5.
Heading – is the time when the panicle begins to exsert from the boot. (Figure 1-8 shows common types of panicle exsertion.) Heading may take over 10 to 14 days due to variations within tillers on the same plant and between plants in the field. Agronomically, “heading date” is defined as the time when 50 percent of the panicles have at least partially exserted from the boot.
Some panicles may never emerge completely from the boot. The Arkansas DD50 Management Program uses this same definition of “heading date.”