have been
particularly prevalent this year. There are several factors that
contribute to the purple color, but the main culprit is likely
restricted root growth. The April rains and early season planting delays
may have caused some growers to “jump the gun” and begin planting
before field moisture conditions were optimal.
Restricted root growth resulting from compacted soil and smeared and
compacted seed furrow side-walls can contribute to the buildup of sugars
in the corn leaf. The abundant sunshine and accumulation of heat units
the past week have resulted in the production of lots of sugars in the
corn plant shoots. These sugars would normally be used for root and
shoot growth, but when accumulated in the leaf, result in the production
of anthocyanins, which give the leaf a purple color. If the purple
color persists after field conditions normalize, the discoloring may be
indicative of other root-related problems such as a severe compaction
problem or phosphorus deficiency in the soil. In addition, some corn
varieties are genetically predisposed to have inherently higher levels
of anthocyanins. These varietal differences are readily apparent when
viewing variety trial plots this time of year, however, they do not
appear to affect final grain yield.
Growers in the sugar beet producing areas of the state often report an
increased incidence of purple-colored corn following sugar beet. This
phenomenon was investigated by Don Christenson at MSU in the mid 1990’s.
The work did not find a correlation with sugar beet carry-over
herbicides, soil P levels and did not appear to be an artifact of soil
compaction. The results indicate there may be an association with the
sugar beet residue and early season purpling of rotational corn.
Nevertheless, the increased incidence and severity of purpling following
sugar beet was not detrimental to corn yield.
The good news is that corn will generally overcome early season
purpling. Continue to monitor nutrient levels, particularly nitrogen and
identify severely compacted areas for remedial tillage in the fall.
Above all, next year use patience and discretion in deciding when to
resume field planting operations following rainfall.
