Increasing Wheat Grain Numbers Per Ear

The grain number is itself a function of the number of fertile shoots per unit area and the number of grains per ear. The grower therefore needs to consider how nutrition can have an impact on the grain numbers per ear.

Wheat yield component targets

Nitrogen increases grain numbers

Nitrogen will affect the number of grains that are set on individual ears/spikes. A high yielding crop of wheat will have approximately 45-50 grains / ear, however if nitrogen supply is limiting this will be reduced.

Effect of high or low nitrogen in three wheat development periods

The timing of the applied nitrogen is important as grain numbers are determined early from double ridge to floret initiation.

Potassium influences grain numbers

Potassium will influence the numbers of grains per ear.

Effect of potassium  supply on 1000 grain weight of wheat

This study from the Potash Development Association shows a clear relationship between potassium supply and the number of grains per ear with potassium deficiency preventing some potential grain sites from developing and reducing grain set.

Micronutrients influence grain numbers

The effect of manganese and zinc on the number of grains per ear in wheat

Effect of boron on the yield of winter wheat


The effect of copper on the yield of winter wheat


Other crop management practices influencing wheat grain numbers

The number of eventual grains per spike (ear) varies from season to season and is affected by a number of factors including:

  • Varietal choice
  • Disease control during flowering
  • Weather conditions during flowering 
  • Temperature and day length before terminal spikelet (Zadoks GS 30)

This variability enables high yields to be achieved through two ways:

  • Low shoot numbers and high grain numbers/spike
  • High shoot numbers and low grain numbers/spike