The two key yield components of wheat are grain numbers per unit area, and the individual grain weight. High yields come from achieving the correct leaf and shoot numbers, maintaining a green leaf canopy, increasing grain numbers/ear and grain size.
A balanced crop nutrition programme including all macro and micro nutrients is essential to help manage all of these components.
Nitrogen and potassium are the nutrients required in the highest quantity for maintaining high wheat yields. Typically a wheat crop will a utilise 60% more potassium than nitrogen with the requirements for phosphate and sulphur being less but still significant.
The phosphate requirement, on the other hand, is similar to sulphur. It is during rapid spring growth that the demand for all macronutrients occurs.
Removal differs from field to field but typically a 10t/ha wheat crop can remove over 230kg/ha of nitrogen and 57kg/ha of potassium in the grain alone.
A balanced crop nutrition strategy is essential and should also include secondary and micronutrients which are essential elements in achieving high yields.
The number of leaves determines the size of the crop canopy and its photosynthetic potential. The number of shoots and how many of these survive through to harvest also determines the number of ears at harvest and so the potential yield.