As farmers begin to plant winter barley across the country it is important to get the seed rate right. Some drills have been busy already this season, but farmers should delay sowing where possible. Rain has stopped those who were out in the fields this week.

Of course, as the harvest has dragged on delaying sowing is not an issue for many farmers who are now finding themselves under pressure to get jobs done like clearing straw, spreading farmyard manure and cutting hedgerows before they take out the plough or the drill.

Before planting farmers should consider the weather and the time available to plant: If you can hold off until October this can reduce barley yellow dwarf virus (BYDV) infection, take-all risk and other disease incidence can be reduced.

Even BYDV tolerant varieties should be delayed in order to reduce disease levels.

Calculating seed rate

Once you’ve chosen your variety it’s time to calculate the seed rate and the amount of seed that will be needed.

Three figures are needed to calculate seed rate. They are: the target plant population (plants/m²); the thousand grain weight (TGW) of the seed; and the estimated plant establishment percentage.

These figures will change as time goes on and establishment percentage will change as soil conditions change. In current conditions establishment percentage should be high.

Figures from Teagasc suggest that winter barley planted in the final week of September should have a target plant population of 270 plants/m²; 318 seeds/m²; and an establishment percentage of 85%.

Teagasc also outlines that the target plant population should increase by approximately 10 plants/m² each week until the end of October. Establishment percentage is estimated at 85% in the first week of October; 75% in weeks two and three; and 70% in week four.

TGW will change between varieties and should be specified on the bag of seed.