Knowing your thousand grain weight (TGW) is essential when calculating your seed rate. You should know this before you order your seed.

Seed rates will differ between varieties.

In total this year there are 16 spring barley varieties available and TGWs will differ between varieties and seed batches, meaning your seed rate will also differ as the weight of the seed affects the number of seeds that you need to sow.

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As a result, you need to know the TGW of the varieties you are planting.

The seed rate will also differ depending on when you plant which makes it difficult to order seed.

To calculate the seed rate you need three things:

  • The thousand grain weight (g).
  • The target plant population (plants/m2).
  • The expected establishment percentage (%).

    • Your target plant population is going to be about 300. In late April, it moves to 325.

    Establishment rates are generally estimated at 85%, but move to 90% in late April.

    Conditions at and after sowing will impact this.

    Dry weather in late April, would be unlikely to deliver 90% establishment for example.

    So, if you plant in late March, aim for 300 plants and an establishment rate of 85%, with a TGW of 52 then your seeding rate is 184kg/ha If you are planting at the same time, but with a TGW of 54 then your seeding rate is 191kg/ha, so there is 7kg/ha in the difference. The higher the TGW, the higher the seed rate.

    SR (kg/ha) = TGW (g) x TPP (plant/m2)

    Est (%)

    SR = Seed rate; TGW = Thousand grain weight; TPP = Target plant population; Est = Establishment