Curfew for Corn

(Progressive Farmer image by Luke Cole)

Corn tells us precisely when it's all grown up. That blackened area at the kernel tip is your sign the crop has reached physiological maturity and will now begin a path to full adulthood (or kernel drydown).

This stage of corn maturation is often referred to as reaching "black layer." But, what does that mean?

Dekalb Asgrow technical agronomist Lance Tarochione explains that placental cells within the kernel actually die, darken and collapse into a thick layer, which appears black. These specialized cells have been absorbing and transferring sugars and other nutrients produced by the plant during photosynthesis.

"This black film or layer seals the kernel from further development or increase in seed weight," Tarochione notes. The kernel moisture content at black layer formation usually ranges from 25 to 40 percent but averages around 30 percent.

Physiological maturity is greatly influenced by an individual product's bred-in relative maturity. Environmental stress also plays a big role.

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