The wheat crop goes through three distinct phases as it grows from planting to harvest. They can be described as follows:
The foundation phase starts from sowing and lasts through to the start of stem extension. During this time yield-bearing shoots / tillers and primary roots form as the canopy develops. The components of yield (ear numbers and grain sites /m2) are set by the end of this stage. The speed of growth will depend on the environment with dull, cool days giving slow growth. In spring wheat’s this phase will be rapid as the days are bright and temperatures increasing.
The construction phase starts from the first node being detectable through to flowering. This is a critical growth period as yield delivering leaves, deep roots, fertile florets and stem reserves form. The canopy will be complete and capable of intercepting 95% of incoming Photosynthetically Active Radiation (PAR). Growth is very rapid with high daily nutrient demand from the soil. It is also referred to as the Grand Growth Phase.
The production phase starts just past flowering, lasting through to the grains filling and ripening. During this period the critical yield components i.e. grains /m2 and the grain weight will be determined. The health of the Flag Leaf and its nitrogen status must be maintained as it will contribute up to 70% of the carbohydrate that ends up in the grain.
Wheat Growth Stages
In more detail the development of wheat can be described using a number of scales that have been defined over the years. There are typically three used; Zadoks, Feekes and Haun, with the Zadoks being the most widely used to help input management decisions. Below is the scale detail.