Why is My Corn Purple?

Several farmers will be noticing the incidence of purple corn in their fields.

Phosphorous Deficient Corn

P-deficient Corn. Note the purpling of the leaves.

Purple corn syndrome results from a number of stress factors.  The purple colour results from anthocyanin production in the leaves due to the accumulation of simple sugars.  The simple sugars build up in the plant because some other factor is limiting their further transformation or translocation in the plant.  Sometimes you will see the purpling at leaf tips of corn that are kinked by damage and the leaf can no longer transport or process the accumulating sugars resulting from the photosynthesis that is still occurring there. Many associate the purpling to reduced phosphorus nutrition of the plant.

Factors that can lead to reduced uptake of phosphorus – either due to lack of phosphorus (low testing soils, inadequate sidebanded application) or reduced rooting efficiency in taking up soil P (lack of mycorrhizae following canola,  root injury by toxic fertilizer bands, cold soils temperatures, dry soils, saturated soil, compaction, herbicide injury, insect feeding, etc).  And usually this is associated with adverse growing conditions – usually cold or saturated soils.

The crop usually “grows out” of this funk once weather and soils warm up and it is rarely seen beyond the V6 stage.  Some hybrids exhibit the purpling more than others.  This does not mean the other hybrids are any better at tolerating low P or cold conditions- they just hide their hurt better.  It would be negligent to shrug and chock it up to cold stress alone – consider whether you P fertilization practices, crop rotation or soil management are contributing to the syndrome,  then plan changes for 2015.

Submitted by: John Heard, MAFRD Crop Nutrition Specialist

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