Zadok scale

Knowing the stages of development of a crop is critical in many management decisions that growers make.
It is represented by a scale going from 10 to 92.
For example, in some countries, nitrogen and herbicide applications must be completed during the tillering stage. In France, recommandations of first nitrogen application on wheat is 6 weeks before Z30, second application on Z30. Wheat growth regulators are typically applied at Z30. Disease control is most critical in the stem extension and heading stage (Z31, Z32, Z35), in particular as soon as the flag leaf is out (Z37). The crop is also more sensible to heat or frost at some stages than others (for example, meiosis stage is very sensible to low temperature).
Knowing the growth stage of the crop when scouting for problems is essential to decide which control measures should be followed.

Examples of typical stages

• during tillering
  • Z10 : one leave
  • Z21 : tillering begins
• during stem extension
  • Z30 : ear is one centimeter long in wheat
  • Z31 : first node visible
  • Z32 : second node visible
  • Z37 : flag leaf
• during heading
  • Z55 : the head is 1/2 emerged.
• during ripening
  • Z92, grains are ripe

Another cereal development scale is the Feekesone.