Editor’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.