Crop management decisions require the knowledge of stage of development of the crop. In particular, spring fertilizers applications, herbicides, fungicides, growth regulators are typically applied at specific stages of plant development.
For example, current recommandations often indicate the second application of nitrogen be done when the ear (not visible at this stage) is about 1 cm in size (Z31 on Zadok scale). Knowledge of stages is also interesting to identify periods of higher risk, in terms of climate. For example, the meïosis stage is extremely suceptible to low temperatures (under 4°C) or high temperatures (over 25°C). Farmers also benefit from knowing when the flag leaf (last leaf) appears as this leaf represent about 75% of photosynthesis reactions during the grain filling period and as such should be preserved from disease or insect attacks to insure a good yield.
Several systems exist to identify crop stages, with the Feekes and Zadoks scales being the most widely used. Each scale is a standard system which describe successive stages reach by the crop during the agricultural season.
- Wheat at anthesis stage (face and side view)