How to increase barley grain numbers per ear

In barley, each spikelet contains only one floret, while wheat spikelets contain two to five fertile florets. All barley, spikelets form in threes, however, in two-row barley only the floret in the central spikelet is fertile, whereas in six-row barley, florets in all three spikelets are fertile. 

Crop management, particularly nutrition, can significantly influence both grains per ear and ears per sq m. Together these determine the number of grains per sq m. Grains per sq m and the size of individual grains determines the total storage capacity during the grain filling period. In winter barley, grain yield is most strongly related to grain number; therefore, early management decisions to optimise tiller production and survival are particularly important.

The grain number is itself a function of the number of fertile shoots per unit area and the number of grains per head. The grower therefore needs to consider the nutrients that can have an impact on the grain numbers / ear  which are mainly nitrogen, potassium, copper, zinc, boron and manganese.

Nitrogen affects the number of grain sites

By using the nitrogen to create the correct leaf canopy and therefore final grain site numbers, the result is more grains / ear at harvest.

Copper and zinc both affect number of grains per ear

Copper and zinc are both important in achieving a high grain number in the ear/spike.

Manganese deficiency reduces grain number

Deficiency of manganese will result in a reduction of grain numbers / ear

Boron affects pollen viability and so grain number

Boron is well documented at having an effect on pollen viability and therefore deficiency can lead to a reduction in the number of grain sites per spike. A measurement used to observe the effect of boron is Grain Set Index and normally expressed as a %. A high Grain Set Index is the target as this will lead to more grains per ear / spike. Care needs to be taken with boron as if applied at the incorrect timing and rate, yield reduction through decreased tillers can result.

These very large differences / effects show how important boron is as an essential plant nutrient.